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 A.
 
 AN ELEMENTARY 
 TEXT-BOOK OF BOTANY
 
 AN ELEMENTARY 
 
 TEXT-BOOK OF BOTANY 
 
 BY 
 
 SYDNEY H. VINES M.A., D.Sc., F.R.S. 
 
 Fellow of Magdalen College and Sherardian Professor of Botany in the University of 
 
 Oxford ; Honorary Fellow of Christ 's College and formerly Reader in Botany in 
 
 the University of Cambridge ; Fellow of the University of London 
 
 WITH 397 ILLUSTRATIONS 
 
 Honbon 
 
 SWAN SONNENSCHEIN & CO Lim. 
 
 NEW YORK : THE MACMILLAN COMPANY 
 
 1898
 
 BUTLER & TANNER, 
 
 THE SELWOOD PRINTING WORKS, 
 
 FROME, AND LONDON.
 
 PBEFACE 
 
 en THE preparation of this work was undertaken to meet a demand 
 en which appeared to exist for a less bulky and expensive volume 
 ^ than my Students' Text-Book of Botany. I have so far succeeded 
 rt that this book contains about 200 pages less than the Students' 
 g Text-Book ; but it is still about so much larger than the last issue 
 z of Prantl's Elementary Text-Book, which it is intended to replace. 
 However, I am convinced that it is not possible, with advantage 
 to the student, to compress even the elementary facts and concep- 
 tions of Botanical Science into a much smaller space than this. 
 
 This book is not, however, merely an abridgment of the Students' 
 Text-Book. More 'important than the diminution of the bulk by 
 one quarter is the simplification which the contents have under- 
 g* gone by the omission of certain difficult and still debatable topics, 
 ,3 such as, for instance, the details of nuclear division, or the alter- 
 nation of generations in the Thallophyta. I have also thought it 
 desirable to follow, in the main, the classification of Phanerogams 
 laid down in the Genera Plantarum of Bentham and Hooker. 
 Moreover, there has been a considerable rearrangement of the 
 matter, and the more fundamental recent discoveries such as that 
 of spermatozoids in the Grymnosperms have been incorporated. 
 Hence the contents of this book differ in various material points 
 from those of the Students' Text-Book a difference which I hope 
 at some future time to render more marked by preparing an edition 
 of the Students' Text- Book of a more advanced character and on a 
 somewhat larger scale. 
 
 A word in conclusion as to how to use this book. It is con- 
 venient to divide as is done here the subject-matter of Botany 
 into the four parts, Morphology, Anatomy, Physiology, Systematic ; 
 but it must not be forgotten that these are all parts of one subject, 
 different methods of studying one object, namely, the plant. 
 Hence they must not be pursued separately, but together. For 
 instance, the morphology of the leaf cannot be profitably studied 
 without a knowledge of its structure and of its functions ; and it 
 
 332077
 
 Vi PREFACE. 
 
 is also important to know what is the systematic position of each 
 of the various plants whose leaves afford the material for study. 
 In a word, the student should not attempt to read the book 
 straight through from the beginning as if it were a novel. On the 
 contrary, he may begin with any one of the four parts as his main 
 subject ; but that part must be studied in close relation with the 
 other three parts, a procedure which is facilitated by the large 
 number of cross-references in the text. 
 
 S. H. V. 
 July, 1898.
 
 ERRATA 
 
 P. 83, line 18 from top ; for " erythrophl " read " erythrophyll." 
 161, 7 ; " the " (last word in the line) read " but." 
 ., 244, 29 ; " Sytonemaceae " read " Scytonemacese." 
 .. 273. 6 from bottom ; for " ooblastema-filaments " read " gonimo- 
 
 blastic filaments." 
 
 ,9 ; " arilode " read " arillode." 
 
 7 from top; for " brocteoles " read " bracteoles."
 
 CONTENTS. 
 
 PART L MORPHOLOGY. 
 
 PASS 
 
 1. Introductory . 1 
 
 2. The Life-History of Plants 2 
 
 3. The Segmentation of the Body 8 
 
 4. The Symmetry of the Body and of the Members .... 4 
 
 5. The Development of the Body and of the Members ... 8 
 
 6. The Arrangement of the Lateral Members 10 
 
 7. Development of Branch-Systems 18 
 
 8. Cohesion and Adhesion 21 
 
 9. The Thallus 22 
 
 10. The Shoot 22 
 
 11. The Stem 27 
 
 12. The Leaf 28 
 
 13. The Boot 44 
 
 14. Hairs and Emergences 46 
 
 15. Reproduction . . .49 
 
 16. General Morphology of the Asexual Reproductive Organs . . 51 
 
 17. General Morphology of the Sexual Reproductive Organs . . 58 
 
 18. The Fruit 61 
 
 19. The Seed 62 
 
 PART IL ANATOMY AND HISTOLOGY. 
 
 20. Introductory 63 
 
 CHAPTER I. THE CELL. 
 
 21. The Structure and Form of the Cell 66 
 
 22. The Protoplasm 68 
 
 23. The Cell- Wall 72 
 
 24. Cell-Contents 78 
 
 25. Cell-Formation 83 
 
 CHAPTER II. THE TISSUES. 
 
 26. The Connexion of the Cells . . . . . . .88 
 
 27. Intercellular Spaces 89 
 
 28. Forms of Tissue 90 
 
 29. General Morphology of the Tissue-Systems 101 
 
 30. The L'riinary Tegumentary Tissue 106 
 
 31. The Primary Ground-Tissue 110 
 
 ix
 
 CONTENTS. 
 
 32. The Stele ............ 116 
 
 33. The Primary Vascular Tissue ...... . .121 
 
 34. Histology of the Development of Secondary Members . . . 132 
 
 35. The Formation of Secondary Tissue ....... 137 
 
 36. Formation of Tissue in consequence of Injury ..... 155 
 
 PART III. PHYSIOLOGY. 
 
 37. Introductory 157 
 
 CHAPTER I. GENEEAL PHYSIOLOGY. 
 
 38. The Functions '. . . . . .157 
 
 39. The External Conditions .159 
 
 40. The Functions of the Tissues . ' . '.. " . ' . . .. . 162 
 
 41. The Functions of the Members . " . . , ...... 167 
 
 CHAPTER II. SPECIAL PHYSIOLOGY OF THE NUTRITIVE 
 FUNCTIONS. 
 
 42. Absorption ;. v ,~ ...-..-_. . . 177 
 
 43. Transpiration . . . . . . . ' ..7, . .179 
 
 44. Distribution of Water and other Substances . . ;..-./. 181 
 
 45. Metabolism 185 
 
 CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 
 
 46. Introductory 205 
 
 47. Spontaneous Movements 206 
 
 48. Induced Movements . . . . . . . . . . .211 
 
 49. Localisation of Irritability 220 
 
 50. Transmission of Stimuli 221 
 
 51. Combined Effects of Different Stimuli 222 
 
 52. Conditions of Movement . .223 
 
 53. Mechanism of the Movements 224 
 
 CHAPTER IV. SPECIAL PHYSIOLOGY OF REPRODUCTION. 
 
 54. Introductory 227 
 
 55. Vegetative Multiplication 228 
 
 56. Spore-Reproduction 230 
 
 PART IV. CLASSIFICATION. 
 Introductory 233 
 
 GROUP I. THALLOPHYTA 237 
 
 Class I. Algae 237 
 
 Sub-Class I. Cyanophycese (Phycochromacese) .... 244 
 
 Sub-class II. ChlorophyceaB 246 
 
 Series I. Protococcoidese 248 
 
 Order 1. Pleurococcacese 248 
 
 2. Protococcacese . 248
 
 CONTENTS. XI 
 
 PAGE 
 
 Series II. Volvocoideae 249 
 
 Order 1. Chlamydomonadaceae 249 
 
 2. Volvocaceaa. . . . . . . - 249 
 
 Series III. Siphonoideae 250 
 
 Order 1. Siphonaceae 250 
 
 2. Cladophoraceae 252 
 
 3. Hydrodictyaceae . . . . . .253 
 
 Series IV. Confervoideae . . . . " . . . . 253 
 
 Order 1. Conjugates 254 
 
 2. Ulothrichaceae 256 
 
 3. Ulvace83 257 
 
 4. (Edogoniaceae 257 
 
 5. Coleochaetaceae 258 
 
 Series V. Charoidess 260 
 
 Order 1. Characess 260 
 
 Sub-Class III. Phaeophycese 263 
 
 Order. Diatomaceae 265 
 
 Series (a). Phaeosporeae 265 
 
 Series (b). Phaeogamse 268 
 
 Order. Fucaceae 268 
 
 Sub-Class IV. Bhodophyceae 271 
 
 Class II. Fungi 275 
 
 Sub-Class I. Schizomycetes 280 
 
 II. Myxomycetes 283 
 
 III. Phycomycetes 285 
 
 Section A. Zygomycetes 285 
 
 Order. Mucorinae 285 
 
 Section B. Oomycetes 287 
 
 Order 1. Peronosporaceae 287 
 
 2. Saprolegniaceaa 289 
 
 Sub-Class IV. Ascomycetes . 290 
 
 Order 1. Gymnoasceae . 294 
 
 2. Pyrenomycetes 295 
 
 3. Discomycetes 296 
 
 Sub-Class V. JEcidiomycetes 298 
 
 Order 1. Uredineae 299 
 
 2. Ustilagineae 300 
 
 Sub-Class VI. Basidiomycetes 301 
 
 Series I. Protobasidiomycetes 305 
 
 II. Autobasidiomycetes . . . . . . 305 
 
 Subsidiary Group. Lichenes 305 
 
 GEOUP II. BRYOPHYTA (MUSCINE^) 
 
 Class III. Hepaticae (Liverworts) 318 
 
 Order 1. March ant iaceae 320 
 
 2. Jungermanniaceae 324 
 
 3. Anthocerotaceae . . 330
 
 Xll CONTENTS. 
 
 Class IV. Musci (Mosses) "332 
 
 Order 1. Sphagnaceae t '.-.;.. . . 340 
 
 Order 2. Bryinese 342 
 
 GEOUP III. PTEKIDOPHYTA (VASCULAR CEYPTOGAMS) . 346 
 
 Class V. Filicinae ; y . . . 854 
 
 Sub-Class. Eusporangiatse 
 
 Homosporese. 
 
 Order 1. Ophioglossacese ........ 354 
 
 2. Marattiacese 355 
 
 Heterosporeae. 
 
 3. Isoetacese 355 
 
 Sub-Class. Leptosporangiatae 
 
 Homosporeae (Filices) . t . . 358 
 
 Order 1. Hymenophyllaceae . . . r .371 
 
 2. Polypodiaceae . .... . . . 371 
 
 3. Cyatheaceae . . . . . . . .372 
 
 4. Gleicheniaceae 372 
 
 5. Schizseacese . ... . . ... .372 
 
 6. Osmundaceae 372 
 
 Heterosporese (Hydropterideae) . . 373 
 
 7. Salviniacese 380 
 
 8. Marsileacese . ,'' , . . .. . 380 
 
 Class VI. Equisetinae \ , '. . . 380 
 
 Order 1. Equisetacese 380 
 
 Class VI I. Lycopodinae. 386 
 
 Sub-Class. HomosporeaB 
 
 Order 1. Lycopodiacese . . . . . .386 
 
 2. Psilotacese 389 
 
 Sub-Class. Heterosporese 
 
 Order 3. Selaginellacese 389 
 
 PHANEROOAMIA (SPERMAPHYTA) . . .394 
 
 GEOUP IV. GYMNOSPEEM^E 419 
 
 Class VIII. Gymnospermae 
 
 Order 1. Cycadacese 431 
 
 2. Coniferse 432 
 
 3. Gnetacese 437 
 
 GEOUP V. ANGIOSPEEMJE 438 
 
 Class IX. Monocotyledones 476 
 
 Sub-Class I. Spadiciflorse 482 
 
 COHORT I. ARALES 482 
 
 Order 1. Aracese 482 
 
 2. Lemnacese 484 
 
 3. Typhacese 484 
 
 COHORT II. PALMALES 484 
 
 Order 1. Palmacese 484 
 
 Sub-Class II. Glumiflorse 486 
 
 COHORT I. GLUMALES 486 
 
 Order 1. Graminacese 486 
 
 2. Cyperaceae 492
 
 CONTENTS. Xlll 
 
 PAG a 
 
 Sub-Class III. Petaloideee . 494 
 
 Series I. Hypogynae. Sub-Series Apocarpce. 
 
 COHORT I. ALISMALES 494 
 
 Order 1. Naiadaceae .494 
 
 2. Juncaginaceae 495 
 
 3. Alismaceae 495 
 
 4. Butoiiiaceae . . ... . 495 
 
 Sub-Series Syncarpce. 
 
 COHORT I. LILIALES 496 
 
 Order 1. LiKacese 496 
 
 2. Juncaceae 499 
 
 Series II. Epigynae. 
 
 COHORT I. HYDRALES 500 
 
 Order 1. Hydrocharidaceae 500 
 
 COHORT II. DIOSCOREALES 500 
 
 Order 1. Dioscoreaceae 500 
 
 2. Bromeliaceae 501 
 
 COHORT III. AMOMALES (SCITAMINEJE) 501 
 
 Order 1. Musacese 501 
 
 2. Zingiberaceae 502 
 
 3. Marantaceae (Cannacese) .... 502 
 
 COHORT IV. ORCHIDALES 503 
 
 Order 1. Orchidacese 503 
 
 COHORT V. NARCISSALES 507 
 
 Order 1. Amaryllidaceae 507 
 
 2. Iridaceae 508 
 
 Class X. Dicotyledones 509 
 
 Sub-Class I. Monochlamydeae 514 
 
 COHORT I. URTICALES ' . .514 
 
 Order 1. Urticaceae 514 
 
 2. Moraceae 515 
 
 3. Cannabinaceae 515 
 
 4. Ulmacese 516 
 
 COHORT II. AMENTALES 517 
 
 Order 1. Betulacse .... ... 517 
 
 2. Corylaceee . .... 518 
 
 3. Fagace83 520 
 
 4. Juglandaceae 521 
 
 5. Salicaceae 522 
 
 COHORT III. CHENOPODIALES .522 
 
 Order 1. Chenopodiaceae 522 
 
 2. Polygonaceae 523 
 
 COHORT IV. ASARALES 524 
 
 Order 1. Aristolochiacese 524 
 
 COHORT V. SANTALALES 524 
 
 Order 1. Santalaceae . 524 
 
 2. Loranthaceae 525 
 
 COHORT VI. EUPHORBIALES 525 
 
 Order 1. Euphorbiaceae 526 
 
 Sub-Class II. Polypetalae 527
 
 CONTENTS. 
 
 PAGE 
 Series I. Thalamiflorse 
 
 COHORT I. RANALES 527 
 
 Order 1. Kanunculacese . . . . ' ,- . .527 
 2. Magnoliacese . . .: ' '. . .530 
 
 3. Nymphseacese . . ' . ..:... .530 
 4. Berberidacese . . . , . . .531 
 
 COHORT II. CARYOPHYLLALKS . 531 
 
 Order 1. Caryophyllacese 531 
 
 COHORT III. PARIETALES . . .'...-. .533 
 Order 1. Papaveracese . . ... . .533 
 
 2. Fumariacese ....... 533 
 
 ., 3. Cruciferse . ... . . ' . . .534 
 
 4. Cistacese ... . ... . . .538 
 
 5. Violaceae . . ... . . . .538 
 
 COHORT IV. GUTTIFERALES . . 539 
 
 Order 1. Hypericacese . . . ; . .539 
 
 COHORT V. MALVALES . . . . ; . . .539 
 
 Order 1. Tiliaceae . . .... . . -: . .539 
 
 2. Malvaceae . . . . . . .540 
 
 Series II. Disciflorse 
 COHORT I. GERANIALES . . .< ... *, . . 541 
 
 Order 1. Geraniacese . 542 
 
 2. Linacese 542 
 
 3. Oxalidacese " . .543 
 
 4. Balsaminacese 543 
 
 5. Eutacese 543 
 
 COHORT II. SAPINDALES 544 
 
 Order 1. Sapindacese 544 
 
 2. Aceraceae 545 
 
 3. Polygalaceas 545 
 
 COHORT III. CELASTRALES 546 
 
 Order 1. Celastracese 546 
 
 2. Ehamnacese 546 
 
 3. Ampelidacese ....... 547 
 
 Series III. Calyciflorae 
 
 COHORT I. UMBELLALES 547 
 
 Order 1. Umbelliferse 548 
 
 2. Araliacese 550 
 
 COHORT II. PASSIFLORALES 550 
 
 Order 1. Cucurbitaceae 551 
 
 COHORT III. MYRTALES 552 
 
 Order 1. Onagracese 552 
 
 2. Lythraceaa 553 
 
 3. Myrtacese 553 
 
 COHORT IV. ROSALES 554 
 
 Order 1. Rosacese 554 
 
 2. Leguminosae 557 
 
 COHORT V. SAXIFRAGALES 559 
 
 Order 1. Saxifragacese 560 
 
 2. Crassulaceae . .561
 
 CONTENTS. XV 
 
 PAGB 
 
 Sub-Class III. Gamopetalse 562 
 
 Series I. Hypogynae 
 
 COHORT I. LAMIALES 562 
 
 Order 1. Labiatse 562 
 
 COHORT II. PERSONALES 564 
 
 Order 1. Scrophulariaceae 564 
 
 2. Plantaginaceae . . . . .565 
 
 3. Orobanchaceae ...*... 566 
 
 4. Lentibulariacese 566 
 
 COHORT III. POLEMONIALES 567 
 
 Order 1. Convolvulaceae 567 
 
 2. Polemoniaceae 567 
 
 3. Solanaceae 567 
 
 4. Boraginaceae 569 
 
 COHORT IV. GENTIANALES 570 
 
 Order 1. Gentianacese 570 
 
 2. Oleacese 570 
 
 COHORT V. PKIMULALES 571 
 
 Order 1. Primulaceae 571 
 
 2. Plumbaginaceae 572 
 
 COHORT VI. ERICALES 572 
 
 Order 1. Ericaceae 572 
 
 2. Pyrolaceae 573 
 
 3. Vacciniaceae 573 
 
 Series II. Epigynae 
 
 COHORT I. CAMPANALES 574 
 
 Order 1. Campanulaceae 574 
 
 COHORT II. RUBIALES 574 
 
 Order 1. Rubiaceae .575 
 
 2. Caprifoliaceas 576 
 
 COHORT III. ASTERALES 577 
 
 Order 1. Valerianacese 577 
 
 2. Dipsaceae 577 
 
 3. Compositae 579 
 
 INDEX, PART I. Morphology, Anatomy, and Physiology . . 583 
 
 II. Classification and Nomenclature . 597
 
 PART I. 
 MORPHOLOGY. 
 
 1. Introductory. An ordinary flowering-plant consists of a 
 number of parts which are distinguished as roots, stems, leaves, 
 fruits, etc. These may be considered scientifically in two ways ; 
 either with reference to their functions in the economy of the 
 plant, when they are regarded as the organs by which these are 
 performed, and are the subjects of physiological study ; or, their 
 functions being disregarded, their relative position, the place and 
 mode of their origin, the course of their growth, and their relative 
 size may be considered ; that is, they may be studied from a purely 
 morphological point of view, when they are regarded merely as 
 parts of a whole, and are designated as members. Hence the pro- 
 vince of morphology is the study of the form of the bod} r of plants, 
 and of the members of which it consists, including the develop- 
 ment of the body and its members, as also the intimate structure 
 (Anatomy and Histology) of the body and its members, in so far as 
 structure throws light upon the morphology of any part of the 
 body. 
 
 The body of a plant, like that of an animal, consists essentially 
 of living substance known as protoplasm. The body may consist 
 only of protoplasm, without any investing membrane to give it a 
 determinate form (e.g. Myxomycetes) ; or it may consist of a mass 
 of protoplasm enclosed by a membrane (e.g. Phycomycetous Fungi 
 and Siphonaceous Algse) ; or it may consist, as in the higher 
 plants, of a mass 6f protoplasm segmented by partition-walls, or 
 septa, into structural units termed cells. In all cases, however, 
 the form and constitution of the body is determined by the proto- 
 plasm ; for the cell-walls of which, in many cases, the body largely 
 consists, and which give to it definiteness of form, are developed 
 from and by the protoplasm. The study of the morphology of 
 plants is, therefore, the study of the processes and products of the 
 formative activity of their protoplasm ; and these are to be traced 
 
 M.B. B
 
 2 PART I. MORPHOLOGY. [ 2 
 
 both in the varietj^ of form presented by different plants, and in the 
 varioias stages in the development of any one individual plant. 
 
 2. The Life-History of Plants. The consideration of this 
 subject is a necessary preliminary to the detailed study of 
 Morphology. The great majority of plants are more or less poly- 
 morphic : that is, the plant assumes, as a rule, at least two quite 
 different forms in the course of its life. Most commonly it presents 
 but two forms which, while they may differ more or less widely in 
 form and structure, are essentially distinguished by the fact that 
 the one, termed the sporophyte, has asexual reproductive organs 
 which produce asexual reproductive cells, termed spores, each of 
 which is capable by itself of giving rise to a new organism ; whilst 
 the other, termed the gametophyte, has sexual reproductive organs, 
 which produce sexual reproductive cells, termed gametes, and 
 though each of these cells is by itself incapable of giving rise to 
 a new organism, yet by the fusion of two of these gametes of 
 different sex, a cell is formed which is of the nature of a spore, 
 since from it a new organism can be developed. These two forms 
 alternate more or less regularly in different plants, the asexually- 
 produced spore of the sporophyte giving rise to a gametophyte ; the 
 sexually-produced spore of the gametophyte giving rise to a 
 sporophyte. Such a life-history presents what is known as alter- 
 nation of generations ; that is, an alternation of a sexual with an 
 asexual form. 
 
 The alternation of generations is conspicuous in the Bryophyta 
 and the Pteridophyta, as is fully explained in the chapters 
 specially devoted to those groups. It also occurs in the life- 
 history of the Phanerogams, and may be traced, more or less 
 imperfectly, in some of the Thallophyta. But since the tracing of 
 it in the last-named group is attended with some uncertainty, that 
 group will be excluded from further consideration here. In the 
 groups Bryophyta, Pteridophyta, and Phanerogamia, the two 
 generations attain very different degrees of development. In the 
 Bryophyta, the gametophyte is the more conspicuous generation ; 
 it is the form to which the name attaches, and upon which the 
 classification is mainly based ; whereas, the sporophyte is, as it 
 were, an appendage to the gametophyte, and is generally known as 
 the Moss-fruit. In the Pteridophyta, the sporophyte is the con- 
 spicuous form to which the name of the plant attaches; but, 
 though small and inconspicuous, the gametophyte is an independent 
 organism known as the prothallus. In the Phanerogamia, as in
 
 O. THE SEGMENTATION OF THE BODY. O 
 
 the Pteridophyta, the sporophyte is the plant such as we know 
 it, whilst the gametophyte is so much reduced that it may be 
 regarded as an appendage upon the sporophyte. Thus, in tracing 
 the morphology of the two generations from the Bryophyta 
 upwards, the relations between them are gradually reversed ; so 
 that the higher the plant is in the scale of organisation, the more 
 conspicuous is its sporophyte, the less conspicuous 'its gametophyte. 
 
 The following pages refer mainly to the morphology of the 
 sporophyte of the higher plants, that is, of the Pteridophyta and 
 Phanerogamia, except when the gametophyte or one of the 
 Bryophyta or Thallophyta is especially mentioned. 
 
 3. The Segmentation of the Body. The body of a plant 
 may be either segmented into members, or unsegmented. The 
 members of a segmented body may either be all similar, or they 
 may be similar and dissimilar. Segmentation into similar mem- 
 bers is termed branching. When the body is segmented into 
 dissimilar members, it is said to be morphologically differentiated. 
 
 When the body is morphologically undifferentiated, that is, 
 when it is either unsegmented or segmented only into similar 
 members (i.e. branched), it is termed a thallus. A Thallophyte is 
 a plant having a body of this constitution and of simple structure 
 (e.g. Yeast, Spirogyra). 
 
 The primary segmentation of the body into dissimilar members 
 consists in the differentiation of root and shoot. 
 
 The Root is usually segmented, but only into similar members. 
 It occasionally gives rise to (adventitious) shoots. 
 
 The Shoot may be either unsegmented, or segmented into similar 
 or dissimilar members. A shoot which is either unsegmented, 
 or segmented only into similar members, is termed a thalloid shoot 
 (e.g. Lemna, the Duckweed). A shoot which is segmented into dis- 
 similar members consists generally of stem and leaves. 
 
 The characteristics of the principal members are as follows : 
 
 The shoot bears the true (spore-producing) reproductive organs : 
 it is generally differentiated into stem and leaf. 
 
 The stem is the axial member of the shoot, and bears the leaves. 
 
 The leaf is the lateral member of the shoot : it is borne upon the 
 stem, but differs from it more or less in form. 
 
 The root never bears leaves or true (spore -producing) reproduc- 
 tive organs. 
 
 The hair is an appendage which may be borne on either root, 
 stem, or leaf.
 
 4 PART I. MORPHOLOGY. [8 4 
 
 The stem, leaf, and root of any one plant present the same kind 
 of complexity of structure : the hair is of much simpler structure 
 as a rule. 
 
 4. The Symmetry of the Body and of the Members. 
 Whatever the form of the body or of a member, it has three axes 
 at right angles to each other. When these three are all equal, the 
 body is a sphere (e.g. Volvox, Fig. 1) : when two are equal, and 
 both longer than the third, the body or the member is a flattened 
 circular expansion (e.g. Pediastrum and the leaf -blade of Tropseolum): 
 when one is longer than either of the others, the body or the mem- 
 ber is cylindrical or prismatic in form when the two shorter axes 
 are equal (e.g. the stem generally), and of a flattened form when 
 one of the shorter axes is longer than the other (most leaves). 
 
 In most cases two opposite ends are distinguishable in the body 
 or member, a base and an apex. The base is in all cases the end 
 by which the body is attached to the substratum, or the members 
 to each other, the free end being the apex. The axis or imaginary 
 line joining the base and the apex, whether or not it be longer 
 than the other axes, is termed the organic longitudinal axis. 
 When the body shows no distinction of base and apex (e.g. 
 Spirogyra), there is no organic longitudinal axis. 
 
 Any section, real or imaginary, made parallel to the longitudinal 
 axis, is a longitudinal section : it is a radial longitudinal section 
 if it includes the longitudinal axis : it is a tangential longitudinal 
 section if it does not include it. A section made at right angles to 
 the longitudinal axis is a transverse section : the section of the 
 longitudinal axis is the organic centre of the transverse section, 
 and it commonly is also the geometrical centre of the transverse 
 section, but occasionally the geometric and organic centres do not 
 coincide. Thus, in transverse sections of tree-trunks, the annual 
 rings are comparatively rarely arranged symmetrically around the 
 geometrical centre. The longitudinal axis, then, is a line passing 
 through the organic centres of the successive transverse sections. 
 
 Two kinds of symmetry may be distinguished ; the multilateral, 
 including the radial ; and the bilateral, including the isobilateral 
 and the zygomorvhic. The determination of the nature of the 
 symmetry of a body or member depends upon (a) its external form, 
 (6) the Arrangement and form of the members which it may bear, 
 (c) its internal structure. 
 
 1. MnlHlfit,,;,l n,nl Radial Symmetry. Absolute multilateral 
 symmetry is only presented by a body or member which is
 
 4. SYMMETRY. 
 
 spherical and has no distinction between base and apex. For 
 example, the body of Volvox can be divided into symmetrical 
 halves in any plane passing through the centre (Fig. 1). 
 
 The more limited form of multilateral symmetry, which, may be 
 conveniently distinguished as radial, is that which obtains in 
 cylindrical bodies or members. It is multilateral symmetry about 
 the longitudinal axis. In this case the body or member can be 
 divided in various planes along the longitudinal axis into a number 
 of similar halves. 
 
 A mushroom with a central stalk, an apple, a cylindrical tree- 
 trunk, are radially symmetrical as regards their external form. 
 
 As regards the posi- 
 tion of the lateral 
 members, the trunks 
 of Pines and Spruces, 
 with branches arising 
 on all sides, are ra- 
 dially symmetrical ; 
 and, as regards the 
 form of the lateral 
 
 FIG. l.-Folro* Globafor (after Cohn ; x about 100), 
 illustrating multilateral symmetry. 
 
 members, the flowers 
 of the Rose and of the 
 Tulip are radial. 
 
 A radial body or 
 member can be divided 
 by radial longitudinal 
 sections in two or 
 more planes, into 
 symmetrical halves, 
 which are to each 
 other as an object and its image reflected in a mirror (in Fig. 2, A, 
 the halves obtained by the sections 1-1, 2-2, 3-3, 4-4, 5-5). The 
 possible number of such similar halves is not always the same, but 
 it is in any case at least four. In a mushroom or a Fir-stem, there 
 are many possible planes of symmetrical section ; but in a Tulip, 
 the sections being taken through the longitudinal axes of the 
 floral leaves, only three are possible ; and in an apple if they pass 
 through the loculi of the core, only five (Fig. 2 A). 
 
 The two halves are not always as exactly alike as an object and its 
 reflected image ; this is not the case, for instance, in a Fir-trunk, because 
 the lateral branches are not borne at the same level. The two halves are,
 
 6 
 
 PART I. MORPHOLOGY. 
 
 [4 
 
 however, essentially similar. When, however, a body is divisible in at 
 least two planes into precisely similar halves, it is said to be polysym- 
 metrical. 
 
 2. Bilateral Symmetry. A body or member is said to be 
 bilaterally symmetrical when it presents an interior, a posterior, 
 and two lateral surfaces ; the lateral surfaces, or flanks, being dif- 
 ferent from the anterior and posterior. Such a body or member is 
 divisible into two symmetrical halves, either in two planes, or in 
 one plane only ; when it is so divisible in two planes, the halves 
 resulting from the section in one plane are different from the 
 halves resulting from section in the other. 
 
 Bilateral members are distinguished as isobilateral or as zygo- 
 morphic (or monosymmetrical), accordingly as they are symmetri- 
 cally divisible in two planes or in one plane. 
 
 FIG. 2. Diagrammatic transverse sections of A an apple; B a walnut; C a peach; 
 1-1, 5-5, are the planes of symmetry. A with five planes of symmetry, is radially sym- 
 metrical ; k carpel. B with two planes of symmetry, is isobilateral ; / the suture ; * the 
 seed. C with a single plane of symmetry, is zygomorphic and dorsiventral ; R dorsal 
 surface ; B ventral surface ; r right, and I left flank ; fc stone. 
 
 a. Isobilateral Symmetry. Isobilateral symmetry is usually 
 manifested in the external form. Thus, a walnut is at once seen 
 to be divisible into two symmetrical halves by section, either 
 through the suture, or at right angles to this plane (Fig. 2 B) ; so 
 also a flattened erect leaf like that of the Iris. 
 
 It may be manifested by the position of the lateral members ; 
 for instance, in many shoots (e.g. the Elm) the leaves are borne in 
 two rows, right and left, one row on each flank. 
 
 It may be manifested also in the internal structure. Thus, a 
 transverse section of a walnut (Fig. 2 B) shows that internal, as 
 well as external, isobilateral symmetry exists. But this does not
 
 4. SYMMETRY. 7 
 
 obtain in all cases ; the internal structure of isobilateral leaves is 
 often not strictly isobilaterally symmetrical. 
 
 b. Zygomorphic Symmetry. A zygomorphic or rnonosymmetri- 
 cal body or member is divisible into two similar halves in one 
 plane only (Fig. 2 (7). Of this there are two principal cases : 
 First, that in which the anterior and posterior halves are similar, 
 whilst the right and left halves are dissimilar, in other words, 
 when the plane of symmetry is lateral ; the body or member is 
 then laterally zygomorphic (e.g. flower of Corydalis) : secondly, 
 that in which the anterior and posterior halves are dissimilar, 
 whilst the right and left halves are similar, in other words, when 
 the plane of symmetry is antero-posterior ; the body or member is 
 then said to be dorsiventrally zygomorphic, or, briefly, dorsi- 
 ventral. Less frequently, as in some flowers, the plane of 
 symmetry is neither lateral nor antero-posterior, but intermediate 
 between the two, the zygomorphy being oblique. 
 
 Of these possible forms of zygomorphic symmetry, the dorsi- 
 ventral is the most common. The term is derived from the use of 
 the terms dorsal and ventral to indicate, respectively, the dis- 
 similar anterior and posterior halves of the body or member. 
 
 The application of the terms dorsal and ventral to the two dissimilar 
 halves of the body or a member requires some explanation. Generally 
 speaking, the under surface of a dorsiventral body is the ventral, the 
 upper the dorsal. In the case of leaves, however, the terms dorsal and 
 ventral are used with reference to the parent stem : the upper or inner sur- 
 face is here the ventral, the outer or lower, the dorsal. 
 
 The difference between the dorsal and ventral halves may be 
 exhibited in their external form. Thus, the dorsal and ventral 
 halves of many fruits (peach, Fig. 2 C ] or a pea-pod) may be 
 distinguished at once by their form. Or the difference may be in 
 the nature of the members which they bear ; thus, creeping dorsi- 
 ventral shoots commonly bear (adventitious) roots or root-hairs on 
 their ventral, and branches or leaves on their dorsal surface ; or 
 the one surface may bear lateral members, and the other none. 
 Or, finally, the difference may exist in their internal structure ; 
 thus, in dorsiventral foliage-leaves, the internal structure of the 
 dorsal half is different from that of the ventral half. 
 
 It must not be overlooked that the terms radial, isobilateral, and 
 dorsiventral, may be all applicable to one and the same body or 
 member, according to the particular feature which is taken into 
 consideration. For example, a branch of the Silver Fir is, in its
 
 8 PART I. MORPHOLOGY. [ & 
 
 general appearance, dorsiventral ; a dorsal and a ventral half are 
 readily distinguishable. But, since the leaves are arranged sym- 
 metrically around it, it is in this respect radial. Again, since the 
 lateral branches arise right and left upon its flanks, it is in this 
 respect isobilateral. Hence it is important to distinguish clearly 
 between the symmetry of any part of the body as a ivhole, and 
 that of its constituent members. Thus in many isobilateral and 
 dorsiventral shoots, the stem, regarded by itself, is radially sym- 
 metrical ; the isobilaterality or dorsiventrality of the shoot being, 
 in these cases, indicated only by the mode of arrangement of the 
 leaves upon the stem. 
 
 The causes which determine the symmetry of the body or of a 
 member are mainly inherent ; but it has been ascertained in many 
 cases that external conditions have a preponderating influence, 
 such as the intensity and direction of the incident rays of light, or 
 (as in certain dorsiventral flowers) the action of gravity. 
 
 When a body or a member cannot be symmetrically divided into 
 two similar halves in any plane whatever, it is said to be asymme- 
 tric. The asymmetry in these cases is frequently associated with 
 dorsiventrality ; as in some Mushrooms (e.g. Lcnzites abietina) ; 
 in some foliage-leaves which are oblique, that is, the right and 
 left halves of which are not symmetrical (e.g. Elm, some Begonias) ; 
 and in some flowers (e.g. Aconitum, Delphinium). 
 
 5. The Development of the Body and of the Mem- 
 bers. The body, consisting of the primary members, is developed 
 from the spore. It is not proposed to enter now into the some- 
 what complicated details of the various modes of embryogeny 
 occurring in the different groups of plants ; but rather to consider 
 the development of the secondary members, that is, of those mem- 
 bers which are produced directly or indirectly by the primary 
 members. 
 
 Whilst the plant is still an embryo, the whole of its protoplasm 
 is capable of growth, and is said to be in the embryonic condition. 
 As the development of the embryo into the plant proceeds, most of 
 the protoplasm passes over into the adult state, and is no longer 
 capable of growth. Certain portions of it, however, retain the 
 embryonic condition and properties, remaining capable of growth : 
 these portions of the protoplasm are termed growing-points, and 
 may persist throughout the whole life of the plant. Such growing- 
 points usually, but not exclusively, exist at the tip or apex of the 
 prinmry stem and of each of its branches, as also at the apex of
 
 5. DEVELOPMENT. 9 
 
 the primary root and its branches. The leaf has, with rare excep- 
 tions (e.g. some Ferns), no persistent growing-point, and this is 
 also true of some stems. Members in which there is no persistent 
 growing-point are said to have limited growth. 
 
 The growing-point adds, in the first instance, to the size of the 
 member to which it belongs, and is the means by which it grows 
 in length. But, in the case of the stem, it does more than this ; 
 it gives rise also to new members, either branches or leaves. It is, 
 in fact, the only source of origin of such new members. When 
 the growing-point is multicellular, the branches and leaves arise 
 from the superficial layers of cells ; so that their mode of origin is 
 exogenous. Moreover, these members are developed in a regular 
 order, such that the youngest of them are to be found nearest to 
 the growing-point, the older ones further away : this order of de- 
 velopment is termed acropetal succession. 
 
 As a general rule, the secondary members are developed laterally 
 on the parent member, the latter continuing its growth in length. 
 But in a few cases, more particularly when the body is a thallus 
 or the stem is thalloid, the growing-point divides into two, each of 
 which forms the growing-point of a new secondary member simi- 
 lar to the parent. This mode of branching is known as dichotomy. 
 
 In the root, the new members, except when dichotomy occurs, are 
 not developed at or from the growing-point, but at some distance 
 behind it. Unlike the branches and leaves produced by the stem, 
 the branches of the root are not developed at the surface, but from 
 a tissue lying deeply within the structure of the parent root. 
 (See Part II.) This layer, although it is situated among cells 
 which have become adult, retains its embryonic properties, and 
 gives rise to the growing-points of the several lateral roots. Hence 
 the origin of the secondary roots is endogenous, as their growing- 
 points are developed within the tissue of the parent root, and have 
 to force their way through it in order to reach the surface. The 
 order of development of the lateral roots is acropetal. 
 
 It sometimes happens that secondary members are developed 
 out of their proper order or not in their proper place ; they are 
 then said to be adventitious. This is rare in the case of stems and 
 leaves, but is common in the case of roots. Roots are, for instance, 
 frequently developed adventitiously on stems, instead of from the 
 primary root which is their normal position. When they are de- 
 veloped on stems their origin is almost always endogenous. 
 
 The secondary members commonly persist ; but frequently they
 
 10 
 
 PART I. MORPHOLOGY. 
 
 [6 
 
 become separated from the member bearing them, and fall off after 
 a time, when they are said to be deciduous. Leaves are nearly 
 always deciduous. In most perennial plants the foliage-leaves all 
 fall off at some season of the year, which, in temperate climates, is 
 the autumn. But in " evergreen " trees and shrubs, the leaves, 
 which may last for more than one year, do not all fall off at once. 
 Those parts of the plant which are connected with reproduction 
 are especially deciduous: for instance, the leaves forming the 
 perianth of the flower, sometimes the whole inflorescence (e.g. 
 catkin), sometimes the fruit (e.g. cherry), the seeds, etc. When a 
 
 member thus falls off it 
 leaves a more or less per- 
 manent scar : the scar which 
 marks the position of a 
 fallen leaf is a leaf-scar. 
 
 Hairs and reproductive 
 organs are generally de- 
 veloped as lateral out- 
 growths upon the members, 
 but they are occasionally 
 developed directly from the 
 growing-point. They are 
 usually developed from one 
 or more superficial cells, but 
 
 \V \lfllllllffill / / in s me cases the dee P er 
 ^PIllIP^ / / layers of cells also take part 
 
 in their formation. 
 
 All lateral members may 
 be developed either singly 
 or several together at the 
 same level on the parent 
 member. When in any cross-section of the parent member not 
 one only, but two or more lateral members occur at the same level, 
 they are said to form a ivhorl ; for instance, of secondary roots 
 round a parent root, or of leaves round a stem as in Herb Paris 
 (Paris quadrifolia). The members of a whorl may be developed 
 either simultaneously, or one after the other ; hence a whorl may 
 be either simultaneous or successional. Members not developed 
 in whorls are said to be scattered. 
 
 6. The Arrangement of the Lateral Members. The 
 arrangement of the leaves on the stem is most intimately con- 
 
 
 Fio. 3. Diagrammatic longitudinal section 
 through the growing-point of a stem: b the 
 leaves; fcn their axillary buds; e epidermis; 
 
 vascular bundles.
 
 6. ARRANGEMENT OF LATERAL MEMBERS. 11 
 
 nected with the acropetal order of their development ; and since 
 the arrangement of the lateral shoots depends on that of the leaves, 
 the same laws determine the arrangement of both these sets 
 of members which apply generally to all acropetally developed 
 members of plants. These laws are most conspicuously exhibited 
 in the arrangement of the leaves, and they will be fully discussed 
 with reference to these members only. 
 
 The leaves are developed in very close apposition at the growing- 
 point of the stem. The portions of the stem, termed internodes, 
 which lie between the individual leaves may either remain quite 
 short, as in the case of the rosette of leaves of the Plantain and of 
 the Houseleek, of the fascicled leaves of the Larch, and in most 
 flowers ; or they may undergo a considerable elongation so that the 
 leaves become widely separated. The boundaries of the iuternodes 
 the places, that is, at which the leaves are inserted termed nodes, 
 are sometimes prominently developed, more particularly when the 
 leaves are arranged in whorls, e.g. Labiatae, or when they ensheath 
 the stem. The portion of the surface or the stem from which the 
 leaf arises is the insertion of the leaf, and its organic centre is 
 called the point of insertion. 
 
 So long as the internodes have not begun to elongate, and the 
 leaves are still folded together so as to cover the apex of the 
 stem, the growing end of each shoot is known as a bud. The bud 
 which lies at the apex of a shoot, the lower portion of which has 
 already undergone elongation, is a terminal bud ; the lateral buds 
 are the early stages of shoots developed laterally upon a growing 
 main shoot, which often remain in this condition for a considerable 
 time. The arrangement of the lateral buds, and consequently that 
 of the branches which are developed from them, is closely related 
 to that of the leaves ; thus whilst in the Pteridophyta the bud 
 may be developed immediately below or by the side of a leaf, in the 
 Phanerogams it is nearly always developed in the axil of a leaf, 
 that is to say, in the angle made by a leaf with the internode 
 above its insertion. In the latter case the buds make their ap- 
 pearance at the first formation of the leaves (Fig. 3 kn). As a 
 general rule, they are developed in the axil of every leaf, typical 
 exceptions being the leaves that form the flower, and those of 
 many of the Conifers. In some cases certain of the internodes do 
 not elongate, and therefore the leaves, which have been really 
 developed singly, or their axillary buds, appear to have been 
 developed at the same level on the stem, thus forming a spurious
 
 1-2 
 
 PART I. MORPHOLOGY. 
 
 [6 
 
 whorl, as in the case of the upper leaves of the Tiger-lily and of 
 the whorled branches of the Pines. 
 
 The distribution of the lateral members over the surface of the 
 parent axis is either (see 4), multilateral, bilateral, or dorsi- 
 ventral. 
 
 1. Radial Arrangement. The arrangement of the leaves on the 
 stem (phyllotaxis') is very various ; this is particularly conspicu- 
 ous in the cases where the leaves are arranged in whorls, for 
 which reason these will be first discussed. If a whorl consists, 
 for instance, of two leaves, it is obvious that they will be placed 
 exactly opposite to each other on the surface of the stem, and that 
 the distance between them, measured from the points of insertion, 
 will amount to just half the cir- 
 cumference of the stem. Similarly, 
 if the whorl consist of three leaves, 
 the distance between any two ad- 
 jacent leaves will be one-third of 
 the circumference, and so forth. 
 The lateral distance between the 
 points of insertion of two adjacent 
 leaves, measured on the circum- 
 ference of the stem, is called their 
 divergence, and it is expressed in 
 fractions of the circumference. 
 
 Moreover, it is a rule, though 
 not without exceptions, that the 
 successive whorls alternate, so that 
 the leaves of any whorl lie opposite 
 to the intervals between the leaves 
 of the whorls above and below it. 
 Thus the leaves of alternate whorls 
 are exactly above each other (Fig. 4). 
 This arrangement, as in fact all relation of position, may be 
 very plainly exhibited by means of diagrams (e.g. Figs. 5 and 6). 
 Such a diagram consists of a ground-plan of the stem, regarded as 
 being a cone, and looked at from above ; the insertion of each leaf 
 will lie upon one of a series of concentric circles, and the higher 
 the insertion of the leaf upon the stem, the nearer to the centre 
 will be the circle of the diagram upon which its insertion is in- 
 dicated. 
 It may be perceived in the diagram Fig. 5, that when the leaves 
 
 FIG. 4. Stem of Lamium with whorls 
 of two leaves : 1-1, 2-2, 3-3, the suces- 
 eive whorls.
 
 6. ARRANGEMENT OF LATERAL MEMBERS. 
 
 18 
 
 FIG. 5. Diagram of a stem 
 with alternate two - leaved 
 whorls : 0, 0, 0, 0, the four or- 
 thostichies : 1, 1, 2, 2, 3, 3, the 
 successive whorls. 
 
 are arranged in alternate whorls, they form twice as many longi- 
 tudinal series on the stem as there are leaves in each whorl, pro- 
 vided, of course, that the number of 
 leaves in each whorl is the same. The 
 longitudinal series, which are indicated 
 in the diagram by radii, are called or- 
 thostichies. 
 
 This particular arrangement of alter- 
 nate whorls of two leaves occurs very 
 frequently, and is termed the decussate 
 arrangement. The two leaves of each 
 whorl are said to be opposite. It is 
 comparatively rare for equal successive 
 whorls to be superposed ; that is, that 
 the leaves of each whorl should lie ex- 
 actly above or below those of the others, so that there are only 
 as many orthostichies as there are leaves in each whorl ; but it 
 sometimes occurs in flowers. 
 
 Examples of decussate leaves : the Caryophyllaceae, the Labiatae, the 
 Caprifoliaceae, to which belong Syringa (Lilac), Lonicera (Honeysuckle), 
 and Sambucus (Elder); the Maple, the Horse-Chestnut, and the Ash. 
 In Rhamnus cathartica the two leaves of each whorl are usually at a 
 slightly different level. 
 
 Alternate whorls of many leaves occur in Equisetum and Hippuris ; al- 
 ternate whorls of 3 (irrespectively of flowers) occur in the common Ju- 
 niper, in Catalpa, and occasionally in the Horse-Chestnut and the Maple. 
 
 When successive whorls consist of unequal numbers of members, the 
 relations of alternation become highly complicated, as in the shoot of 
 Polygonatum verticilla- 
 
 tum and in the flowers o 
 
 of the Pomeae (Apple, 
 etc.) 
 
 When the leaves 
 are arranged in a 
 scattered manner it 
 is easy to detect 
 that, within a cer- 
 tain region of the 
 stem, their diverg- 
 ence is constant ; 
 that is, that the dis- 
 tance between any leaf and its immediate predecessor and successor 
 
 Fio. 6. A, Diagram of a stem bearing leaves with a 
 divergence of \ ; B, a utem bearing leaves with a diver- 
 gence of J.
 
 14 
 
 PART I. MORPHOLOGY. 
 
 [6 
 
 is a certain fraction of the circumference. In the simplest case, 
 when the divergence is i (Fig. 6 A\ starting with any leaf 0, the 
 insertion of the next leaf, in succession on the stem, which may 
 be numbered 1, will be on the opposite side to that of the leaf ; 
 and the next leaf, numbered 2, will be opposite to 1 and exactly 
 above 0. Thus there are two orthostichies. But since each leaf 
 is at a different level, in proceeding from leaf to 1, 2, 3, and so 
 on, always in the same direction, the circumference of the stem 
 is traversed in a spiral which, in the course of each whole turn, 
 touches the bases of two leaves and intersects the same orthostichy. 
 This spiral will pass through the insertion of every leaf, and as it 
 does so in the order of their development, it is known as the, 
 (jcnetic spiral. The number of leaves through which the genetic 
 
 spiral passes in its course 
 between any two on the 
 same orthostichy is termed 
 a spire. When the di- 
 vergence is ^, the leaf 
 numbered 3 comes exactly 
 above leaf 0, 4 over 1, 
 5 over 2, and so on : and 
 there are three orthosti- 
 chous lines, the spire being 
 composed of three leaves. 
 It might be said with 
 equal accuracy that the di- 
 
 FIG. 7. Diagram of a stem with a constant di- Vergence is -|, since leaf 1 
 vergence of |: I. II, III, etc., the orthostichous is distant f of the cirCUm- 
 lines. (After Sachs.) 3 
 
 ference from leaf 0, if the 
 
 spiral be followed in the other direction. If it be continued in this 
 direction, it will pass round the stem twice in each spire. For the 
 sake of simplicity, the spiral is not traced in this longer way, but 
 in the shorter way. When the numerator of the fraction of diver- 
 gence is not 1, but some other rational number, the spiral passes 
 round the stem more than once within the spire, in fact, just as 
 many times as is expressed by the numerator of the fraction of 
 divergence ; the denominator of the fraction expresses the number 
 of the orthostichies. In Figs. 7 and 8, which represent a constant 
 livergence of --, it is easy to see that eight orthostichies are pres- 
 ent, leaf y being over 1, 10 over 2, and so on ; also that the spiral 
 returns to a leaf on the same orthostichy after three turns, and 
 thus goes thrice round the stem in one spire.
 
 ARRANGEMENT OF LATERAL MEMBERS. 
 
 15 
 
 If it is required to determine the arrangement of the leaves 
 (phyllotaxis) on a stem, it is necessary to find the leaf which is 
 exactly above the one, numbered 0, selected as a starting-point, and 
 then to count the number of leaves which are met with in following 
 the shorter spiral round the stem between thesfc two leaves. The 
 number of the leaf which lies in the same orthostichy is the 
 denominator of the fraction of divergence, and the numerator is the 
 number of turns made by the spiral between 
 the two leaves. 
 
 When the number of orthostichies is 
 greater than 8, it becomes very difficult to 
 detect them, particularly when the leaves are 
 closely arranged as in the rosette of the 
 House-Leek, the florets in the capitulum of 
 the Sunflower, or as the scales in a Mr-cone. 
 Another set of lines lying obliquely then strike 
 the eye, called parastichies, which also run 
 round the stem in a spiral, but touch only some 
 of the leaves ; for instance, in Fig. 8, the line 
 which connects the leaves 3, 6, 9, and 12. It 
 is evident that the number of parallel para- 
 stichies must be as great as the difference 
 between the numbers of the leaves in any 
 one such line. Thus in Tig. 8, again, another 
 parastichy connects the leaves 2, 5, 8, 11, 
 and so on ; and a third, the leases 1, 4, 7, 
 10, etc. From this it is possible to deduce 
 a simple method for ascertaining the phyl- 
 lotaxis in complicated cases ; the parastichies 
 which run parallel in one direction are 
 counted, and the leaves in one of them are 
 numbered according to the above-mentioned 
 rule ; by repeating the process in another 
 system of parastichies which intersects the 
 first, the number of each leaf will be found. 
 
 The commonest divergences are the follow- 
 ing : 
 
 i, i, *, I, TV, A, M- 
 
 This series is easy to remember, for the numerator of each 
 fraction is the sum of those of the two preceding, and it is the 
 same with the denominator. There are, however, divergences 
 
 FIG. 8. Diagram of a 
 stem the leaves of which 
 have the constant diver- 
 gence of f, the leaves of 
 the anterior surface are 
 indicated by their inser- 
 tions, those of the pos- 
 terior by circles ; they 
 are connected by eight 
 orthostichies, I, I ,11, IT, 
 etc.
 
 16 PART I. MORPHOLOGY. [ 6 
 
 which are not included in this series, e.g. , f , f , etc. In some 
 cases the construction of a spiral with a constant divergence is 
 impossible, as in Salvinia. 
 
 The causes of this regularity of arrangement of the leaves lie 
 partly in the mode of origin of the leaves at the apex of the stem, 
 and partly in the displacements which they undergo in the course 
 of their subsequent growth. 
 
 Instances of the divergence : all Grasses, and the smaller branches of 
 the Elm,-the Lime, the Hornbeam, and the Beech ; in these, particularly in 
 the last, the leaves undergo displacement, so that on the under side of the 
 branch the divergence is less, and on the upper side it is greater than . 
 
 Divergence of is found in all the Sedges, and in the branches of the 
 Alder and Aspen. 
 
 Divergence of f may be regarded as the most frequent ; it occurs in 
 many herbaceous plants and in most of the smaller branches of the Willow, 
 the Poplar, the Oak, the Rose, the Cherry, and the Apple. 
 
 The acicular leaves of the Firs and Spruces usually have a divergence of 
 jj and ^ 3 : jf r occurs very commonly in the cones. 
 
 Finally, it may be observed that the genetic spiral turns sometimes to 
 the right and sometimes to the left on the stem ; in botanical terminology, 
 a spiral is said to be right-handed when it runs in such a direction that if 
 the observer ascended along it he would have the axis on his right ; and 
 left-handed, when it runs in the contrary direction. 
 
 It has been already pointed out that these laws of position stand 
 in the closest relation to the progressive development of the lateral 
 members. It can be demonstrated that the relation of position, when 
 once established, is maintained, because each new lateral member 
 arises just at the spot on the growing-point where there is the 
 greatest amount of space between the members already formed, 
 and it thus falls into the order which its predecessors have es- 
 tablished. So long as the relation of size between the rudiments 
 of the lateral members and the surface of the common axis remains 
 constant, the divergence will likewise remain constant ; but if this 
 relation be altered, if, for example, the newly developed members 
 are smaller than their predecessors, it will be readily understood 
 that the number of orthostichies and parastichies must be in- 
 creased. Hence we find changes in the divergence taking place 
 just in those regions in which the size of the lateral members 
 alters, for instance, at the base and at the apex of Pine-cones, and 
 at the base of the inflorescences of Compositse. Furthermore, sub- 
 sequent alterations may be induced by the growth either of the 
 axis or of the developing lateral members.
 
 G. ARRANGEMENT OF LATERAL MEMBERS. 17 
 
 2. Isobilateral Arrangement obtains when similar lateral mem- 
 bers arise on two diametrically opposite sides of the common axis, 
 and thus form two rows or orthostichies. Usually the members 
 of the two rows arise at different levels, so that they alternate 
 (Fig. 6 A}. In this case, also, it is possible to. construct a genetic 
 spiral ; such that at every half-turn it passes through the insertion 
 of a lateral member, and connects all the existing members in the 
 order of their age. Since the divergence is |, it is obviously quite 
 immaterial in which direction this spiral may be traced. Examples 
 of this alternate arrangement are given on the previous page. It is 
 only rarely that the members of the two rows stand in pairs at the 
 same level, thus forming superposed whorls of two members each ; 
 this is the case with the leaves of many Naiadacese, probably in 
 consequence of subsequent displacement. 
 
 3. Dorsiventral Arrangement. This arrangement of lateral 
 members may be manifested in very different ways. In some cases 
 the common axis bears lateral members on one side only ; in others, 
 the common axis bears dissimilar lateral members on its different 
 sides. As examples of the former, the flowering shoots of Vetches 
 and their allies, which bear flowers on one side only, may be 
 mentioned. The stem of Marsilea is an example of the latter ; it 
 bears leaves on the dorsal surface, lateral branches on the flanks, 
 right and left, and roots on the ventral surface : this relation holds 
 good also in the case of Azolla and Pilularia. In Salvinia the 
 dorsal surface of the stem bears the foliage-leaves, the flanks the 
 branches, and the ventral surface the aquatic leaves : in Selaginella, 
 likewise, the leaves are borne on the dorsal and ventral surfaces, 
 and the branches on the flanks. In Utricularia and in the inflor- 
 escence of the Boraginacese, the branches are borne on the dorsal 
 surface, the leaves (when present) on the flanks. In the Lemnaceae 
 the branches are produced on the dorsal, the roots on the ventral, 
 side of the shoot. 
 
 The members borne on the flanks, in these cases, are in rows, one 
 on each flank; and a similar serial arrangement can usually be 
 traced in the members borne on the dorsal and ventral surfaces. 
 Thus, in the inflorescences of the Boraginaceae, the flowers are 
 arranged in two longitudinal rows ; in those of the Vetches there 
 may be two rows (Vicia Faba, commonly), or many rows (Vicia 
 Graced). Similarly in some Ferns (Lygodium palmatum, Poly- 
 podium Heracleum] there is a single dorsal row of leaves. In 
 Azolla, Pilularia, and Marsilea, there are two dorsal rows of leaves ; 
 
 M.B. C
 
 18 PART I. MORPHOLOGY. [ 7 
 
 in Selaginella there are two ventral and two dorsal rows of leaves, 
 and in Salvinia two ventral and four dorsal rows. 
 
 The whorled arrangement is not excluded by dorsiventrality : 
 for instance, in Salvinia, the leaves are arranged in alternating 
 whorls of three, two of the leaves being borne dorsally, and the 
 third ventrally, and thus the four dorsal and the two ventral rows 
 of leaves are produced. 
 
 The affinity between the dorsiventral arrangement and the 
 isobilateral is indicated by the fact that whilst many axes develope 
 their lateral appendages on their flanks, they eventually come to 
 be dorsal. For instance, the creeping shoots of Butomus and other 
 plants produce their leaves in two lateral rows, which, however, 
 eventually undergo displacement on to the dorsal surface : again, 
 in the twigs of the Beech, the two rows of leaves approach each 
 other on the ventral surface, and the lateral branches approach 
 each other on the dorsal (p. 16). 
 
 Dorsiventral or isobilateral arrangement may not uncommonly 
 be found in the same plant with radial arrangement, but in 
 different parts : thus in the Hornbeam and the Elm the leaves of 
 the primary shoot of the seedling are arranged radially, whilst 
 on the twigs of the adult plant the leaves are arranged bilater- 
 ally (see p. 16). 
 
 7. Development of Branch-Systems. Just as it is 
 possible to ascertain the laws governing the relative positions of 
 all members growing in acropetal succession from a study of the 
 leaves (which are alway developed in that order), so the study 
 of the branching of stems will lead to the general laws which 
 regulate branching. Any member with its branches composes a 
 branch-system ; and every branching member is, with reference to 
 its branches, the axis of a system. The following types of 
 branch-systems may be distinguished, according to the arrange- 
 ment of the members : 
 
 1. The branching is termed a Dichotomy or Polytomy, when 
 the direct apical growth of a member ceases, two or more grow- 
 ing-points which are equally vigorous, at any rate at their first 
 development, being formed at the apex. The member which bears 
 the branches is called the base or podium, and each of these 
 branches may become the base of a new dichotomy or polytorny. 
 They may either continue to grow with equal vigour, and then, 
 in the case of a dichotomy, the branching remains distinctly 
 bifurcate (Fig. 9 A) ; as in the leaf of Schizcea dichotoma, where
 
 7. BRANCH-SYSTEMS. 
 
 1!) 
 
 the branches all lie in one plane, and the roots of Selaginella r 
 where the branches lie in various planes : or the system may be- 
 come sympodial, if at each bifurcation one branch becomes more 
 strongly developed than the other; in such a case the bases of 
 the successive bifurcations appear to constitute an axis, which is 
 called the pseud-axis or sympodium, on which the weaker 
 branches appear as lateral branches (Fig. 9 B, Cf). The sym- 
 podium may consist of bifurcations belonging to the same side of 
 the successive dichotomies, either to the left or to the right (Fig. 
 9 -B), when it is said to be a hdicoid (bostrychoid) dichotomy, 
 e.g. the leaf of Adiantum pedatum : or it may consist alter- 
 nately of the right and left 
 bifurcations of successive di- 
 chotomies (Fig. 9 C), when it 
 is said to be a scorpioid (cin- 
 cinnal}, dichotomy, as in the 
 stem of most Selaginellas. 
 
 2. The branching is said to 
 be racemose when the member 
 continues to grow in its ori- 
 ginal direction, and produces 
 lateral branches in acropetal 
 succession behind its apex ; it 
 is therefore the common base 
 of all the lateral shoots, and 
 hence the system is termed 
 monopodial. Each branch 
 may subsequently branch again 
 in the same manner. The pri- 
 mary axis continues to grow 
 more vigorously than the la- 
 teral axis, and each lateral 
 axis stands in the same rela- 
 tion to its lateral axes. 
 
 3. The branching is said to 
 
 be cymose, when at an early stage the growth of each lateral axis 
 begins to be more vigorous than that of the primary axis above 
 the point of origin of the lateral axis, and when the lateral axis 
 becomes more copiously branched than the primary axis. Hence 
 two forms may arise : 
 
 (a) There may be no pseud-axis ; this is the case when two or 
 
 FIG. 9. Diagram of the various modes of 
 development of adichotomous branch-system. 
 A One developed by repeated "bifurcation. 
 B Helicoid dichotomy; here the left-hand 
 branch is always more vigorous than the 
 right (r). C Scorpioid dichotomy; the right 
 and left branches are alternately more 
 vigorous in their growth.
 
 20 
 
 PART I. MORPHOLOGY. 
 
 more lateral axes are developed in different directions and grow 
 with nearly equal vigour (Fig. 10) and more vigorously than the 
 
 primary axis, 
 
 ir* which soon 
 
 ceases to 
 grow ; such 
 a system has 
 a certain re- 
 semblance to 
 a dichotomy 
 or polytomy, 
 and is called 
 a false di- 
 chotomy (Di- 
 chasium) or 
 a false poly- 
 tomy (Poly- 
 chasium) : or 
 (/3) a pseud- 
 axis is formed / this takes place when only one lateral axis de- 
 velopes vigorously in each case, as in Fig. 11 A where the lateral 
 axis 2 has grown more vigorously than the mother-axis 1, and so 
 on. (In the diagram the dark lines indicate the more vigorous 
 
 FJG. 10. Diagram of a False Dichotomy or Dichasium ; the Boman 
 numerals indicate the order of development of the shoots of the 
 *.\ wieni. (From Sachs.) 
 
 In- ll.-Cyraose branchings represented diagrammatically. A B Scorpioid (cincinnal) 
 cyme. C Dichaeial cyme. D Helicoid (bostrychoid) cyme. The numerals indicate the 
 order of succession of the lateral shoots which spring from en.ch other. (Figs A B and D 
 are ground-plans ; Fig. C is a projection hit > the plane of the paper.)
 
 8. COHESION AND ADHESION. 
 
 Jl 
 
 growth.) The pseud -axis which is thus formed is at first crooked, 
 but in most cases it subsequently becomes straight (Fig. 11 A 
 becomes B\ If the stronger growth always occurs in the lateral 
 shoots of the same side, the system is called a helicoid cyme (Fig. 
 11 D) ; if alternately in those of both sides,- it is called a scor- 
 pioid cyme (Fig. 11 A,B). Such a branch-system is said to be 
 sympodial. 
 
 As examples of these various modes of branching, the inflorescences, 
 which will be treated of subsequently (Part IV.), may be especially men- 
 tioned; the following are selected from the vegetative organs: 
 
 Racemose branching 'is very evident in Conifers ; the trunk is always 
 more strongly developed than its lateral branches, and these than their 
 lateral branches. 
 
 False Dichotomy is exhibited in the stem of Viscum, the Mistletoe, the 
 apex of which either terminates in a flower or else dies ; only the axillary 
 buds of the two leaves develope into new annual shoots. As regards - 
 the arrangement of the annual shoots, the same occurs in Syringa, the- 
 Lilac, in which the axillary buds of the uppermost pair of leaves form 
 the continuations of the stem, whilst the terminal bud dies; also in 
 filiamnus cathartica, in which the- main axis is metamorphosed into a^ 
 thorn. In this case the branching of each annual shoot is racemose, but 
 the successive annual shoots form a cyme. 
 
 The succession of the annual shoots of many trees, as the Birch, Elm, 
 Beech, and Hazel, affords examples of the sympodial cyme; in these, each 
 annual shoot either terminates in a 
 flower, or it dies, and the uppermost 
 lateral bud forms its continuation. 
 Here, also, the branching of each an- 
 nual shoot, apart from its apex, is 
 racemose. 
 
 8. Cohesion and Ad- 
 hesion. It sometimes happens 
 that the originally free edges of 
 parts subsequently grow together ; 
 for instance, the margins of the 
 carpellary leaves to form ovaries. 
 As a rule the rudiments of distinct 
 members become united into one 
 whole by the growth of their com- 
 mon base. For example, a gamo- 
 petalous corolla (see Part IV.) 
 arises in this way, that the whorled 
 leaf -rudiments are raised up by 
 
 FIG. 12. Flower of Petunia : A very 
 young ( x 50) ; B mature (nat. size) ; k 
 the calyx ; V the line along which the 
 calyx has been removed; r the tube, 
 I the lobes or teeth of the corolla.
 
 22 PART I. MORPHOLOGY. [ 9, 10 
 
 the intercalary growth of their common base (Fig. 12 A, r), and 
 come to be merely lappets on the rim of a tube (Fig. 12 }. 
 This explanation applies also to perfoliate and connate leaves (see 
 Fig. 20). 
 
 The union brought about in either of these ways may affect 
 members developed at the same level, or members developed at 
 different levels ; in the former case the term cohesion is used ; 
 in the latter, the term adhesion. Examples of the former are 
 afforded by gamopetalous corollas, syncarpous ovaries, ta; and 
 of the latter by epipetalous stamens, by leaves adhering to the 
 shoots borne in their axils, as in the Lime, etc. 
 
 9. The Thallus. The thallus offers considerable variety 
 of form. It may be spherical ; or filamentous, branched or un- 
 branched ; or a flattened expansion, branched or unbranched ; or 
 a massive tuberous body. It commonly bears hairs. The sym- 
 metry of the thallus is multilateral, isobilateral, or dorsiventral. 
 Complete multilateral symmetry is exhibited when the thallus is 
 spherical (e.g. Volvox, Fig. 1) ; isobilateral symmetry when the 
 thallus is flattened (e.g. Desmids, Coleochsete) with similar sur- 
 faces ; dorsiventral symmetry, when the thallus is flattened, with 
 dissimilar dorsal and ventral surfaces (e.g. most Hepaticse, and 
 Fern-pro thallia). 
 
 The branching of the thallus takes place in accordance with the 
 general laws laid down in 7 ; the flattened thallus frequently 
 branches dichotomously (e.g. some thalloid Hepaticse). The main 
 axis and the branches maybe either limited or unlimited in growth. 
 The branches of the thallus may be modified in form in connexion 
 with some special function. Thus, the development of reproductive 
 organs is in some cases confined to certain branches, and these then 
 differ in form from the ordinary vegetative branches (e.g. some 
 Hepaticse). 
 
 10. The Shoot. The shoot may be either thalloid (see p. 3) 
 or leafy. The morphology of the thalloid shoot hardly requires 
 special consideration : it is much the same as that of the thallus. 
 
 The general form of the leafy shoot varies widely. Even on one 
 and the same plant there may be different forms of leafy shoots. 
 the differences being due either to peculiarities in the conditions 
 of development, or of function. Marked differences exist, for 
 instance, between submerged, or subterranean, and aerial shoots ; 
 also between vegetative shoots and those bearing the repro- 
 ductive organs.
 
 10. THE SHOOT. 23 
 
 The form of the shoot depends largely upon the amount of 
 elongation which the internodes of the stem undergo. Thus, there 
 is in some plants (e.g. the Larch, Pine, and Taxodium, among the 
 Coniferae ; and many Angiosperms) a well-marked distinction of 
 two forms of vegetative shoots. These are the. ordinary elongated 
 branched shoots ; and short shoots, termed dwarf -shoots, which 
 elongate but little, branch scarcely at all, and are frequently of but 
 short duration (see p. 9). Again, in some plants (e.g. most Ferns 
 and Conifers) the primary shoot continues to grow throughout the 
 life of the plant ; whilst in others, the growth of the primary 
 shoot is limited, the further development of the shoot being 
 effected by a lateral branch, itself of limited growth ; so that, by 
 the repetition of this process a cymose branch-system is produced 
 (see p. 21). This mode of development by innovation occurs in 
 many so-called uniaxial plants whose primary shoot terminates in 
 a flower ; and in the seedlings of the Lime, and of the Elm, which 
 form no terminal bud at the close of the first year, the further 
 development of the shoot being effected by the highest lateral bud. 
 
 In plants which live for more than one year, the shoot may 
 either persist from year to year, or it may die down to the surface 
 of the soil in each year, the subterranean parts being alone per- 
 sistent. Shoots which last only one year are termed annual. 
 
 In those shoots of trees which are produced in one season's growth, the 
 lowest internodes, especially those lying between the bud-scales, are very 
 short ; so that it is easy, by noticing the closely-arranged scars of the bud- 
 scales, to determine, in a shoot several years old, the amount of growth 
 during each year. The terminal and the lateral buds of such an annual 
 shoot usually remain in the bud-condition during the first year until the 
 beginning of the next period of growth, so that the age of such a branch- 
 system can be determined by the extent of the branching, the number of 
 years corresponding to the number of times that branching has taken 
 place. In some trees, however (e.g. the Oak), a second shoot, which had 
 hitherto existed in the bud-condition, is regularly developed in the middle 
 of summer. As a general rule, it is only the more anterior (near the apex) 
 of the lateral buds on the shoot which develope in the subsequent year 
 into branches, as is very clearly seen in the whorled branches of the 
 Coniferse ; when, however, the more posterior lateral buds do develope, the 
 branches produced are successively the shorter the further they are from 
 the apex (e.g. Elm). Whilst in many trees (Coniferae, Oak) the ter- 
 minal bud of a shoot always grows into a new shoot in the next year, in 
 others (Lime, Elm, sometimes Beech) this is not the case, but the elongation 
 of the shoot is effected in a sympodial manner by means of the highest 
 lateral bud (see p. 21). 
 
 In the Larch, the dwarf-shoots bear the fascicled leaves, and spring
 
 PART I. MORPHOLOGY. 
 
 10 
 
 from the axils of the leaves of an ordinary shoot of the same year; they 
 usually elongate but slightly each year, but they may, under certain cir- 
 cumstances, develope into ordinary shoots. In the Scotch Pine, the dwarf- 
 shoots bear only two green leaves, in addition to scaly leaves ; they arise 
 in the axils of the scaly leaves of the ordinary shoots of the same year, and 
 
 Fio. 13. Various forms of shoots. A Tubers of Helianthm tuberoses (i nat. size); 
 lower part of the stem springing from last year's tuber fc'; in the axils of the upper 
 leaves arise the buds Jen, and in those of the lower leaves the tubers fc with very small scaly 
 leaves and buds. B Bulb of Hyacinthut orientals (reduced); fc the discoid stem, z the scaly 
 leaves, the stalk which subsequently elongates and bears the flowers above ground, with 
 the bads b ; I foliage-leaves ; w roots ; Icn an axillary bud which becomes next year's bulb. 
 C Elongated rhizome of Care* Arenaria (i) ; scaly leaves n ; a erect shoot with scaly and 
 foliage-leaves I. D Runner of the Strawberry, Fragaria (reduced), springing from the 
 plant o, with scaly leaves ti, from the axil of which a new leafy shoot b arises. E Creeping 
 shoot of the Ground Ivy, Glchomo hederacea (reduced) ; //decussate leaves ; the internodes 
 are twigted ; a axillary shoot ; w root. 
 
 they fall off when the leaves die. In dicotyledonous trees, these dwarf- 
 shoots occur especially in advanced age, or when the growth of the tree 
 is stunted. They are very conspicuous in the Apple, Pear, and other
 
 10. THE SHOOT. 
 
 25 
 
 similar trees, and are the only parts of the tree which produce flowers 
 and fruit : they are the fruit-spurs. 
 
 The Bulb and the Corm are examples of shoots with short stems ; they 
 are, in fact, forms of the bud produced underground. 
 
 The Bulb consist of a flattened discoid stem, bearing a number of scaly 
 leaves closely arranged on its upper surface, and roots on the lower sur- 
 face. The leaves may either invest each other, as in the Onion, when the 
 bulb is said to be tunicate (Fig. 13 B) ; or they may only overlap at their 
 edges, as in the Lily, when the bulb is said to be imbricate. 
 
 Aerial buds develope in some plants into small bulbs, termed bulbils, as 
 in Lilium bulbiferum, Denlaria bulbifera, and in some species of Onion. 
 
 The Corm consists of a rounded or flattened stem which occupies a rela- 
 tively larger proportion of space than that of the bulb, and is invested by 
 only a few scaly leaves. It occurs in Crocus and other Iridese. 
 
 The Tuber is a dwarf -shoot, consisting of a swollen stem bearing small, 
 
 Fi&. 14. A Rhizome, with unlimited growth, of Oxalis Acetosella (wood-sorrel) ; n scales ; 
 I foliage-leaves ; V remains of older foliage-leaves ; bl flower ; 7i bracts. B Rhizome with 
 limited growth of Potygonatum officinale (Solomon's Seal) ; I scar of last year's herbaceous 
 aerial shoot; II aerial shoot of this year, which is the anterior portion of the shoot 2 ; III 
 bud of next year's herbaceous aerial shoot, which is the continuation of the shoot 3 ; 
 n, scales ; b and b' leaves from the axils of which the shoots 2 and 3 have arisen ; w roots. 
 
 scaly leaves ; it is usually developed underground, as in the Potato and 
 and the Jerusalem Artichoke (Helianthus tuberosus, Fig. 13 A). 
 
 The morphological nature of the tuber is readily demonstrated by un- 
 covering the underground shoots of a Potato-plant, when they develope 
 into ordinary foliage-shoots. Again, if the development of tubers be pre- 
 vented by cutting off the underground shoots, the buds in the axils of the 
 leaves above the ground develope into tubers. 
 
 The Flower is another form of dwarf-shoot, the leaves of which, when 
 present, are arranged closely together. The morphology of the flower is 
 discussed in subsequent paragraphs.
 
 26 PART I. MORPHOLOGY. 
 
 Shoots may grow erect into the air; or they may grow horizontally 
 either above or below the surface of the soil. 
 
 A shoot which grows horizontally on the surface of the soil is terme 
 creeping shoot (Fig. 13 E). 
 
 The Runner or Stolon is allied to the creeping shoot. It is an elongated 
 lateral shoot which takes root at some distance from the parent plant, and 
 which by the dying away of the intermediate portion, becomes a new indi- 
 vidual. The runner may grow either just above (Fig. 13 D), or just below 
 the surface of the soil ; it bears sometimes scaly leaves, sometimes foliage- 
 leaves (e.,j. Hieracium Pilosella). Banners usually spring from shoots 
 
 with limited 
 growth, but 
 s o me times 
 from those 
 with unlimit- 
 ed growth, e.g. 
 Struthiopteris. 
 When a 
 shoot grows 
 horizontally 
 beneath the 
 soil, it is 
 termed a Rhi- 
 zome. It is 
 characteristic 
 of those plants 
 the subterran- 
 ean parts of 
 which alone 
 are persistent. 
 The growth in 
 length of the 
 rhizome is 
 sometimes un- 
 limited, some- 
 times limited. 
 When the 
 former is the 
 case, it con- 
 tinues to elon- 
 gate at its 
 apex, and 
 
 bears either only foliage-leaves (e.g. Pteris aquilina)] or foliage-leaves 
 and scales in regular alternation (Fig. 14 A, I, w), in the axils of which 
 annual shoots arise ; or only scales in the axils of which annual shoots 
 bearing foliage-leaves and flowers arise, as in Herb Paris. More com- 
 monly, the growth in length is limited, in which case the apex grows out 
 into an aerial annual shoot, whilst from the axil of a leaf at its base one 
 
 Fio. 16. -A Part of the shoot of the Vine ( nat. size) with two 
 tendrils r r ; the upper one bears small leaves ?i and branches ; the 
 lower one has become attached to a support x and has rolled up 
 spirally ; b h petioles ; in this case the tendrils are branches which 
 are peculiar in that they are opposite to the leaves. B Twining 
 Bhoot of Ipomoea s, with leaves b and a bud fc; x is the support.
 
 11. THE STEM. 27 
 
 or more subterranean shoots are produced which carry on by innovation 
 the elongation of the rhizome. If the older portions of the rhizome persist 
 for a long time, the basal portions of the annual shoots together form a 
 sympodium (Fig. 14 B) ; if, however, they soon perish, then each annual 
 shoot appears to constitute a distinct individual (e.g. Ranunculus acris, 
 Neottia). It is by the simultaneous formation of a number of short 
 innovation-shoots that the tufts of Grasses and Sedges are produced. The 
 innovation-shoots commonly develope roots of their own, but they may 
 remain connected with the main root of the plant as in Anemone PulsatUla. 
 
 In rare cases (Psilotum among Vascular Cryptogams) the functions of 
 roots are performed by subterranean shoots ; these shoots are more slender 
 than the subaerial shoots, and bear the merest rudiments of leaves. 
 
 Shoots which are unable to grow erect by themselves obtain, in some 
 cases, the Advantages of that position by climbing. The structure of the 
 shoot may be modified so as to subserve climbing. Branches are in some 
 cases (Uncaria) developed in the form of hooks, and may or may not bear 
 leaves ; these hooks serve to attach the plant to others. In other cases, 
 branches bearing small scaly leaves are developed into tendrils, which 
 twine round supports. In other cases the whole shoot twines round a 
 support (Fig. 15 A, B). 
 
 Branches are sometimes developed as thorns (Fig. 16). Thorns are hard, 
 pointed structures ; they sometimes form the extremity of an ordinarj' 
 shoot, as in Rhamnus cathartica ; or they are dwarf-shoots, as in Cratcegus 
 coccinea ; they may bear branches which spring from the axils of scaly 
 leaves, as in Gleditschia and the Sloe (Fig. 16). 
 
 The morphology of the constituent members of the leafy shoot, 
 namely the stem and the leaf, will now be considered. 
 
 11. The Stem. The stem of an annual plant or of an 
 annual shoot is succulent in texture, and 
 is said to be herbaceous. 
 
 A primary stem which persists for 
 several years, though it is herbaceous at 
 first, becomes hard and woody in tex- 
 ture, and is termed a trunk. 
 
 The stem is commonly branched ; but 
 it may be unbranched, as in Tree-Ferns, 
 Cycads, many Palms and Grasses. 
 
 The form of the Stem varies Very, leaf -scar, from the axil of which 
 
 widely. It may be short and much tbe thorny branch z 8prings ; on 
 
 ,,. , , . J the thorn are // leaf -scars; in 
 
 thickened, as in the bulb, corm and the axil of the upper one is the 
 tuber, mentioned above (p. 24) and in branch z - in that of the lower - 
 
 . ... , the bud fc. 
 
 some Uacti ; or a portion of it may be 
 
 much thickened into a tuber, as in certain epiphytic Orchids, 
 
 where one or more of the basal internodes form a pseudo-bulb
 
 28 PART I. MORPHOLOGY. [ 12 
 
 and in Vitis gongylodes, where any internode may become tu- 
 berous. 
 
 The form of the elongated stem is commonly cylindrical or 
 prismatic. The prismatic form is, in some cases, determined by 
 the arrangement of the leaves ; thus, stems bearing decussate leaves 
 (see Fig. 4, p. 12), that is, leaves arranged in four orthostichies, 
 are quadrangular. When the stem has an angular form, the 
 edges frequently grow out into a leafy expansion : such a stem is 
 said to be winged. In some cases, as in Grasses, Bamboos, Pinks, 
 etc., the stem presents a jointed (tumid) appearance at the nodes ; 
 a stem with this peculiarity is termed a culm or haulm. 
 
 When the development of the foliage-leaves of a shoot is de- 
 generate, the stem performs the functions of the leaves : it is then 
 of a green colour, and generally assumes such a form as to have a 
 relatively large surface. Thus, the 
 whole stem and its branches may 
 become flattened, as in Opuntia 
 (Cactacese) and in Genista sagittalis 
 (Papilionacese) : or certain branches 
 only, termed phyllodades, are flat- 
 tened and leaf-like as in Ruscus 
 (Liliacese), Phyllanthus (Euphorbi- 
 acese), Miihlenbeckia (Polygonacese), 
 Carmichaelia (Papilionacese), Phyl- 
 locladus (Coniferse), and are either 
 FIG. i7.-Ph y iiociade of Ruscus isobiliterally or dorsiventrally sym- 
 
 Hvpo^um (nearly nat. size) : . met rical. The phylbclades fre- 
 stem; b leaf, m the axil of which the r J 
 
 phyiiociade p is developed ; d leaf of quently bear flowers, but not always 
 
 the phyiiociade bearinR flowers bl in i n the Same position. Thus, in 
 its axil. 
 
 Ruscus androgynus the flowers are 
 
 borne on the margin of the phyiiociade ; in Ruscus aculeatus and 
 R. Hypoglossum, they are borne on the upper surface of the phyi- 
 iociade ; and in R. Hypophyllum, on the under surface. 
 
 Leaf-like branches are also formed in Asparagus ; they are not 
 flattened, but are small and acicular ; something of the same kind 
 also occurs in Equisetum. 
 
 12. The Leaf. All leaves, except the primary leaves or 
 cotyledons, are developed exogenously as lateral outgrowths upon 
 the growing-point of a stem. 
 
 In most plants the leaf undergoes differentiation or segmentation 
 along its longitudinal axis or phyllopodium. In the most com-
 
 12. THE LEAF. 
 
 29 
 
 plete case, the phyllopodium is differentiated into three regions : a 
 basal portion, the leaf-base or hypopodium ; an apical portion, the 
 epipodium ; and an intermediate portion, the mesopodium, leaf- 
 stalk, or petiole ; but the last-named portion is frequently absent. 
 Most commonly the leaf assumes a flattened fcfrm in consequence 
 of the development of a relatively thin membranous icing along 
 one or other of these regions in the lateral plane : the epipodium 
 is typically winged, and then constitutes what is known as the 
 blade or lamina of the leaf ; the mesopodium is rarely winged, the 
 hypopodium more frequently so. 
 
 The growth in length of the leaf is at first apical in all cases ; it 
 may continue to be apical (e.g. Ferns generally) ; or apical growth 
 may be early arrested, further elongation being effected by basal 
 growth (e.g. Iris, Onion, Myriophyllum, Poten- 
 tilla anserina) ; or, more rarely, basal and 
 apical (e.g. Achillea MillefoUum, and other 
 Composite) growth may occur simultaneously. 
 
 A characteristic feature of leaves is that 
 their growth in length is limited ; but this is 
 not without exception ; in fact, there are all 
 intermediate forms between those which have 
 limited and those which have unlimited 
 growth. Thus, in most Phanerogams the 
 leaves have limited growth ; the cells of the 
 leaf are all actually formed at the time of its 
 unfolding, and all that takes place subsequently 
 is that the cells grow to their definitive size. 
 In a few of these plants, however, (e.g. Gruarea 
 and other Meliaceae) the pinnate leaves have 
 an apical growing-point by which new cells 
 are formed, and the growth in length of the leaf and the de- 
 velopment of lateral branches is carried on after the leaf has 
 unfolded. Long-continued apical growth appears to be the general 
 rule in Ferns : in Pteris aquilina and in Aspidium Filix-Mas 
 the leaf grows for three years ; and in Grleichenia, Lygodium, many 
 Hymenophyllacese, and Nephrolepis, the leaf grows for many years 
 after its appearance above the soil. The most striking example of 
 long-continued basal growth is that of the two leaves of Wel- 
 witschia which persist and grow basally as long as the plant lives, 
 and consequently attain a great length. 
 
 The leaves are inserted upon the nodes (p. 11) of the stem, the 
 
 FIG. 18.-Leafof Ban- 
 unculus Ficaria: v leaf- 
 base (hypopodium) ; p 
 petiole (mesapodium) ; 
 t lamina (epipodium).
 
 30 
 
 PART I. MORPHOLOGY. 
 
 12 
 
 plane of insertion being usually transverse to the longitudinal 
 axis of the parent stem. 
 
 The Hypopodium or Leaf-Base. The leaf-base commonly de- 
 velopes into a cushion of tissue, termed the pulvinus, which forms 
 the articulation by which the leaf is attached to the stem ; in the 
 Gooseberry the pulvinus developes into a spine. In many cases 
 the leaf-base is sheathing, and embraces a part or the whole of the 
 circumference of the node ; in the former case the leaf is said to 
 be semi-amplexicaul ; in the latter, amplexicaul (e.g. Grasses, 
 Onion, Fool's Parsley). 
 
 The leaf-base sometimes produces a pair of opposite lateral 
 
 Fto. 19. 4 Part of a sessile leaf of Grass (Poa trivialis) with the ligule t ; a the haulm ; 
 v the sheathing leaf-base ; I lamina of the leaf. B Leaf of a Willow (Soli* Caprea) ; a 
 stem ; 8 stipules ; p petiole ; / lamina ; fc axillary bud (nat. size). C Leaf of a Pea (Pisum 
 arvente) ; a stem ; 8 s stipules ; r mesopodium or petiole ; // leaflets ; rf r/ the upper leaflets 
 metamorphosed into tendrils ; r' end of the epipodium, likewise transformed into a 
 tendril. 
 
 branches which are termed stipules ; when they are present the 
 leaf is said to be stipulate, and when they are absent, as is more 
 commonly the case, the leaf is said to be exstipulate. The stipules 
 are commonly winged appendages, similar in colour and texture to 
 the lamina, and they are then said to be leafy (Fig. 19 B, O), as in 
 the Willow, the Violet, and the Rubiacese where they are branched ; 
 and they are especially large in plants, like the Pea, where the 
 lamina is relatively small : in other plants, on the contrary, they 
 are small brownish scales, which fall off soon after the leaf is un-
 
 12. THE LEAF. 
 
 31 
 
 folded, as in the Beech, the Elm, and the Lime. Sometimes the 
 stipules appear as teeth on the upper margin of the sheathing leaf- 
 base, as in the Rose. Occasionally the two stipules are connate, 
 that is, they are more or less united ; when they cohere by their 
 outer margins they form a single opposite stipule, opposite, that 
 is, to the leaf to which they belong, as in Astragalus ; when they 
 cohere by their inner margins they form an axillary stipule, that 
 is, a stipule in the axil of the leaf to which they belong, as in Meli- 
 anthus and Houttynia cordata ; in the Polygonacese they cohere 
 by both their inner and outer margins, thus forming a tube, termed 
 an ocrea, which surrounds the intemode above the insertion of the 
 leaf ; when the stipules of opposite leaves cohere they form on each 
 side an interpetiolar stipule, as frequently in the Rubiacese and in 
 the Hop ; this 
 may also take 
 place when 
 there are several 
 leaves in a 
 whorl, as in the 
 epicalyx of cer- 
 tain Rosaceae. 
 
 In some cases 
 (e.g. Smilax) the 
 stipules are de- 
 veloped in the 
 form of tendrils, 
 and in other 
 cases (e.g. Ro- 
 binia) as spines. 
 
 Stipules are 
 
 comparatively common in Dicotyledons ; they are absent in the 
 Coniferse ; absent in Monocotyledons, excepting the Naiadacese and 
 Smilax ; absent in most Pteridophyta, except the Marattiaceae 
 among Ferns. In Tropoeolum majus only the two leaves which 
 succeed the cotyledons have stipules. 
 
 The leaflets of a compound leaf sometimes have stipules at their 
 bases, as in Phaseolus, which are distinguished as stipels. 
 
 In a leaf without a petiole it sometimes happens that the leaf- 
 base is winged in continuity with the lamina ; the result is that 
 the wings extend round the stem, either incompletely (Fig. 20 .4) 
 when the leaf is said to be auriculate ; or completely (B) when it 
 
 FIG. 20. The insertion of sessile leaves. A Auricnlate leaf of 
 Thlaspi per/oliotum. B Perfoliate leaf of Bupleurum rotundt- 
 /olium. C Connate leaves of Lonicera Capri/oHum.
 
 32 PART I. MORPHOLOGY. [12 
 
 is said to be perfoKate ; when this occurs in two opposite leaves, 
 the leaves become connate (C ; see p. 22). 
 
 There is, in some cases, a delicate membranous ventral outgrowth on 
 the leaf at the junction of epipodium and hypopodium, termed the ligule ; 
 it occurs in Grasses (Fig. 19 .4), in Selaginella and Isoetes, and in the 
 perianth-leaves of some flowers (Narcissus, Lychnis). 
 
 The Mesopodium or Petiole is commonly, but not always, 
 present. When it is present the leaf is said to petiolate ; when 
 it is absent, sessile. It is developed by intercalary growth in a 
 portion of the primordial leaf lying between the hypopodium on 
 the one side and the epipodium on the other. The most common 
 form of the petiole is somewhat cylindrical ; though, where the 
 dorsiventrality of the leaf is well-marked, it is convex on the 
 lower (dorsal) surface, and flattened or grooved on the upper 
 (ventral) surface. In the Aspen (Populus tremula) it is flattened 
 laterally. 
 
 Occasionally (e.g. Orange, Fig. 23 G ; Nepenthes, Fig. 28; 
 Dionsea) the petiole is winged. 
 
 In some cases (e.g. Australian Acacias) the petiole has somewhat 
 the form of a lamina. Its flattened surfaces are directed laterally, 
 the edges upwards and downwards, so that the symmetry is isobi- 
 lateral. A petiole of this form is termed a phyllode. In such 
 cases, the lamina, originally present, soon falls off. 
 
 Tlie Epipodium may be either icinged or unicinged. The 
 winged epipodium constitutes the lamina or blade of the leaf, and 
 is typically flattened and expanded in form and dorsiventral in 
 symmetry : but this is not always the case, for in some plants it 
 assumes the form of a sac or pitcher (e.g. Utricularia, Nepenthes, 
 etc.), and in others the symmetry is isobilateral (e.g. adult leaves 
 of Eucalyptus Globulus). 
 
 The form of the unwinged epipodium presents great variety ; 
 thus, in Lathyrus Aphaca the epipodium branches into leaf- 
 tendrils, and this is partially the case also in the Sweet Pea (Fig. 
 19 C) ; it may be cylindrical or prismatic, as in Onion, Sedum, 
 Mesembryanthemum, Aloe; acicular as in Pinus ; narrow, and 
 flattened anteroposteriorly (ensiform] so that the margins corres- 
 pond to the dorsal and ventral surfaces of a dorsiventral leaf, 
 with isobilateral symmetry, as in Iris and Gladiolus. 
 
 The flattened dorsiventral lamina is normally so placed with 
 regard to the parent stem that a plane, which includes the longi-
 
 12. THE LEAF. 
 
 33 
 
 tudinal axes of both the stem and the leaf, cuts the lamina into 
 two lateral halves ; in other words, it is so placed that its upper 
 (ventral) surface faces the apex of the stem, and its lower (dorsal) 
 surface is directed away from it. As a rule, the two lateral halves 
 of the lamina are symmetrical; but in some cases (e.g. Elm, 
 Begonia) they are unsymmetrical, when the lamina is said to be 
 oblique. 
 
 The ultimate form of the lamina mainly depends upon the 
 degree of elongation of the epipodium. When the epipodium 
 elongates considerably, the lamina has a well-marked primary 
 axis from which more or less numerous secondary axes of growth 
 successively spring, and these in turn bear lateral axes of a higher 
 
 Fie. 21. A Pinnate leaf of the Beech, Fagus syloatica; m mid-rib, n lateral ribs. B Pal- 
 mate leaf of Alchemilla vulgaris (nat. size.) C Pedate leaf of the Plane (} nat. size). 1, 2, 
 3, are the ribs or axes of the 1st, 2nd, and 3rd order. 
 
 order : the resulting lamina is then of the pinnate type (Fig. 21 
 A). When, however, the epipodium remains short, it constitutes 
 merely an intercalary growing-point from which a number of 
 equal secondary axes spring, and the resulting lamina is of the 
 palmate type (Fig. 21 B). 
 
 The development of the peltate lamina, closely connected with 
 that of the palmate type, is effected by a peculiar form of basipetal 
 growth. In peltate foliage-leaves (e.g. Tropseolum, Nelumbium, 
 Hydrocotyle, Cotyledon, Lupinus, etc.) the petiole is inserted in 
 the middle of the under surface of the lamina, so that the long 
 
 M.B. D
 
 PART I. MORPHOLOGY. 
 
 [12 
 
 axis of the former is perpendicular to the plane of expansion of 
 the latter. At first the development is that of a palmate leaf, 
 the petiole being inserted at the base of the lamina, and at the 
 point of insertion there is an intercalary growing-point from which 
 spring several axes (Fig. 22 B, i 2,3) in basipetal succession. But 
 in this case the last-formed axes(j-,5-5, in the. figure) grow out 
 in front of the petiole, with the result that the whole lamina 
 gradually comes to lie perpendicularly to the petiole. 
 
 The main axes of growth frequently grow thicker than the 
 rest of the lamina, so that they project as ribs on the under 
 
 surface. The thickened pri- 
 mary axis (epipodium) of a 
 pinnate lamina is termed a 
 mid-rib. 
 
 The Branching of the Leaf 
 is commonly confined to the 
 epipodium, and then it takes 
 place in the lateral plane ; 
 less commonly it occurs in 
 the mesopodium (e.g. species 
 of Ophioglossum, Botry- 
 chium, Marsilea), and then 
 (as in these plants) the 
 branching frequently takes 
 place in the antero-posterior 
 (or dorsiventral) plane. 
 
 The branching of the epi- 
 podium is, like that of a stem 
 or a root, either dichotomous 
 or lateral, and essentially the 
 same forms of branch-systems 
 are produced. Dichotomous 
 branching is comparatively 
 rare ; it has been observed in the Hymenophyllacese, the branches 
 either remaining distinct or forming sympodia. The two first 
 leaflets of Marsilea are said to be formed by dichotomy. Lateral 
 branching is the more common form, and the resulting branch- 
 systems are typically monopodial. But in some cases (e.g. leaf of 
 Plane, Fig. 21 C ; of Helleborus, and of some Aroids) there is 
 apparently cymose branching with formation of a sympodium. 
 The ribs of the lamina are branches of the epipodium. The 
 
 Fio. 22. Development of peltate leaf of Hy- 
 drocotyle : A full-grown (nat. size) ; B very 
 young; C somewhat older (B and 0x60); S 
 petiole ; 1-5 primary axes of growth in young 
 leaves, ribs in adult leaf; a secondary axes of 
 growth.
 
 12. THE LEAF. 35 
 
 degree of segmentation of the lamina depends upon the relation 
 between the growth of the various main axes and the marginal 
 growth of their respective wings (see Figs. 21 and 22). When 
 these keep pace with each other the lamina is_ altogether unseg- 
 mented, that is, its margin is entire : when the growth of the 
 axes is rather more vigorous than that of the corresponding wings, 
 the margin becomes somewhat uneven (dentate, serrate} ; when 
 the difference between them is considerable, the lamina is lobed ; 
 and when still greater, it consists of a number of distinct seg- 
 ments, leaflets, connected only by their common attachment to 
 the mid-rib, in the case of pinnate leaves, or to the petiole in 
 the case of palmate or peltate leaves. Whilst inequalities of 
 the margin are indications of branching, the lamina is regarded 
 as simple so long as the segmentation is incomplete ; it is only 
 when the segmentation is complete, as in the last-mentioned 
 case, that the leaf is said to be compound. 
 
 The following examples will serve to illustrate the foregoing principles. 
 The simple leaf of the Beech (Fig. 21) has an entire pinnate lamina; 
 the leaf of the Shepherd's Purse (Capsella Bursa-Pastoris, Fig. 23 C) is 
 simple, but the lamina is deeply pinnately lobed. Various forms of com- 
 pound pinnate leaves are represented by Fig. 19 C and by Fig. 23 B, Z>, 
 E, F, H, where the distinct segments or leaflets, termed pinna;, are inserted 
 on the common primary axis. In H each pinna is itself compound, being 
 segmented into pinnules which bear che same relation to the secondary 
 axis of each pinna as that secondary axis does to the primary axis of the 
 whole leaf ; such a leaf is said to be bipinnate, and when the segmentation 
 is carried further the leaf becomes tripinnate, etc. 
 
 In compound pinnate leaves, the leaflets are commonly opposite to each 
 other. When only one pair of leaflets is present, the leaf is said to be 
 unijugate; when two pairs, bijugate ; when many pairs, multijugate. When 
 the axis (whether primary or secondary) is terminated by a leaflet, the 
 leaf is said to be imparipinnate (Fig. 23 D) when there is no terminal 
 leaflet, the leaf is paripinnate (Fig. 23 E). When, as in the Potato and 
 Potentilla anserina. pairs of small leaflets alternate with pairs of larger 
 ones, the compound leaf is said to be interruptedly pinnate. The difference 
 in size of the leaflets is simply due to the more active growth of the larger 
 ones. 
 
 The order of development of the leaflets of compound pinnate 
 leaves depends upon the position of the growing-point in the 
 longitudinal axis (see p. 29). When it is apical, the leaflets are 
 developed in acropetal succession (e.g. Pea, Ailanthus, etc.) ; 
 when it is basal, in basipetal succession (e.g. Myriophyllum, Poten- 
 tilla anserina} ; when there is both an apical and a basal growing-
 
 36 
 
 PART I. MORPHOLOGY. 
 
 [12 
 
 point, in divergent succession, that is, both acropetally and basi- 
 petally (e.g. Achittea MillefoUum, etc.). 
 
 With regard to palmate leaves, Fig. 23 A is an example of a deeply 
 lobed lamina; and B, of a compound palmate leaf of the Clover in which 
 will be observed that there are three leaflets ; such a leaf is said to be 
 
 FIG. 23. Segmentation of leaves, p Petiole ; p' petiolule ; /' leaflet ; r phjllopodiutn. A 
 Palmatifldor palmately lobed leaf of Geranium. B Temate (compound palmate) leaf of 
 Clover. C Pinnaticected leaf of Shepherd's Purse (Capsella). Compound pinnate leaves : 
 D Imparipinnate leaf of Hippocnpit comoo; t terminal leaflet. E Paripinnate leaf of 
 Pistacia Lentitcus ; a wing of the phyllopodinm. F Imparipinnate unijugate lenf of Medi- 
 cago. This differs from B, which is teraate, inasmuch as the secondary leaf-stalks p' do 
 not all spring from one point, but the common leaf-stalk ji extends beyond the insertion 
 of the single pair of pinnse ; projecting rib, or mucro. G Leaf of the Oranae ; the articu- 
 lation a between the blade and the winged petiole shows that it is really a compound 
 leaf with a single terminal leaflet. H Bipinnate leaf of Acacia : r' secondary axis ; /" 
 secondary pinnae or pinnules.
 
 12. THE LEAF. 37 
 
 ternate. This segmentation may be repeated in the leaflets, when the 
 leaf is said to be Alternate, triternate, etc. On comparing Fig. 23 B and F, 
 the close relation between pinnate and palmate leaves becomes apparent. 
 A ternate leaf is usually considered to belong to the palmate type, but it 
 might almost equally well be regarded as an imparipinnate unijugate 
 leaf. 
 
 Occasionally the margin of the lamina bears outgrowths which 
 are not connected with branching, but are of the nature of 
 emergences, as in the Cherry Laurel, Naias, various Conifers, etc.. 
 
 A number of terms are used in Descriptive Botany for the purpose of 
 precisely describing the various parts of plants. The more important of 
 these terms, and those the meaning of which is not obvious, will now be 
 denned. 
 
 (1) The Outline of bilateral bodies, such as the lamina of the leaf, but 
 of multilateral bodies, such as fruits, as well, is said to be linear when 
 the two margins run nearly parallel to each other ; e.g. the leaves of most 
 Grasses. If the margins are curved and intersect at each end at aoi 
 angle, the outline is said to be lanceolate or elliptical, accordingly as the 
 long axis is many times longer than, or only twice as long as, the 
 transverse axis. If the two curved margins round off at each end, then 
 the terms oblong and oval are to be substituted for the two preceding. 
 
 If the longest transverse diameter lies relatively near to the base, then 
 the outline is said to be ovate ; if relatively near to the apex, obovate. 
 
 (2) The Apex may be either acute or obtuse ; when it is long drawn out 
 it is said to be acuminate ; when there is a sharp projecting point, it is 
 said to be mucronate (Fig. 23 F) 5 truncate, when it is, as it were, cut short 
 across (Fig. 23 Z>) ; emarginate, when there is a depression in the obtuse 
 apex ; obcordate, when the apical depression is deep. 
 
 (3) The Base may be described by many of the preceding terms, but 
 the following are especially applied to it: it is cordate when it is deeply 
 indented in the median line ; sagittate, when the lobes on each side of the 
 indentation are angular and diverge backwards ; hastate, when the lobes 
 diverge outwards. 
 
 (4) The Margin is said to be entire when it does not present any de- 
 pressions or prominences ; when the prominences are slight and rounded, 
 the margin is said to be crenate ; dentate or toothed, when the prominences 
 are pointed and stand straight outwards ; serrate, when the pointed 
 prominences slant forward. 
 
 If the incisions in the margin are deep, the part, a leaf-blade for 
 instance, or a gamosepalous calyx, is said to be lobed when the incisions 
 do not extend to the middle ; if they extend to the middle, it is said 
 to be partite; and dissected when they extend nearly to the base (Fig. 23 C). 
 
 The segmentation of the lamina takes place in some Monocotyledons 
 (Palms) in an altogether different manner from that described above. 
 The lamina is at first entire, but it becomes divided by the dying away 
 of strips of tissue.
 
 38 
 
 PART I. MORPHOLOGY. 
 
 12 
 
 The Venation of the Lamina. The mid-rib and other ribs of 
 the lamina indicate the course of the larger vascular bundles ; 
 and from these numerous branches are given off which permeate 
 the tissue of the lamina, constituting its Venation. When the 
 leaf decays, the ribs and the vascular tissue persist longer than 
 than soft parts as a skeleton which retains the general form of the 
 lamina. In Onvirandra fenestralis most of the softer tissue 
 decays whilst the leaf is still living, so that the lamina consists of 
 little more than the vascular skeleton. 
 
 The main features of the venation are determined by the type of 
 development of the lamina. In a pinnate lamina, the venation is 
 pinnate ; in a palmate lamina, palmate ; in a pedate leaf, pedate ; 
 in a dichotomously branching lamina, the venation is also dicho- 
 tomous, or as it is specially termed, 
 furcate. But there is considerable 
 variety in the distribution of the 
 smaller vascular bundle ; thus the 
 venation of the individual segments 
 of a palmate or a pedate leaf is fre- 
 quently pinnate. 
 
 According to the distribution of the 
 veins and their branches, the following 
 varieties of venation may be distin- 
 guished ; they are, however, connected by 
 intermediate forms. 
 
 a. The venation is said to be free when 
 the veins end free, without forming ana- 
 stomoses, at the margin of the leaf ; this 
 is the case in the leaves of many Ferns 
 (Fig. 24) ; of Ginkgo (Salisburia), Arau- 
 caria imbricata and others, among Coniferse ; of most Cycads ; of Water- 
 Crowfoots, etc. 
 
 b. The venation is said to be parallel, when numerous adjacent veins run 
 parallel to each other towards either the apex (Fig. 25) or the margin of 
 the blade, and then unite by curving inwards (Fig. 25 a). They are con- 
 nected in their course by short veinlets (Fig. 25 ) which run usually at 
 right angles to them. This form of venation is to be found in the leaves 
 of most Monocotyledons, such as Grasses, Lilies, and Palms, with various 
 modifications. For example in some cases (e.g. Orchis Mario) many veins 
 enter the blade, but they branch scarcely at all ; in other cases lateral 
 veins spring at an acute angle from a midrib which is prominent at the 
 base at least, and then run towards the apex (e.g. Maize and other Grasses, 
 Dracaenas, etc.) ; in others, again, the lateral veins spring almost perpen- 
 dicularly from the well-developed mid-rib, and run out to the margin 
 
 Fio. 21. Leaf of a Young Fern, 
 with free pinnate venation : m the 
 midrib; the large lower lateral 
 veins; n the weak upper lateral 
 veins, (x 3.)
 
 12. THE LEAF. 
 
 3!) 
 
 parallel to each other, and then turn towards the apex of the leaf (e.g. 
 Canna, Musa, etc.). 
 
 c. The venation is said to be reticulate, when the veins branch repeatedly 
 at various angles, and the branches for the most part anastomose (Fig. 26). 
 Some of them, however, end blindly in the meshes of the network. This 
 kind of venation is characteristic of Dicotyledons" ; but it also occurs in 
 some Monocotyledons (e.g. Paris, Dioscorea, Smilax, many Aracese) and 
 many Ferns. 
 
 The Different Kinds of Leaves. The leaves of different plants, 
 as might be expected, are not alike, but differ more or less widely 
 in size, shape, colour, and texture. But even the leaves borne on 
 
 FIG. 25. Apex of a Grass-leaf showing 
 parallel venation : 711 middle vein ; a ana- 
 stomoses ; D veinlets. (x4.) 
 
 FIG. 26. Portion of a leaf of Salix Ca- 
 prea with reticulate venation : TO midrib ; 
 n the larger lateral ribs ; c the anasto- 
 mising veins (nat. size). 
 
 one and the same plant are not all alike, the reason of their dissimi- 
 larity being that, as there are different functions to be performed, 
 the leaves are variously adapted in form and structure to the per- 
 formance of these functions. 
 
 1. Foliage-leaves are usually known simply as leaves (Fig. 27 
 Li). They are conspicuous on account of their green colour, and in 
 accordance with their nutritive function (see Part III.) they are 
 expanded as much as possible to the sun-light. If they are small 
 they are very numerous (Conifers), and the larger they are the 
 fewer they are (Sunflower, Paulownia). They nearly always
 
 40 
 
 PART I. MORPHOLOGY. 
 
 [12 
 
 possess a well-developed lamina, which presents the various pecu- 
 liarities of conformation previously described. 
 
 The texture of the leaf is dependent upon the mode and duration 
 of its existence. The texture of most leaves may be described as 
 herbaceous. Leaves of this kind last usually for only a single 
 season, and die or fall off in the autumn. Leaves of firmer .texture, 
 
 which are said to be cori- 
 aceous, survive the winter, 
 and either fall off when 
 the new leaves are de- 
 veloped (the Privet), or 
 continue to live for several 
 years (Holly, Box, and 
 most Conifers) ; the acicu- 
 lar leaves of the latter 
 may persist for as many 
 as twelve years (Silver 
 Fir). Fleshy or succulent 
 leaves occur in plants in- 
 habiting dry regions or 
 positions, such as Aloe, 
 Sedum, etc. 
 
 It is worthy of note 
 that foliage-leaves of dif- 
 ferent form sometimes 
 occur on the same shoot. 
 For instance, it is com- 
 monly the case that the 
 first leaves of young 
 plants are of a form dif- 
 ferent from, and usually 
 simpler than, that of those 
 which are subsequently 
 
 P roduced > and exhibit a 
 
 greater resemblance to 
 
 fhn^P nf nlliVrl nlanfa 
 jn Se O1 alliea plants. 
 
 Thus, Eucalyptus Globu- 
 lus has at first oval dorsiventral leaves, and subsequently elon- 
 gated isobilateral leaves. Again, the primary leaves or cotyledons, 
 when they develope into foliage-leaves, are always different in 
 form from the subsequently developed foliage-leaves, being much 
 
 region; L region of the foliage-leaves; H hypso- 
 
 phyllary region ; d the bracts i b the flowers in 
 their axils ; roots.
 
 12. THE LEAF. 41 
 
 simpler. In many water-plants, the submerged leaves are different 
 from those which float at the surface; thus, in many species of 
 Potamogeton, the submerged leaves are narrow and ribbon-like, 
 whereas the floating leaves are broadly elliptical ; in many aquatic 
 species of Ranunculus, the former are finely divided, whereas the 
 latter have a circular lamina. Again, the submerged leaves of 
 Salvinia are filamentous, whereas the floating leaves are flattened 
 and oval. 
 
 The simultaneous occurrence of two forms of foliage-leaf on a plant 
 is termed Jietcrophylly . 
 
 In certain plants the foliage-leaves assume remarkable forms in 
 connection with their adaptation for catching small animals or for 
 collecting water (e.g. Nepenthes, Cephalotus, Sarracenia, Utricularia, 
 Dischidia, etc.). In these the lamina 
 is metamorphosed into a pitcher or 
 ascidium. The development of the 
 pitcher begins in very much the same 
 way as that of the lamina of a peltate 
 leaf ; but instead of remaining flat, it 
 becomes tubular by continued basal in- 
 tercalary growth (see p. 34). The leaf 
 may, as in Sarracenia and Darlingtonia, 
 be sessile ; or it may be petiolate, as 
 in Cephalotus and Nepenthes : in Ne- 
 penthes (Fig. 28) the petiole is winged 
 for some distance in its lower portion. 
 The lid, when present, is a development 
 of the apical, or sub-apical (Nepenthes), 
 portion of the lamina ; as its first de- 
 velopment it adheres firmly to the rim 
 of the ascidium, from which it eventu- 
 ally separates, except at the point of 
 attachment ; the lid is bilobed. 
 
 2. Leaf -Tendrils (see p. 32) are 
 leaves or parts of leaves which have 
 a somewhat filamentous form, and which possess the property of 
 twisting spirally round foreign bodies, thus fixing the plant (see 
 Part III.). In species of Clematis, Tropseolum, etc., this function 
 is performed by the petiole of the foliage-leaf ; but in the Vetches 
 and Peas there is a division of labour of this kind, that the anterior 
 leaflets of the pinnate leaf are modified into tendrils (Fig. 19 C, 
 
 FIG. 28. Pitchered leaf of Ne- 
 penthes : a organic apex of leaf ; 
 b leaf-base ; pet petiole, winged 
 in its basal portion ; as ascidium ; 
 I its lid; /r fringe of ascidium 
 (reduced).
 
 PART I. MORPHOLOGY. 
 
 12 
 
 rf) ; in Lathyrus Aphaca all the leaflets undergo this metamor- 
 phosis, and the special functions of the foliage-leaves are discharged 
 by the stipules. The tendrils of the Cucurbitacese are also metamor- 
 phosed leaves. 
 
 3. Leaf-Spines are leaves or parts of leaves which are modified 
 into pointed, hard, woody structures. Spiny teeth are often present 
 on foliage-leaves (e.g. Holly, Thistles) ; in species of Caragana and 
 Astragalus the phyllopodium of the pinnate leaf becomes a spine 
 after the falling-ofF of the green leaflets ; finally, the entire leaf 
 becomes spiny in Berberis (Fig. 29). 
 
 4. Scales or cataphyllary leaves (Fig. 27 N). These are usually 
 
 of a yellow or brown colour, of simple 
 structure, without projecting veins, and 
 are attached to the stem by a broad 
 base. They may be regarded in some 
 case as leaf-bases, the laminse of which 
 have not developed ; and in other cases, 
 as entire leaves which have remained 
 in a rudimentary condition. They al- 
 ways occur on subterranean stems (e.g. 
 the scales of the Onion, see also Figs. 
 13 and 14 n\ and sometimes on aerial 
 stems. Many plants which are not 
 green (Orobanche, Neottia) produce only 
 cataphyllary leaves in addition to the 
 floral leaves. The most common form 
 in which they occur upon aerial stems 
 is that of scales investing the buds of 
 trees. In this case they are the lowest 
 leaf-structures borne by the annual 
 shoot, and usually fall off as the bud 
 developes. 
 Some few indigenous trees have naked buds without scales, as 
 
 Viburnum Lantana, Cornus sanguinea, Rhamnus Frangula; 
 
 their buds are protected by a dense growth of hairs. 
 The following varities of bud-scales may be distinguished : 
 a. The bud-scales are the stipules of leaves which develop a lamina ; as 
 
 m Alnus, Liriodendron, Marattiacese. 
 6. The bud-scales are the stipules of leaves which develop no lamina : 
 
 Oak, Beech. 
 
 c. The bud-scales are leaf-bases, the lamina not being developed ; Maple, 
 Ash, Horse-Chestnut, Prunus Padus. 
 
 FIG. 29. Leaf-spines of Berberif 
 tulgaru, at the base of a shoot of 
 one year's growth : a leaf-spine 
 with broad surface; b with a 
 smaller surface ; fc fc axillary buds 
 (nat. size).
 
 12. THE LEAF. 43 
 
 d. The bud-scales are laminae: Lilac, Privet, Abietineae. 
 
 In the last case the bud-scales may be caused to develop into foliage- 
 leaves by cutting off the top of the branch, or removing its leaves, at the 
 time when the bud-scales are developing. 
 
 Cataphyllary leaves are sometimes thickened "so as to serve as 
 depositories for nutritive substances, as in the bulbs of the Onion, 
 Lily, etc. 
 
 5. Bracts and Floral Leaves (Hypsophylls and Sporophylls ; 
 Tig. 27 H). These leaves are generally peculiar in form, texture, 
 and colour ; their morphology is discussed in connection with 
 that of the reproductive organs in 16, as also in Part IV. 
 
 Vernation and Prefoliation. The forms of young leaves and 
 their relative position in the bud, that is their vernation and 
 pre foliation (aestivation and prefloration of floral leaves), require 
 special consideration. 
 
 The vernation (or (estivation) is said to be plane when the leaf is not folded 
 at all; it is conduplicate when the two halves of the leaf are folded 
 inwards face to face on the midrib as on a hinge (e.g. the Bean) : it is 
 plicate when the leaf is folded in numerous longitudinal or oblique pleats 
 (e.g. the Beech); it is crumpled, when the foldings are in all directions (e.g. 
 the petals of the Poppy) ; it is involute, when the lateral halves are rolled 
 inwards towards the mid-rib on the ventral surface (e.g. the Violet) ; it is 
 revolute, when they are rolled inwards towards the mid-rib on the dorsal 
 surface (e.g. the Dock); it is convolute when the whole leaf is rolled up 
 from one lateral margin to the other, so as to form a single roll (e.g. 
 Canna) ; or, finally, it is circinate, when the leaf is rolled longitudinally 
 on itself from the apex downwards (e.g. Ferns). 
 
 The prefoliation (or prefloration) is said to be valvate when adjacent leaves 
 in the bud merely touch by their margins ; when some are overlapped by 
 others it is imbricate ; an intermediate form is that in which one margin 
 of each leaf is directed obliquely inwards, and the other obliquely outward 
 overlapping the inner margin of the next leaf, and is termed contorted or 
 twisted (e.g. petals of the Periwinkle.) 
 
 Valvate prefoliation is only possible in the case of whorled leaves, whereas 
 imbricate prefoliation is characteristic of spirally arranged leaves. A 
 common form of imbricate prefoliation or prefloration is the quincuncial, 
 which occurs in the many dicotyledonous flowers which have a $ calyx ; 
 the five imbricate sepals are so arranged that two are wholly internal, 
 two wholly external, and one partly internal and partly external, connect- 
 ing the outer two with the inner two (see Part IV., Phyllotaxy of the 
 flower). Where the phyllotaxy is distichous (^), the vernation of the 
 leaves is generally conduplicate, and the margins of each older leaf over- 
 lap those of the next younger leaf, giving rise to a form of imbricate 
 prefoliation distinguished as equitant (e.g. Iris) ; in some cases the over-
 
 44 PART I. MORPHOLOGY. [ 13 
 
 lapping is by one margin only, in which case the prefoliation is to be 
 semi-equitant. 
 
 13. The Root. It must be clearly apprehended that a sub- 
 terranean member is not necessarily a root ; nor can a member be 
 termed a root because it is found to absorb water and salts in 
 solution, for in rootless plants this function may be discharged by 
 shoots, or leaves, or hairs; nor can a member be termed a root 
 because it serves as an organ or attachment to the substratum, for 
 such organs may be emergences (see p. 48) ; only such members 
 can be regarded as roots which bear neither leaves nor true 
 reproductive organs. 
 
 The root is sometimes wanting in plants where it might be 
 expected to be present, in plants, that is, of which the body is not 
 a thallus (e.g. Salvinia, Psilotum, Utricularia, Epipogum, Coral- 
 lorhiza). 
 
 There are certain peculiarities connected with the structure and 
 development of the root which contribute to its morphological 
 distinction. As a rule, the growing-point of the root is not ex- 
 posed, like that of stems or leaves, but is covered by a structure 
 termed the root-cap. As a rule also, the growing-point of the root, 
 whether normal or adventitious, is developed, not at the surface, 
 but in the interior of the tissue, that is, endogenously (p. 9). 
 
 There are exceptions to both these rules. The primary root of some 
 parasitic plants, such as Orobanche and Cuscuta, has no root-cap, as also 
 the small lateral roots which spring from the larger roots of the Horse- 
 Chestnut. In some cases (e.g. old roots of Azolla caroliniana, Hydrocharis, 
 Pistia Stratiotes) a root-cap is present at first, but eventually disappears, 
 the growth in length of the root being arrested. 
 
 Exogenous development has been observed in the adventitious roots 
 of Cardamine pratensis (roots of adventitious buds developed on leaves) ; of 
 Neottia Nidus Avis ; of Nasturtium oflicinale and nilvestre ; of Ruppia rostdlata 
 (embryo); Lycopodium, Phylloglossum. 
 
 The root which is developed at the opposite pole of the embryo 
 to the primary shoot, is termed the primary root. When the 
 primary root persists and continues its growth (as in Oak, Rad- 
 ish, Bean, etc.), it is termed a tap-root. In many cases (generally 
 in Monocotyledons) the growth of the primary root is limited, so 
 that it attains but feeble development. In other cases (e.g. 
 Orchids, Selaginella) no primary root is developed, all the roots 
 being adventitious. The symmetry of the root is most com-
 
 13. THE ROOT. 45 
 
 monly radial. In some cases, however, the root is isobilateral, 
 as is shown as well by its internal structure as by the develop- 
 ment of two opposite longitudinal rows of lateral roots. In 
 other cases (e.g. attached aerial roots of epiphytic Orchids ; roots 
 of Podostemacese) its symmetry is more or less distinctly dorsi- 
 ventral. 
 
 Roots branch either dichotomously (e.g. Isoetes), or laterally 
 (see p. 9). In lateral branching the secondary roots are devel- 
 oped in acropetal succession on the primary root, and so on. Since 
 the lateral roots are not developed upon the growing-point of the 
 parent root, the terminal apical portion of the parent root con- 
 sequently bears no lateral roots. On anatomical grounds (see 
 Part II.) the secondary roots are arranged in longitudinal rows 
 on the primary roots ; an ar- 
 rangement which also obtains in 
 the branches of the secondary roots, 
 and of higher orders. 
 
 The form of the root is usually 
 cylindrical ; when it is very delicate, 
 as in Grasses, it said to be fibrous. 
 The primary or the secondary roots 
 may become much swollen, serving 
 as- depositories for nutritive sub- 
 stances ; the Turnip, the Carrot, the 
 Beet, the Radish, have swollen 
 primary roots ; the Dahlia has 
 swollen secondary roots. 
 
 FIG. 30. The lateral roots n aris- 
 ing endogenoualy from the peri- 
 cycle of the tap-root of Vicia Faba 
 (longitudinal sec. mag. 6 times) : 
 / axial cylinder (stele) ; r cortex 
 of the main root; h root-cap. of the 
 lateral root. 
 
 Various terms are employed to de- 
 signate the different forms of swollen 
 roots; that of the Turnip is termed 
 
 napiform ; that of the Carrot, conical ; that of the .Radish, fusiform or 
 spindle-shaped; those of the Dahlia and of some terrestrial Orchids, 
 tuberous. 
 
 Many plants have aerial roots which are peculiar both morpho- 
 logically and physiologically. The roots of epiphytes, that is, 
 plants (mostly Orchids and Bromeliaceae) which grow on trees 
 without, however, being parasitic, never reach the ground, but 
 serve as means of attachment : they frequently contain chlorophyll 
 and serve as organs of assimilation, especially in Podostemacese. 
 Some plants climb by means of aerial roots (e.g. Ivy, Tecoma radi-
 
 46 PART I. MORPHOLOGY. [ 14 
 
 cans), which are developed on the ventral surface of the dorsiven- 
 tral stem, and adhere closely to the tree- trunk or wall on which 
 the plant is climbing. 
 
 In some rare cases the aerial root is a tendril, as in Vanilla 
 aromatica, Lycopodium rupestre and other species, and in some 
 Melastomacefe (Mcdinilla radicans, Dissochseta). 
 
 Roots are occasionally developed as thorns, as in the Palms 
 Acanthoriza and Iriartea, and in Myrmecodia (Rubiaeese). 
 
 In some species of Jussisea (e.g. J. repens] which live in swamps, 
 some of the adventitious roots develope into floats, containing large 
 intercellular spaces. 
 
 14. Hairs and Emergences. Under these terms are 
 included various appendages of a lower morphological value than 
 the stem, the leaf, or the root, upon all of which they may be 
 borne. 
 
 (a) Hairs. Hairs are always developed from superficial cells ; a 
 hair usually takes origin from a single superficial cell, but some- 
 times from more than one. Their growth is generally apical, but 
 sometimes basal. 
 
 Hairs vary in form and structure ; they may be unicellular, 
 when they are termed simple; or multicellular, when they 
 are termed compound or articulate : they may be branched 
 or unbranched ; they may be filamentous or scaly. They 
 subserve various functions, being protective, secretory, or ab- 
 sorbent. 
 
 Various terms are used to describe hairs : filamentous hairs which are 
 secretory have frequently a dilated apex, and are termed capitate ; flattened 
 hairs which are star-shaped, are termed stellate ; discoid flattened hairs are 
 termed radiate or peltate ; the erect flattened hairs of Ferns are termed 
 palece or rametita. When hairs are stiff they are termed bristles or 
 setce. 
 
 Special terms are used to indicate the nature and the distribution of the 
 hairs on a member. A surface which bears no hairs is said to be glabrous ; 
 when the hairs are scattered the surface is pilose; when the hairs are 
 close and short, villous ; when they are longer, tomentose. When the hairs 
 are rather stiff, the surface is hirsute ; when bristly, hispid. When the 
 hairs are borne on the margin only, the member is said to be ciliate. A 
 surface with closely appressed hairs islepidote ; a member bearing ramenta 
 is ramentaceous. 
 
 The root-hairs demand special notice. Root-hairs are hairs which 
 perform the functions of absorption and attachment ; they are com- 
 monly developed on roots, though not always, for they are absent
 
 14. HAIRS AND EMERGENCES. 
 
 47 
 
 from the roots of a number of aquatic plants (e.g. Butomus um- 
 bellatus, Caltha palustris, Hippuris, Myribphyllum, Menyanthes, 
 Nymphaea, Lemna) ; they may be developed on the thallus, or the 
 thalloid shoot, in the gametophyte of Liverworts and homo- 
 sporous Vascular Cryptogams ; on the stem, thpugh rarely (e.g. 
 
 Fio. 31. Different form of hairs. A Branched compound hair (Verbascum). E b 
 Stinging-hair with basal cushion p ; ?i simple hair (Urtica). C Branched simple hair, 
 seen from the surface ; e epidermis (Matthiola). D Scaly compound hair (Hippophae) ; a 
 seen from the surf ace; b seen in section; c central cell; r radiating cells; s stalk-cell ; e 
 epidermis. E Ramentum (Asplenium) ; b the point of attachment. 
 
 Corallorhiza, Epipogum, Psilotum), or even on leaves. They are 
 always unicellular, and it is only rarely that they are found
 
 PART I. MORPHOLOGY. 
 
 [14 
 
 to branch. On roots, at any rate, they are developed in acropetal 
 
 succession. 
 
 (6) Emergences. These appendages differ from hairs in that 
 
 they are developed not only from superficial cells, but from others 
 lying beneath them. 
 
 The commoner forms of emergences are prickles, 
 (Fig. 32) and warts ; more specialised forms are 
 the tentacles of the leaf of Drosera (Figs. 33 and 
 34) ; the ligule of the leaf of Grasses (Fig. 19 A), 
 Selaginella, and Isoetes ; and the corona of Nar- 
 cissus. 
 
 The more highly developed emergences (e.g. 
 many prickles, tentacles of Drosera) of Vascular 
 Plants frequently contain vascular tissue. 
 
 A remarkable kind of emergence is the organ 
 of attachment, termed a 
 hapteron, developed on the 
 
 stalks of some Algae (e.g. Laminaria), on the 
 
 stems and branches of Podostemacese and on 
 
 the tendrils of some Ampelidese and Bigno- 
 
 niaceae among Phanerogams : it contains no 
 
 vascular tissue even in Vascular Plants. 
 The suckers, or haustoria, of parasitic 
 
 plants (e.g. Cuscuta, Orobanche, Thesium, 
 
 Rhinanthus, etc.), are also emergences, being 
 
 FIG. 32. Prickles 
 on the stem of the 
 Rose (nat. size). 
 
 Fio. 33.-Leaf of Drotera rotundifoha. A Expanded ; d the 
 mdular tentacles of the edge of the leaf ; m the short ten- 
 tacles in the middle. B The marginal tentacles have bent 
 towards the middle at the touch of an insect, x. 
 
 FIG. 34. Tentacle of 
 Drosera rotundifolia. (Af- 
 ter Strasburger : x 60.)
 
 15. REPRODUCTION. 49 
 
 developed from the cortical tissue of the root or stem bearing 
 them. Those of Rhinanthus, Thesium and Orobanche, are de- 
 veloped exogenously ; those of Cuscuta, endogenously. They con- 
 tain vascular tissue. 
 
 15. Reproduction. Reproduction consists essentially in 
 the development of one or more new organisms from the whole or 
 from a part of the protoplasm of a parent organism. 
 
 This may be effected either by the separation of a member or 
 a portion of the body, which, by developing the missing members, 
 constitutes a new individual ; or by the production of special re- 
 productive cells termed spores. Two modes of reproduction are 
 therefore distinguishable: vegetative multiplication, and spore- 
 reproduction. 
 
 1. Vegetative Multiplication is essentially connected with the 
 process of growth. 
 
 The simplest modes of this occur in unicellular plants. In 
 Pleurococcus, for instance, the cell divides into two, each of 
 which constitutes a new organism. In this case the parent 
 ceases to exist as an individual. In Yeast, the cell produces 
 out-growths each of which becomes an independent unicellular 
 organism. In this case the number of the progeny is not limited, 
 and the parent organism persists. This is termed multiplication 
 by gemmation. 
 
 In more complex plants vegetative reproduction is commonly 
 effected in this way, that the main axis of the shoot or of the 
 thallus, dies away : the branches thus become isolated and consti- 
 tute independent organisms. This occurs very commonly in the 
 protonema of Mosses, in the rhizomes of many Phanerogams, etc. 
 In those cases in which the leaves produce adventitious buds (e.g. 
 JBryophyllum calycinum, many Ferns), the adventitious buds de- 
 velope into independent plants after the leaf has fallen from the 
 plant bearing it. 
 
 In many plants special organs for vegetative multiplication are 
 produced, which may be generally termed gemma?. In a few cases the 
 gemmae are unicellular, as those of some Algae, Fungi, and Hepaticae. 
 In other plants, multicellular gemmae are produced : as in other 
 Hepaticae where they are developed in special receptacles (cupules) 
 on the upper surface of the thallus (Lunularia, Marchantia), or on 
 the margin of the leaves. In some Mosses flattened gemmae are 
 produced in receptacles formed of leaves at the apex of the shoot, 
 as in Tetrapliis pellucida, and Aulacomnion androgynum : and
 
 50 PART I. MORPHOLOGY. [ 15 
 
 rounded tuberous gemmae are frequently formed on the protonema. 
 The prothallia of some Ferns (Trichomanes) are reproduced by few- 
 celled filamentous gemmae ; and that of Lycopodium Phlegmaria 
 by ovoid tuberous gemmae. 
 
 In the Vascular Cryptogams and Phanerogams, vegetative 
 reproduction is generally effected by buds, the leaves or stem of 
 which have become swollen, serving as depositories for nutrient 
 substances. These buds may be subterranean, and then they 
 are of considerable size, when they are termed bulbs or corms 
 according to their structure (see p. 25) : or the buds may be 
 borne on a swollen subterranean stem (e.g. potato-tuber) ; or be 
 associated with tuberous roots (e.g. many terrestrial Orchids). 
 Sometimes they are aerial, being borne on the stem ; on ac- 
 count of their small size they are termed bulbils (e.g. Lilium bul- 
 biferum, Dentaria, Nephrolepis tuberosa, etc.). In Psilotum, 
 however, vegetative propagation is effected by small flattened 
 gemmae, oval in shape, and consisting of a few large cells forming 
 a single layer. 
 
 2. Spore- Reproduction. The term spore is applied to a 
 specialised asexual reproductive cell which is capable, by itself, of 
 giving rise to a new organism. 
 
 There are two principal modes of origin of spores, and all plants 
 produce spores in one or other of these modes. In the one, the 
 spores are formed from the protoplasm of any part, or of some 
 special part, of an organism ; in the other, they are formed by the 
 fusion of two masses of protoplasm derived either from two dis- 
 tinct organisms, or from distinct parts of the same organism. In 
 the former case they are said to be formed asexually ; in the latter, 
 they are formed sexually, the fusion of the two masses of proto- 
 plasm being a sexual process (p. 2) ; the organs concerned are 
 distinguished respectively as asexual and sexual, and are in all 
 cases confined to the shoot. 
 
 The spore is generally a single cell, consisting of a nucleated 
 mass of protoplasm containing various nutritive substances (oil, 
 starch, etc.). It generally has a cell-wall, which is commonly 
 thick, and in some cases consists of two layers, an outer, the exine 
 (or exospore], which is cuticularised, and an inner, the inline (or 
 endospore), which is delicate and consists of cellulose. 
 
 In some cases the spore has no cell-wall. It may then be cap- 
 able of spontaneous movement. When motile, it usually swims by 
 means of one, two, four, or many delicate protoplasmic filaments
 
 16. ASEXUAL REPRODUCTIVE ORGANS. 51 
 
 termed cilia. Motile spores are termed zoosporcs. Ciliated zoo- 
 spores are common among the Algae, and they occur in some Fungi. 
 
 The spores produced asexually by the sporophyte of any one 
 plant are commonly of one kind only ; when this is the case the 
 plant is said to be homosporous. But in some of the Pteridophyta, 
 and in all Phanerogams, which are therefore said to be heterospor- 
 ous, there are two kinds of asexually produced spores, which differ 
 in size and in the nature of the organisms to which they respec- 
 tively give rise, and are distinguished as microspores and macro- 
 spores. In the Phanerogams, the microspores are commonly termed 
 pollen-grains ; and the macrospores, embryo-sacs. 
 
 16. General Morphology of the Asexual Reproduc- 
 tive Organs. In the great majority of plants the asexual pro- 
 duction of spores takes place in the interior of an organ termed a 
 sporangium. 
 
 Whilst in some plants the asexual production of spores is not 
 limited to any particular portion of the body, in others it is so 
 limited. When this is the case, the portion of the body which 
 performs this function differs more or less widely in form from 
 the vegetative portions, and it is distinguished as the sporophore. 
 When the body is differentiated into root and shoot, the sporophore 
 is always part of the shoot. 
 
 In those plants in which the shoot is differentiated into stem 
 and leaf, the development of spores is commonly confined to the 
 leaves. A leaf bearing one or more sporangia is termed a sporo- 
 phyll. 
 
 (a) The Sporangium. In unicellular plants (e.g. Yeast, Haema- 
 tococcus) the cell, that is the whole body of the organism, becomes 
 one sporangium. In this case the development of spores closes the 
 life of the organism, for the protoplasm is used in the formation 
 of the spores, and the cell-wall is ruptured to allow of their escape. 
 
 In simple multicellar plants ( e.g. Ulva, Ulothrix) each cell 
 eventually acts as a sporangium, giving rise to spores. W T ith the 
 formation of spores the life of each cell is closed ; so that when all 
 the cells have formed spores the life of the organism is ended. 
 
 In plants of higher organization the formation of spores is 
 limited to certain cells, so that the formation of spores no longer 
 necessarily puts a term to the life of the organism. It is in these 
 plants that distinct sporangia are to be found. 
 
 In the Algae and Fungi, the sporangium, when present, usually 
 consists of a single cell. In all plants higher than the Algae and
 
 52 PART I. MORPHOLOGY. [ 16 
 
 the Fungi, the sporangium is multicellular. It is, however, unilo- 
 CM/ar, that is, it contains but one cavity in which spores are 
 developed, though this is sometimes chambered by incomplete walls 
 (trabeculce) as in Isoetes. 
 
 In the Bryophyta, where the sporophyte apparently produces 
 only a single sporangium, termed the capsule or theca, this organ 
 constitutes the whole (Riccia) or a considerable portion of the 
 sporophyte. Its structure is simple in Riccia and other Hepaticse, 
 but it becomes highly elaborate in the true Mosses (e.g. Polytri- 
 chum). It must, however, be borne in mind that the theca of the 
 Bryophyta does not correspond to a single sporangium of a Fern or 
 a Phanerogam, but to at least a cluster (sorus} of such sporangia : 
 hence the exceptional complexity of its structure. 
 
 In the Pteridophyta and the Phanerogams the sporophyte pro- 
 d uces a number of sporangia. In the heterosporous forms there are 
 two kinds of sporangia which respectively produce the two kinds 
 of spores ; those which produce macrospores are termed macrospor- 
 angia ; those which produce microspores, microsporangia. In 
 the Phanerogams the macrosporangium is commonly termed ovule, 
 and the microsporangium pollen-sac. 
 
 When the shoot of the sporophyte is differentiated into stem and 
 leaf, the sporangia are generally borne on the leaves (sporophylls) : 
 but in some plants they are borne on the stem. This is the case 
 in most Selaginellas, among the Pteridophyta : the macrosporangia 
 (ovules) are borne on the stem in various Phanerogams ; among 
 Gymnosperms, in the Taxese ; among Angiosperms, in the Poly- 
 gonace?e, Chenopodiacese, Amaranthacese, Primulacese, Composite, 
 Graminese, Naiadaceae, Piperacese, and others, the macrosporangia 
 being either terminal or lateral : the microsporangia are less com- 
 monly borne on the stem, but this is the case- in some Angiosperms, 
 such as Naias and Casuarina. 
 
 The sporangia may be borne singly, or, as is more commonly the 
 case, in groups, each such group being termed a sorus. The spor- 
 angia of a sorus are generally quite distinct from each other ; but 
 in some cases (e.g. most Marattiaceae, Psilotum, Tmesipteris) the 
 sporangia are coherent, forming what appears to be a multilocular 
 sporangium but is really a synangium. 
 
 In those heterosporous plants in which the sporangia are in sori, 
 the two kinds of sporangia are borne in distinct sori, the only ex- 
 ception to this rule is afforded by the Marsileacese, where each 
 sorus includes both microsporangia and macrosporangia.
 
 16. ASEXUAL REPRODUCTIVE ORGANS. 53 
 
 The mature sporangium of these higher plants is either borne 
 upon a stalk (sometimes termed funicle) ; or it is sessile, and then 
 it is commonly more or less imbedded in the tissue of the parent 
 member, as in the case of the sporangia of the Ophioglossacese, and 
 of the pollen-sacs of most Phanerogams. 
 
 The development of the sporangium begins, in all cases, at the 
 surface of the parent member. The area which bears the spor- 
 angium, especially when a number of sporangia are developed close 
 together, generally projects more or less as a cushion of tissue to 
 which the term placenta is applied. In the Ferns (except Marat- 
 tiaceae, Ophioglossacese, and Isoetacese) and in the Hydropteridese 
 (Rhizocarps), the sporangium is developed from a single superficial 
 cell : in the rest of the Pteridophyta and in the Phanerogams it is 
 developed from a group of superficial cells, and in some cases from 
 cells of deeper layers as well. These Ferns and the Hydropteridese 
 are hence distinguished as leptosporangiate from the rest of the 
 Vascular Plants which are said to be eusporangiate. 
 
 The most important morphological feature in the development of 
 the multicellular sporangium is the differentiation of the sporogen- 
 ous tissue, that is, of the mother-cells of the spores. These are 
 derived from a hypodermal cell or group of cells, termed the arclie- 
 sporium, which may be distinguished at an early stage in the de- 
 velopment of the sporangium, by the highly granular protoplasm 
 and the large nucleus. The mother-cells of the spores are usually 
 formed by the division of the archesporial cell or cells, but oc- 
 casionally the archesporial cells themselves become spore-mother- 
 cells. The sporogenous cells, as they develope, become more or 
 less completely invested by a layer of highly granular cells, form- 
 ing a membrane termed the tapetum, which temporarily separates 
 them from the wall of the sporangium ; the tapetum may be 
 derived wholly or in part from the archesporium or from the wall 
 of the sporangium. 
 
 In most cases the asexually-produced spores are set free from the 
 organism producing them. An exception to this is offered by the 
 macrospore (embryo-sac) of Phanerogams, in which plants the 
 macrospore remains permanently enclosed in the macrosporangium 
 (ovule), and the macrosporangium remains attached for a consider- 
 able time to the plant bearing it. It is on account of this peculi- 
 arity that seeds are produced in Phanerogams. The production of 
 seeds is the characteristic difference between Phanerogams and 
 Cryptogams. The spores are usually set free by the rupture or
 
 54 PART I. MORPHOLOGY. 
 
 1G 
 
 dehiscence of the sporangium. In some cases the wall of the 
 sporangium simply degenerates ; in other cases there is a special 
 mechanism, sometimes very elaborate, for its dehiscence. In a few 
 cases the whole sporangium falls off from the parent plant, e.g. the 
 microsporangia and macrosporangia of Salviniacese ; here the 
 spores never become free from the wall of the sporangium, but 
 germinate inside it. 
 
 (b) The Sporophore. Beginning with the lower plants, a well- 
 marked asexual spore-producing organ is to be found in many 
 Fungi, where it represents, in fact, the shoot of the body, and is 
 a specialized, erect-growing branch of the mycelium. It may be 
 simple (e.g. Mucor, Peronospora, Eurotium) or compound (Agaricus). 
 
 The sporophyte of the Bryophyta affords a good example of a 
 highly specialised sporophore in an organism the shoot of which 
 is not differentiated into stem and leaf. The entire shoot of the 
 sporophyte constitutes the sporophore, which consists (except in 
 Riccia) of a longer or shorter stalk (seta\ bearing a terminal cap- 
 sule (theca) of more or less complex structure. 
 
 In the majority of the higher plants, in which the shoot of the 
 sporophyte is differentiated into stem and leaf, there are well- 
 marked sporophores (see Fig. 27). The sporophore may be the 
 terminal portion of the primary shoot or of a branch ; or it may 
 be an entire branch. It is commonly known, among Phanerogams, 
 as the inflorescence, but there is no reason for confining the use of 
 this term to this group of plants. The sporophore or inflorescence 
 is characterised by its limited growth in length, and can usually 
 be distinguished from a vegetative shoot by peculiarity of form, 
 and, when they are present, by the nature of its leaves. 
 
 The distinction of an inflorescence from a vegetative shoot is easy when 
 the former is an entire branch borne latterly on the latter ; but when 
 a monopodial vegetative shoot terminates in an inflorescence, the tran- 
 sition from the one region to the other is so gradual, that it is difficult to 
 determine where the one begins and the other ends. 
 
 The sporophore may be simple, or it may be branched, and it 
 then affords some of the most striking examples of the various 
 branch-systems (see p. 18). When the branch-system is such that 
 there is a well-defined main axis, this is termed the rhachis, of 
 the inflorescence. The rhachis and the branches of the inflorescence 
 are commonly elongated and cylindrical, or flattened, or prismatic 
 in form ; but they are in many cases dilated at the apex into a 
 flattened, depressed or conical receptacle, as in the Composite, etc.
 
 16. ASEXUAL REPRODUCTIVE ORGANS 55 
 
 The sporophore may be destitute of leaves (e.g. Salisburia adian- 
 tifolia). When it bears leaves they usually differ more or less 
 widely in form, colour, and structure from the foliage-leaves of 
 the plant. Of these leaves there are two kinds : those which bear 
 sporangia, hence termed sporophylls ; those which do not bear spo- 
 rangia, termed hypsophylls (see p. 43). 
 
 When no sporophylls are present, the sporangia are borne 
 directly by the rhachis or the branches of the sporophore, at or 
 near the apex, in a cluster if there are several. When sporo- 
 phylls are present, they are also usually collected together at the 
 apex of the rhachis or of a branch, in consequence of the short- 
 ness of the terminal internodes. Any axis of the sporophore, bear- 
 ing one or more sporangia or sporophylls, is termed & flower (p. 25). 
 
 When hyposophylls are present, some of them are commonly 
 aggregated round the sporangia or the sporophylls, as in most 
 Angiosperms, constituting what is termed the perianth of the 
 flower. 
 
 When the rhachis is unbranched, it bears a single terminal 
 flower (e.g. Equisetum, Violet) ; when it branches, each axis, 
 of whatever order, terminates in a flower. It is on this account 
 that the growth of the axes of inflorescences is limited. It occa- 
 sionally happens, as a monstrosity, that the axis grows through 
 the flower and produces foliage-leaves ; this is termed prolifera- 
 tion. 
 
 When the rhachis bears a single terminal flower it is commonly termed 
 the peduncle of the flower ; when the rhachis is branched, the branches may 
 be so short that their flowers appear to spring directly from the rhachis 
 and the flowers are said to be sessile; when the branches are longer 
 and bear terminal flowers, they are termed pedicels, and the flowers 
 are said to be pedicillate. For further details as to inflorescences, see 
 Part IV. 
 
 When no sporophylls are present, the form of the flower is ex- 
 tremely simple. When sporophylls are present, the form of the 
 flower varies with the degree of elongation attained by the termi- 
 nal internodes of the axis. When they elongate to some extent, 
 the flower forms a cone, as in Equisetum, Lycopodium, Selaginella, 
 Pinus. When they remain short, as generally in Angiosperms, 
 the apex is more or less broadened, forming a flattened, depressed, 
 or shortly conical torus on which the sporophylls and the perianth- 
 leaves are borne. The various forms of flowers are described in 
 detail in Part IV.
 
 56 PART I. MORPHOLOGY. 
 
 In heterosporous plants it is commonly the case that the two 
 kinds of sporangia are borne together on the same axis of the 
 sporophore ; that is, they are included in the same flower (e.g. Sela- 
 ginella, most Angiosperms), but they are frequently confined to 
 distinct axes, as in the Gymnosperms, and in some Angiosperms 
 (e.g. Beech, Birch, Oak, Walnut, etc.) ; these distinct flowers 
 are distinguished, according to the kind of sporangia which 
 they respectively bear, as micro sporangiate or macrosporangiate ; 
 in some cases one individual bears exclusively microsporangiate, 
 and another exclusively macrosporangiate flowers, as in the Hemp, 
 the Yew, etc. 
 
 (c) The Sporophylls. In many cases, most Ferns and Lycopo- 
 dinae, for example, the sporophylls are similar to the foliage- 
 leaves, differing only in that they bear sporangia ; but more com- 
 monly the sporophylls are distinguished by some peculiarity in 
 form or structure. Thus in the Flowering Fern (Osmunda rcgalis) 
 the sporophylls differ from the foliage-leaves in that no green 
 leaf-tissue is developed in them; and in the Phanerogams they 
 differ widely from the foliage-leaves. 
 
 The distribution of the sporangia among the sporophylls in 
 heterosporous plants is an important point. In the Hydropteridese 
 (Rhizocarpse), both the microsporangia and the macrosporangia 
 are borne by the same sporophyll ; but in all other heterosporous 
 plants they are borne by distinct sporophylls, which may be dis- 
 tinguished respectively as microsporophylls and macro sporophylls. 
 In the Phanerogams the microsporophyll is termed a stamen ; the 
 macrosporophyll, a carpel ; but there is no reason for applying 
 special terms to this group of plants. 
 
 In heterosporous plants, both kinds of sporophylls are gener- 
 ally present in one and the same flower : when, however, the 
 flower includes only microsporophylls, it is termed microsporophyl- 
 lary or staminate ; and when it includes only macrosporophylls, it 
 is termed macrosporophyllary or carpcllanj. 
 
 In some cases the sporangia are borne, not upon, but in close relation 
 with, a leaf, which is nevertheless regarded as a sporophyll. Thus, 
 in Selaginella, the sporangium is in the axil of the sporophyll. Again, 
 the leaves which invest the macrosporangia (ovules) of Polygonacea?, 
 Primulaceae, etc., are termed carpels, though they do not actually bear 
 the sporangia. 
 
 The distribution of the sporangia on the sporophyll is various. 
 They may be borne exclusively on the under (dorsal) surface,
 
 16. ASEXUAL REPRODUCTIVE ORGANS. 57 
 
 as in most Ferns, Equisetum, and Gymnosperms (pollen-sacs) ; 
 or exclusively on the upper (ventral) surface as in the Lyco- 
 podirise, Marsileacese, macrosporangia of Coniferse and of some 
 Angiosperms (e.g. Butomus) ; or on both surfaces, as in Osmunda ; 
 or on the lateral margins, as in Ophioglossum ' and the Hymeno- 
 phyllacese, and in many Angiosperms (e.g. Leguminosse, Violacese, 
 Liliacese) ; or on the apices of segments of the sporophyll, as in the 
 Salviniacese. 
 
 The number of the sporangia borne by a sporophyll also varies 
 widely. In some cases there is only one, as in Selaginella, Lyco- 
 podium, Isoetes ; or two, as in most Coniferse ; or four, as in most 
 Angiosperms (microsporangia) ; or many, as in the Filicinse. 
 
 In most cases the sporangia are free on the surface of the 
 sporophyll ; but in some cases they are enclosed in a cavity formed 
 either by the infolding and junction of the margins of the sporo- 
 phyll, or by the junction of the margins of adjacent sporophylls. 
 The sporangia of the Marsileaceae are thus enclosed by the sporo- 
 phyll, as are also the macrosporangia of all Angiosperms. In the 
 latter group the resulting structure is termed the ovary. 
 
 (b) The Hypsophylls (Fig. 27, p. 43). Under this common term 
 are included bracts and perianth-leaves. 
 
 Bract. This term is generally applicable to the leaves, other 
 than the sporophylls and perianth-leaves, which are borne by the 
 rhachis or branches of the inflorescence : those which are borne 
 on the pedicels of individual flowers are, however, distinguished as 
 bractcoles or prophylla. 
 
 The bract is frequently not distinguishable from a foliage-leaf ; 
 but it may be reduced to a scaly leaf ; or it may be very large and 
 even highly coloured, when it is said to be petaloid. An example 
 of the occurrence of bracts in the Pteridophyta is afforded by 
 Equisetum, where there is a whorl of small bracts, forming what 
 is known as the ring, just below the cone or flower. In some 
 Monocotyledons (e.g. Palms, Arums, etc.) there is a large bract, 
 termed a spathe, which invests the whole inflorescence ; it is 
 usually not green in colour, as in the Trumpet Lily (Zantedeschia 
 cethiopica) where it is white. In some cases the bracts are 
 arranged in whorls round the inflorescence (e.g. Composite) forming 
 an involucre. 
 
 The bracteoles sometimes form an investment, termed an epicalyx, 
 to the flower (e.g. Malva, Camellia, etc.). 
 
 The Perianth-leaves are leaves developed in immediate relation
 
 58 PART I. MORPHOLOGY. [ 17 
 
 with the sporophylls, or with the sporangiferous axis, of a flower, 
 to which they form an investment termed the perianth. A perianth 
 is present only in Phanerogams, and is confined almost exclusively 
 to the Angiosperms: the Grnetacese are the only Gymnosperms 
 in which it is represented. The leaves may be arranged in a single 
 whorl, or in two or more : they may be all alike, either green and 
 inconspicuous, or of other bright colours and conspicuous ; but 
 most frequently the leaves of the outer whorl (sepals constituting 
 the calyx] are small and green in colour, being especially protec- 
 tive in function, whilst those of the inner whorl (petals consti- 
 tuting the corolla) are large and brightly coloured, being especially 
 attractive in function. (For further details, see The Flower, 
 Part IV.) 
 
 17. General Morphology of the Sexual Reproductive 
 Organs. The general morphology of the sexual reproductive 
 organs agree in many respects with that of the asexual reproduc- 
 tive organs. 
 
 In the great majority of plants the sexual reproductive organs 
 give rise to sexual reproductive cells, termed gametes (p. 2) ; hence 
 the organs may be generally termed gamctangia. In some cases 
 the formation of gametangia is limited to a certain portion of the 
 body of the gametophyte which differs more or less from the 
 vegetative portions of the shoot and may be distinguished as 
 a gameiophore. When a part of the body is differentiated as 
 a shoot, the gametophore is part (or the whole) of the shoot. 
 
 (a) The Gametes. A gamete is a sexual reproductive cell a 
 reproductive cell, that is, which is incapable by itself of giving 
 rise to a new organism ; in this respect it differs from a spore. A 
 spore is, however, formed from the fusion of two gametes of 
 different sexes : that is, by a sexual process (see p. 50). 
 
 In those of the lower Algae and Fungi in which sexual spore- 
 formation takes place, the gametes produced by the organism are 
 all externally similar ; hence these plants are termed isogamous ; 
 the sexual process, which consists here in the fusion of two similar 
 gametes, is termed conjugation ; and the spore formed by conjuga- 
 tion is termed a zygospore. 
 
 In all the higher plants, hence termed heterogamous, the gametes 
 are not all alike ; but there are two kinds, the male and the female. 
 The male and female gametes may be generally distinguished by 
 their difference in size, the male being the smaller, and by the 
 greater activity of the male gamete in connection with the sexual
 
 17. SEXUAL REPRODUCTIVE ORGANS. 59 
 
 process which is here termed fertilisation, the male gamete being 
 considered to fertilise the female ; product, an oospore. 
 
 The gametes of isogamous plants, in those cases in which they 
 are set free from the gametangium and are free-swimming, are well 
 defined, ciliated, somewhat pear-shaped masses of protoplasm 
 destitute of a cell-wall (e.g. Botrydium, Ulothrix, Ectocarpus, etc.), 
 and are distinguished as planogametes. When, however, they are 
 not free-swimming (as in the Conjugate Algae) they have no defined 
 form nor are they ciliated. 
 
 The gametes of heterogamoiis plants. The male gamete, when 
 the conditions are such that it must of necessity be free-swimming, 
 is generally a well-defined ciliated mass of protoplasm, termed a 
 spermatozoid. Spermatozoids occur in the heterogamous Green 
 and Brown Algse (e.g. Vaucheria. Volvox. Sphseroplea, (Edogonium, 
 Chara, Fucus), in the Bryophyta, in the Pteridophyta, and in a few 
 Gymnosperms. In the lower forms the spermatozoid is more or less 
 rounded or pear-shaped, somewhat resembling a planogamete of the 
 isogamous forms : but in the higher it is club-shaped or fila- 
 mentous, thicker at the posterior end, pointed at the anterior end 
 where the two or more cilia are borne, and more or less spirally 
 coiled. It has no cell-wall. 
 
 When, owing to the proximity of the male and female organs at 
 the time of fertilisation, the male gamete has no considerable dis- 
 tance to traverse (e.g. most Phanerogams), it is not differentiated as 
 a spermatozoid, but is simply an amorphous cell without a cell-wall. 
 
 The female gamete, or oosphere, is not ciliated, nor is it, as a 
 rule, set free, but remains in the female organ until after fertilisa- 
 tion : but in some Algse (e.g. Fucus), the oosphere is extruded from 
 the female organ before fertilisation. It is, generally speaking, 
 spherical in form, as its name denotes. It has no cell-wall. 
 
 The gametes are developed from one or more mother-cells in 
 the gametangium. In isogamous plants, as a rule, each mother-cell 
 gives rise to more than one gamete, and commonly to a considerable 
 number (e.g. Botrydium, Ulothrix) ; but in Ectocarpus and some 
 other Phseosporous Algse, each mother-cell produces but a single 
 gamete. Whilst in the higher heterogamous plants the male 
 gametes are each developed singly from a mother-cell, in the lower 
 it is the rule that the male gametes are produced several together 
 from one mother-cell. The female gametes are developed singly in 
 the mother-cell, except in the Saprolegniacese among Fungi, and in 
 some genera of Fucacese (Pelvetia, Ozothallia or Ascophyllurn,
 
 60 PART I. MORPHOLOGY. [ 17 
 
 Fucus), in which from two to eight (Fucaceae) or up to twenty 
 (Saprolegniacese) oospheres are produced from one mother-cell. 
 
 (b) The Gametangia. The general morphology of the gainetan- 
 gia is very much the same as that of the sporangia. 
 
 With regard to the terminology employed in designating these 
 organs, they are said to be male when they contain protoplasm 
 which is capable of effecting fertilisation ; and female, when they 
 contain protoplasm capable of being fertilised. When there is no 
 external indication of the physiological nature of the organ, it 
 is simply termed a gametangium. But when the male and female 
 organs respectively are clearly differentiated, special names are 
 given to them in order to indicate peculiarities in their structure 
 or function, or the group of plants to which they belong. In the 
 first place a distinction must be drawn, in the case of these differ- 
 entiated gametangia, between those which give rise to clearly 
 differentiated gametes, and those the protoplasm of which does not 
 undergo such differentiation. To the former category belongs 
 the male organ, termed antheridium, in which spermatozoids are 
 developed, and the female organs, termed oogonium or archegon- 
 ium, in which one or more oospheres are differentiated. To the 
 latter category belong the male organ termed pollinodium (e.g. in 
 Peronosporaceae and some Ascomycetes), and the female organs 
 termed pi-ocarp (Florideae) or archicarp (Ascomycetous Fungi). 
 
 In the lowest plants in which the sexual formation of spores 
 takes place, the whole cell, when the organism is unicellular, or 
 any cell, when the organism is multicellular, becomes a game- 
 tangium, without being specially modified for the purpose. This 
 is the case, not only in isogamous plants (e.g. Pandorina, Ulothrix, 
 Conjugate?), but in some heterogamous plants (e.g. Sphseroplea) 
 in which the gametes are perfectly differentiated into spermato- 
 zoids and oospheres. 
 
 In plants of higher organisation there are specialised game- 
 tangia. In the simpler forms of these the male and female 
 gametangia are externally similar, as in the Volvocaceae, Ecto- 
 carpus, and Cutleria, among the Algae, and in the Zygonrycetes 
 and some Ascomycetes (e.g. Eremascus) among the Fungi. In the 
 more complex forms, the male and female gametangia are dis- 
 similar. 
 
 The undifferentiated gametangia are generally unicellular and 
 unilocular; but they are multicellular and rnultilocular in some 
 Phaeosporous Algae (e.g. Ectocarpus, Cutleria).
 
 18. THE FRUIT. 61 
 
 The differentiated gametangia are of various structure. The 
 antheridium is unicellular in most of the lower plants (Green 
 Algte, except Characese ; Fucacese). In all the other cases it is 
 multicellular, and of simple structure, except in the Characese, 
 where the structure is extremely complex. In some cases (Rhizo- 
 carps) the antheridium consists almost entirely of the mother- 
 cells of the spermatozoids ; in most cases the mother-cells are sur- 
 rounded by a parietal layer of cells. The pollinodium is generally 
 unicellular. 
 
 The oogonium is unicellular. The archegonium is generally 
 multicellular, consisting of a cellular wall investing the oosphere, 
 usually prolonged into a tubular neck ; but in most of the higher 
 plants, the archegonium is reduced to a single cell, the oosphere. 
 The archicarps and procarps are unicellular in some cases, multi- 
 cellular in others ; in most cases the organ is prolonged into a 
 filament, the trichogyne, by means of which fertilisation is effected. 
 The oogonia (except those of Peronosporacese, Saprolegniacese, and 
 Characeae) and the archegonia, open, so that their contents are in 
 direct relation with the surrounding medium ; in the procarps and 
 archicarps this is not the case. 
 
 Further details are given in Part IV. in connexion with the 
 plants to which the various organs belong. 
 
 (c) TJie distribution of the Sexual Organs. The male and 
 female organs are either borne by the same gametophyte, or they 
 are borne by distinct male or female gametophytes ; in the former 
 case the organism is said to be monoecious, in the latter dioecious. 
 
 When in monoecious plants the male and female organs are both 
 present in the same sorus, as in some Algae (e.g. Fucus platy carpus, 
 Halidrys and other monoecious Fucacese) and in some Mosses, the 
 sorus is said to be bisexual or hermaphrodite, and the plant is said 
 to be monoclinous ; when they are borne in different sori on the 
 same plant (e.g. in Hepaticse generally, some Mosses), the sorus is 
 said to be unisexual, male or female as the case may be, and the 
 plant diclinous. These terms are also applied to the flowers of 
 Phanerogams. 
 
 18. The Fruit. Although the forms of fruit occurring among 
 plants are so various in their form and in their structure, it is 
 possible to include them all in a single definition. A fruit is the 
 product of a process of growth initiated as a consequence of a sexual 
 act in structures which are not themselves immediately concerned 
 in the sexual act.
 
 62 PART I. MORPHOLOGY. [ 19 
 
 To begin with instances among the lower plants ; in most of the 
 Red Algse and Ascomycetous Fungi, the effect of the fertilisation 
 of the female organ is not merely that the female organ gives rise 
 to sporangia ; but the adjacent vegetative tissues are stimulated to 
 growth, forming an investment to the structures developed directly 
 from the fertilised female organ, the whole constituting a fruit, 
 known in the one case as a cystocarp, in the other as an ascocarp. 
 
 Similarly, in the Bryophyta, and to a less extent in the Pterido- 
 phyta, the effect of the fertilisation of the oosphere is not merely to 
 cause the formation of an oospore and the development of an embryo, 
 but the wall of the archegonium is stimulated to fresh growth and 
 forms an investment, the calyptra, which encloses the embryo ; 
 sporophyte for a longer or shorter period, the whole constituting at 
 this stage a fruit. 
 
 The most remarkable instances of fruit-formation are, however, to 
 be found in the Phanerogams. Here, as a result of the fertilisation 
 of the oosphere, various parts of the flower are stimulated to 
 growth ; most commonly it is only the macrosporophylls (carpels) 
 which are so affected, but the stimulating influence may extend to 
 the perianth-leaves or to the axis of the flower, the resulting tissues 
 being either hard and Woody, or soft and succulent (see Part IV., 
 under Phanerogams). The peculiar feature of the fruit of these 
 plants, as contrasted with those of the lower plants, is that here the 
 tissues affected all belong to the sporophyte, whereas in the lower 
 plants they belong to the gametophyte ; this is the necessary result 
 of the peculiar relation of the female gametophyte to the sporophyte 
 which obtains in the Phanerogams (see p. 3). 
 
 19. The Seed. As this is a structure which is peculiar to 
 Phanerogams (p. 53), its morphology is discussed in connection with 
 that group (see Part IV.).
 
 PART II. 
 ANATOMY AND HISTOLOGY. 
 
 20. Introductory. The body of a plant, like that of an 
 animal, consists essentially of living matter termed protoplasm. 
 The body may consist simply of a mass of protoplasm, as the plas- 
 modium of the Myxomycetes ; or it may consist of a mass of proto- 
 plasm invested at the surface by a definite membrane which is not 
 protoplasmic (e.g. Phycomycetous Fungi and Siphonaceous Algse) ; 
 or it may consist of a mass of protoplasm segmented into portions 
 by non-protoplasmic partition-walls. A body of this last type of 
 structure may be conveniently distinguished as septate, from those 
 of the two former types which are unseptate. 
 
 On examining the protoplasm of any plant, it will be found to 
 contain certain well-defined protoplasmic bodies termed nuclei ; it 
 is, in fact, the case that all protoplasm is nucleated. In an un- 
 septate body, such as those mentioned above, the nuclei, which are 
 very numerous, are scattered irregularly throughout the proto- 
 plasm. In the septate body of certain plants (e.g. higher Fungi ; 
 some Algse, such as Cladophora and Hydrodictyon) the septation of 
 the body and the distribution of the nuclei stand in no direct rela- 
 tion to each other, the protoplasm being segmented into portions 
 each of which includes a number of nuclei ; such a plant-body may 
 be designated as incompletely septate. In the rest of the septate 
 plants, the septation of the protoplasm and the distribution of the 
 nuclei stand in a direct relation to each other, such that each of 
 the portions into which the protoplasm is segmented contains but a 
 single nucleus ; a plant-body of this structure may be described as 
 completely septate. 
 
 The portions of protoplasm which are delimitated by the septa in 
 the body of a completely septate plant, are, both morphologically 
 and physiologically, units of protoplasm. They are frequently 
 spoken of as ceZ/s, but it is more accurate to reserve this term to 
 the protoplasmic unit together with the wall (cell-icall) by which 
 it is invested. The structure of the body or any part of it can
 
 64 PART II. ANATOMY AND HISTOLOGY. [ 20 
 
 only be accurately described as cellular when it consists of one or 
 more such cells, that is, when it is either unicellular (e.g. Yeast, 
 Hsematococcus, etc.) or multicellular. The body of an unseptate 
 plant (such as the Phycomycetous Fungi and the Siphonaceous 
 Algae), as also a segment of the body of an incompletely septate 
 plant (such as Cladophora, Hydrodictyon, etc.), is not a single cell, 
 but is an aggregate of protoplasmic units enclosed within a common 
 wall. Such a body, or part of a body, may be conveniently distin- 
 guished as a coenocyte, and the plants in which it occurs may be 
 said to have coenocytic structure. 
 
 Even in typically cellular plants structures occur which are 
 coenocytic. Thus, in the early stages of its development in the 
 embryo-sac of a Phanerogam, the endosperm is generally unseptate, 
 consisting of a layer of protoplasm with many nuclei scattered 
 through it ; it eventually becomes a cellular tissue by the delimit- 
 ation of the constituent units by means of cell-walls. Again, 
 a " laticiferous cell " of a Euphorbia (and other Phanerogams) is 
 essentially a coenocyte like the body of a Vaucheria or a Botry- 
 dium. 
 
 On the other hand, there is such a thing as a multinucleate cell. 
 It has been observed, for instance, in old internodal cells of Chara, 
 and in old parenchymatous cells of Lycopodium and of various 
 Phanerogams (e.g. Tradescantia, Taraxacum, Cereus, Solanum, etc.) 
 that, from being uninucleate, they become multinucleate by the 
 direct division or fragmentation of the nucleus. 
 
 The distinction between a coenocyte and a multinucleate cell 
 would appear to be this : that the former is either multinucleate 
 from the first or becomes so at a very early stage in its develop- 
 ment, whilst the latter becomes multinucleate at a quite late 
 period. 
 
 There is another kind of structure occurring in cellular plants 
 which has to be distinguished from both the cell and the coenocyte : 
 that is the syncyte. This structure is formed by the fusion of 
 already-formed cells, the cell-walls, when present, being more or 
 less completely absorbed, so that the cavities of the fused cells 
 becomec ontinuous. The commonest case of this occurs in the de- 
 velopment of vessels, where the transverse septa of a longitudinal 
 row of cells are absorbed so that a continuous tube is formed. 
 
 But even in the fully-developed cellular plant-body it appears to 
 be very frequently the case that the protoplasm in one cell is not 
 absolutely cut off from that of the adjacent cells, but that there is
 
 20. INTRODUCTORY. 
 
 65 
 
 continuity of the protoplasm] that is, that the protoplasm of one 
 cell is connected with that of the contiguous cells by means of very 
 delicate protoplasmic fibrils which traverse the pits or pores of the 
 intervening cell-walls (Fig. 35). This connection appears, how- 
 ever, to exist from the first development of the cells, and thus 
 differs from the case of the syncyte where the absorption of the 
 intervening cell-walls is a secondary process. 
 
 The term tissue is generally applied to any continuous aggregate 
 of cells ; but it is essential to define the term more accurately. A 
 true tissue is an aggregate of cells which (1) have a common origin, 
 whether formed simultaneously (e.g. development of endosperm of 
 Phanerogams), or successively, as in the case of a tissue developed 
 from a growing- 
 point ; which (2) are 
 coherent from the 
 first and are 
 governed by a com- 
 mon law of growth ; 
 and which (3) are 
 physiologically in- 
 terdependent and 
 cannot, in fact, exist 
 otherwise than as 
 part of the tissue. 
 
 The tissue of 
 which the body of a 
 plant consists may 
 be either homo- 
 geneous or hetero- 
 geneous ; that is, 
 the cells may be all 
 alike, constituting 
 therefore but one kind of tissue ; or they may not be all alike, 
 the different kinds of cells being more or less grouped together so 
 as to form different kinds of tissue. A body which consists of 
 different kinds of tissues is said to be histologically differentiated. 
 The structural differences between the various forms of tissue in a 
 histologically differentiated body are essentially connected with the 
 special adaptation of each form of tissue to the performance of some 
 particular function in the economy. 
 
 It is a remarkable fact that, whilst the cells of the various 
 
 M.B. F 
 
 FIG. 35 (highly magnified, after Gardiner). Continuity 
 of the protoplasm of contiguous cells of the endosperm of 
 a Palm-seed (Bentinckia) : a contracted protoplasm of a 
 cell; b a group of delicate protoplasmic fibrils passing 
 through a pit in the cell- wall.
 
 66 PART II. ANATOMY AND HISTOLOGY. [ 21 
 
 tissues of a histologically differentiated body present characteristic 
 peculiarities of form, size, and relative arrangement, the most 
 striking distinctive peculiarities are exhibited, not, as in animals, 
 by the protoplasm of the cells, but by the cell-walls in respect of 
 their thickness, their chemical composition and physical properties, 
 and their markings. 
 
 Inasmuch as the cellular plants are the more numerous, and 
 present greater variety of structure, the following account deals 
 almost exclusively with them. And since the cell is the structural 
 unit of these plants, it will be advantageous to study the cell as 
 such first, and then to proceed to the study of the tissues. 
 
 CHAPTER I 
 
 THE CELL 
 
 21. The Structure and Form of the Cell. In a fully 
 developed living cell the following three principal constituents 
 may be distinguished (Fig. 36 B, C and Z>) : 
 
 (1) A closed membrane, ihe^ell-wall (7i), consisting generally of 
 a substance termed cellulose. 
 
 (2) A layer of semi-fluid substance, the jtrotojolasm (p\ lyingjn 
 close contact at all points with the internal surface of the cell-wall ; 
 the protoplasm gives the chemical reactions of proteid. In it lies 
 a nucleus ,(fc), in which one or more smaller bodies, nucleoU (kk) 
 may generally be distinguished. 
 
 (3) Cavities, one or more, in the protoplasm, termed vacuolcj (s), 
 which are filled with a watery liquid, the cell-sap. 
 
 The structure of a ccenocyte is essentially the same as that just 
 described, except that several (sometimes very many) nuclei are 
 present. 
 
 The young cell presents a somewhat different appearance (Fig. 
 36 A). At this stage the protoplasm occupies the whole cell- 
 cavity. But, in the subsequent development of the cell, the in- 
 crease in bulk of the protoplasm does not keep pace with the 
 superficial growth of the cell-wall. Hence, since thejjrptopjasm 
 must remain in contact with the cell-wall at all pjjinJts, the result 
 is that cavities, the vacuoles, are formed which become filled with 
 cell-sap (Fig. 36 5). The vacuoles, small at first, increase with 
 the growth of the cell, and may fuse together to a greater or less
 
 21] 
 
 CHAPTER I. THE CELL. 
 
 87 
 
 extent owing to the gradual withdrawal of more and more of the 
 protoplasm into the now extensive parietal layer. 
 
 Cells such as these are examples of the kind of cells which com- 
 pose the succulent parts of plants, such as the cortex of stems and 
 roots, the tissue of leaves, succulent fruits, etc.," in fact the bulk of 
 the actually living tissues of the plant. In the higher plants it is 
 generally the case that a considerable number of the cells of the 
 body eventually lose the whole of their protoplasmic contents, con- 
 taining, in fact, nothing but air or water ; such are cork-cells and 
 vascular wood-cells. Such structures are no- longer living cells, 
 but are merely 
 their skeletons, 
 and are of use 
 only in virtue of 
 the mechanical 
 properties of their 
 cell-walls. 
 
 On the other 
 hand, there are 
 frequently found 
 in connection 
 with the pro- 
 cesses of repro- 
 duction, what 
 have been termed 
 
 FIG. 36. Cells and their structure. A Young cells from tbe 
 ovary of Sj/mphoricarpu* rticemosus (x 300); B cells from an 
 older ovary of the same plant ( x 300) ; C and D from the fruit 
 of the same plant (x 100); 7i cell-wall; p protoplasm; fc 
 nucleus; fefc nncleolus; vacnole. In C there is a f>injrle 
 large vacuole, the whole of the protoplasm forming the parietal 
 layer. In D there are several vacuoles, and the nucleus lies in 
 a central mass of protoplasm connected with the parietal layer 
 by numerous strands. 
 
 such as zoospores, 
 gametes, sperma- 
 tozoids, and 
 oospheres (see p. 
 59), each of which 
 is simply an unit 
 of protoplasm 
 without any cell- 
 wall, though the 
 zoospores event- 
 ually secrete a cell-wall when they come to rest, as do also the 
 oospheres after fertilisation. 
 
 The size and form of the cell vary widely. While some cells 
 are so small that little more than their outline can be discerned 
 with the help of the strongest magnifying power (about O001 of a
 
 68 PART II. ANATOMY AND HISTOLOGY. [ 22 
 
 millimeter in diameter), others obtain a considerable size (from 
 0-1 to 0-5 millim.), so as to be distinguishable even by the naked 
 eye (e.g. in pith of Dahlia, Impatiens, Sambucus). Many grow 
 to a length of several centimetres, as the hairs upon the seed of 
 Gossypium (cotton) ; and if coenocytes be included, such as the 
 laticiferous tubes of the Euphorbiacese, the Siphonaceous Algse, 
 and the Phycomycetous Fungi, very much larger dimensions in 
 length are attained. 
 
 The Form of such cells as constitute an entire individual, or 
 exist independently, not forming part of a tissue (e.g. spores), is 
 generally spherical, or ovoid, or cylindrical. The different organs 
 of highly organised plants consist of many varieties of cells, and 
 even in the same organ cells lie side by side which are of very 
 different form. The two main types of cells are, first, such as are 
 spheroidal or polyhedral, with nearly equal or slightly differing 
 diameters (Fig. 36), as in pith, juicy fruits, fleshy tubers; and 
 secondly, such as are narrow and greatly elongated (Fig. 72), as in 
 the case of fibres. 
 
 22. The Protoplasm. The protoplasmic contents of a cell 
 present certain clearly differentiated portions. In the first place 
 there is a nucleus ; and there are more or less numerous plastids. 
 These all lie in the general protoplasm of the cell which may be 
 distinguished as the cytoplasm. 
 
 a. The Cytoplasm is of viscid tenacious consistence, but it is not 
 a fluid. Chemical examination shows that it consists (at least, 
 when dead) of proteid substance ; intimately 
 associated with this are varying quantities 
 of other organic substances, such as fats, 
 and carbohydrates, together with water, 
 and a small proportion of inorganic ash- 
 constituents. As it is the seat of all the 
 nutritive processes of the cell, it must ob- 
 viously contain at different times all the 
 various chemical substances which enter 
 
 FIG. 37. Resting nucleus 
 from the young endosperm lnto > or are formed within the Cell. 
 
 of F,;iairia imperial*. b. The Nucleus is always situated in the 
 
 bowing the flbrillar net- i =rr * 
 
 work with iu chromatin- cytop^sm. It consists of various proteid 
 granules, and several i. u - substances. Its structure, when at rest, 
 xTl)!^ y ^ generally described as follows. It 
 
 is bounded at the surface by a membrane 
 which belongs, however, to the cytoplasm. It consists mainly of
 
 22] 
 
 CHAPTER I. THE CELL. 
 
 69 
 
 a semi-fluid clear ground-substance, the nucleohyaloplasm. In 
 the nucleo-hyaloplasm lies a fibrillar network in which are dis- 
 tributed a number of granules of a substance termed chromatin. 
 One or more small granules, termed nucleoli, are to be seen lying 
 in the ground-substance. On treating the nucleus with staining 
 reagents, the fibrillar network becomes stained on account of the 
 absorption of the colouring-matter by the chromatin-granules, as 
 also do the nucleoli. Its^form is most commonly spherical, but it 
 may be lenticular, or elongated, and straight or curved. 
 
 A formation of a nucleus de novo does not take place under any 
 circumstances ; hence all 
 the nuclei in a plant 
 have been derived by re- 
 peated division from the 
 nucleus of the spore from 
 which the plant was de- 
 veloped. The nucleus 
 divides into not more 
 than two parts, which 
 are similar to each other 
 in all respects. 
 
 c. The Plastids are 
 differentiated portions of 
 the protoplasm which, 
 like the nucleus, are not 
 formed de novo, but 
 multiply by division. 
 Their form varies widely. 
 Structurally, they seem 
 to consist of a ground- 
 substance, denser at the 
 surface, with imbedded 
 fibrils. 
 
 The .plastids may either be_colourless, when they are termed 
 leiLcoplastids ; or coloured, when they are termed chromatopliores. 
 The chromatophores are distinguishable as chloroplastids, when 
 they contain the green colouring-matter chlorophyll ; or as 
 chromoplastids when they contain no chlorophyll, but some other 
 colouring-matter. Plastids are not found in theJFungi, nor, ap- 
 parently, in the Cyanophycese among the Algse. 
 
 The Leucoplastids may be spheroidal, fusiform, or cylindrical in 
 
 PIG. 38. Chloroplastids in the cytoplasm of the 
 cells of the prothallium of a Fern. A Optical section 
 of the cells ; B part of a cell seen from the surface- 
 Some of the plastids have begun to divide. ( x 400.)
 
 70 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [22 
 
 shape ; they are especially numerous in the neighbourhood of the 
 nucleus. In parts of plants which, in the ordinary course, 
 eventually become exposed to light, the leucoplastids__deyelope - 
 Into chloroplastids. Conversely, when a part which is normally 
 exposed to light is kept in darkness, the chloroplastids become_ 
 replaced by leucoplastids. The essential function of the leuco- 
 plastids is to form starch-grains. 
 
 The Chloroplastids or Chlorophyll-bodies, are of various form. 
 The characteristic feature of them is their function, which is two- 
 fold. In the first place, they can, like the leucoplastids, generally 
 produce starch-grains ; in the second place, they are capable, in 
 virtue of the colouring-matter present in them, of constructing 
 organic substance from carbon dioxide and water under the in- 
 
 FIG. 39. Gronp of rod-h'ke leuco- 
 plastids, each bearing a pyramidal 
 starch-grain, collected round the nu- 
 cleus in a cell of the pseudo-bulb of an 
 Orchid (Phajus grandifolius). (x860: 
 after Schimper.) 
 
 FIG. 40. Isolated chloroplastids with 
 starchy contents from the leaf of Funaria 
 'kygrometrica (550). a A young corpuscle ; 
 b an older one, V and V have begun to 
 divide ; c d e old corpuscles in which the 
 starchy contents fill almost the whole 
 space ; /and g after maceration in water 
 by which the substance of the corpuscle 
 has been destroyed and only the starchy 
 contents remain. (After Sachs.) 
 
 fluence of light (see Part III.). Their function is thus not only 
 starch-forming or amyloplastic, but also assimilatory. These two 
 functions may be, and usually are, carried on simultaneously ; 
 hence when, under the influence of light, organic substance is 
 being produced in the chloroplastid, it usually becomes filled with 
 starch-grains, and sometimes to such an extent that the substance 
 of the chloroplastid constitutes but the wall of a vesicle i^Fig. 40). 
 But starch-grains may be formed in a chloroplastid, as in a 
 leucoplastid, in the absence of light ; the organic substance 
 required for the building-up of the starch-grain being not produced
 
 22] 
 
 CHAPTER I. THE CELL. 
 
 71 
 
 in the chloroplastid itselfj but supplied from other parts of the 
 plant. 
 
 These plastids are termed chloroplastids, because the colouring- 
 matter upon which their assimilatory function depends is most 
 commonly the familiar green colouring-matter, chlorophyll. But 
 thy_arejioXalways green. In some of the Algae they are red or 
 brown, because in addition to chlorophyll there is present in the 
 one case (Rhodophyceae), a red colouring- matter, phycoerythrin, 
 and in the other (Phseophyceae) a brown colouring-matter, 
 phycoxanthin or phycophcein. These substances are, however, 
 related to chlorophyll. 
 
 When the colouring-matter is dissolved out by alcohol or some 
 other solvent, the protoplasmic plastid is left colourless, but un- 
 changed in form or size. Thej^hlorpphyll appears to exist in an 
 ojlv__splutipnj and to be con- 
 fined to the fibrillar portions 
 of the plastid, in the form of 
 draplets (#ro2ia). 
 
 The most common form of 
 chloroplastid the only one oc- 
 curring in the higher plants 
 is the chlorophyll -corpuscle 
 (Fig! 40), which is flattened 
 and discoid. Usually, many 
 corpuscles are present in a cell, 
 but occasionally (e.g. Antho- 
 ceros) there is only one. In 
 the Algse the chromatophores, 
 though sometimes small and discoid (e.g. Vaucheria, Fucus, etc.), 
 are more commonly large, occurring singly, and of very various 
 form. 
 
 The chromatophores of the Algse present a great variety of form. 
 Generally speaking, those of the higher forms are small corpuscles of a 
 more or less discoid form ; while in the lower forms the chromatophores 
 are few in number, often single, in each cell, and are relatively large, 
 assuming commonly the shape of a flattened plate, sometimes elongated 
 and straight or spirally coiled (Fig. 41). In the latter case the large 
 flattened chromatophores present one or more spherical thickenings, each 
 of which is termed a gjtrenoid (Fig. 41), and consists of a homogenous 
 colourless mass of proteid substance. The pyrenoid is generally sur- 
 rounded by a layer of starch-grains : this is, in fact, the only part of the 
 chromatophore in which starch can be detected. 
 
 FIG. 41. Spirogyra majuscuZa (after Stras- 
 burger: x2VO). A cell of a filament, showing 
 the nucleus suspended in the centre ; also 
 the spirally-wound chromatophore with py- 
 renoids.
 
 72 
 
 PART H. ANATOMY AND HISTOLOGY. 
 
 23 
 
 Chromatophores multiply by division into two, effected by 
 median constriction (Figs. 38 B ; 41) : pyrenoids, when present, 
 are multiplied in the same way. 
 
 The chloroplastids ultimately undergo degeneration, when, as in 
 the case of falling leaves, for instance, all that remains of them is 
 a few yellow granules. 
 
 In many cases the green colour of parts of plants containing 
 chloroplastids is masked by the presence of other colouring-matters 
 held in solution in the .cell-sap (e.g. the leaves of Amaranthus, 
 Coleus, Copper Beech, Copper Hazel, etc.). 
 
 The Chromoplastids are generally derivatives of chroi 
 which have undergone a change both in form and colour. They 
 occur most commonly in the cells of yellow floral leaves, such as 
 those of Tropseolum (Fig. 42) : in the super- 
 ficial cells of many fruits of a red or orange 
 colour (e.g. berries of Solanum, fruit of 
 Tomato). The yellow colour of the root of 
 the Carrot is due to the presence of leuco- 
 plastids, in each of which there is a large 
 orange-coloured crystal of carotin. The 
 chloroplastids of many Coniferse (e.g. Biota 
 orientalis) assume a reddish colour at the 
 beginning of winter. 
 
 Many of the primordial reproductive cells are 
 motile (zoospores, planogametes, spermatozoids), 
 and move by means of cilia. A cilium is a 
 delicate filament of protoplasm which is con- 
 tractile, and by its oscillations serves to propel 
 through the water the body to which it be- 
 longs. The number of cilia borne by these cells 
 varies considerably: there may be a single 
 cilium (e.g. zoospores of Botrydium, and occa- 
 sionally those of Hydrodictyon) : or a pair (generally in planogametes ; 
 frequently in zoospores ; less commonly in spermatozoids, as those of most 
 heterogamous Algae, of the Bryophyta, and of Lycopodium and Selagin- 
 ella): or four (e. a . zoospores of certain green Algae, Ulothrix, Cladophora, 
 Ulva); or many (e.g. all motile cells of (Edogonium ; zoospores of 
 Vaucheria; spermatozoids of Filicinse and Equisetinae). Cilia also occur 
 in free-swimming Algae, such as Volvox, etc. 
 
 23. The Cell- Wai I is a non-protoplasmic membrane_con- 
 sisting, at least at its first formation, of an organic substance 
 termed cellulose, of water, and of a small proportion of Inorganic 
 
 FIG. 42. From the upper 
 side of the calyx of Trojxeo- 
 lum majut. The inner wall 
 of an epidermal cell with 
 the chromoplastids. (After 
 Strasburger : x 540.)
 
 23] CHAPTER I. THE CELL. 73 
 
 mineral constituents. Its growth, as well as its first formation, is 
 the result of the vital activity of the protoplasm ; it is, in fact, 
 formed from and by the protoplasm. 
 
 1. 'The Growth of the Cell- Wall. The cell-wall grows in surface 
 and in thickness. 
 
 a. The growth in surface of the cell-wall may take place in 
 either of two ways, both of which are, however, dependent upon 
 pressure exerted from within upon the wall. In the one case the 
 stretched wall grows continuously by means of material supplied 
 to it by the cytoplasm, the wall remaining unbroken. In the 
 other, the stretched wall is ruptured at certain parts, new portions 
 of cell-wall being at once intercalcated to close the gap. The 
 former is of more common occurrence : the latter has been observed 
 in some Algae, for instance in the growth of the cells of (Edo- 
 gonium, and in connexion with the apical growth and with the 
 development of lateral members in Caulerpa, Cladophora, and 
 Polysiphonia. 
 
 Growth in surface takes place to such an extent that the volume 
 of the cell not infrequently becomes a hundred-fold greater than it 
 was originally. Thus, for instance, in a leaf still enclosed in a 
 leaf-bud, the cells of which it will consist when fully developed 
 are all actually present, and it is simply by their increase in 
 volume that the leaf attains its full size. 
 
 In the comparatively rare cases in which the superficial growth 
 of the cell-wall is equal at all points, the cell preserves its original 
 form : but more commonly the cell-wall grows more vigorously 
 at certain points than at others ; thus, 
 for instance, a primarily spheroidal or 
 cuboidal cell may become tubular, cylin- 
 drical, fusiform, stellate, etc. 
 
 b. The growth in thickness of the cell- 
 wall is effected by the deposition of sue- 
 cessive layers on the internal surface of 
 the first-formed layer. The cell-wall does 
 
 FIG. 43. Ripe pollen-gram 
 
 not usually begin to thicken until after of cichorium, intybus ; the ai- 
 Its growth in surface has ceased, the cell m 8t 8 P herica ; 8urf ^ e of th 
 
 , ? cell-wall is furnished with 
 
 having then attained its definite size ; but ridge-like projections pro- 
 cases of simultaneous growth in surface lon g ed int spines, and form- 
 
 j . , i i ing a network. (After Sachs.) 
 
 and iu thickness have been observed. 
 
 The growth in thickness of the cell-wall is also rarely uniform ; 
 the cell-wall commonly becomes more thickened at some points
 
 74 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [23 
 
 than at others, and thus acquires inequalities of surface. In the 
 case of isolated cells or of free cell-walls, the prominences existing 
 in this way on the external surface appear as warts, tubercles, 
 spines, etc. (Fig. 43). Cells that are united to form tissues have 
 their inequalities on the internal surface of the cell-wall, the 
 prominences sometimes having definite form, and projecting into 
 the interior of the cell ; such are the annular (Fig. 44 r) and 
 spiral thickening (Fig. 44 ) of the walls of certain vessels ; in the 
 so-called reticulated cell-walls, the thickening is in bands which 
 are united into a network, so that circular or oval thin spaces are 
 left. In other cases, isolated and relatively small thin spaces are 
 left in the wall in the course of the growth in thickness, which 
 appear, when seen on the external surface, 
 as bright spots, commonly called pits, and 
 are seen in section to be canals of greater 
 or less length, according to the relative 
 thickness of the walls (Figs. 45, 46). Very 
 frequently the pit, when_seen from the 
 surface, presents the appearance of two 
 concentric circles, or ellipsesj_j.or this 
 reason, that the opening of the .canal into 
 the interior of the cell is .narrow, whereas 
 the external opening is broad (Fig. 48 A}. 
 Such bordered pits occur in the wood-cells 
 of Conifers (Fig. 49), in the walls of many 
 vessels (Fig. 48), and elsewhere. The 
 scalar if orm thickening of the walls of 
 many vessels arises from the regular and 
 close arrangement of bordered pits which 
 are much elongated transversely. 
 
 The Structure of the Cell-icall. When 
 the cell- wall is at all thickened it presents indications of structure. 
 It presents, in the first place, a layered appearance when ex- 
 amined in longitudinal or transverse action (Fig. 46). This layer- 
 ing or stratification of the cell-wall is readily intelligible when it 
 is remembered that the thickening of the wail is due to the depo- 
 sition of successive layers from within. 
 
 It presents, secondly, a delicate striation, when examined in 
 surface-view, the lines running at a larger or smaller angle to the 
 long axis of the cell, sometimes even transversely. The planes of 
 striation are commonly different in the different layers constitu- 
 
 Fia. U.r Annular, spiral 
 thickening of the walls of ves- 
 sels ; r seen from outside, s in 
 longitudinal section highly 
 magnified (diagrammatic).
 
 23] 
 
 CHAPTER I. THE CELL. 
 
 FIG. 45. A cell with 
 pitted walls, from the 
 wood of the Elder (Satn- 
 bucus). A longitudinal 
 section showing the pits 
 in tbe lateral walls as 
 channels, a; and in the 
 farther wall as roundish 
 spots, b. ( x 240.) 
 
 FIG. 48. Transverse sec- 
 tion of a bast-cell from the 
 root of DaJiU'a arinbi!is (x 
 800); I the cell-cavity ; A' pit- 
 canals which penetrate the 
 stratification ; sp a crack by 
 which an inner system of 
 layers has become separa- 
 ted. (After Sachs.) 
 
 Fio. 47. Cells from the endo- 
 sperm of OrnitJwgalum tunbella- 
 tum showing simple pits : 
 m pits seen in surface view ; p 
 closing membrane seen in lon- 
 gitudinal section ; nucleus. 
 (x2X): after Strasburger.) 
 
 ting the thickness of the wall, and these seem in the surface-view 
 to cross each other (Fig. 50). The cause of striation appears to be 
 this, that when a considerable area of cell-wall has to be formed, 
 it is deposited by the protoplasm not as one continuous sheet, but 
 
 FIG. 49. Oval bordered pits in the 
 wall of a vessel of Helianthus. A In 
 longitudinal section. B As seen from 
 the surface ; t the pit ; h the pit-chamber. 
 (x 600). 
 
 FIG. 49. Circular bordered pits on 
 the wood-cells of the Pine. A Seen from 
 the surface. B In section ; s the closing 
 membrane ; m the middle lamella. C An 
 earlier stage, in section. ( x SOO.diagram.)
 
 76 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 in the form of delicate spirally-wound bands with their edges in 
 contact. The lines of the striation are the planes of contact of the 
 edges of these spiral bands. A well-marked illustration of the 
 spiral mode of deposition of cell-wall by protoplasm is afforded by 
 the spiral vessels already mentioned (Fig. 44 s). 
 
 3. The Chemical Composition of the Cell-ivall. As a rule, the 
 organic constituent of the newly formed cell- wall is cellulose 
 (C 6 H ]0 5 ), a carbohydrate, the characteristic reaction of which 
 is that it turns blue when treated with sulphuric acid and iodine, 
 or with a mixture of iodine, iodide of potassium, and chloride of 
 zinc (chlor-zinc-iod). 
 
 It is, however, commonly the case that when a cell-wall has 
 
 undergone thickening, some 
 at least of its constituent 
 layers do not consist of 
 cellulose. The chemical 
 changes which are pre- 
 sented by cell- walls may be 
 distinguished as follows : 
 a. The cell- wall may un- 
 dergo cuticularisation: e.g. 
 walls of epidermal cells or 
 cork-cells, of spores. The 
 cuticularised or corky cell- 
 wall contains a substance 
 termed cutin. It is but 
 slightly permeable to water ; 
 FIG. so.-surface view of the wall of a ceil it is extensible and highly 
 
 showing striation, from the pith of Dahlia varia- elastic ; it turns yellow 
 btlw. ( x 249: after Strasburger.) / 
 
 when treated with sul- 
 phuric acid and iodine, or with iodised chloride of zinc. The cuti- 
 cularisation of the cell- wall is most marked in the external layers ; 
 in fact the external layer consists entirely of cutin, whilst the 
 internal layers (of which there may be several, as the cuticularised 
 wall is often much thickened) consist more and more largely of 
 cellulose, the innermost layer consisting frequently of pure cellu- 
 lose, though it is sometimes more or less lignified (cork). This can 
 be shown by treating the cuticularised tissue with strong chromic 
 acid for some time, or by warming it in a mixture of nitric acid 
 and chlorate of potash, when the cutin is removed, and the re- 
 maining tissue gives the characteristic cellulose-reactions.
 
 23] CHAPTER I. THE CELL. 77 
 
 ft. The cell- wall may undergo lignification; that is, the cell-wall 
 becomes impregnated with a substance termed lignin, which 
 makes it hard and elastic, and though readily permeable to water 
 it cannot absorb or retain much in its substance. The character- 
 istic tests for lignin are, that a cell-wall containing it (a) turns 
 yellow when treated with aniline chloride and hydrochloric acid, 
 and (&) turns pink when treated with phloroglucin and hydro- 
 chloric acid. When a lignified cell-wall is macerated in a mixture 
 of nitric acid and chlorate of potash, or in a strong solution of 
 chromic acid, the lignin is dissolved out and the wall ceases to 
 give the lignin-reactions, and now gives the cellulose-reactions. 
 Lignincation takes place in the sclerenchymatous and tracheal 
 tissues, less commonly in the parenchymatous tissue, of the 
 sporophyte of the Pteridophyta (Vascular Cryptogams) and 
 Phanerogams ; it does not occur in any of the lower plants, nor 
 in any gametophyte. 
 
 y. The cell-wall may become more or less mucilaginous] in its 
 dry state it is then hard and horny; when moistened, it absorbs 
 a large quantity of water, becoming greatly increased in bulk and 
 gelatinous in consistence ; it usually turns blue when treated 
 with sulphuric acid and iodine, or with iodised chloride of zinc, 
 but in some cases it does not give this reaction ; and in yet others 
 (e.g. asci of Lichens, bast of Lycopodium, endosperm of Peony, and 
 cotyledons of various leguminous seeds) it turns blue with iodine 
 alone. Mucilaginous cell-walls are common in the coats of seeds 
 (e.g. Flax or Linseed, Quince) ; they are very remarkable in the 
 case of the macrospores of Pilularia and Marsilea ; in tissues^ Ihey 
 are^ well seen in the Malvaceae: they occur in all sub-divisions of 
 the vegetable kingdom. 
 
 In some cases the change goes so far as to result in the con- 
 version of the cell-wall into gum, soluble in water, as in some 
 species of Astragalus and in certain Rosaceous trees (Cherry, 
 Plum, Almond, Peach, etc.). 
 
 These modifications may occur either singly or together in the 
 different layers of one cell-wall, as in corky, or suberised cell-walls, 
 where cuticularisation and lignification occur simultaneously. 
 
 S. Mineral matters are also frequently deposited during growth 
 in considerable quantity in the cell-wall, particularly salts of lime 
 and silica ; they are usually intercalated between the solid organic 
 particles of the cell-wall, so that they cannot be directly detected, 
 but remain, after burning, as a skeleton which retains the form of
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [24 
 
 the cell. Silica is present in the stems of Grasses and of Equi- 
 setacese. Calcium oxalate sometimes occurs in a crystalline form 
 (Fig. 51.) Calcium carbonate is also frequently deposited in cell- 
 walls, as in certain Algse (e.g. Ace tabu laria, Coralline^ Jama, etc.) ; 
 also in hairs of some of the higher plants (e.g. many Boraginacese) ; 
 but most peculiarly in the cystoliths present in the epidermal cells 
 of the leaves of Ficus clastica, and of the Urticacese and Acan- 
 thacese : it may occur either as granules or as crystals. 
 
 A cystolith (Fig. 52 A) consists of a basis of cellulose incrusted with 
 calcium carbonate. On treating a section, containing a cystolith, with 
 acid, the calcium carbonate is dissolved with evolution of bubbles of CO 2 , 
 leaving the cellulose basis (B) which presents both striation and strati- 
 fication. The cellulose basis is, in fact, a local thickening of the cell-wall. 
 
 Fio.] 61. Crystals o 
 calcium oxalate in the 
 wall of the bast-cells of 
 Cephalotaxut Fortune*. 
 (x600:afterSolms.) 
 
 FIG. 62. A cystolith from the leaf of Celtis 
 Tala ( x 200) . A Normal condition ; c cysto- 
 lith ; e epidermal layer; p palisade-tissue. 
 B The cystolith after treatment with hydro- 
 chloric acid which has dissolved the calcium 
 carbonate, leaving the stratified cellulose 
 basis. 
 
 24. Cell-Contents. The following are the principal cell- 
 contents which are not protoplasmic and are, in fact, not living : 
 they are moreover not universally present in cells, but are con- 
 fined to special cells, and frequently to special plants: starcL- 
 grams ; fatsj proteid grains and crystalloids ; mineral crystals ; 
 the cell-sap, and the substances dissolved in it. 
 
 a. Mm-cli-grains are small solid granules of various shape- 
 rounded, oval, lenticular, etc. consisting of starch_with a certain 
 amount of water and a small proportion of incombustible ash. 
 They are specially abundant in those parts of plants which serve
 
 24] CHAPTER I. THE CELL. 79 
 
 as depositories of reserve-materials, e.g. rhizomes, jmd roots_of 
 perennial plants during the winter, tubers of the potato, seeds . 
 such as those of the cereal and leguminous plants. They canjbe 
 extracted by maceration from the organs in which they occur, and 
 then appear as a white powder which is known as' starch. Starch 
 is a carbohydrate ; its percentage composition is the same as that 
 of cellulose, and may be represented as C 6 H 10 5 , but its molecule 
 is smaller and less complex. It is readily detected by the cha- 
 racteristic blue colour which it assumes on treatment with an 
 aqueous solution of iodine. When boiled with water, or when 
 treated with potash, the grains swell enormously and form a paste. 
 
 The substance of the starch-grain is always stratified, being 
 disposed in layers round an organic centre, the hilum + this stra- 
 tification, as also in the case of cell-walls, is the result of the 
 deposition of successive layers one on the other. The hilum is 
 the most watery portion of the grain, whilst the external layer is 
 the most dense. 
 
 It is, as already mentioned (p. 70), the rule that starch-- 
 grains are produced by means of plastids : in parts of plants ex- 
 posed to light, by chloroplastids ; in parts of plants not__ex|)osed 
 to light, by leucoplastids. In the former case the_ grains are 
 usually formed in the interior of the plastid (see Fig. 40) ; in the 
 latter case, on its surface (Fig. 39). 
 
 It not uncommonly happens th&t^compound starch-grains are to 
 be found. Sjmn'ouxly compound grains are simply grains which 
 have become adherent in consequence of mutual pressure : they 
 occur frequently in the interior of the plastids (see Fig. 40). The 
 truly compound grains (Fig. 53 B E) are formed in this way, 
 that one plastid produces simultaneously two or more rudimentary 
 starch-grains ; as these increase in size, they eventually come into 
 contact ; the further deposition of starchy layers must necessarily 
 be of such a kind that they surround, not each individual grain, 
 but the aggregate of adjacent grains ; the young grains thus be- 
 come bound together by investing layers, and a grain is produced 
 which has apparently a number of hila. 
 
 The form of the starch-grains is characteristic in the different 
 plants in which they occur ; thus those of the Potato (Fig. 53) are 
 excentrically oval ; those of leguminous plants (Fig. 55), concen- 
 trically oval ; those of Rye, Wheat, and Barley, lenticular (Fig. 
 56). 
 
 The distribution of starch throughout the different classes of
 
 80 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [24 
 
 plants is a matter of considerable interest. Generally speaking, 
 it is confined to plants which possess chloroplastids, though a sub- 
 stance turning blue with iodine has been found to occur, diffused 
 throughout the protoplasm, in certain Schizomycetes (Clostridium 
 butyricum, Sarcina ventriculi, Bacterium pastorianum). But, on 
 the other hand, it is not always present in plants which possess 
 typical chloroplastids ; thus, it is absent, for instance, from__the 
 Onion, species of Vaucheria, etc. In the case of plants which 
 have other colouring-matters besides chlorophyll, starch may be 
 
 altogether absent (Cyano- 
 phycese, Diatomacese) ; or it 
 may be replaced by some 
 other substance (most Phseo- 
 phycese and Rhodophycese). 
 
 /?. Fats occur very com- 
 monly in the cells of plants 
 as oily drops scattered 
 throughout the cytoplasm. 
 They are more particularly 
 abundant in seeds, in many 
 of which oil is the form in 
 which the non-nitrogenous 
 reserve material is deposited 
 (e.g. Palm, Castor-Oil plant, 
 Rape, Flax, etc.) ; it is also 
 present in some fniits (e.g. 
 Olive). 
 
 y. Proteid Grains, or Ale- 
 juron, are granules of various 
 sizes, oval or spherical in 
 form, which occur in seeds, 
 and are of physiological im- 
 portance in that they are the 
 source from which the em- 
 bryo is supplied with nitro- 
 genous food when the seed germinates. They consIsT'oTlTmTxture 
 of proteid substances belonging to the globulins and the albumoses. 
 They present no indications of structure, and are much larger in 
 oily_than in starchy seeds. 
 
 The proteid grain generally contains a mass of mineral matter. 
 Most commonly this is a rounded body, the globoid (Fig. 54), con- 
 
 FIG. 63. Excentric starch-brains from the 
 tnber of a Potato ( x 800). A A fully developed 
 simple grain, B-E Compound grains ; a f> 
 young simple grains ; c young compound grain. 
 (After Sachs.)
 
 24] 
 
 CHAPTER I. THE CELL. 
 
 sisting of double phosphate of lime and magnesia ; lessjrequently 
 there is a crystal, or a cluster of crystals, of calcium oxalate. 
 
 In the large grains of oily seeds it is frequently the case that a 
 portion of the proteid (globulin) of the grain crystallises out, con- 
 stituting the crystalloid ; there are occasionally two or more 
 crystalloids in the grain (Fig. 54). 
 
 8. Mineral Crystals are frequently found in the cells of plants. 
 They sometimes consist, but in comparatively few cases, of calcium 
 carbonate ; for example, the crystals in the protoplasm of Myxo- 
 mycetes, and the crystalline masses occurring in the cells of the 
 
 FIG. 64. Cells from the endosperm 
 of Bicinii* communia (x 800) : A fresh, 
 in thick glycerine ; B in dilute gly- 
 cerine ; C warmed in glycerine ; D after 
 treatment with alcohol and iodine ; the 
 grains having been destroyed by sul- 
 phuric acid, the cytoplasm remaining 
 behind as a net-work. In the grains 
 the globoid may be recognised, and in 
 B C the crystalloid. (After Sachs.) 
 
 Fie. 55. Cells of a very thin section through 
 a cotyledon of the embryo in a ripe seed of 
 Pisum sativum ; the large concentrically strati- 
 fied grains St are starch-grains (cut through) ; 
 the small granules a are aleuron, consisting 
 of proteids ; i the intercellular spaces. (After 
 Sachs.) 
 
 pericarp and testa of some plants (e.g. Celtis australis, Litlio- 
 spcrmwn officinale, Cerinthe glabra). 
 
 In all other cases the crystals consist of calcium oxalate, which 
 crystallises in two systems according to the proportion of water 
 which it contains ; to the one system, the quadratic, belong the 
 octahedra (Fig. 57 fc) ; to the other, the clinorhombic, belong the 
 acicular crystals, distinguished as raphides, which occur in 
 bundles in the cells of Monocotyledons more especially (Fig. 58), 
 and are generally associated with mucilage in the cell. 
 
 M.B. G
 
 82 FART II. ANATOMY AND HISTOLOGY. [ 24 
 
 It sometimes happens that the crystal, or group of crystals, be- 
 comes surrounded by a layer of cellulose attached to the wall at 
 
 one or more points (e.g. 
 
 _^^ leaf of Citrus vulgaris, 
 
 ^ < ^=?^c^~I^ : -) pith of Kerria japonica). 
 J^rf^^TrTTTY^ )P c. The Cell-Sap satur- 
 -t ates ~tEe celPwall, the 
 protoplasm, in fact the 
 whole organised struc- 
 ture of the cell ; it also 
 fills the vacuole, when 
 present, in the cyto- 
 plasm. It is a watery 
 solution ^f~the~most va- 
 rious substances. In all 
 cases it holds salts in 
 solution, consisting 
 mainly of alkalineTblises 
 in combination either 
 with inorganic acids, 
 such as the nitric, phos- 
 phoric, or .._snlpliuric 1 _ or 
 with organic acids, such 
 as malic (e.g. apple and other fruits), citric (lemon, etc.), and 
 others. It frequently contains tannin, and nitrogenous substances 
 j, such as asparagin. 
 
 It very commonly 
 
 <F- ^OP' ^W "^ * s r i c k *- su g ar: 
 
 either grape-sugar 
 
 (C 6 H 12 6 ), as in 
 the grape and 
 other fruits, and in 
 fact most parts of 
 plants at particu- 
 lar times ; or cane- 
 sugar (C ]2 H 22 O n ) 
 as in the Sugar- 
 cane, the Maple, 
 and the Beetroot. 
 
 FIG. 67. Crystals of calcium oxalate in the cells of the 
 petiole of a Begonia (x 200) : fc solitary crystals ; dr cluster. 
 
 oC/ 1 
 
 FIG. 66. Part of a section of a grain of wheat, 
 Triticum vv.lga.re; p pericarp; t seed-coat or testa; 
 internal to which are cells belonging to the endo- 
 sperm; the external layer contains small proteid- 
 grains (al) but no starch, the more internal cells con- 
 tain starch-grains am ; n the nucleus. (After Stras- 
 burger : x 240.) 
 
 Jerusalem Arti-
 
 25] 
 
 CHAPTER I. THE CELL. 
 
 83 
 
 FIG. 58. Raphides (fc) in a cell of a bulb-scale of Urginea 
 arirott(x 200). 
 
 choke, Dahlia, Globe Artichoke) the cell-sap is rich in inulin, a 
 substance having the same percentage composition as starch (re- 
 presented by the 
 formula C G H 10 5 ): 
 when a portion of 
 tissue of one of 
 these plants, such 
 as a piece of the 
 tuberous root of 
 the Dahlia, is kept 
 in spirit, the inulin 
 slowly precipitates 
 in the form of 
 sphserocrystals 
 (Fig. 59) adhering to the walls. 
 
 The cell-sap also very frequently holds colouring-matters in 
 solution ; for instance, the colouring-matters of most red and blue 
 flowers (erythrophyl and anthocyanin) ; of many fruits, such as 
 the Cherry and Elderberry ; of 
 " copper leaves," such as those 
 of Copper Beech and Hazel, and 
 of the Beet-root. 
 
 25. Cell - Formation. 
 The formation of a cell is ne- 
 cessarily dependent upon a 
 pre-existing cell ; the direct 
 development of a cell from the 
 necessary chemical substances 
 that is, spontaneous genera- 
 tion has not yet been ob- 
 served. Moreover, it can only 
 take place when the proto- 
 plasm concerned is in the 
 embryonic condition ; as, for 
 instance, in growing- points, 
 germinating spores, etc. 
 
 The development of cells 
 always takes place in such 
 
 Wise that the whole Or part Fm. 69.-Sphajrocrystals of inulin in the 
 
 Of the protoplasm of a Cell, tissue of the tuberous root of Dahlia variaUlis 
 ,, 7, T after prolonged action of alcohol. (After 
 
 the mother-cell, undergoes re- strasburger: x 240.)
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 25 
 
 arrangement. The following are the principal modes of cell-forma- 
 tion : 
 
 I. Cell-division. The protoplasm of the mother-cell divides 
 into two or more parts, each of which constitutes a new cell. The 
 division of the cytoplasm is usually preceded by that of the 
 nucleus. 
 
 In the simplest case of cell-division the nucleus divides into two, 
 the cytoplasm does the same, and a cellulose-wall or septum is 
 formed in the plane of division. In other cases the secondary 
 nuclei and their investing cytoplasm may again divide before any 
 cell-wall is formed. Finally, the formation of a cell-wall may be 
 postponed until the division of the 
 nuclei and of the cytoplasm has 
 been repeated an indefinite number 
 of times. The varieties of cell- 
 division which thus arise may be 
 arranged as follows : 
 
 1. In growing vegetative organs, 
 a division of the cell takes place, 
 such that the whole of its proto- 
 plasm, without any rounding-off 
 or contraction, is divided into two 
 parts : the new wall is formed be- 
 tween the two masses of proto- 
 plasm only along the plane of 
 division (Fig. 60). The wall is 
 sometimes formed simultaneously 
 at all points of the plane of divi- 
 sion, as in the development of 
 stomata, and sometimes, as in cer- 
 tain Algae, e.g. Spirogyra, it grows 
 as a ring from without inwards. 
 
 2. The formation of the cells 
 which subserve reproduction (see 15) is always accompanied by 
 a rounding-off of the protoplasm. These cells are generally set 
 free, and may or may not have a wall when set free : the wall, 
 when present, is always formed over the whole surface of the 
 young cell. 
 
 a. The whole cytoplasm of the mother-cell may become aggre- 
 gated around four newly-formed nuclei ; this process occurs 
 principally in the formation of the pollen of phanerogamous 
 
 PIG. 00. Cell-division in the cortex of 
 the growing stem of Vicia Faba ( x 300). 
 At a the division hag just taken place, 
 the nucleus still adheres to the new 
 wall ; at b it has retreated to the older 
 wall : fc the nucleus.
 
 25] 
 
 CHAPTER I. THE CELL. 
 
 85 
 
 plants (Fig. 61), and in the formation of the spores of Mosses and 
 Vascular Cryptogams. The details of this process are not the same 
 in all cases. In some (development of the pollen-grains of Mono- 
 cotyledons and of the microspores of Isoetes) the nucleus of the 
 mother-cell divides into two, and this is followed- by a corresponding 
 division of the cytoplasm, a cellulose wall being formed between 
 the two cells. Each of these now divides in the same manner, in a 
 plane at right angles to that of the first division, and thus the four 
 special mother-cells are produced lying in one plane. In other 
 cases (development of the pollen-grains of Dicotyledons, of the spores 
 of Mosses, Ferns, and Ec[uisetums) the nucleus of the mother-cell 
 divides into two, and each of these secondary nuclei divides again 
 
 FIG. 61. Division of the mother-cells of the pollen- 
 grains of Althaea ro*o. At A and B the division of the 
 protoplasm into four has begun ; in D the in-growth 
 of the membrane is shown, and in E the walls are 
 complete. (After Sachs.) 
 
 FIG. 62. Rejuvenescence as ex- 
 hibited in the formation of the 
 zoospores of (Edogonium. A 
 Portion of a filament ; in the lower 
 cell the protoplasm is begin- 
 ning to contract, in the upper the 
 young primordial cell is escaping 
 (Z). B A zoospore. C The be- 
 ginning of germination. ( x 350.) 
 
 into two, the divisions taking place in planes at right angles to each 
 other and to that of the first division ; as a consequence, the four 
 nuclei do not lie in one plane, but are arranged tetrahedrally. Cell- 
 walls are now formed, so that four special mother-cells are produced. 
 In the case of the pollen-grains of Dicotyledons, the wall of the 
 primary mother-cell thickens and grows inwards at certain points 
 (Fig. 61 Z>) so as to constrict the cytoplasm somewhat, and the 
 newly-formed walls become attached to these projections. In all 
 cases the protoplasm in each of the four special mother-cells
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [25 
 
 surrounds itself with a proper wall which becomes the coat of the 
 pollen-grain or of the spore. 
 
 b. The number of the nuclei derived by repeated division from 
 the nucleus of the mother-cell before any cell-wall is formed is 
 indefinite. Each of them becomes surrounded by a portion of the 
 cytoplasm. 
 
 FIG. 63. Zoosporangia of 'an Achlja 
 ( x 560) : A still closed ; B allowing 
 the zoospores to escape, beneath it a 
 lateral shoot c ; a the zoospores just 
 escaped ; b the abandoned membranes 
 of the zoospores which have already 
 swarmed ; e swarming zoospores. 
 (After Sachs.) 
 
 FIG. 64. Cell-formation in the asei of Pirn 
 convorula ; af successive steps in the develop- 
 ment of the asci and spores: sh mycelium. 
 (After Sachs : x 550.) 
 
 It is in this way that the zocspores of many Algse and Fungi are 
 formed (Fig. 63), and it is usually not until some time after their 
 escape from the mother-cell that they become clothed with a cell- 
 wall. The spores formed in the asci and sporangia of Fungi (Fig.
 
 25] 
 
 CHAPTER I. THE CELL. 
 
 87 
 
 64) are also developed in this way, but in this case the cells are 
 always invested by a cell- wall before they are set free from the 
 mother-cell. A further example of this is to be found in the 
 development of the endosperm-cells in the embryo-sacs of phanero- 
 gamous plants. This mode of cell-formation is" known &sfree cell- 
 formaiion. 
 
 II. Rejuvenescence. The whole protoplasm of the mother-cell 
 may undergo rejuvenescence, when it contracts and reconstitutes 
 itself as the new protoplasmic body of a daughter-cell, which 
 usually does not surround itself with a new membrane for some 
 time. It is in this manner that the single zoospores of many 
 Algse are formed, as in Vaucheria, Stigeoclonium, (Edogonium 
 (Fig. 62), as well as isolated sexual cells such as oospheres. 
 
 Fio. 05. Conjugation of the cells of Spirogyra (x 400). A The cells of two filaments 
 which are prepared for conjugation. At a the filaments have begun to swell towards each 
 other. The spiral bands of chlorophyll are recognisable at cl, and the nucleus at K. At B 
 the protoplasm of the cell p is fusing with that of the other p'. At C is a perfectly-formed 
 zygospore Z. 
 
 III. Conjugation. In conjugation the protoplasmic contents of 
 two or more cells coalesce to form a new cell, which acquires a 
 membrane. This process occurs in a typical manner in various 
 groups of Algae, e.g., Spirogyra (Fig. 65), and of Fungi. 
 
 The formation of new cells does not therefore necessarily imply 
 an increase in number ; this is the case only when division into 
 two, four, or many cells occurs ; in the process of rejuvenescence the 
 number is unaltered, and in conjugation it is actually diminished.
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [26 
 
 CHAPTER II. 
 
 THE TISSUES. 
 
 26. The Connexion of the Cells. According to their 
 arrangement in space, the following combinations of cells may be 
 distinguished : 
 
 A. Filaments, where the cells are connected only by their con- 
 tiguous ends, and so form a filament, e.g., many Algae, as Spirogyra 
 (Fig. 65), (Edogonium (Fig. 62), and many hairs. 
 
 B. Surfaces, when the cells form a single layer and are in con- 
 tact in two directions of space (length and breadth), e.g. many Algae 
 and the leaves of many Mosses. 
 
 C. Masses, when the cells are in contact on all sides. 
 
 The tissues commonly consist of cells which have originated from 
 common mother-cells by their repeated division into two, and which 
 have been connected from the first in consequence of the mode of 
 formation of the septa (Fig. 60). In a few special cases tissues are 
 formed otherwise (spurious tissues) ; either cells which have been 
 hitherto isolated become adherent and then continue their growth 
 in common ; or filaments consisting of rows of cells become inter- 
 woven and exhibit a common growth, without however having be- 
 come adherent in every case (Fig. 64 sK). 
 
 The Common Wall of cells combined into a tissue is, in the 
 first instance, usually extremely thin and delicate, and appears 
 under the strongest magnifying 
 power as a simple plate (Fig. 60). 
 As it increases in thickness a 
 middle lamella usually becomes 
 visible (Fig. 66), which divides 
 the wall into two parts, one of 
 which apparently belongs to each 
 of the contiguous cells. This 
 middle lamella is nothing more 
 than a specially differentiated part 
 of the wall which belongs to both 
 of the cells in common. Its chemi- 
 cal composition, which is different 
 to that of the remainder of the 
 wall, permits of its solution (in 
 nitric acid and chlorate of potash), 
 
 FIG. 66.- Transverse section of the 
 cortical cells of Trichomaneg speciosum 
 (x600). Middle lamella (m) ; ti the 
 cell-wall adjoining the lamella; I cell 
 cavity; bordered-pits which meet in 
 adjoining cells ; the pits on each side 
 are divided by the middle lamella.
 
 27] CHAPTER II. THE TISSUES. 89 
 
 so that the individual cells may be separated. When the common 
 wall of similar cells is pitted, the pits on each side accurately 
 meet (Fig. 66 ) ; if, however, certain cells of a tissue undergo a 
 special modification, as in the vessels, the unequal thickening of the 
 membrane may be confined to one side only of the common wall ; 
 in the case of spiral thickening of the cell-wall this is self-evident. 
 
 In certain cases the septa between the cavities of adjacent cells 
 become wholly or partly absorbed, as, for instance, occasionally the 
 thin partition between bordered-pits ; the transverse walls of such 
 cells as combine to form the vessels are wholly absorbed, if they lie 
 at right angles to the long axis of the vessel (Fig. 73 C a V) ; if 
 they lie obliquely, they are broken through in various ways. In a 
 similar manner the transverse septa (and more rarely isolated areas 
 on the longitudinal wall also) of the sieve-tubes ( 28, Fig. 74 B) 
 are perforated by closely-set and very fine open pits, and are then 
 known as sieve-plates. Hence a vessel is a syncyte (see p. 64). 
 
 27. Intercellular Spaces are lacunae between the cells of 
 a tissue. They may be formed in two ways : either by a splitting 
 of the common wall of adjacent cells, that is schizogenously ; or by 
 the disorganization of certain cells, that is lysigenously. They 
 contain either air or certain peculiar substances. 
 
 The intercellular spaces which contain air are usually formed 
 schizogenously. They occur almost exclusively in parenchymatous 
 tissue, at the angles of junction of a number of cells (Fig. 67 z)> 
 Sometimes these 
 spaces then called 
 air-chambers at- 
 tain a considerable 
 size, so that whole 
 masses of tissue are 
 separated from each 
 other, as in the 
 petioles of the Water 
 Lily and of other 
 aquatic plants. 
 
 The large cavities 
 
 in the Stems and FlG- 6 7.-Intercellular spaces (*) between cells from the 
 
 leaves of Rushes and stem of Zea Mais ( x ;60) ; gto the common wall. (After 
 
 of other allied plants, 
 are produced lysigenously by the drying-up and [rupture of con- 
 siderable masses of cells : this is true also with reference to the
 
 90 PART II. ANATOMY AND HISTOLOGY. [ 28 
 
 cavities extending through whole internodes of many herbaceous 
 stems (Grasses, Umbelliferae, Equisetacese), and those occiirring in 
 leaves (Leek). 
 
 The intercellular spaces which contain certain peculiar sub- 
 stances are treated of under the head of Glandular Tissue in 28. 
 
 28. Forms of Tissue. According to the form and arrange- 
 ment of the constituent cells, the thickness and chemical composi- 
 tion of their walls, the nature of their contents, etc., it is possible 
 to classify the forms of tissue in various ways. 
 
 Taking, first, the capacity for growth and cell-formation, 
 embryonic tissue or meristem is distinguishable from adult or 
 permanent tissue. The former consists of cells (e.g. in the growing- 
 point of a cellular plant) which grow and divide: whereas the 
 latter consists of cells which have ceased to grow and divide, 
 having attained their definitive form 
 and size ; and whilst meristem consists 
 entirely of true cells, permanent tissue 
 may consist wholly or in part of cells 
 which have lost their protoplasm. 
 
 Taking, next, the form of the indi- 
 vidual cells and the mode of combination 
 into a tissue which their form determines, 
 two forms of tissue termed parenchyma 
 and proscnchyma are distinguished. In 
 parenchymatous tissue there_Js^ no great 
 difference in the three axesjrf_jjie_sojne- 
 what cubical cells, and the_ ells_are in 
 contact by broad flat surfaces (Figs. 60, 
 68). In prosenchymatous tissue, on the other hand (Figs. 68, 70/), 
 the cells are much longer than they are broad, having pointed 
 ends which overlap and dovetail in between those of other cells of 
 tli<! tissue. 
 
 By combining the distinctive characters which have just been 
 mentioned, with others which relate to the nature of the cell- 
 contents and to the constitution of the cell-wall and are intimately 
 connected with the functions of the cells, the following forms of 
 permanent tissue may be distinguished : 
 
 1. Thin-walled parenchymatous tissue consists of cells having 
 cell-walls of cellulose. So long as the cells are functionally active 
 they contain protoplasm ; they may eventually lose their cell-con- 
 tents and become dry and filled with air (e.g. pith of Elder). This 
 
 ii 
 
 FIG. 63. Prosenchymatous 
 tissue, longitudinal section (dia- 
 gram, magnified), the pointed 
 ends of the elongated cells fit in 
 between each other.
 
 28] 
 
 CHAPTER II. THE TISSUES. 
 
 ill 
 
 form of tissue is the main seat of the protoplasm in the plant, and 
 it is in the cells of this tissue that the chemical processes con- 
 nected with nutrition are more particularly carried on. It is 
 especially well-developed in fleshy and succulent parts (e.g. leaves, 
 fruits, tubers, tuberous roots, etc.). 
 
 2. Thick-walled parenchymatous tissue. Of this there are two 
 principal forms: (1) that in which the cell-walls are lignified ; 
 (2) that in which they are not lignified but consist of cellulose. 
 The former occurs as wood-parcnchyma_in. the secondary woodj 
 and in the secondary medullary rays, of Dicotyledons. The latter 
 commonly occurs as collenchyma just below the surface of her- 
 baceous parts such as mid-ribs of leaves, petioles, young shoots, 
 etc., and serves to give them firmness (Fig. 69). Both forms of 
 this tissue retain their protoplasm 
 
 for a long time after complete dif- 
 ferentiation. The middle lamella 
 (p. 88) of thick-walled paren- 
 chyma with cellulose walls, con- 
 sists of a peculiarly dense form of 
 cellulose. 
 
 3. Cuticularised tissue consists 
 of cells of various form, generally 
 pareuchyinatous 1 the. walls of which 
 have undergone more or less com- 
 plete cuticularisation (see p. 76). 
 The most conspicuous examples of 
 this tissue are the .epidermis, and 
 the cork ^ in_the former, the cuti- 
 cularisation is confined almost ex- 
 clusively to the external wall of 
 the cell (Fig. 69 e), and the_cells re^ 
 tain their cytoplasm ; in the latter, 
 the, cuticularisation extends over 
 the whole cell-wall, and the cyto- 
 plasm is soon lost. In both cases 
 the cuticularisation is most marked 
 
 in the external layers of the cell- wall. In cork-cells there is a 
 certain amount of lignification of the walls as well. The middle 
 lamella (p. 88) of cuticularised tissue consists entirely of cutin 
 (or suberin). Whilst cuticularisation generally occurs in the walls 
 oTTree cells (e.g. spores), or of the superficial cells (epidermis) 
 
 FIG. 69. Transverso section nf part 
 of leaf-ttalk of a Begonia (x 650: after 
 Sachs), e epidermis, the cellsof which 
 have thickened and cuticularised ex- 
 ternal walls ; c cuticle. B Collenchy- 
 matous tissue, with walls thickened at 
 tbe angles v ; the walls of the epidermal 
 cells are similarly thickened where they 
 abut on the collenchyma ; cl individual 
 collenchymatous cells ; cM chloro- 
 plastids ; p large thin-walled parenchy- 
 matous cell.
 
 92 PART II. ANATOMY AND HISTOLOGY. [ 28 
 
 of a multicellular body, it occurs sometimes in internal tissue 
 (e.g. endodermis). 
 
 4. Sdcrenchymatous tissue, or sclerenchyma, consists .typically 
 of_prosenchymatous cells which lose their protoplasm relatively 
 early, and then contain only water or air, and are distinguished as 
 fibres ; but in., some cases., they retain their protoplasm, and are 
 then distinguished as fibrous cells. The cell-walls are thickened, 
 sometimes so much so as almost to obliterate the cavity or 
 lumen (Fig. 70) ; they are frequently lignified throughout, or only 
 partially, or not at all (e.g. bast-fibres of Flax and Hemp) ; they 
 commonly have simple round pits, or oblique and narrow bordered 
 pits (Fig. 72). 
 
 Fio. 70. Longitudinal section of the cortex of 
 the Oak. showing 8 short sclerotic cells : / fibrous 
 sclerenchytna ; p parenchymatous cells. ( x 300.) 
 
 Fio. 71. Isolated sclerotic 
 cell from the leaf of Exostemma 
 (Rubiacete). (x 300.) 
 
 Sclerenchymatous tissue usually occurs in masses so as to give 
 firmness and rigidity to the various parts in which it is present ; 
 it constitutes, together with the collenchyma, the mechanically 
 supporting-tissue or stereom of the plant. 
 
 Isolated sclerotic cells (without protoplasm) of irregular form 
 (Fig. 71) are of frequent occurrence (e.g. in the flesh of Pears, in 
 coriaceous leaves as those of Camellia, Hakea, Olea, etc.) : when 
 these cells project freely into air-cavities (e.g. Nymphseacese, 
 Aroids, Limnanthemum, Rhizophora) they are sometimes called 
 internal hairs ; short, straight cells occur in the secondary bast 
 and cortex of many trees (Fig. 70).
 
 28] 
 
 CHAPTER II. THE TISSUES. 
 
 93 
 
 5. Tracheal tissue consists of cells which early lose their proto- 
 plasm ; their cell-walls are generally, but not always, lignified, and 
 are either pitted with simple or bordered pits, or have annular, 
 spiral, or reticulate, etc., thickenings (see p. 74) ; when fully 
 developed the tissuejjontains only either air or water. 
 
 The following varieties of this tissue may be distinguished : 
 
 FIG. 72. Sclerenchymatous tissue. A The end of a bast-fibre, with strongly thickened 
 pitted walls (longitudinal section x 300). S Wood-fibres from the root of the Cucumber 
 ( x 300), surface view and section. C Fibres from the stem of Helianthus tu^crouus ( x 300). 
 
 a. The tr 'ache ids, which are closed, generally prosenchymatpus 
 cells (Fig. 73 J5), occur characteristically in the wood of certain 
 plants (e.g. most Pteridophyta, Coniferse) and are then completely 
 liguified ; but they also occur elsewhere, as in the tegumentary 
 tissuB (velamen) of the aerial roots of certain Orchids, where 
 they are partially lignified ; in certain cells of the anther-wall ;
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [28 
 
 and in the leaves and cortical tissue of the stem of Sphagnum 
 (gametophyte) where they are not lignified at all (Fig. 73 A). 
 
 b. The tracheae, are true vessels, that is, syncytes (p. 64), the 
 contiguous cell-cavities having been rendered continuous by the 
 complete or partial absorption of the intervening walls (Fig. 73 
 C a) ; the former is more frequently the case when the interven- 
 ing walls are horizontal, the latter when they are oblique ; they 
 occur in the wood of many Phanerogams. 
 
 Tracheal tissue is the characteristic constituent of the vascular 
 tissue-system to be described subsequently ; it is especially adapted 
 for the conduction of water. It should be noted that in all forms 
 
 of lignified tissues, whether 
 tracheal, sclerenchymatous, or 
 parenchymatous, the middle 
 lamella is the most highly lig- 
 mfied part (p. 88) ; it dissolves 
 readily in a mixture of nitric 
 acid and chlorate of potash, thus 
 leading to the isolation of the 
 constituent cells. 
 
 When a vessel with a pitted 
 wall abuts upon cells containing 
 living protoplasm, it not un- 
 frequently happens that the 
 thin pit-membranes begin to 
 bulge, in consequence of the 
 pressure upon them of the con^" 
 tents of the living cells, into the 
 cavity of the tracheal cell, and 
 actually grow. Cell - division 
 may take place in these in- 
 growths, so that a mass of cel- 
 lular tissue is formed in the 
 cavity of the vessel. These in- 
 growths are termed tylosesj they are constantly to be found in 
 some kinds of wood (e.gr.'Robinia), and occasionally in many others. 
 6. Sieve-Tissue.. This tissue consists mainly of long articulated 
 tubes, the contents of the contiguous segments communicating by 
 means of the sieve-plates, which usually lie on the transverse 
 walls, either singly, when the transverse wall is horizontal, as 
 generally in herbaceous plants (Fig. 74), or several together, when 
 
 FIG. 73. Tracheal tissue. A Tracheid 
 from the leaf of Sphagnum ; j The holes in 
 the external wall. B Scalariform tracheid 
 from the leaf of Polypodium vulgare. C 
 Part of a trachea with bordered pits from 
 the stem of Helianthus; it has been cut 
 into at the upper end ; a and b the articula- 
 tions, where the absorbed transverse walls 
 existed.
 
 28] 
 
 CHAPTER II. THE TISSUES. 
 
 95 
 
 the transverse wall is oblique, as generally in woody plants 
 (Fig. 75). Each sieve-plate is a thin area of the wall which is 
 perforated by a number of closely placed open pits. The sieve- 
 plate is covered on both surfaces and the pits are lined by a 
 peculiar substance termed callus (Figs. 74 (7 c; 75 BCc), which 
 at least in. many plants periodically closes the pits in autumn. 
 Sieve-plates may also occur on the lateral walls. The rest of the 
 wall of the sieve-tube is rather thin : it is never lignified, but 
 consists of cellulose. The long straight sieve-tubes are connected 
 in their course by short transverse branches, so that they form one 
 continuous system of tubes. 
 
 FIG. 74. Sieve-tissue of an herbaceous Angiosperm (Cucurbtta Pepo). A Transverse 
 sieve-plate in surface- view; B in longitudinal section; C sieve-plate closed by a plate of 
 callus c; c* sieve-plate on lateral wall, closed by callus; D contents of tube left after 
 solution of the wall by sulphuric acid ; s companion-cells ; pr lining layer of protoplasm ; 
 u mucilaginous contents. (x540: alter Strasbnrger.) 
 
 In their normal active condition each segment of the sieve-tube 
 is lined by a layer of protoplasm (Fig. 74 B pr), in which starch- 
 granules are sometimes to te found, enclosing some mucilaginous 
 substance ; there is, however, no nucleus present ; the reaction of 
 the contents is alkaline. 
 
 With the sieve-tubes of Angiosperms are closely associated cells, 
 termed companion-cells (Fig. 74 s), which are filled_with granular 
 proteid contents and have well-marked nuclei; each companion-
 
 96 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 28 
 
 cell is of common origin with the corresponding segment of a 
 sieve-tube, both being derived from one mother-cell. Companion- 
 cells are not developed in G-ymnosperms and Pteridopbyta^.. 
 '"The sieve-tissue, like the tracheal tissue, is a characteristic 
 constituent of the vascular tissue-system : it is very frequently 
 associated with tracheal tissue so as to form one vascular bundle, 
 but it may occur in independent bundles (e.g. in the pith of the 
 stem of some Solanacese, Campanulacese, and Compositse, and in the 
 cortex of the stem of Cucurbitacese, and some other plants), and 
 generally in roots. Tissue of this kind has been found to be pre- 
 sent in plants so low in the scale as some of the larger Algae 
 (Laminariacese). 
 
 7. Glandular Tissue. Under this general term are included 
 
 cells which 
 produce more 
 or less peculiar 
 subs t ances 
 termed secreta, 
 by a process 
 known as se- 
 cretion. The 
 cells may be 
 isolate^ or 
 they may be 
 collected into 
 groups;; tile 
 secretum may 
 be a c c u m u- 
 lated in the 
 cavity of the 
 secreting cell, 
 or it may be 
 thrown out at 
 
 the surface (excreted) ; the process of secretion may or may not 
 involve the destruction of the secreting cell. 
 The following are the chief varieties of glandular tissue : 
 (a) Solid multicdlular glands. Good examples of these are the 
 chalk-glands of the leaves of many Saxifragacese and Crassulacese, 
 :md the nectaries present in ilowers (floral nectaries) or in other 
 parts (extra-floral nectaries) of various plants. In both these 
 forms of gland the secretum, chalk in the one case and sugar in 
 
 C. 
 
 Fio. 76. Sieve-tissue of woody plants. Portions of sieve-tubes 
 from the secondary bast of the Vine. A Entire transverse wall and 
 adjacent parts in longitudinal section (x300) ; pi the sieve-plates; 
 fc the thicker portions of the cell- wall; h the protoplasmic lining; 
 si mucilaginous substance ; st starch-granules. B Part of a trans- 
 verse wall seen from the surface. C The same in section ( x 700) : 
 P pits ; c callus; pi the four sieve-plates.
 
 28] 
 
 CHAPTER II. THE TISSUES. 
 
 97 
 
 the other, is in solution, and is excreted at the surface. In the 
 chalk-gland the secretum escapes through a special channel, a 
 ivater-stomq_ (p. 108). In the nectary the secretum is simply 
 poured out on the surface of the gland. 
 
 (6) Hollow multicellular glands are intercellular spaces sur- 
 rounded by secreting cells, and are, in some cases, of schizogenous, 
 in others of lysigenous, origin (see p. 89). The secretum may be 
 mucilage, or gum, or a mixture of gum and resin (gum- resin), or 
 
 Fia. 76. Lysigeuous oil-gland below 
 the upper surface of the leaf of Dicta in- 
 nut Fraxinella ( x 320) : B at an early 
 stage ; C mature ; c mother-cells of the 
 gland before their absorption ; o a large 
 drop of ethereal oil. (After Sachs.) 
 
 Fia. 77. Schizogenoua resin-duct in the 
 young stem of the Ivy (Hedera Helix), transverse 
 section ( x 800) : A an early, E a later, stage ; 
 g the resin-ducts ; c the cambium ; icb the soft 
 bast; b bast-fibres: rp cortical parenchyma. 
 (After Sachs.) 
 
 ethereal oil, or a mixture of ethereal oil and resin (balsam). The 
 cavities are either rounded closed spaces, or are elongated canals, 
 extending for some distance through the tissue ; the former are 
 usually of lysigenous, the latter of schizogenous, origin. 
 
 As examples of lysiyenous hollow glands, may be mentioned the 
 cavities filled with gum, which occur in the tissue of Cherry-trees ; 
 the oil-glands of the Orange and Lemon, and in the leaves of the
 
 98 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 28 
 
 Rue, the Myrtle, and Hypericum, where they can be discerned 
 with the naked eye as transparent dots. The development of these 
 oil-glands begins with the division of one or two cells of the young 
 leaf, a group of cells being formed, in the cytoplasm of which oil- 
 drops make their appearance. The walls between the cells (Tig. 
 76 B. C} undergo absorption, so that a cavity is formed which is 
 bounded by the closely-packed adjacent cells, and contains a large 
 oil-drop formed by the fusion of the oil-drops of the original cells. 
 
 The most striking examples ofjschisqgenous hollow glands are 
 the various kinds of ducts, such as the resin-ducts which permeate 
 the tissues of most Coniferae and Anacardiacese ; the gum- or 
 mucilage-ducts of the Marattiacese, some species of Lycopodium, 
 Cycads, Canna, Opuntia, etc. ; the gum-resin-ducts of the Umbelli- 
 ferse, and of some Araliacese (e.g. Ivy, Fig. 77) and Compositee 
 
 ODQQC 
 
 PIG. 78. Sac containing a crystal, 
 from the leaf of Rhamnus Frangula : e 
 upper epjdermis; p palisade-tissue: c 
 chloroplastids ; fc the crystal. ( x 200 ) 
 
 FIG. 79. Part of section of the petiole 
 of the Camphor-tree ( Cinnamomum 
 Camphora), showing a resin-sac 7i. 
 
 (e.g. the Sunflower). Here the cells of the group formed by a series 
 of divisions (Fig. 77 A E), separate from each other so as to leave 
 a passage, of which they form the wall, and into which they pour 
 their secreta. 
 
 (c) Sacs, each consisting of a single cell. To this category 
 belong the cells which contain crystals, as those in the tissues of 
 many Monocotyledons (Fig. 58), in the bast of many dicotyledonous 
 trees, in leaves (Fig. 78) and petioles (Fig. 57) : the cells which con- 
 tain mucilage, as in the parenchyma of the Lime and the_Mallo\v, 
 in the bark of Elms and Firs, in the pseudo-bulbs of Orchids, etc. : 
 the cells which contain tannin, as in many Ferns and other plants : 
 the cells which contain oil-resin, as in the Lauracese (Camphor, Fig. 
 79), the Zingiberacese, many Conifers (wood of Silver Fir), etc. 
 
 These cells are frequently arranged in longitudinal rows : for
 
 28] 
 
 CHAPTER II. THE TISSUES. 
 
 instance, the tannin-sacs of the Hop ; the sacs containing raphides- 
 and mucilage in Tradescantia and many other Monocotyledons - 
 the gum-resin sacs (" vesicular vessels ") of the bulb-scales of the 
 Onion ; the sacs containing crystals of calcium oxalate in the 
 cortex of many woody Dicotyledons ; the sacs, containing milky 
 juice or latex (com- 
 monly gum -resin) in 
 the Sycamore, the Con- 
 volvulaceae, and the 
 Sapotacese (especially 
 in Isonandra Gutta, 
 the latex of which con- 
 stitutes gutta-percha). 
 
 (d) Laticiferous ves- 
 sels. These structures 
 resemble the sacs con- 
 taining milky juice 
 (latex) in the nature of 
 their contents, and 
 differ from them struc- 
 turally only in that the 
 walls between adjacent 
 cells have become ab- 
 sorbed, thus forming 
 syncytes (p. 64). 
 
 In the simplest case, 
 the laticiferous vessel 
 merely consists of a 
 longitudinal row of 
 cells whose transverse 
 septa have become ab- 
 sorbed, thus forming a 
 syncyte of the nature 
 of a vessel. When two 
 such vessels are in con- 
 
 , , 1 , I-, ,, ,, FIG. 80. Laticiferous vessels from the cortex of 
 
 terally, tfi the root of Scorzonera hi epan i ca , tangential section : A 
 
 walls are absorbed at slightly magnified; B & small portion highly magni- 
 
 the point of junction, fled ' (After *"*> 
 
 and in this way a continuous system of laticiferous vessels is formed. 
 This occurs in the greater Celandine (Chelidonium majus}, and in 
 the Banana (Musa) where, however, the latex is not milky.
 
 100 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [28 
 
 More commonly, as in the Cichoriese (e.g. Dandelion, Scorzonera), 
 the Campanulacese, and in most Papaveracese (e.g. Poppy), the 
 cell-fusions take place in all directions, producing a dense network 
 (Fig. 80). 
 
 Structures apparently of the nature of laticiferous vessels occur 
 in certain Basidiomycetous Fungi (e.g. Lactarius). 
 
 (e) Laticiferous ccenocytes, commonly known as ''laticiferous 
 cells," occur in some Euphorbiacese (the Spurges), in the Urti- 
 cacese (Nettles), Apocynaceae, and Asclepiadacese. As already ex- 
 plained (p. 64), these " cells " are really 
 coenocytes ; they are visible in the early 
 stages of the development of the embryo, 
 and they grow and branch in the tissue 
 as if they were independent organisms 
 (Fig. 81). As they extend from one end 
 of the plant to the other, they attain a 
 very considerable length in many cases. 
 Their walls are frequently thickened 
 (e.g. Euphorbia), but, like those of the 
 laticiferous vessels, they are not lignified. 
 They contain protoplasm with many 
 nuclei which multiply by division, and 
 in the older parts latex is abundantly 
 present. The latex of the Euphorbiacese 
 contains curious rod-like or dumb-bell- 
 shaped starch-grains. 
 
 (/) Epidermal Glands. Whilst all 
 the preceding forms of glandular tissue 
 are developed in the internal tissues of 
 plants, somewhat similar glandular 
 structures are developed from the super- 
 ficial layer (epidermis), most commonly 
 in the form of hairs (p. 46), either 
 unicellular or multicellular. When the 
 multicellular hair consists of a single row of cells, the secretion is 
 generally confined either to a large terminal cell, or to several of 
 the distal cells ; in any case the secretion begins with the terminal 
 cell, and extends backwards to other cells towards the base. The 
 gland, though epidermal in origin, does not, however, always pro- 
 ject from the surface, but may be more or less sunk in the internal 
 tissue (e.g. glands in the leaf of the Psoralea hirta}. 
 
 FIG. 81. A portion of a lati- 
 ciferous coenocyte dissected out 
 of the leaf of a Euphorbia. ( x 
 120: after Haberlandt.)
 
 29] CHAPTER II. THE TISSUES. 101 
 
 The secretum (which, may consist of mucilage, or gum-resin, or 
 ethereal oil, balsam, etc.) is accumulated either in the cavity of the 
 secreting cells (e.g, mucilaginous hairs at the 
 growing-point of Liverwort gametophytes and of 
 Fern-sporophytes), or between the external cuticle 
 and the deeper layers of the cuticularised cell- 
 wall (e.g. mucilaginous hairs [colleters] on the 
 buds of many Phanerogams, resinous hairs gener- 
 ally ; Fig. 82). 
 
 29. General Morphology of the Tissue- 
 Systems. When a form of tissue constitutes a 
 complex which extends continuously throughout FIG. 82. Gian- 
 the body of a plant, or over considerable areas, dular hair from the 
 
 J baseofaramentum 
 
 it is spoken of as a tissue-system : for instance, O f A*pidium mix 
 a laticiferous system; a resin-duct system; a mas ( X2 <x>):, "* 
 
 , . , ,. secretum, lying be- 
 
 sieve-tube system; a mechanical tissue-system tween the outer and 
 (stereom) including collenchyma and scleren- inner layers of the 
 chyma ; a glandular tissue-system ; a tegumen- 
 tary tissue-system : or a more elaborate system may be produced 
 by the combination of two or more systems: for instance, the 
 sieve-tube system and the tracheal system taken together con- 
 stitute the vascular tissue-system. 
 
 These tissue-systems are, however, characterised rather by their 
 function, that is physiologically, than by their development, that 
 is morphologically. From the latter point of view the following 
 primary tissue-systems are distinguished: (1) The Tegumentary 
 Tissue; (2) The Ground-Tissue; (3) The Stele. The study of 
 these tissues will be begun by the consideration of the structure 
 of the growing-point in stems and roots. 
 
 As already pointed out (p. 8), the growing-point consists, in 
 the higher plants, of embryonic tissue, the cells of which may be 
 of approximately uniform size, constituting a small-celled primary 
 meristeyt ; or there may be at the organic apex a cell conspicuously 
 larger than the rest, the apical cell ; or a group of several larger 
 initial cells. 
 
 a. Grouping-points consisting of small-celled meristem are, 
 with rare exceptions, to be found in the roots and stems of 
 Phanerogams, as also in the root of Lycopodium and Isoetes 
 among the Pteridophyta. Although the cells are all embryonic, 
 they nevertheless present such a degree of differentiation as to 
 make it possible to distinguish the three primary tissue-systems.
 
 102 PART II. ANATOMY AND HISTOLOGY. [ 29 
 
 In the stem, a growing-point of this kind usually presents the 
 appearance shown in Fig. 83. It consists, in the first place, of a 
 well-defined superficial layer which, on being traced backwards, 
 is seen to be continuous with the primary tegumentary tissue 
 (epidermis) of the older parts ; this layer is, in fact, the embryonic 
 epidermis or dermatogen (d} ; it is quite distinct, morphologically, 
 from the subjacent cells, and is characterized by the fact that its 
 cells only undergo division in planes perpendicular to the surface 
 (anticlinal), and not in any plane parallel to the surface (periclinal). 
 Consequently, whilst the dermatogen increases in area, so as to 
 keep pace with the growing tissues within, it does not become 
 many-layered, but remains a single layer of cells. 
 
 In the middle of the growing-point is a solid mass of somewhat 
 
 elongated cells (pp) con- 
 stituting the plerome, and 
 terminating in one or 
 more initial cells ; on trac- 
 ing this backwards into 
 the older part of the stem 
 it is found to give rise to 
 a single axial cylinder of 
 tissue, the stele, in which 
 the vascular tissue is de- 
 veloped. Such a stem is 
 /* P said to be monostelic : 
 
 Fxo. 83.-Medianlongitudinal section of the grow- 
 ing-point of the stem .of Hippuris vvlgaris. The point of this structure 
 growing-point census of a small-celled meristem & ^^ without excep . 
 differentiated into dermatogen a, plerome p p, and ^ " 
 periblem consisting of the five layers of cells between tion, monostelic. 
 the plerome and the dermatogen ; I rudiment of a Between the dermato- 
 
 leaf. (After de Bary : x225.) 
 
 gen externally and the 
 
 plerome internally, is a layer less frequently several layers of 
 cells constituting the periblem ; below the apex the cells undergo 
 divisions both anticlinally and periclinally, so that both the area 
 and the number of the layers are increased. On tracing the peri- 
 blem backwards into the older parts, it is found to be continuous 
 with the ground-tissue which, in monostelic members, is known as 
 the primary cortex. 
 
 The growing-point of the root (Fig. 84) of one of these plants 
 essentially resembles that of the stem in its structure ; the small- 
 celled meristem is differentiated, at least primarily, into dermatogen,
 
 29] 
 
 CHAPTER II. THE TISSUES. 
 
 103 
 
 plerome, and periblein. But there is this distinctive peculiarity 
 about the dermatogen of the root, that its cells undergo division, 
 not anticlinally only, as in the stem, but periclinally also, so that 
 the epidermis of the root is many-layered (except in Hydrocharis 
 
 FIG. 81. Median longitudinal section through the growing-point of the root of Hbrdettm 
 vulgare (Barley) : r root- cap ; fc initial cells of the dermatogen of the many-layered epider- 
 mis; d-<m cortex; d epiblem with mucilaginous external layer of cell-wall c ; t cortical 
 tissue with intercellular spaces; en endodermis ; the whole periblem (pr) is derived from 
 the single layer of two initial cells at the apex ; pi plerome ;.a row of cells which give rise 
 to a large central wood-vessel. (After Strasburger : x 180.) 
 
 and Lemna, where it remains a single layer). This many-layered 
 epidermis, however, is gradually exfoliated as the parts grow
 
 104 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 29 
 
 older, and persists only at the apex constituting the root-cap 
 (see p. 44). The only other important fact to be noticed at present 
 is that the root, as a rule, is monostelic. 
 
 b. Growing-points iv ith a single apical cell are to be found in 
 stems and roots of most Pteridophyta : for instance, in the stems 
 and roots of all Leptosporangiate Filicinse, and in those of. 
 Ophioglossacese) ; in those of the Equisetinse ; and in those of 
 some species of Selaginella (S. Martensii and Kraussiana). The 
 shape of the apical cell is generally a three-sided pyramid with 
 a spherical base, the base being at the surface of the member 
 and the apex being directed inwards ; less commonly the apical 
 cell has only two sides or flanks and is then somewhat lenticular 
 in shape (e.g. that of the rhizome of Pteris aquilina, stem of 
 Salviniacese, and frequently in the above species of Selaginella). 
 In growing-points of this structure it is seen (Fig. 85) that the 
 
 embryonic tissue- 
 systems are not 
 continuous as in 
 the Phanerogams, 
 but are inter- 
 rupted at the 
 apex by the large 
 apical cell. The 
 apical cell is, in 
 fact, the initial 
 cell for all the 
 three primary 
 tissue- systems. 
 
 The apical cell undergoes division by walls formed parallel to 
 each of its (two or three) flanks successively, the segments thus 
 formed growing and dividing to form the tissues of the stem or 
 root. In the root the apical cell also undergoes divisions parallel 
 to its curved base. After the cutting off of a segment the apical 
 cell grows to its previous size, so that the repeated segmentation 
 does not diminish the bulk of the apical cell. 
 
 The segments cut off parallel to the base of the apical cell of 
 the root (Fig. 8G k) constitute the derrnatogen. These dermatogen- 
 segments grow and divide both anticlinally and periclinally to 
 form the root-cap ; but this many-layered epidermis only persists 
 at the growing-point, since it becomes entirely exfoliated as the 
 parts grow older. 
 
 FIG. 86. Diagrams illustrating the division of the apical 
 cell of the stem of Equisetum : A longitudinal section ; B sur- 
 face view. The numbers 1-7 indicate the successive segmental 
 walls; the fainter lines indicate the walls of subsequent divi- 
 sions of the segments.
 
 29] 
 
 CHAPTER II. THE TISSUES. 
 
 105 
 
 c. Groidng-points with a group of common initial cells occur in 
 certain Pteridophyta (e.g. in the stems and roots of Marattiacese, 
 of Osmunda sometimes ; stems of Lycopodium, Isoetes, some 
 Selaginellas). In these cases, there is a grcrap of frequently fovir 
 cells which are the common initials of the tissue-systems. The 
 general relations of the tissue-systems are here essentially the 
 
 PIG. 86.-Median longitudinal section through the apex of the root of Pter'.t cretica ; t 
 apical cell; fc initial segment of dermatogen; fc, outermost layer of root-cap ; p wall mark- 
 ing limit between the plerome P and the periblem Pb ; c wall marking the inner limit of 
 the outer cortex. (After Strasburcrer : x 2 10.) 
 
 same as in those forms in which the growing-point has a single 
 apical cell. 
 
 The Growing-jjoint in the lower plants. In the gametophyte of the Bryo- 
 phyta, the growing-point of the stem or of the thallus has either a single 
 apical cell (all Mosses ; Jungermanniacese) or a group of apical cells
 
 106 PART II. ANATOMY AND HISTOLOGY. [ 30 
 
 (Marchantiacese, Anthocerotacese) : the growing-point of the sporophyte of 
 the Liverworts has a group of four initial cells, whilst that of the Mosses 
 has a single two-sided apical cell. 
 
 In the higher Algae, the shoot (or thallus) also grows by means of a 
 single apical cell : in the more filamentous forms (e.g. some Floridese, 
 Characeee) the apical cell is hemispherical in form, and segments are only 
 cut off by transverse walls parallel to the flat base; in other more bulky 
 forms of Floridese there is a group of initial cells ; in nearly all these forms 
 a more or less distinct differentiation of a central medullary tissue and of a 
 cortical tissue takes place : in the Fucacese there is a single apical cell in 
 the growing-point, with either three or four flanks, along which the seg- 
 ments are cutoff; when the apical cell is four-sided, segments are also cut 
 off internally along the truncate base of the cell; the tissues soon show 
 differentiation into a cortical and a medullary region. 
 
 In unseptate or imperfectly septate plants, having apical growth (e.g. 
 Siphonaceous Algse, CJadophora, etc.), the growing-point (like the rest of 
 the body) is not cellular, but consists merely of embryonic protoplasm. 
 
 30. The Primary Tegumentary Tissue. The primary 
 tegumentary tissue may be generally described as the external 
 layer of cells covering the body of the plant, and is commonly 
 termed the epidermis. 
 
 Morphology. A^rwe epidermis only exists in_tho^ej)lants, and in 
 those parts of them, where there is a definite dermatogen ; and the 
 word epidermis is, strictly speaking, only applicable to such a 
 tegumentary tissue. It is, however, convenient to apply this term 
 generally to the primary tegumentary tissue of the shoot, and to 
 apply the term epiblem to the primary tegumentary tissue of the 
 root, apart from the root-cap. 
 
 Structure. In the great majority of cases the primary tegumen- 
 tary tissue consists of a single layer of cells; but to this rule 
 there are several important exceptions. Thus, the epidermis of the 
 foliage-leaves of certain plants (e.g. Ficus, Peperomia, Begonia) 
 consists of two or more layers of cells. Similarly, the root-cap to 
 be found in nearly all roots is a many-layered epidermis. Again, 
 the aerial root of certain epiphytic plants (Orchids, Aroids) has 
 a many-layered epiblem, known as the velamen, consisting of 
 empty tracheidal cells with reticulated and perforated walls (see 
 p. 93). 
 
 The cells of the epidermis of the shoot of land-plants, are 
 characterised by the thickening and cuticularisation of their cell- 
 walls (see p. 76). The external wall is usually much more thickened 
 than the other walls ; its outermost layer, termed the cuticle, is
 
 30] 
 
 CHAPTER II. THE TISSUES. 
 
 107 
 
 always cuticularised, and is clearly defined from the inner layers, 
 which may be also more or less cuticularised. The cuticle may be 
 stripped off as a membrane, over a considerable area ; it frequently 
 forms surface-projections. Particles of wax are included in the 
 cuticle of many plants, and serve to prevent the surface from being 
 wetted by water. Thisjwax often appears on the surface in the 
 form of small granules, rods, or flakes, and this forms the bloom, 
 which is easily wiped off: it some- 
 times attains a considerable bulk, as 
 in the fruits of Myrica cerifcra and 
 the trunks of some Palms (Ccratoy- 
 lon andicola and Klopstockia ceri- 
 fcra}. The epidermal cells are some- 
 times sclerotic, as in prickles, thorns, 
 and leaf -spines. Chloroplastids are 
 not usually present in the epidermal 
 cells of land-plants : they are, how- 
 ever, to be found in the epidei-mal 
 cells of most Terns, of Selaginella, 
 and of some Phanerogams, and 
 generally in those of aquatics. 
 
 The form of the epidermal cells, as 
 seen in surface view, presents con- 
 siderable variety. Generally speak- 
 ing, the cells of an elongated member 
 are themselves elongated in the 
 same direction as the member ; 
 whereas, in broad, flattened mem- 
 bers, there is less difference between 
 the diameters of the cells : in either case the side-walls of the 
 cells very frequently have an undulating outline, so that adjoining 
 cells fit closely together forming a continuous membrane, the con- 
 tinuity of which is, however, interrupted in certain cases by well- 
 defined apertures, termed stomata, which permit communication 
 between the intercellular spaces of the internal tissues and the 
 external air. 
 
 T^& Stoinata^YQ confined exclusively to the sporophyte-genera- 
 tion, and make their first appearance in the Moss-sporogonium. 
 Each stoma is an aperture_ bounded by two (sometimes only one, 
 as in the Mosses) specialised epidermal cells, termed guard-cells, 
 which always contain chloroplastids. The aperture of the stoma 
 
 FIG. 87. Part of a transverse sec- 
 tion of the air-root of an Orchid : v 
 many-layered epiblem, or velamen ; 
 c cortex; e exodermis. (Magnified; 
 after Unger.)
 
 108 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [30 
 
 leads into the air-cavity (Fig. 88), a large intercellular space 
 between the epidermis and the subjacent tissue, which communi- 
 cates with other more internal intercellular spaces. The_stoma 
 originates thus : a young epidermal cell is divided 
 
 a septum 
 
 r 
 
 into two halves, each of which becomes a guard-cell; the septum 
 
 then gradually splits into 
 two, and thus the aperture 
 between the guard-cells is 
 formed ; when the septum 
 does not quite reach across 
 the mother-cell, the aper- 
 ture is surrounded by a 
 single annular guard-cell, 
 as in the Mosses. The 
 size of the aperture may 
 be increased or diminished 
 by changes in the bulk of 
 the guard-cells ; the me- 
 chanism and conditions of 
 this process are considered 
 in Part III. 
 
 Stomata are found on 
 almost all sub-aerial parts 
 of the sporophyte of laud- 
 plants from the Mosses 
 upward ; they are especi- 
 ally abundant on leaves 
 (as many as 600 to the 
 square millimetre"), and, in 
 dorsiventral leaves, more 
 
 particularly on the lower (dorsal) surface, but in. floating dorsi- 
 ventral leaves (e.g. Nymphsea) they are confined to the upper 
 surface ; in radial and isobilateral leaves the distribution of the 
 stomata is uniform on all sides ; they are wanting in submerged 
 leaves, and are always absent from roots. 
 
 FIG. 83. Epidermis with Rtonmta, from the 
 lower surface of the leaf of Helle'ioi-tis fixtidus: A 
 in section ; B surface view ( x 300) ; epidermal 
 cells; c cntiele; I thickenings of the external 
 wall; / folds of the lateral walls; s stoma; ss 
 guard-cella ; p aperture; a air-cavity; cl meso- 
 
 Aj>eculiarform_of stoma is found in some plants, known as a icater- 
 stoin*t_(~FiK.7&). In consist^ of two large, almost sphericalTguard-cells 
 
 which cannot alter their form so as to close the aperture. Water-stomata 
 -K'cur on the 1, .fives of some of those plants (e.g. Alchemilla, Crasnla, Flcus, 
 Saxifraira, Colocasia, Papaver, Tropreolum) which excrete water in the 
 form of drops; they are situated over the termination" of the vascular
 
 30] 
 
 CHAPTER II. THE TISSUES. 
 
 109 
 
 bundles on the margins or at the apex of the leaf ; when chalk-glands are 
 pivsunt i"p. !)7), water-stomata are developed in connexion with them. 
 ~Tn some plants (e.g. Grasses) which excrete drops of water, the water 
 
 escapes through fissures in the epidermis of the leaf. 
 
 The epidermis of the submerged shoots of water-plants differs 
 from that of land-plants in that it is not cuticularised, in the 
 absence of stomata, and in that its cells frequently contain chloro- 
 plastids. 
 
 The epiblemof_the subterranean root is commonly known as 
 the piliferous layer be- 
 TTause it is the layer from 
 which the root-hairs (see 
 p. 46), when present, .are 
 developed. Its cell-walls 
 are not cuticularised, but 
 are frequently (especially 
 in the root-hairs) more or 
 less mucilaginous. It is 
 generally of but short du- 
 ration, and to be found 
 only on the younger parts 
 of roots which are the 
 regions of active absorp- 
 tion : on its disappearance 
 the exodermis becomes the 
 superficial layer. 
 
 In aerial roots (Orchids, 
 etc.) where the epiblem persists as a velamen (see Fig. 87, p. 107) 
 of one or several layers of cells, the walls are thickened, cuti- 
 cularised (especially the superficial layer), and somewhat lignified. 
 
 The many-layered root-cap (see p. 103), in^its younger, more 
 internal part, consists of parenchymatous cells, with cell-walls cf 
 cellulose, forming a compact tissue without intercellular spaces. 
 As the cells grow older, and come to be situated more externally, 
 they lose their protoplasmic contents. TEe" disintegration of the 
 root-cap is due, iu some cases, to the mucilaginous degeneration of 
 the middle lamella of the cell-walls ; whilst in other cases, where 
 the cell-walls become cuticularised, the superficial layers of the 
 cap are successively split off and exfoliated by the pressure of the 
 internal growing tissues. 
 
 Hairs (see p. -46), are frequently developed on the primary 
 
 Water-stoma from the margin of the 
 leaf of Tropccolum majus, with surrounding epider- 
 mal cells. (After Strasbureer : x 240.)
 
 110 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [80 
 
 tvmunentary tissue, and are generally formed each as a,u outgrowth 
 of a single superficial cell (Fig. 90; see also Fig. 31, p. 47; and 
 F'ig. 82, p. 101). 
 
 The hairs of the subaerial parts of plants are, like the epider- 
 mal cells, cuticularised. In many cases the protoplasmic contents 
 disappear at an early stage (as in Cotton, the hairs on the outer 
 coat, or testa, of the seed of Grossypium) and are replaced by air. 
 Sometimes the cell-wall contains deposits of lime or of silica. The 
 hairs are frequently glandular (see p. 100). 
 
 FIG. 90. Hairs on a young ovary of 
 Cucurbits (x 100): b glandular hair ; eef 
 early stages of development. 
 
 wl 
 
 FIG. 91. Root- 
 hairs (h) on the 
 primary root (ic) 
 of a seedling of 
 the Buckwheat : 
 he hypocotyl ; c c 
 cotyledons. 
 
 The root-hairs (Fig. 91 ; also see p. 46) are developed each from 
 a single cell of the piliferous layer ; they are not developed in the 
 immediate neighbourhood of the growing-point, but at some little 
 distance behind it. Moreover, as they grow older, the root-hairs 
 die off ; hence they are only to be found on a very limited region of 
 a primary or a secondary root. 
 
 31. The _ Primary Ground-Tissue is constituted, by the 
 tissue which belongs neither to the epidermis, on the one hand, 
 nor to the stele on the other.
 
 31] CHAPTER II. THE TISSUES. Ill 
 
 Morphology. The limits of this tissue vary with the structure of 
 the part concerned. The external limit of the ground-tissue is the 
 layer of cells lying immediately beneath the primary tegumentary 
 tissue. Again, when the member is monostelic, the internal limit 
 of the ground-tissue is the layer termed the endodermis, which 
 abuts upon the central stele ; in this case the ground-tissue consists 
 of several layers of cells bounded externally by the true epidermis (if 
 present), or reaching to the surface, and bounded internally by the 
 stele, when it is spoken of as the cortex of the member of which 
 it forms part. In a polystelic member, the internal limit of the 
 ground-tissue is still the eudodermis, but each individual stele is 
 invested by a distinct endodermis ; here the primary ground- 
 tissue includes not merely the superficial layers (cortex), but also 
 the tissue between and among the steles. 
 
 The following are the regions or layers of the primary ground- 
 tissue which can be distinguished morphologically. 
 
 1. The hypoderjnff, is the external region of the ground-tissue: 
 the external layer of the hypoderma is distinguished as the 
 exodermis. 
 
 2. The general ground-tissue. 
 
 3. The cndodermis, the layer of the ground-tissue which abuts 
 on a stele ; in monostelic members the endodermis is the inner- 
 most layer of the cortex. 
 
 Structure. Speaking generally, the ground-tissue consists 
 mainly of parenchymatous cells which have cellulose walls and 
 retain their protoplasmic cell-contents ; however, supporting- tissue 
 (stereom) is largely differentiated in the ground-tissue, whether as 
 eolUnicliyma or as sclerenchyma. In cylindrical members isteins. 
 roots, etc.) the cells are generally somewhat elongated in the 
 direction of the long axis of the member. 
 
 1. The hypoderma of stems and leaves commonly consists of 
 either collenchymatous or sclerenchymatous stereom (see p. 92) : 
 
 collenchymatous hypoderma is especially characteristic of the 
 stems and leaf-stalks of herbaceous Dicotyledons (see Fig. 69, p. 
 91), but it occurs also among Pteridophyta in the petioles of the 
 Marattiacese : 
 
 sclerenchymatous hypoderma may form a continuous layer of 
 more~^oFn[ess prosencnymatous cells (e.g. stem of some Ferns, 
 Equisetum hiemalc, most Selaginellas, leaf of many Cycads, 
 Conifers, some Orchids, etc.) ; or it may form numerous isolated 
 strands (e.g. stems of Cyperacesee, species of Juncus [Fig.
 
 112 PART II. ANATOMY AND HISTOLOGY. [ 31 
 
 98 C], some Umbelliferae and Papilionacese, many Equisetums ; 
 leaf-blade of Cyperaceae, Typha, Sparganium, many Palms). 
 The spines of leaves (e.g. Holly), also entire spiny leaves or 
 stipules, various emergences, such as the warts of Aloe verrucosa 
 and the prickles of the Rose, and the thorny branches of many 
 plants (e.g. Hawthorn, etc.) owe their hardness mainly to the 
 development of sclerenchymatous hypoderma, the cells of which 
 are generally elongated and fibrous, though they may be short as 
 in Aloe verrucosa and the Rose. 
 
 The hypoderma of the root commonly consists of a single layer 
 of cells, which is then the exodermis ; but in some plants the 
 hypoderma consists of several layers (e.g. the Date, Pandanus, 
 Asparagus, etc.). 
 
 The walls of the exodermal cells generally undergo cuticularisa- 
 tion and frequently become very much thickened, especially on 
 the lateral and external walls, in view of the position which it 
 eventually occupies as the external layer of the root (see p. 109). 
 In some cases it presents a peculiar localised thickening in the 
 form of a band extending round the upper, lower, and lateral 
 walls of the cells, a thickening which is therefore confined just to 
 the surfaces which are in contact with other cells belonging to 
 the same layer, and which appears in a transverse section as a 
 dark dot on the radial walls of the cells. 
 
 In some cases the cells of the exodermis are prosenchymatous 
 and sclerenchymatous (e.g. species of Carex). 
 
 When the exodermis is invested by tegumentary tissue, as in 
 aerial roots of Orchids (Fig. 87), some of its cells retain then-Thin 
 unaltered walls, and are the passage-cells, by means of which 
 water can penetrate into the interior of the root. 
 
 3. The general ground-tissue, of stems, leaves, and roots, lying 
 within the hypoderma, consists mainly of parenchymatous tissue, 
 with, frequently, a considerable differentiation of masses of fibrous 
 sclerenchymatous stereom. 
 
 In aerial stems and foliage-leaves, the more external, at least, 
 of these cells frequently take part in the assimilatory processes of 
 the plant ; the cells contain chloroplastids and constitute assimi- 
 latory tissue. Towards the most highly illuminated surface of the 
 member, the cells are frequently so arranged that their longer 
 axes are perpendicular to the surface, that is, are parallel to the 
 incident rays of light; assimilatory tissue of this structure is 
 termed palisade-tissue : the whole of the internal ground-tissue of 
 a leaf-blade is termed generally mesophyll.
 
 M.B.
 
 114 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [31 
 
 In view of its great physiological importance a somewhat detailed ac- 
 count of the structure of the mesophyll of the leaf-blade seems necessary. 
 
 The mesophyll consists of parenchymatous thin-walled cells of various 
 form. When the blade is thin, the whole mesophyll consists of assimila- 
 tory tissue ; but when it is more or less fleshy and succulent, the more 
 central part consists of cells without chloroplastids, the assimilatory 
 tissue being confined to the surface. 
 
 When the mesophyll is altogether assimilatory, the arrangement of the 
 cells is correlated with the symmetry of the leaf-blade. In a dorsiventral 
 lamina (Fig. 92) the structure of the mesophyll is different an relation 
 with the upper (ventral) and the lower (dorsal) surfaces. Towards the 
 upper surface, Avhich is more directly exposed to light, the somewhat 
 elongated cylindrical cells form a compact palisade-tissue one or more 
 layers in thickness ; whereas, towards the lower shaded surface, the cells 
 are less regular, frequently somewhat stellate in form, leaving lai-ge 
 intercellular spaces between them, constituting what is known as the 
 spongy parenchyma. The loose structure of the 
 mesophyll towards the lower surface of the 
 blade is correlated with the presence of nu- 
 merous stomata in the epidermis of that surface 
 (see p. 108). 
 
 When the palisade-parenchyma consists of 
 several layers, the transition from the one form 
 of tissue to the other is gradual. The vascular 
 bundles run along the junction of the two forms 
 of tissue. 
 
 When it so happens that all sides of the leaf 
 are equally exposed to light, the palisade-paren- 
 chyma is developed in relation with both the 
 dorsal and the ventral surfaces ; this is true, 
 not only of isobilateral and of radial leaves, but 
 also of dorsiventral leaves (e.g. leaf-blade of 
 Anchusa italica, Linosyris vulgaris, Silene inflata, 
 Dianthus Caryophyllus, etc.) ; in which case the 
 spongy parenchyma is either absent, or consists 
 of a few layers in the middle of the blade, but 
 the intercellular spaces between the palisade- 
 cells are, however, relatively large. 
 In some cases, the mesophyll is not differentiated into palisade and 
 sj>ongy parenchyma, but consists of rounded cells (e.g. succulent leaves, 
 such as those species of Crassula, etc.). 
 
 The cells of the assimilatory tissue sometimes present other forms and 
 arrangements. Thus the assimilatory tissue of the leaf of Pimis and 
 Cedrus consists of polyhedral cells, the walls of which present infoldings. 
 the elfect of which is to increase the surface of the cell-wall. In other 
 cam* it consists entirely or in part of elongated cells. reseml>Hng_palisade- 
 ci-lls, which are arranged with their long axes parallel to the surface. 
 either parallel to the long axis of the leaf (e.rj. Galanthus nil-alls, the Snow- 
 
 Fio. 93. Diagrammatic 
 transverse section of the 
 acicular leaf of a Fir : e 
 epidermis ; es sclerenchy- 
 matous hypoderma ; p sto- 
 mata ; /i resin-ducts ; s en- 
 dodermis enclosing the 
 single meristele ; gwood; b 
 bast.
 
 31] 
 
 CHAPTER II. THE TISSUES. 
 
 115 
 
 drop; Leucojum vernum, the Snow-flake;) or transversely (e.g. Iris germa- 
 nica. Erythronium Dens-Canis, species of Gladiolus and Tritonia). 
 
 Tin' colourless mesophyll of succulent and coriaceous leaves consists of 
 large cells containing much watery sap constituting in fact an aqueous 
 tissue (e.g. leaves of Alo'^, Mesemhiyanthemum, some Myrtaceae etc.). 
 In some Orchids (e.g. Oncidium maximum), the cells of the aqueous tissue 
 are scatterecFamong the assimilatory cells ; in many Orchids the cells of 
 the aqueous tissue are tracheidal, having spirally-thickened walls, as they 
 are also in the stem and leaf of Nepenthes. 
 
 In jirainvjcases, especially in aquatic plants, the ground-tissue 
 has large air-cavities, either lysigenous or schizogenous (see p. 
 N!i : generally 
 , they 
 schizo- 
 genous origin in 
 aquatic plants, 
 of lysigenous 
 origin in land- 
 plants. These 
 cavities fre- 
 quently extend 
 throughout the 
 whole length of 
 the root or the 
 leaf and through 
 an entire inter- 
 node of the 
 stem ; but they 
 may be inter- 
 rupted at inter- 
 vals by__dia- 
 p h r a g m s (e.g. 
 leaf of some 
 Monocotyledons ; 
 
 root of Hydrocharis ; stem of Alisma, Pontederia, Marsilea). 
 When these cavities^are largely developed the member becomes a 
 float (e.g. root of Jussisea). 
 
 4. The^Endodermis is, in the great majority of cases, a single 
 layer of cells ; it is but rarely altogether wanting ; it sometimes 
 consists of t\vo layers, formed by the tangential division of the cells 
 of the primitively single layer (e.g. root of Equisetum ; stem of some 
 Pteridophyta, such as Aspidium, Pteris, Salvinia and Azolla). 
 
 td 
 
 Fio. 94. -Trans verse section of central portion of the root of 
 Bonunculus repent (x 300): ed the endodermis, enclosing the 
 single central stele ; its radial walls show the sections of the 
 cuticularised thickening-bands ; x the four protoxylem-bundles ; 
 t the solid xylem; s the four phloem-bundles ; pc the pcricycle ; 
 r the cortical tissue.
 
 116 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 Most commonly the cells of the endodermis are thin-walled, with 
 a suberised thickening-zone extending round the lateral and upper 
 / and lower surfaces of the wall, and showing in transverse section 
 (Fig. 94) as a black dot on the radial wall. This peculiar mark- 
 ing is by no means always present : it is frequently wanting in 
 the endodermis of the stem, in which case the endodermisjsan, 
 in many cases, be distinguished by the presence of starch-grains 
 in its cells. When the endodermis is double, this marking is 
 confined to the outer of the two layers. 
 
 This marking is not confined to the endodermis ; it sometimes 
 occurs also in the exodermis of roots (see p. 112), and in one or 
 more layers of the internal cortex in some roots (one layer, next 
 the endodermis, in Cupressus, Taxus, Prunus, Rosa, Lonicera, etc. ; 
 several layers, Juniperus, Seqxioia, many Cruciferse such as 
 Mustard and Wallflower, Fig. 95). 
 
 The walls of the endodermal cells frequently 
 become sclerotic either over their whole surface, 
 or more frequently on the internal lateral sur- 
 faces. W T hen this is the case, some of the cells 
 remain thin- walled, as passage-cells, opposite to 
 the wood-bundles within. 
 
 32. The Stele. The plerome, constitut- 
 ing the young stele, always gives rise to vas- 
 cular tissue and usually to a certain amount of 
 other tissue which is termed conjunctive tissue. 
 The first indication of the development of 
 vascular tissue in the stele is afforded by the 
 differentiation of a varying amount of pro- 
 cambium, consisting of somewhat elongated 
 narrow cells formed by repeated longitudinal 
 division, which is the embryonic tissue from 
 which the vascular tissue is eventually formed. The procam- 
 bium frequently constitutes one solid central strand, surrounded 
 by more or less conjunctive tissue constituting the pericyclc; 
 this is sometimes the case in slender roots (see Fig. 94), in 
 slender monostelic stems (e.g. many aquatic Phanerogams, such 
 as Callitriche, Elodea, etc.; among Pteridophyta, Isoetes, Sal- 
 viniacese, Lycopodiaceae, Hymenophyllum, Schiztea), and gene- 
 rally in the steles of polystelic stems. More commonly, however, 
 the procambium of stout roots and monostelic stems is developed 
 as a number of strands variously arranged in the stele, generally 
 
 Pio. 96.-A cell 
 
 cortex of tbe root 
 of the Mustard, seen 
 obliquely from tho 
 internal surface, 
 showing the su- 
 berised thickening 
 zone. (After van 
 Ticghcm: x 350.)
 
 32] 
 
 CHAPTER II. THE TISSUES. 
 
 117 
 
 in a circle or in several circles ; the strands thus forming an in- 
 complete hollow cylinder enclosing a central mass of conjunctive 
 tissue, the medulla or pith, whilst the conjunctive tissue between 
 the strands constitutes the medullary rays. 
 
 In all cases the stele (whether one or more) Is at anjearly jtage 
 marked off from the ground tissue, the layer of the grQund : tis8ue 
 which abuts on the stele being specially differentiated as a sheath, 
 the endodermis (p. 115), which forms a continuous covering to the 
 stele or any isolated portion of it. 
 
 All primary stems are typically monostelic to begin with, but 
 as they increase in bulk this type of structure is departed from 
 in various ways ; typical monostely is, however, the rule in the 
 stem of Phanerogams, and is 
 frequent in that of Pteridophyta 
 (in Hymenophyllum, Osmunda, 
 Lycopodium, Isoetes, some 
 species of Selaginella). Some 
 stejns are, however, polystclic. 
 In these the original single stele 
 passes over, as the stem, grows 
 and enlarges, into a varying 
 number of steles which can be 
 traced to the growing-point as 
 distinct plerome-strands. Poly- 
 stely is rare in stems which 
 have a growing-point without 
 an~apical cell, whilst it is com- 
 mon in steins where the grow- 
 ing-point has an apical cell, or 
 a group of common initial cells : 
 hence it is rare in Phanerogams 
 (occurs in Auricula and Gun- 
 nera), and is common in Pteridophyta (especially Leptosporangiate 
 Ferns, and some Selaginellas : see p. 102). 
 
 A common modification of the polystelic structure is that which 
 is termed gamostelic ; in this case the several steles are not dis- 
 tinct for any considerable distance in their longitudinal course ; 
 but some or all of them fuse with each other at more or less 
 frequent intervals ; this is common in Ferns. 
 
 The general morphology of the tissues of the leaf is essentially 
 the same as that of the stem which bears it. When the stem is 
 
 FIG. 96. Part of a transverse section of 
 the stele of a root of Iris florentina : e scle- 
 rotic endodermis, with / a thin-walled pass- 
 age-cell; v bast; wood-vessel; c cortical 
 ground-tissue; p pericycle. (After Stras- 
 bnrger:x240.)
 
 118 
 
 PART II. ANATOMY AXD HISTOLOGY. 
 
 polystelic, one or more complete steles enter the petiole of the leaf 
 which is, consequently, either monostelic or polystelic. ~lVEen 
 the stem is monostelic, each leaf receives a portiqn^Jermed a 
 meristefc, of the stele of the stem; thisjneristelejnaj be either 
 entire, or be split up into a number of parts, each of which may 
 consist of but a single vascular bundle. 
 
 The Conjunctive Tissue. The morphology of the conjunctive 
 tissue of the stele varies somewhat in accordance with the develop- 
 ment of the vascular tissue. When a solid vascular cylinder is 
 produced, there may be no conjunctive tissue at allj the whole of 
 t he plerome having developed into vascular tissue ; or the conjunc- 
 tive tissue may be limited to one or more peripheral layers, th.e 
 
 pericycle, investing the 
 vascular cylinder ; or, 
 again, in addition_J,o the 
 pericycle, the Conjunct i ve 
 tissue may extend inwards 
 to some extent between 
 the bundles (interfascicu- 
 lar) of the stele. On the 
 other hand, when the vas- 
 cular cylinder is hollow 
 (see Fig. 97). the central 
 space is occupied by me- 
 dullary conjunctive tis- 
 sue, constituting the }>ith, 
 and connected with the 
 pericvcle by interfascicti- 
 lar conjunctive tissue con- 
 stituting the medullary 
 rays. Pith and medullary 
 rays are generally absent 
 from the steles of a poly- 
 stelic member. 
 
 FIG. 97. A transverse section of a young stem 
 of Arixtolochia Sipho, illustrating the arrangement 
 of the primary tissues in a monostel'c stem, in 
 which the vascular cylinder is hollow, enclosing a 
 pith (after Strasburger: x 9) : c cortical tissue, 
 with collenchyma cl ; e endodennis ; pc pericycle, 
 continuous by means of interfascicular conjunctive 
 tissue (medullary rays) with the medullary con- 
 junctive tissue m (pith) ; sfc ring of sclerenchyma 
 belonging to the pericycle ; fv vascular bundles in 
 an interrupted circle ; they are open and collateral ; 
 cb bast ; p protophloem ; fc fascicular cambium ; 
 /c interfascicular cambium ; t>l wood ; the central 
 pointed end of each wood-bundle consists of 
 protox.ylem, and the central ends of the whole ring 
 of wool-bundles constitute the medullary sheath. 
 
 A remarkable form of tis- 
 sue is that which invests 
 the two vascular bundles in 
 the acicular leaves of Pinus, 
 
 and, to a less degree, of other Conifers (Fig. 93). The tissue consists of 
 parenchyma with some fibrous sclerenchyma: in the parenchyma two 
 special kinds of cells can be distinguished, which constitute what is some-
 
 32] CHAPTER II. THE TISSUES. 119 
 
 times termed the trannfusion-tisstte] namely, cells with unlignified and 
 unpitted walls, distinguished by their abundant protoplasmic and proteid 
 contents ; tracheidal cells with slightly lignified walls and bordered pits, 
 without protoplasmic contents ; the former may be regarded as an ex- 
 tension of the sieve-tissue of the bundle, the latter-as an extension of the 
 tracheal tissue. 
 
 The Pericycle is altogether wanting in a few cases only ; it is 
 absent when the endodermis consists of two layers (see p. 115) ; it 
 is also absent from the slender roots and stems of some water- 
 plants. 
 
 It is usually a continuous membrane; but in some cases it is 
 interrupted by projections of the vascular tissue (e.g. by the- 
 xylem-bundles in the root of some Graminese and Cj^peraceae). It 
 may consjst throughout of a single layer of cells (e.g. roots of most 
 Angiosperms [Fig. 96] and of some Vascular Cryptogams) ; or of 
 more than one layer throughout (roots of some Dicotyledons, e.g. 
 Vine, and of Gymnosperms generally ; commonly in the stem and 
 leaf-stalk) ; or in part of one layer and part of more than one (e.g. 
 root of some Perns and Leguminosse). 
 
 The pej-icycle-jnay be hamogeneous or heterogeneous ; that is, it 
 may consist of the same kind of tissue throughout, or of several 
 kinds of tissue. The typical homogeneous pericycle consists of 
 thin-walled parenchymatous cells, with protoplasmic contents, 
 which are capable of becoming merismatic. In some cases the 
 primarily thin-walled cells eventually become sclerotic, either 
 throughout the whole pericycle, or in certain parts only ; this 
 commonly occurs in the roots of Monocot} r ledons. 
 
 Generally speaking, the pericycle of the root is homogeneous ; 
 when it is heterogeneous, it is so in consequence of the presence 
 of glandular tissue (secretory ducts) (e.g. Umbelliferae, Hyperi- 
 cacese) ; ^t never contains fibres. 
 
 The pericycle of the stem and of the leaf-stalk, on the contrary, 
 is generall}'- heterogeneous, owing principally to the differentiation 
 of a portion of it into collenchyma (e.g. some Composite, Bark- 
 hausia foetida, Sonchus oleraceus}, or into fibres (Fig. 97) which 
 are generally sclerotic, but not in all cases (e.g. Apocynacese, Con- 
 volvulacese, Flax) ; or it may be heterogeneous in consequence of 
 the presence of secretory ducts (e.g. Hypericum, some Umbelli- 
 ferse) ; or, in consequence of the presence of both secretory ducts 
 and of fibres (e.g. Ligulifloral and Tubulifloral Composites). 
 
 The Pith (or medulla) consists, typically, of parenchymatous
 
 120 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [32 
 
 cells with thin walls and protoplasmic contents; but in many 
 cases sclerenchyma is differentiated in it. 
 
 The most important fact with regard to the parenchyma of the 
 pith is that, in many cases, the cells forming the central portion 
 of the pith soon die, or even the whole of them (e.g. Elder). When 
 this is the case, the dead cell-walls freqviently undergo disorganisa- 
 tion, so that the stem becomes hollow. 
 
 The sclerenchyma of the pith may consist of scattered strands 
 
 (e.g. stems of some Palms) ; or it may form a ring connecting the 
 
 inner ends of the bundles of the hollow vascular cylinder (e.g. 
 
 Bongainvillea spectabilis, woody Piperacese. 
 
 The bulk of the pith varies very much. It is relatively very 
 
 large in tuberous 
 shoots, such as 
 Potato, Apios, etc. 
 The Interfasci- 
 cular Conjunc- 
 tive Tissue con- 
 sists typically of 
 p a r e n chy matous 
 cells with thin 
 walls and proto- 
 plasmic contents ; 
 but it is fre- 
 quently scleren- 
 chymatous where 
 it abuts on the 
 vascular bundles, 
 thus contributing 
 to the formation 
 of a more or less 
 complete sheath of sclerenchyma round them (e.g. many Mono- 
 cotyledons) : in woody plants the cells of the medullary rays 
 become lignified. 
 
 The various systems of sclerenchymatous supporting-tissue (stereom) 
 described above, the hypodermal, the cortical, the pericyclic, the inter- 
 fascicular, and the medullary, may be connected with each other in 
 various combinations. Thus, the hypodermal and the cortical systems 
 may be continuous ; or the hypodermal, cortical, and pericyclic ; the 
 pericyclic and the interfascicular, etc. ; as the mechanical conditions of 
 the member may render necessary (see Fig. 98). 
 
 FIG. 98. Diagram (after Schwendener) illustrating the dis- 
 tribution of the supporting-tissue or srereom, as seen in trans- 
 verse section of stems: A of Arum moculatum having isolated 
 cortical stereom-strands ; B of Allium vineale, with continuous 
 pericyclic stereom-ring ; C of Juncws glaucus (hollow), with 
 hypodermal stereom-strands and conjunctive stereom-strands ; 
 / vascular bundles ; 8 stereom-strands ; 1 air-cavities.
 
 33] CHAPTER II. THE TISSUES. 121 
 
 33. The Primary Vascular Tissue. The primary vas- 
 cular tissue is differentiated from the procambium of the stele in 
 the form of strands or bundles, vascular bundles. The vascular 
 tissues of the bundles are either tracheal tissue (p. 93), which is 
 always lignified, and is termed icood or xylem ; or sieve-tissue 
 (p. 94), which is termed bast or phloem. A vascular bundle may 
 consist, either exclusively of wood or of bast ; or of both wood and 
 bast, when it is said to be a conjoint bundle. It is generally the 
 case that a varying proportion of sclerenchyma (stereom) is associ- 
 ated with the vascular tissue; hence the bundles are frequently 
 spoken of as fibro-vascular bundles. As a rule, an equal number 
 of wood-bundles and of bast-bundles are differentiated in a stele, 
 whether they be isolated or conjoined ; there may be only one of 
 each (e.g. finer branches of the dichotomous roots of most Lycopo- 
 diums) or there may be a very considerable number (e.g. stems of 
 Monocotyledons). 
 
 With regard to the occurrence of vascular tissue in the gametophyte- 
 generation, and in the sporophyte of the lower plants, it may be stated 
 that lignified vascular tissue (i.e. wood) does not occur in any gameto- 
 phyte, nor in the sporophyte of any plant below the Pteridophyta. How- 
 ever, in the stem of the gametophytic shoots of some Mosses there is a 
 solid central stele consisting of tissue which is functionally vascular 
 tissue; the same is true of the stem (seta) of the Moss-sporophyte in 
 certain cases. Sieve-tissue has been found in some of the larger Brown 
 Seaweeds (p. 96). 
 
 The primary vascular tissue-system extends continuously 
 throughout the body of the sporophyte of the higher plants ; the 
 vascular bundles of root, stem, and leaf are all in direct com- 
 munication. 
 
 The arrangement and course of the vascular bundles are in- 
 timately connected with the morphology of the plant and with the 
 differentiation of its members. In elongated members (stems, 
 petioles, roots) the bundles run longitudinally, so that a transverse 
 section of such a member shows transverse sections of its vascular 
 bundles. 
 
 In the primary root the longitudinal course of the bundles is 
 simple ; there is an axial vascular cylinder, either solid or hollow, 
 consisting of straight. more or less distinct, bundles of wood and 
 bast, and extending from the growing-point backwards to where 
 the root merges into the stem ; from this cylinder there arise
 
 122 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [33 
 
 lateral offsets, which constitute the steles of the lateral branches 
 of the root. 
 
 In the stem the course of the bundles is more complicated, on 
 account of the fact that the stem bears lateral members, leaves, 
 which differ from itself or from its branches. In some cases, the 
 bundles of the stem, when traced upward toward the growing- 
 point, are found to terminate in the young leaves ; whilst in other 
 
 cases the bundles end 
 (like those of the root) 
 in the plerome of the 
 growing-po i n_t ; 
 bundles of the former 
 kind are distinguished 
 as common (i.e. com- 
 mon to stem and 
 leaf), and, in their 
 course in the stem, 
 are termed leaf- 
 traces ; bundles of the 
 latter kind are dis- 
 tinguished as cauline 
 (i-e. confined to the 
 stem). 
 
 Stems with common 
 bundles are generally 
 monostelic ; the leaf- 
 traces do not, how- 
 ever, follow a uniform 
 course in all cases. 
 Thus, they may pro- 
 ceed to the centre of 
 the stem and form a 
 solid vascular cylinder 
 (e.g. Isoetes among 
 Pteridophyta ; and 
 certain aquatic Mono- 
 cotyledons, such as 
 species of Potamoge- 
 ton, etc.). Or they may 
 form a hollow cylinder. 
 In the simplest case 
 
 FIG. 99. Diagram of the course of the vascular 
 bundles in stems. A Longitudinal section through the 
 axis of a Palm-stem, showing a transverse section of half 
 of it. The leaves (cut off above the insertion) are hypothe- 
 tically conceived of as distichous and amplexicaul, and so 
 are seen on both sides of the stem, 1 m 2 m 3 m being the 
 median line of each. B Outside view and transverse 
 section of Cerastium (hypothetically transparent, to show 
 the internal bundles). The decussate leaves (1, 2, 3) are 
 cut off. The bundle proceeding from each leaf divides into 
 two above the leaf immediately below it, and the branches 
 of all the bundles unite to form the four thin bundles 
 which alternate in the Hection with the thicker ones. In 
 the section, m is the pith, r the cortex, v the medullary 
 ray. The xylem in the nbro-vascular bundles is indicated 
 by shading.
 
 33] CHAPTER II. THE TISSUES. 123 
 
 of this (as in Osmundacese, most Gymnosperms and Dicotyledons) 
 the bundles (leaf-traces) entering the stem from a leaf are few in 
 number, or even only one ; they penetrate to an egu^l depth in the 
 stem, and run vertically downwards through one or two internodes, 
 joining at a node with the bundles entering the -stem from a lower 
 leaf ; sometimes their lower ends are bifurcate so that they join 
 with the bundles of the lower leaves (Fig. 99 JB}. When the 
 leaf-traces entering the stem from a leaf are more numerous, they 
 penetrate to various depths in the stele, and tljeir course is 
 usually not vertical, but more or less curved : they may then form 
 two circles (e.g. Cucurbitacese, Phytolacca, Piperacese) ; or many 
 circles, more or less irregular, trenching on the pith (e.g. many 
 Ranunculacese, such as Cimicifuga, Thalictrum ; Nymphseacese ; 
 Monocotyledons generally). A good example of this is afforded by 
 a Palm stem (Fig. 99^4). The median leaf-traces first tend to- 
 ward the centre of the stem ; they then bend outward, thinning 
 out gradually as they descend, and coalesce with the lateral bun- 
 dles, which do not penetrate so deeply, in the pericycle at a point 
 much lower down. Furthermore, each bundle is somewhat twisted 
 in its course, so that the lower end lies toward a different side of 
 the stem from that on which it entered it. In these cases, when 
 there is a well-defined external ring, the more internal bundles 
 are termed medullary bundles. 
 
 The relative position of the phloem and of the xylcm in a con- 
 joint bundle is subject to some variation ; they may either be 
 side by side, when the bundle is said to be collateral ; or the one 
 may more or less completely invest and surround the other, when 
 the bundle is said to be concentric. 
 
 In the collateral bundle, the wood and the bast are so situated 
 that they both lie on a straight radial line drawn through the 
 bundle from the centre of the member to the surface, the wood 
 being nearer the centre, and the bast nearer the surface (see 
 Fig. 97). This type of bundle is common in the stems and leaf- 
 stalks of Phanerogams and of some Pteridophyta (Osmundacese, 
 Ophioglossacese, Equisetum). 
 
 In some stems (e.g. Solanacese, most Convolvulacese, Cucurbitacese, 
 etc.) there is a second bast-bundle on the inner (medullary) side 
 of the wood of the conjoint bundle ; such a bundle is distinguished 
 as bicollatcral. 
 
 In a concentric bundle, either the bast is surrounded by the 
 wood, or the wood by the bast, more or less completely : the
 
 124 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [33 
 
 bicollateral bundle is, in fact, a structure intermediate between 
 the collateral and the concentric bundle. The former type of con- 
 centric bundle occurs in the rhizomes of various Monocotyledons 
 (Acorus, Iris, Cyperus, Carex, etc.), and in the medullary bundles 
 of the stem of some Dicotyledons (Rheum, Statice, Ricinus, Piper, 
 etc.). The latter type is rare in Phanerogams (e.g. the cortical 
 
 FIG. 100. Transverse section of an open, collateral, conjoint, vascular bundle of the 
 stem of Ranunculus repent : s spiral vessel of the protoxylem at the inner (central) end of 
 the wood j m pitted vessel of the wood ; c cambium ; v a sieve-tube of the bast with 
 adjacent granular companion-cells; vg sheath of sclerenchymatous conjunctive tissue. 
 (After Strasburger: x 180.) 
 
 and medullary bundles of the Melastomacese) ; but it prevails in 
 the Filicinse and in Selaginella, when the bundles (two_or jnore) of 
 each stele of the polystelic stem, form a central mass of wood 
 completely, or nearly completely, surrounded by a ring of bast.
 
 33] 
 
 CHAPTER II. THE TISSUES. 
 
 125 
 
 The relative 
 position of the 
 plilo em-bundles 
 and xylem-bundles 
 tchen they are dis- 
 tinct from each 
 other is such that 
 they alternate with 
 each other so that 
 a radius drawn 
 from the centre to 
 the surface of the 
 member cuts 
 through either a 
 phloem or a xylem- 
 bundle, but not 
 through both (Fig. 
 102). This ar- 
 rangement obtains 
 only in mono- 
 stelic mem- 
 bers ; it is 
 common to all 
 roots, and oc- 
 curs in the 
 stem of Lyco- 
 podium and 
 Psilotum 
 though in a 
 less regular 
 manner than 
 in roots. It 
 is commonly 
 termed the 
 radial a r- 
 rangement. 
 
 The Differ- 
 entiation of 
 the Primary 
 Vascular Bun- 
 dle. The first 
 
 Fia. 101. Transverse section of a concentric bundle, with 
 external wood, from the rhizome of Iris (x 350) : t trachea; 
 V protoxylem ; s sieve-tubes ; g companion-cells, of the in- 
 ternal bast.] 
 
 vi 
 
 FIG. 102. Part of a transverse section of the stele of the Sar- 
 saparilla-root (Smilax) : r cortex; ed endodermis with passage- 
 cells d ; the pericycle and the interfascicular conjunctive tissue o 
 are sclerenchymatous ; v' the pith ; * the protoxylem, and t a pitted 
 vessel of a wood-bundle: s a bast -bundle. The alternation, or 
 radial arrangement, of the wood and bast-bundle is shown. ( x 300.)
 
 126 PART II. ANATOMY AND HISTOLOGY. [ 33 
 
 indication of the development of vascular tissue in the plerome 
 is the differentiation of one or more strands of narrow elongated 
 merismatic cells, the procambium (p. 116) ; each procambium- 
 strand_pf the plerome becomes a vascular bundle of thejitele. 
 
 The development of the vascular tissue does not take place 
 simultaneously throughout the whole transverse section of the 
 procambium-strand, but bgins at one definite point, and extends 
 in one or more directions from that point. 
 
 The development of the xylem-bundle (or part of a conjoint 
 bundle) begins with the differentiation of one or a few tracheids 
 or tracheae, constituting the protoxylem ; the walls of the corre- 
 sponding procambium-cells become spirally thickened and liguified, 
 and the protoplasmic contents of the cells disappear. It is an 
 important generalisation that spiral or annular vessels (or tra- 
 cheides) are characteristic of, ' and absolutely confined, to, the 
 protoxylem of the bundle. The remainder of the primary wood 
 (i.e. the wood which is developed from the procambium) is then 
 gradually differentiated, the walls of the tracheides or trachese 
 presenting one or other of the various kinds of pitted marking 
 (p. 74). 
 
 Similarly, the development of the phloem-bundle (or the phloem 
 of a conjoint bundle) begins with the differentiation of a small 
 group of sieve-tissue, constituting the protophloem, which does 
 not, however, differ in any marked manner from the rest of the 
 primary phloem, but their cavities soon become obliterated, so 
 that they then look like strands of swollen cell-wall (Fig. 
 103). 
 
 The details of the differentiation of the primary vascular tissue 
 are essentially the same as in the case of the secondary vascular 
 tissue described on p. 145. 
 
 The longitudinal differentiation of the primary vascular tissue 
 does not take place in the same order in all cases. In roots, and 
 in stems with cauline vascular tissue, the longitudinal differenti- 
 ation proceeds acropetally. In stems with common bundles the 
 differentiation usually begins in the procambium-strand at a node, 
 proceeding both downwards in the internode of the_stem, and out- 
 ward into the young leaf. 
 
 In the majority of instances, the whoU of the procambium-strand 
 becomes differentiated into permanent tissue, either wood or bast : 
 this is true for all roots, and for the stems of nearly all Pterido- 
 phyta and Monocotyledons (Fig. 103). Bundles of this kind are
 
 33] CHAPTER II. THE TISSUES. 127 
 
 said to be closed. In the stems of most G-ymnosperms and Dicgty- " ' 
 ledons, on the other hand, the whole of the procambium is not 
 converted into the primary wood and bast of the collateral conjoint 
 bundle, but a portion of it persists as an embryonic merismatic 
 tissue, the cambium, forming a transverse zone- Jbetween the wood 
 
 Fio. 103. Transverse section of a conjoint, collateral, closed, vascular bundle of the stem 
 of a Monocotyledon (Zea Mais) : a outer or peripheral end of the bundle ; i inner or central 
 end ; p conjunctive tissue, the portion immediately investing the bundle being sclerenchy- 
 matous ; I lysigemus intercellular space ; g r spiral and annular vessels constituting 
 the protoxylem ; g g large pitted vessels, between which lie the smaller pitted vessels of 
 the wood ; v v v sieve-tubes of the bast with intervening companion-cells ; just outside the 
 bast, and within the sclerenchymatous sheath, the remains of the protophloem are visible. 
 (After Sachs : x 553.; 
 
 on, the inner (central) side and the bast on the outer side (see 
 Figs. 97, 105). Such a bundle is said to be open.
 
 128 PART II. ANATOMY AND HISTOLOGY. [ 33 
 
 Some few Dicotyledons have closed bundles (i.e. no cambium) in the stem, 
 e.g. Adoxa, Ranunculus Ficaria, Nymphseacese, Myriopliyllum, Utricularia. 
 etc. 
 
 The position of the protoxylcm and of the protophloem in the 
 transverse section of the bundle is not the same in the different 
 members. The protophloem is in all cases superficial : and though 
 the protoxylem is also generally superficial, it is sometimes in- 
 ternal (as in the bundles in the petiole of Cycads, in the stem of 
 Isoetes, and in the concentric steles of stems and petioles of many 
 Ferns), being more or less surrounded by the rest of the primary 
 xylem. 
 
 In members, whether monostelio or polystelic, in which the 
 primary bundles or the steles are arranged in one or more circles 
 (or other figure corresponding to the sectional outline of the mem- 
 ber), the orientation of the bundles in the stele, as indicated by the 
 position of the protoxylem, bears a definite relation to the symmetry 
 o^ the transverse section of the member. For instance^ in medullate 
 monostelic stems (Fig. 97) the protoxylem forms the innermost 
 or central portion of the bundle ; the broken circle of protoxylem- 
 groups is sometimes specially designated the medullary sheath. 
 In the root, whether the vascular cylinder be medullate or not, the 
 protoxylem is always outermost or peripheral, abutting on the 
 pericycle (Fig. 102). This is also the case in monostelic stems 
 which are not medullate (e.g. stem of Lycopodium). The proto- 
 phloem is always external, abutting on the pericycle._ 
 
 The transition from the root to the stem. Inasmuch as, generally 
 speaking, the type of primary structure of the root differs so con- 
 siderably from that of the corresponding stem, the transition from 
 the one to the other is a matter of some importance. Taking as an 
 illustration the case of a plant with a monostelic stem, the passage 
 from the radially arranged separate bundles of the primary rooj to 
 the collateral conjoint bundles of the stem is effected on this wise : 
 generally speaking, on tracing the wood- and bast-bundles of the 
 root upwards into the stem, the wood-bundles are found to twist 
 on themselves so that the protoxylem of each bundle, from being 
 peripheral in the root, comes to be central in the stem ; at the same 
 time they change their position somewhat so that they come to lie 
 on the same radii as the bast-bundles, or the bast-bundles may also 
 deviate somewhat from their straight course, and thus the conjoint 
 collateral bundles come to be constituted. As a rule, these changes 
 of position are accompanied by an increase in number of the bun-
 
 33] 
 
 CHAPTER II. THE TISSUES. 
 
 129 
 
 dleSj each of the bundles of the root bifurcating above, so that 
 there are commonly twice as many bundles in the stem as in the 
 corresponding root. 
 
 The structure of the primary bundle. The primary wood 
 (whether in an isolated or a conjoint bundle) consists essentially of 
 lignified tracheal tissue (tracheae, or tracheids, p. 93), together with 
 a varying proportion of wood-parenchyma, more or less lignified, the 
 cells being occasionally somewhat fibrous. The protoxylem (see p. 
 
 cp 
 
 n' 
 
 FIG. 104. F?adial longitudinal section of a conjoint, closed, collateral bnndle from the 
 stem of a Monocotyledon (Zea Mais ; after Strasburger, x 180) ; to the right is the central 
 (medullary) limit of the bundle ; to the left the peripheral (cortical) limit : c p protophloem ; 
 v sieve-tubes of the bast, with companion-cells * ; p a a', the protoxylem ; a a' remains of 
 ruptured annular vessel lying in the lytigenous lacuna I ; vg sheaths of sclerenchymatous 
 conjunctive tissue. (Compare this with Fig. 103.) 
 
 126) is usually a conspicuous feature; in transverse section, on 
 account of the relative smallness of its tracheae (or tracheids) ; j.n 
 longitudinal section, on account of the loose spiral or annular 
 thickenings of their walls. The looseness of the spiral or annular 
 markings is due to the fact that these vascular cells are the first 
 formed constituents of the bundles, and that consequently they 
 are considerably stretched by the continuance, for a time, of the 
 
 M.B. K
 
 130 PART II. ANATOMY AND HISTOLOGY. [ 33 
 
 growth in length of the adjacent undifferentiated tissues; hence 
 the successive thickenings become more or less widely separated, 
 and the wall of the vessels may be torn and destroyed (Fig. 104). 
 
 The primary bast or phloem consists essentially of jsieye-tissue 
 (p. 94) and of parenchyma. The sieve-tissue consists in_alLeases 
 mainly of sieve-tubes of simple structure (Fig. 74, p. 95), con- 
 stituting the vascular tissue of the bast, with which companion - 
 cells are associated in Angiosperms but not in Gymnosperms and 
 Pteridophyta. In some Angiosperms, particularly in the closed 
 bundles of Monocotyledons (Fig. 103), there is no bast-parenchyma, 
 the whole bast consisting of sieve-tubes and companion : cells : but 
 this tissue is generally present, and is readily distinguishable 
 from the companion-cells by the larger size of its cells. In some 
 cases (e.g. some Palms) the bast-parenchyma is to some extent 
 replaced by sclerenchymatous fibres ; otherwise the occurrence of 
 fibres in the primary bast is rare. 
 
 The cambium is present in the collateral primaryjbundles of 
 the stem of most Gymnosperms and Dicotyledons; it is never 
 present in primary bundles of any other type of structure; nor, on 
 the other hand, is it always present in a collateral bundle (absent 
 in Equisetum, Monocotyledons, some herbaceous Dicotyledons, see 
 p. 128). It lies between the bast externally and the wood in- 
 ternally, and consists essentially of a single layer of merismatic 
 embryonic cells rich in protoplasmic contents, and with walls of 
 cellulose. In transverse section (see Fig. 100) the cells are oblong, 
 with their longer axes placed tangentially ; in longitudinal section 
 the cells are seen to be elongated and somewhat prosenchymatous, 
 like the procambiurn-cells, where they abut on the wood or on the 
 bast; but where they abut on primary medullary rays they are 
 short and parenchymatous. 
 
 The Termination of the Vascular Bundle. The gradual thinning 
 out and termination of the vascular bundle can nowhere be more 
 satisfactorily studied than in leaves. The bundles, when traced 
 towards their ultimate ramifications, are seen to diminish in bulk 
 in consequence, partly, of a reduction in number of the constituent 
 elements, and partly also to the smaller size of the elements which 
 still remain. The mode of termination of the vascular bundles in 
 foliage-leaves is briefly as follows. In many cases the bundles 
 have only free ends, as in most Pteridophyta (e.g. Adiantum, 
 Selaginella), and generally in small reduced leaves. In othejs, 
 there are no free ends, but the finer branches anastomose with each
 
 33] 
 
 CHAPTER II. THE TISSUES. 
 
 131 
 
 other to form a closed system ; this is characteristically the case 
 where the venation is parallel (e.g. Monocotyledons, see p. 38). 
 In others, again, the finer branches anastomose, forming a network 
 from the meshes of which the ultimate branches project among the 
 mesophyll-cells as free ends : this obtains generally among Dicoty- 
 
 FIG. 105. A Tranverse section of an open conjoint, collateral, vascular bundle in the 
 stem of the Sunflower, if Pith. X Xylem. C Cambium. P Phloem and pericycle. 
 R Cortex ; s small, and s' large spiral vessels (protoxylem) ; t pitted vessels ; t' pitted 
 vessels in course of formation from the cambium ; h wood-fibres ; sb sieve tubes ; b fibres 
 of the heterogeneous pericycle; e endodermis or bundle-sheath; tc inter-fascicular con- 
 junctive tissue. B Radial vertical section through a similar bundle (somewhat simplified) 
 lettered like the former. ( x 150.) 
 
 ledons. The free ends of the bundles consist of one or two rows 
 of short tracheids with close spiral markings ; no sieve-tubes can
 
 132 PART II. ANATOMY AND HISTOLOGY. [ 34 
 
 be traced quite to the extremity ; they disappear further back, 
 and their place is taken by parenchymatous cells. 
 
 Bundles often terminate in connection with glandular Jissue ; 
 for~instance, in chalk-glands and nectaries. 
 
 34. Histology of the Development of Secondary 
 Members. It has been already pointed out (p. 9) that the 
 growing-point is the seat of development, not only of new tissue, 
 but also of new members ; and further (p. 18), that secondary 
 members are developed either by dichotomy or by lateral out- 
 growth. 
 
 A. Development of normal branches of the shoot_Q3L_Q_the 
 thallus only takes place at the growing-point. 
 
 a. By dichotomy. Two modes may be distinguished accordingly 
 as the growing-point has or has not an apical .cell : 
 
 when there is an apical cell, true dichotomous branching is 
 
 A 
 
 Vio. 108. A B C successive stages in true dichotomons branching by longitudinal 
 division of an apical cell; from the shoot of an Alga Dictyofa dichotoma (highly magni- 
 fied; after Naegeli). 
 
 effected by the longitudinal division of the apical cell into two, 
 each of which becomes the apical cell of a branch : 
 
 when there is no apical cell, the growing-point becomes 
 broadened, and the central portion of it passes over into condition 
 of permanent tissue, leaving two distinct masses of embryonic 
 tissue, which constitute the growing-points of the two branches 
 (e.g. Marchantiaceae). 
 
 b. By lateral outgrowth : 
 
 irlii-n there is a single initial cell in the growing-point, the 
 growing-point of the branch is developed either directly__from the 
 initial cell itself, as in some Algse, or more commonly from a seg- 
 ment of the initial cell, as in many Algse, Mosses, Liverworts, etc. : 
 
 when there is not a single initial cell (e.g. Phanerogams), the 
 growing-point of the branch is formed by division of cells of the 
 periblem, including several layers, which grow and divide, form- 
 ing a lateral protuberance with the growth of which the dermato-
 
 34] CHAPTER II. THE TISSUES. 133 
 
 gen. keeps pace ; the primary meristem of the branch vindergoes 
 differentiation into tissue-systems corresponding to those of the 
 parent members, and continuous with them. 
 
 Normal branches, however the details of their development may 
 vary, agree in this, that they are, with rare exceptions^ exogenous 
 origin. 
 
 B. Development of Leaves only takes placeji^the^rowing-poiut 
 of a stem, andjdways by lateral outgrowth (see p. 28). 
 
 When the growing-point of the stem has a single initial cell, the 
 growing-point of the leaf is developed either from the apical cell 
 itsetf,l>r,'more commonly, from the whole or a part of a segment of 
 the apical cell. 
 
 When the groicing-point of the stem has not a single initial cell, 
 as in Phanerogams, the growing-point of the leaf is formed by the 
 division of _cells belonging to one or more of the superficial layers 
 of the periblem, accompanied by growth and division of the cor- 
 responding cells of the dermatogen. 
 
 The primary meristem of the leaf becomes differentiated into 
 tissue-systems corresponding to, and continuous with, those of the 
 stem which bears it. In the developing leaves of those vascular 
 plants which have common bundles (see p. 127), the differentiation 
 of the protoxylem begins at the point of junction of leaf and stem, 
 extending outwards in the procambium-strands of the leaf, and in- 
 wards in those of the stem. 
 
 The development of secondary branches of the leaf takes place 
 in essentially the same manner as that of the leaf from the stem. 
 Dichotomous branching of the leaf (see p. 34) takes^ place in the 
 same way as dichotomous branching of the stem. 
 
 It will be seen that the development of a leaf on any stem takes 
 place in essentially the same way as the development of a lateral 
 branch on that stem ; it is only later that leaves and branches 
 assume their distinctive characters. 
 
 C. Development of Branches of the Root. It has been pointed 
 out that the only normal secondary members produced by the root 
 are root-branches or secondary roots ; these may be developed 
 either by dichotomy or by lateral outgrowth. 
 
 a. By dichotomy. This has only been observed in certain sporo- 
 phytes among the Pteridophyta (Lycopodium, Isoetes). Here the 
 growing-point broadens, under the root-cap, the central portion 
 passing over into permanent tissue, whilst the two sides remain 
 merismatic and form the growing-points of the two secondary
 
 134 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [34 
 
 roots; the old root-cap is exfoliated, and each growing-point forms 
 a new one for itself. The successive dichotomies take place in 
 planes at right angles to each other. 
 
 b. By lateral outgrowth. It has been already stated (p. 9) that 
 the lateral development of secondary members does not take place 
 at the growing-point of the root, but at a considerable distance 
 behind it, where the tissues have already assumed their permanent 
 differentiation. The lateral roots are developed endogenously from 
 a layer of this tissue which remains embryonic longer than the 
 
 FIG. 107. Illustrating the development of a secondary root in a Phanerogam. A trans- 
 verse, D longitudinal, section ; ep epiblem ; en endodermis ; pe pericycle ; w protoxylem 
 and b phloem of the parent-root ; re root cap ; c periblem, and 2^ plerome, of the de- 
 veloping lateral secondary root. (Teesdalia nudicaulis ; x about ZOO ; after van Tieghem). 
 
 adjacent tissues. This layer may be either the pericycle, as in 
 Phanerogams, or the endodermis, as in most Vascular Cryptogams. 
 In_the Phanerogams (Fig. 107), the growing- point of a lateral 
 root is formed by the growth and division of a group of pericycle- 
 cells, lying usually just externally to the outer end of a xylem- 
 bundle ; hence there are as many longitudinal rows of lateral roots 
 produced as there are xylem-bundles in the parent root, and cor- 
 responding with them in position. But to this rule there are some 
 exceptions; for instance, when, as in the Grasses and Cyperacese,
 
 34] CHAPTER II. THE TISSUES. 135 
 
 the pericycle is wanting opposite to the xylem-buudles, the lateral 
 roots are developed, not opposite to the xylem-bundles, but opposite 
 to the phloem-bundles. Again, when there are only two xylem- 
 bundles in the parent root, four rows of lateral roots are produced, 
 each root being developed on one side of a xylem-bundle of the 
 parent root : a similar displacement occurs in Umbelliferse, 
 Araliacese and Pittosporacese, where the pericycle is interrupted 
 opposite to each xylem-bundle by an oil-duct (see p. 119). 
 
 In most Vascular Cryptogams (except Lycopodium and Isoetes, 
 where secondary roots are produced only by dichotomy), the apical 
 cell of a secondary root is formed from one of a row of large 
 endodermal cells, the rhizogentc cells, lying just externally to 
 each xylem-bundle of the parent root. In Equisetum, where the 
 endodermis consists of two layers (see p. 115), the secondary roots 
 are developed from cells belonging exclusively to the inner layer, 
 which are adjacent to the xylem-bundles. 
 
 It will be understood that, in order to reach the surface, the lateral 
 secondary roots must penetrate the external tissues of the parent root. 
 This is nq^effected by purely mechanical means, but by chemical action, 
 leading to solution and absorption, exerted on the tissues, either by the 
 rootlet itself, or, more commonly, by a digestive sac which invests the root- 
 let, and is formed in Phanerogams by the growth and division of the cells 
 of the endodermis (and sometimes one or two layers of cortical cells), in 
 Vascular Cryptogams, by the growth and division of one or more of inner 
 layers of cortical cells just external to the endodermis of the parent root. 
 
 D. Development of Hairs. These structures are m_all cases 
 developed from the superficial cells of the parent member, that is, 
 from dermatogen-cells in those parts in which this layer is differ- 
 entiated ; in the great majority of cases each hair arises from a 
 single superficial cell. Hairs are generally developed in acropetal 
 succession, but considerable irregularity is not uncommon, and 
 they are frequently developed on members in which the tissues 
 have already acquired their permanent characters (see p. 46). 
 
 E. Development of Emergences. When exogenous they are 
 developed from the superficial and from one or more of the sub- 
 jacent layers of tissue of the parent member, that is, from the 
 dermatogen and periblem of those members in which this differen- 
 tiation of the primary meristem obtains. When they are endo- 
 genous (e.g. haustoria of Cuscuta, see p. 49), they are developed 
 exclusively from the periblem. 
 
 F. Development of Reproductive Organs. The question as to
 
 136 PART II. ANATOMY AND HISTOLOGY. [ 34 
 
 the relation of these members to the primary meristem, only arises 
 with reference to those plants, the bodies of which consist of many 
 layers of tissue ; their origin in plants, the bodies of which consist 
 either of filaments, or of flattened expansions of a single layer of 
 cells, need not be considered here. 
 
 In the cases under consideration, the reproductive organs may 
 be developed either from the superficial layer alone, or from that 
 and one or more of the subjacent laj'ers. 
 
 Organs developed from the superficial layer alone Jderinatogen 
 when differentiated) : these may be developed each from a single 
 cell, as all sexual organs, and the sporangia of all leptosporangiate 
 Ferns and Rhizocarps (Hydropteridese) ; or they may be developed 
 from a group of superficial cells, as the sporangia of the Ophio- 
 glossacese and Marattiacese (eusporangiate Ferns), of Equisetum, 
 and of Lycopodinse. 
 
 Organs developed from the superficial and deeper layers. In 
 most cases the organ is developed from the superficial and one 
 or more of the subjacent layers, e.g. microsporangia (pollen-sacs) 
 and macrosporangia (ovules) of most Phanerogams. 
 
 The primitive sporogenous tissue (archesporium, see p. 53) is, in the 
 sporangia of all Vascular Plants, derived from the hypoclermal layer of 
 the young sporangium ; it may consist of a single cell, or of_a row of 
 cells, or of a layer of cells. In the Mosses the archesporium is more 
 deeply seated, arising from the external layer of the endothecium 
 (rudimentary plerome) as in most Mosses, or from the innermost layer of 
 the amphithecium (rudimentary periblem) as in Sphagnum and in the 
 Liverwort Anthoceros. 
 
 G. The Development of Adventitious Secondary Members (see 
 p. 9). 
 
 1. On the stem. The most common case is that of the develop- 
 ment of roots, but occasionally shoots (buds) are developed ad- 
 ventitiously. 
 
 The adventitious development of roots on the stem takes place 
 most commonly by the division of a group of pericycle-cells to 
 form a growing-point, in the way described on page 134 with 
 reference to the development of normal lateral roots on the 
 parent root. In any one plant the two processes are similar in 
 every detail. 
 
 The adventitious development of biids on the stem may take 
 place either exogenously or endogenously. In the former case__the 
 buds may be developed each from a single epidermal cell (e.g.
 
 35] 
 
 CHAPTER II. THE TISSUES. 
 
 137 
 
 Begonia prolifera, underground shoots of Psilotum), or from the 
 epidermis and subjacent layers (e.g. Linaria vulgaris}. In the 
 latter case the adventitious bud arises from the pericycle (e.g. 
 Cuscuta, hypocotyl of Convolvulus arvensis). 
 
 2. On the root. Adventitious buds may be formed either exo- 
 genously or endogenously on the root ; in the former case they arise 
 from the superficial .layers (e.g. Aristolochia Clematitis) ; in the 
 latter, from the pericycle (e.g. Alliaria ojftcinalis, Anemone 
 sylvestrisj etc.). 
 
 B._0n the leaf. Adventitious buds developed on leaves are 
 oj exogenous origin, the epidermis being more especially concerned 
 in their production (Begonias). Adventitious roots are usually of 
 endogenous origin, being derived from cells of the pericycle. 
 
 Adventitious buds and roots are also developed from the callus 
 (see 36) formed on the injured surfaces of stems, roots, and leaf-stalks : 
 the former may be endogenous or exogenous, the latter are endogenous. 
 
 35. The Formation of Secondary Tissue. In addition 
 to the formation of primary tissue from the primary meristem of 
 the growing-point, as 
 above described, a for- 
 mation of secondary 
 tissue takes place in 
 many plants, which 
 is in most cases asso- 
 ciated with a growth 
 in thickness. 
 
 A. The Normal 
 Formation of Second- 
 ary Tissue, in_the 
 stem takes place in 
 most Gy mnosperms 
 and Dicotyledons, and is Affected by the continuous merismatic 
 activity of the cambium of their open collateral bundles. These 
 are arranged in a circle in a transverse section (Fig. 108 A) : 
 the commencement of growth in thickness is preceded by tan- 
 gential divisions in the conjunctive tissue (Fig. 105) which lies 
 between the bundles ; this gives rise to cambium which becomes 
 continuous with that of the vascular bundles. A closed hollow 
 cylinder is thus formed, which appears, in a transverse section, as 
 a ring, the cambium-ring (Fig. 108 B c), completely separating 
 
 FIG. 108. Diagrammatic transverse sections of a 
 normal dicotyledonous stem which grows in thickness. 
 A Very young : there are five isolated bundles ; m pith ; 
 r cortex ; V primary bast ; V primary wood ; c cambium. 
 -B After growth in thickness has commenced ; Ji 2 secon- 
 dary wood ; b 2 secondary bast.
 
 138 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [35 
 
 the pith from the cortex : it consists of two portions corresponding 
 to its mode of origin ; fascicular cambium, i.e. the cambium be- 
 longing to the vascular bundles, and the inter fascicular cambium, 
 i.e. that which is formed between the bundles in the primary 
 medullary rays (see Fig. 97). 
 
 A cambium-ring is likewise formed in the root of these plants 
 (Fig. 109). The first indication of the formation of ji cambium- 
 layer is the division of the cells of the conjunctive parenchyma on 
 the inner surface of each bast-bundle : then those on the flanks 
 of the bast-bundles begin to divide ; and thus a number of^ arcs 
 of cambium are formed, extending from the inner surface of each 
 bast-bundle to the pericycle. The pericycle-cells lying externally 
 
 to Jhe outer ends_(protoxy- 
 lem) of the wood-bundles now 
 divide, and connect the arcs 
 of cambium. Thus a con- 
 tinuous cambium -layer is 
 formed, which has at first a 
 wavy outline, as seen in 
 transverse section, but which 
 becomes circular as the de- 
 velopment of the secondary 
 tissue proceeds. 
 
 The cambium-layer of the 
 primary root is continuous 
 with that of the primary 
 stem; hence, in a plant in 
 which stem and root grow in 
 thickness, there is a continu- 
 ous layer of merismatic tissue 
 extending from one end of it 
 to the other ; for the cambium 
 
 of the branches of both stem, and root is continuous with that 
 of the primary members ; and further, the cambium is continuous 
 with the merismatic tissue of the growing-points of the primary 
 stem and root and of their branches. 
 
 The cells of the cambium-ring, in the stem and root alike 3 con- 
 stantly undergo both tangential and radial division, so that the 
 number of the cells increases in the radial direction as well as in 
 the circumferential ; the growth of these cells produces an exten- 
 sion of the organ in both these directions. Of the cells formed by 
 
 B. 
 
 FIG. 109. Transverse section of the stela of 
 the root of Sambucus nigra, where secondary 
 growth in thickness is commencing, r Cor- 
 tex ; ed endodermis ; pc pericycle ; xxx the 
 three groups of protoxylem ; p p p the three 
 groups of phloem ; c dividing cells of the con- 
 junctive tissue forming part of the developing 
 cambium-ring.
 
 35] 
 
 CHAPTER II. THE TISSUES. 
 
 139 
 
 tangential division, those lying on the inner side of the cambium, 
 jtre transformed into the elements of the wood (Fig. 108 B /i 2 ), 
 those on the outer side, into the elements of the bast, while the 
 cells of the intermediate zone continue to be capable of dividing. 
 The activity of the cambium thus gives rise t6 secondary wood 
 and secondary bast, as distinguished from the primary con- 
 stituents of the bundle, which existed previously to, and indepen- 
 dently of, the activity of the cambium. The primary wood of the 
 bundle is thus the innermost part of it, and the primary bast the 
 most external. 
 
 Not only does the fascicular cam- 
 bium add secondary wood and bast 
 to the primary bundles of the stem, 
 but the interfascicular cambium 
 generally forms (except Cucurbita- 
 cese, Aristolochia, and some other 
 plants, where it only forms conjunc- 
 tive tissue) new secondary bundles 
 between the primary, and in this 
 way a compact ring of wood and of 
 bast is formed. These secondary 
 bundles are of course destitute of 
 protoxylem and protophloem. 
 
 In roots the secondary vascular 
 tissue is developed in essentially the 
 same manner as in the stem; the 
 wood inwards, the bast outwards, 
 from the cambium-layer ; and the 
 same forms of tissue are produced. 
 It is, however, only in certain cases 
 (e.g. Taraxacum, Rubia, Taxus, Cu- 
 pressus, etc.) that the cambium of 
 
 the root produces Wood internally, bundles. B Transverse section of an 
 
 and bast externally, over its whole older root of * be * ame plant ' which 
 
 J ' is growing in thickness : 
 
 surface, so that a complete ring of 
 secondary vascular tissue is formed : 
 in most cases secondary vascular 
 
 tissue is formed Only Opposite to wood-bundles. (Slightly magnified; 
 
 the primary bast-bundles, whereas, ' 
 
 opposite to the primary wood-bundles, the cambium produces only 
 ground-tissue, thus giving rise to broad medullary rays opposite 
 to these bundles (Fig. 110). 
 
 FlG . no.-^ Transverse sectiou of 
 young root of Phaseoius muiti/ion** . 
 
 secondary 
 bast ; k periderm : the four rays ex- 
 
 tendin & to near the centre consist 
 
 of secondary ground-tissue, and cor- 
 respond in position to the primary
 
 140 PART II. ANATOMY AND HISTOLOGY. [ 35 
 
 The Tissues developed from the Cambium. In stems and roots 
 in which the growth in thickness is normal, the cambium gives 
 rise to secondary wood, secondary bast, and secondary conjunctive 
 tissue (medullary rays). 
 
 The structure of the secondary wood differs essentially from 
 that of the primary wood only in that it includes no_ spjirad or 
 annular vessels resembling those of the protoxylem (see p. 126). It 
 always includes tracheal tissue ; nearly always wood-parenchyma 
 (see p. 91); frequently sclerenchyma: the cell-walls of all these 
 forms of tissue are usually more or less completely lignified. 
 
 The secondary tracheal tissue may consist either solely of 
 tracheae (e.g. Platanus, Fraxinus excelsior and Ornus, Citrus, 
 Viscum, Hydrangea) ; or solely of tracheids (e.g. Coniferse, Drimys 
 Winter I) ; or, as is generally the case, of both tracheae and 
 tracheids. The cell-walls of the tracheal tissue are, as a rule, 
 marked with bordered pits; but occasionally, especially in soft 
 wood, the walls are reticulately thickened. 
 
 The secondary icood-parenchyma consists of oblong cells, which 
 are generally so arranged that their long axes are parallel to that 
 of the member of which they form part : they occur in short 
 longitudinal strands, consisting commonly of a single row of cells 
 (Fig. Ill (7), but sometimes, in the middle only, of more than one 
 row. They are true cells, containing protoplasm and a nucleus, 
 and other substances, such as starch (especially in perennial steins 
 and roots in winter), tannin, etc. Their walls are generally 
 lignified, but usually not very much thickened, and have .circular 
 or elliptical simple pits. In many soft fleshy stems ._ and_jLQOts 
 (e.g. Potato, Radish, Turnip, Beetroot), where this tissue is the 
 principal product of the activity of the cambium, the cell- walls are 
 not lignified. 
 
 The secondary sclerenchyma consists of elongated prqsenchy- 
 matous cells, with more or less thickened lignified Avails marked 
 Avith narrow oblique bordered pits (Fig. 72, p. 93; Fig. Ill 
 A, B). Two forms of this tissue are distinguishable: woody 
 fibres destitute of protoplasmic contents, Avhich are connected 
 by transitional forms with the tracheids (see p. 92) : fibrous 
 cells, with protoplasmic cell-contents, which are allied to the 
 wood-parenchyma ; in fact, one fibrous cell corresponds to a row 
 of wood-parenchyma cells ; the walls of the fibrous cells sometimes 
 remain thin, as in Viscum and some other plants, Avhere they 
 replace the Avood-parenchyma both structurally and functionally.
 
 35] 
 
 CHAPTER II. THE TISSUES. 
 
 141 
 
 Both the woody fibres and the thick-walled fibrous cells may 
 eventually become chambered by the formation of delicate 
 transverse septa. 
 
 The structure of the secondary wood of the root is, in 
 some cases (e.g. Conifers), almost identical with 
 that of the corresponding stem ; this is the case, 
 to a somewhat less degree, in woody Dicotyledons ; 
 whilst in herbaceous Dicotyledons the structure 
 may be very different in the two members, owing, 
 
 FIG. 111. Isolated constituents of the secondary wood of the Lime (Tilia 
 parvifolia). A and B wood-fibres ; C wood-parenchyma ; D and E tracheids ; 
 F segment of a wood- vessel (trachea). G is a bast-fibre. ( x 180 : after Stras- 
 burger.) 
 
 chiefly, to the development of more medullary ray, but 
 less woody tissue, in the root (see above p. 139). 
 
 A transverse section of a stem or a root of most coni- 
 ferous or dicotyledonous trees or shrubs exhibits, even 
 to the naked eye, a series of concentric layers in the 
 secondary wood known as the annual rings (Fig. 112). 
 These layers result from the fact that the wood formed 
 in the spring is differently constituted from that which is formed
 
 142 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [35 
 
 later in the year. The anatomical cause of the distinctness of 
 the annual rings is the same in all cases, namely, that thejast- 
 formed xylem-elements of an annual ring have a very small radial 
 diameter as compared with those formed when growth is resumed 
 in the following spring. In Conifers this distinction is emphasized 
 by the fact that the spring-wood is formed of thin-walled 
 tracheids (Fig. 113 /") and the autumn-wood of smaller thick- 
 walled tracheids (Fig. 113 fi). In dicotyledonous trees the num- 
 ber and size of the vessels diminishes in each annual ring from its 
 inner to its outer limit. When this takes place very gradually, 
 the eye cannot detect any conspicuous difference between the 
 spring- and autumn-wood (as in the wood of the Beech, Lime, 
 Maple, and Walnut) ; but some kinds of wood show a ring of 
 
 FIG. 112. Part of a transverse section of a 
 twig of the Lime, four years old (slightly 
 magnified) : m pith ; ms medullary sheath ; x 
 secondary wood ; 1 2 3 4 annual rings; c cam- 
 bium ; pa dilated outer ends of primary medul- 
 ary rays ; b bast ; pr primary cortex ; fc cork. 
 
 FIG. 113. Transverse section of por- 
 tion of the secondary wood of a branch 
 of the Fir at the junction of two annual 
 rings : m a medullary ray all the other 
 cells belong to the wood ; / large-celled 
 spring- wood ; ih small-celled autumn- 
 wood; w the limit between the autumn- 
 wood of one year and the spring-wood 
 of the following year ; between h and w 
 is the flattened limiting layer ( x 250) . 
 
 conspicuously large vessels in the spring-wood, while in the 
 autumn-wood there are numerous much smaller vessels (as in the 
 wood of the Oak, Elm, and Ash). 
 
 The thickness of the annual ring varies in different plants, and 
 even in any one plant, under different conditions of growth : and 
 not only the thickness, but also the number and relative distribu- 
 tion of the constituents of the wood. 
 
 The secondary wood gradually becomes distinguishable into an
 
 35] CHAPTER II. THE TISSUES 143 
 
 older internal portion, the heart-wood (duramen\ and a younger 
 outer portion, the sap-wood (alburnum). This arises from the fact 
 that^ as the wood becomes older, the cells of the wood-parenchyma 
 and the fibrous cells die and lose their protoplasmic cell-contents ; 
 as a consequence, the heart-wood has less water, in its composition 
 than the sap-wood. In some cases this change is accompanied by 
 a coloration of the cell-walls of the heart-wood, with the result 
 that the distinction of duramen and alburnum is most marked 
 (e.g. Pine, Larch, Oak) ; it is but rarely that this distinction is not 
 observable (e.g. Buxus, Acer pseudoplatanus and platanoides). 
 
 The structure of the secondary bast essentially resembles that of 
 the primary bast. It always consists of sieve-tubes and of paren- 
 chyma, and very frequently of thick-walled fibres as well. 
 
 The sieve-tubes of the secondary bast have the compound sieve- 
 plates shown in Fig. 75, p. 96 ; in Dicotyledons they have com- 
 panion-cells developed in relation with them. The parenchyma 
 very much resembles that of the secondary wood, except that its 
 cell-walls are not lignified ; it is abundantly developed in certain 
 fleshy roots (e.g. Taraxacum, Rubia, and the Carrot and Parsnip), 
 where it constitutes the chief part of the secondary bast. Prosen- 
 chymatous cells with unlignified walls, corresponding to the thin- 
 walled fibrous cells of the secondary wood (p. 140), are sometimes 
 present. The bast-fibres closely resemble the woody fibres, but 
 their walls are not lignified (Fig. Ill G). 
 
 In many cases the secondary bast contains no bast -fibres (e.g. 
 Abietinese, Fagus, Betula, Alnus, Platanus, Cornus, Ephedra, etc.). 
 When, as is usually the case, bast-fibres are present, their arrange- 
 ment presents considerable variety : there may be alternating tan- 
 gential layers of fibres (hard bast) and of sieve-tubes and paren- 
 chyma (soft bast), as in the case of the Cupressinese and some 
 Taxoidese, and, though with less regularity, in many Dicotyledons 
 (e.g. Vitis, Spiraea, species of Acer, Tilia, species of Salix, etc.) ; 
 more commonly the tangential layers of fibres are interrupted here 
 and there by soft bast (e.g. Quercus, Corylus, Carpinus, Pyrus, 
 Juglans, Sambucus, Rhamnus, Ulmus, Populus) ; or there may be 
 scattered groups of fibres (e.g. Cinchona, Morus, Larix, Celtis 
 Ficus elastica). 
 
 The secondary bast does not, as a rule, attain so considerable a 
 size as the secondary wood, nor does it exhibit annual rings : this 
 is due to the fact that, except in some fleshy roots, it is formed in 
 smaller quantity, and further, to the fact that the older bast be-
 
 144 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [35 
 
 comes crusted and flattened by the development of the more inter- 
 nal layers subsequently formed. 
 
 The structure of the secondary conjunctive tissue (medullary 
 rays). The cambium-ring not only adds to the existing primary 
 medullary rays, but gives rise to new (secondary, tertiary} rays in 
 the successive years of growth (see Fig. 112), amongst the vascular 
 tissue. 
 
 The cells of the medullary rays are typically parenchymatous, 
 somewhat brick-shaped, with their long axes along radii from the 
 
 FIG. 114. Radial longitudinal section of the wood of the stem of a Pine, along the length 
 of a medullary ray q p q, consisting of six horizontal rows of cells, one above the other : 
 t tracheids with bordered pits ; the tracheids h with smaller bordered pits are the autumn- 
 wood of one year, those to the right with larger pits constitute the spring-wood of the next 
 year ; q tracheidal elements of the medullary ray ; p true cells of the ray : where the cells 
 of the medullary ray abut on the tracheids the pits are simple and large ( x 300). 
 
 centre to the periphery of the member (Fig. 112); their more or 
 Irss thickened walls are lignified, and they have protoplasmic eon- 
 tents. Occasionally, however, some of the cells of a ray lose their 
 protoplasmic contents and constitute tracheids (e.g. Abietinese, 
 Fig. 114 q q) ; in some few cases the ray consists of long fibrous 
 cells, in place of parenchyma (e.g. shrubby Begonias^. 
 
 The medullary ray is, then, a strand of cells p_assing_radially
 
 35] CHAPTER II. THE TISSUES. 145 
 
 among the longitudinally arranged tissues of the wood and of the 
 bast (Fig. 112). Its size varies, even in the same member, both 
 as regards its vertical (height) and its lateral (breadth) dimen- 
 sions. With regard to the former, the ray may consist of only a 
 single row of cells (as in Abietinese, Quercus, Fagus) ; the limits 
 may be generally stated at 112 rows of cells, though in some 
 cases they are considerably larger than this when they include 
 resin-ducts (e.g. Abietinese) or other forms of secretory tissue. In 
 any case, the secondary medullary rays, unlike the primary, do not 
 extend throughout the whole length of an internode. The breadth 
 of the secondary medullary rays is never nearly so great as their 
 height : as seen in tangential longitudinal section, they are narrow 
 above and below and broader in the middle ; it is only in the 
 middle that they ever consist of more 
 than one row of cells in breadth, the 
 upper and lower margins consisting 
 of a single row only. With regard 
 to their radial extent, it is only the 
 primary medullary rays which extend 
 
 from pith to pericyde; the Subse- FjG . ns :.D iagrammatic repre- 
 
 quently formed rays (secondary, ter- sentation of the course of the 
 tiary, etc.) extend between the wood medulla 7 y s in a segment cut 
 
 , . out of the wood of a tree-trunk: 
 
 and the bast of the year in which they Q horizontal surface; R radial 
 
 were formed. surface; T tangential (external) 
 
 surface of the wood; the shaded 
 AS instances of especially large portions m are the medullary rays. 
 
 secondary medullary rays should be 
 
 mentioned those formed in roots (see Pig. 110, p. 139) where the 
 cambium forms only conjunctive tissue opposite the primary 
 xylem-bundles. Again, in some few stems (see p. 139) the forma- 
 tion of secondary vascular tissue^ is confined to the f ascicular cam- 
 bium > the interfascicular cambium in the primary medullary rays 
 giving rise only to conjunctive tissue; hence the primary medul- 
 lary rays persist as broad bands of conjunctive tissue between the 
 bundles, and are not broken up, as is usually the case, by the 
 formation of secondary bundles from the interfascicular cambium. 
 
 The Differentiation of the Secondary Tissues. The cells, 
 formed as the result of division in the cambium, which are to 
 become transformed into secondary permanent tissue have, to begin 
 with, the same form and structure as the corresponding cambium- 
 cells, but they gradually under- go^changes in both respects, as they 
 become transformed into permanent tissue.
 
 146 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 [ 35 
 
 The development of the young cell into one or other of the 
 various forms of permanent tissue already described, may be 
 either accompanied or unaccompanied by cell-division. In the 
 former case, the divisions may be transverse or longitudinal ; the 
 cell undergoes transverse division when the 
 product is a row of short cells (e.g. wood- 
 parenchyma, Fig. 116 Z>, and Fig. Ill C: 
 bast-parenchyma ; secondary medullary 
 rays, wood-vessels with short segments) : 
 the cell generally undergoes longitudinal 
 division once or twice, by tangential walls, 
 soon after it has been cut off from the 
 cambium ; but this does not take place in 
 the line of the medullary rays, where the 
 radial diameter of the young cells is greater 
 than it is near the bast or the wood : again, 
 the young cell may undergo longitudinal 
 division in a plane other than the tan- 
 gential, as for instance the longitudinal 
 division of the mother-cell, which separ- 
 ates the sieve-tube-segment from the com- 
 panion-cell in the bast of Angiosperms. 
 
 The developing cell may retain its 
 original form and size (e.g. small medul- 
 lary rays ; rows of parenchyma-cells, bast 
 or wood ; thin-walled fibrous cells) : but 
 more commonly the mature product differs 
 very materially from the young cell, being 
 very much wider (e.g. tracheae), or very 
 much longer longitudinally (wood- and 
 bast- fibres), or very much longer radially 
 (e.g. cells of medullary ray) ; that is to 
 say, the development of the young cell into 
 permanent tissue is generally accompanied 
 by very considerable growth. 
 The radial and tangential divisions of the cambium-cells take place 
 in such a manner that the products are, at first, arranged in very 
 definite radial rows. When the resulting tissue consists of ele- 
 ments which are for the most part essentially alike, this regular 
 radial arrangement persists in the permanent tissue ; for instance, 
 in the wood of Conifers (Fig. 113), which consists almost exclu- 
 
 FIG. 116. A Developing 
 vascular cells, derived from 
 the cambium, seen in tan- 
 gential section. JB Tracheid 
 seen from outside. C Woody 
 fibre ; and J) vertical row of 
 wood-parenchyma-cells seen 
 in section, from the Oak ; 
 isolated by maceration.
 
 35] CHAPTER II. THE TISSUES. 147 
 
 sively of tracheids ; but where some of the elements (as generally 
 in the wood of Dicotyledons) attain a much greater size (as seen 
 in transverse section, Fig. 105), the original radial arrangement 
 is lost. 
 
 In those cases in which the permanent tissues consist of very 
 long or very wide fibres or vessels, it is evident that the relative 
 position of the original cells must have undergone considerable 
 change in the course of development ; the long fibre is in contact, 
 longitudinally, with a greater number of cells than was originally 
 the case ; and similarly, the wide trachea touches, at its circum- 
 ference, a larger number of cells than did the cell, originally, from 
 which the segment of the vessel was developed. This gradual 
 change of relative position constitutes what is termed sliding- 
 groicth ; it is the expression of the independent growth of each 
 cell in the course of its development into the particular element 
 of the permanent tissue which it is destined to form. This process 
 is by no means confined to the vascular tissues, but takes place 
 wherever a young developing cell grows more actively, in any 
 dimension, than the cells with which it is at first in contact ; a 
 notable example is the growth of the laticiferous coenocytes of 
 Euphorbia (see p. 100). 
 
 Whilst undergoing these changes of form, the developing cells 
 undergo, as already indicated, changes in the structure and 
 chemical composition of their cell-walls in accordance with the 
 particular kind of tissue to which they are to give rise ; and, in 
 some cases (tracheae, tracheids, fibres) they lose their protoplas- 
 mic cell-contents ; the walls become more or less thickened, not 
 spiral or annular as in primary wood, but pitted (with simple 
 pits ; or circular bordered pits ; or oval bordered pits, either small 
 and numerous, or large extending across a whole face of the wall, 
 giving it a scalariform appearance, see p. 74) ; and then the 
 absorption, more or less complete, of the septa takes place, which 
 leads to the formation of the vessels. 
 
 Glandular tissue is frequently developed in the secondary wood and 
 bast, in the form, sometimes, of sacs containing crystals, in the paren- 
 chyma (including medullary rays) of the wood (e.g. Vitis, and some 
 leguminous trees) or more commonly in that of the bast : of resin-ducts 
 which occur in the secondary wood of certain Abietineae, running hori- 
 zontally in the medullary rays and vertically in the wood, but rarely 
 found in the secondary bast, whereas in other plants which possess these 
 structures, they are rare in the wood but abundant in the bast (e.g. 
 Anacardiaceae, etc.) : of laticiferous vessels, rare in the wood (except the
 
 148 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 35 
 
 Papayacese, where the wood consists largely of parenchyma), abundant in 
 the bast. 
 
 In Monocotyledons there is no primary cambium-layer, the bundles 
 being all closed. In some cases, however, secondary growth in thickness is 
 effected by a ring of meristem quite external to the primary bundles; this 
 occurs in the stems and roots of some arborescent Liliaceae, such as 
 
 Yucca and Dracaena, where 
 a rin S of meristem is usually 
 developed in the pericycle, 
 but in the roots of Dracaena 
 it is formed partly from the 
 pericycle and partly from the 
 cortex. This meristem-ring 
 is not termed a cambium- 
 ring, because it does not form 
 wood on one side and bast 
 on the other, but it forms, 
 centrifugal ly, entire closed 
 concentric (with external 
 
 ^j/ wood) bundles, together with 
 intervening ground-tissue 
 (Fig. 117). 
 
 The development of 
 secondary vascular tissue 
 takes place almost exclu- 
 sively in such stems as are 
 monostelic and in which 
 the primary bundles are 
 common. It is clear that 
 the additions to the prim- 
 ary bundles in the older 
 internodes of the stem, as 
 well as any secondary 
 bundles which may have 
 been formed from the cam- 
 bium are not common, but cauline ; they are, however, in communi- 
 cation with the primary common bundles of the young unthickened 
 internodes which are bearing leaves ; in fact, the newly-formed 
 secondary vascular tissue of the lower internodes of the stem is in 
 communication, on the one hand with the root, and on the other 
 with the leaves ; and the channels of communication between root 
 and leaf are maintained year by year by the annual formation of 
 young conductingrtissue, both wood and bast, in the older parts of 
 the stem and of the root. 
 
 F:o. 117. Portion of a transverse section of the 
 stem of a Dracaena: e epidermis; k periderm ; r 
 primary cortex, with a leaf-trace-bundle b; x 
 merismatic zone in which new bundles g-g are in 
 course of development ; m primary, and st second- 
 ary, ground tissue. (Magnified : after Sachs.)
 
 35] CHAPTER II. THE TISSUES. 149 
 
 It will be remarked that the development of secondary vascular 
 tissue takes place in those plants the stems of which branch more 
 or less (e.g. an Oak), while it usually does not take place in those 
 plants the stems of which do not branch (e.g. the Palm), or do so 
 only slightly. It is obvious that, wlien the ste'm is of branching 
 habit, the number of leaves must increase year by year, whereas 
 when the stem does not branch the number of leaves does not vary 
 materially. Hence the whole matter may be summed up thus, 
 that the development of secondary vascular tissue in a stem is 
 directly correlated with an increase in the area of leaf -surf ace : as 
 in each year the leaf-surface of a tree increases in consequence of 
 repeated branching, so does the annual ring of secondary vascular 
 tissue become larger in circumference and possibly also of greater 
 thickness ; when, however, the tree begins to grow old, and its 
 branches, instead of increasing in number, begin to die off, then 
 the annual growth in thickness becomes arrested. Some further 
 explanation of this is given in Part III. 
 
 B. The formation of Secondary Tegumentary and Cortical 
 Tissue. It is clear that the more or less considerable development 
 of secondary tissue in the interior of a young stem or root, must 
 have a very considerable effect on the primary cortex, and on the 
 primary tegumentary tissue. This effect will be one of pressure 
 and tension ; the radial growth of the stelar tissue will exert a 
 radial pressure upon the external tissues, while the tangential 
 growth of the stelar tissue will exert a tangential tension on the 
 external tissues. The radial pressure of so firm a structure as is 
 usually that of the secondary vascular tissue tends to cause more' 
 or less rapid obliteration of the softer cortical tissue ; whilst the 
 tangential tension stretches the cortical cells and tends to cause 
 them to grow tangentially, and to multiply by radial division. 
 According to the predominance of the radial pressure or of the 
 tangential tension, the primary cortex is either rapidly destroyed, 
 or it persists for a very considerable period. 
 
 It may be stated generally that the epidermis and the primary 
 cortical tissue of herbaceous dicotyledonous stems keep pace by 
 growth with the formation of new tissue in the interior. This is- 
 true also of most woody shoots during the first year of their- 
 growth and in certain cases (e.g. Mistletoe, Holly, Acer striatuirij- 
 etc.) of woody shoots during their entire existence ; in some cases 
 (e.g. Euonymus) the epidermis persists and grows for several 
 years, but is at length disorganised. These primary tissues per-
 
 150 PART II. ANATOMY AND HISTOLOGY. [ 35 
 
 8\st also in some roots (e.g. Vicia Faba, Alchemilla vulgar is), in 
 which the development of secondary vascular tissue is not very 
 active. The extension of the tissue is effected by tangential 
 growth and radial division of the cells. 
 
 The secondary tegumentary and cortical tissue is formed by 
 a layer of merismatic cells, which is known as the Phellogen. 
 
 In fhc stem the place of origin of the phellogen is by no means 
 uniform. It is sometimes formed by the epidermis becoming mer- 
 ismatic (e.g. Pomese, Salix, Viburnum Lantanctj Euonyrnus, So- 
 larium, etc.) ; most commonly it is the hypodermal layer of cells, 
 the outermost layer of the cortex, which becomes merismatic and 
 constitutes the phellogen (e.g. Platanus, Acer, Fagus, Quercus, 
 Castanea, Betula, Alnus, Ulmus, Populus, Ailanthus, Abies pec- 
 tinata, etc.) : in other cases the phellogen is formed at a greater 
 depth from the surface, being developed from a more internal 
 layer of cells of the cortex, sometimes even from the endodennis 
 (e.g. Cojfea ctrabica ; subterranean shoots of some LeguminosaB 
 such as Lotus corniculcttus, Trifolium alpestre) ; or, finally, it is 
 stelar, being formed from a layer of cells belonging to the peri- 
 cycle (e.g. Hypericum, Erica, most Caryophyllacese, Lonicera, Vitis, 
 Clematis, Berberis, Rosa, Spiraea, Ribes, etc.). 
 
 The development of tissue from the phellogen follows the same 
 law as in the case of the cambium. Generally speaking, a 
 tissue, the periderm, is formed on the outer side of the phel- 
 logen by repeated centripetal division ; whilst on the inside of 
 the phellogen a tissue, the phettoderm, is formed by repeated 
 centrifugal division. The periderm constitutes the secondary 
 tegumcntaiy tissue of the stem or root ; the phelloderm consti- 
 tutes the secondary cortex. The developmental relations between 
 the two tissues are not constant. In some cases the formation 
 of phelloderm only begins after a considerable mass of periderm 
 has already been produced ; but in others, the formation of the 
 two tissues goes on almost simultaneously. The relation between 
 the amount of periderm and the amount of phelloderm formed 
 by one and the same phellogen is by no means uniform : whilst 
 the development of periderm is most marked in subaerial stems 
 with superficial phellogen, there is little or no phelloderm in 
 these stems ; again, in subaerial stems with a deeply-placed (e.g. 
 pericyclic) phellogen, periderm and phelloderm are developed about 
 equally ; finally, in subterranean stems with a pericyclic phellogen, 
 the well-developed phelloderm may exceed the periderm.
 
 35] CHAPTER II. THE TISSUES. 151 
 
 In the root, as in the stem, the position of the phellogen, and the 
 products of its activity, are various. The phellogen is developed 
 but rarely (e.g. Solidago) from the epiblem ; more commonly from 
 the exodermis, or from the next internal layer of the primary 
 cortex, as in a few woody Dicotyledons (e.g. Jasminum) in which 
 the formation of secondary vascular tissue takes place relatively 
 late ; and in the Cycads among Gymnosperms. In the great ma- 
 jority of Dicotyledons and Gymnosperms the phellogen of the root 
 is stelar in origin, being derived from the pericycle. 
 
 As in the stem, so in the root, the phelloderm is more highly 
 developed when the phellogen is deeply placed than when it is 
 superficial ; but even with a uniform position of the phellogen, the 
 relation between the periderm and the phelloderm developed, varies 
 considerably : thus, among plants with a pericyclic phellogen, 
 whilst the development of periderm and phelloderm is sometimes 
 about equal (e.g. Willow), no phelloderm but only periderm is 
 developed in Nerium, whilst in some others (e.g. Vicia Faba, 
 Alcliemilla vulgaris), where the primary cortex persists (see 
 p. 149), only phelloderm is developed. 
 
 It frequently happens in both stems and roots that the first- 
 formed primary phellogen has but a limited period of merismatic 
 activity ; this is always the case when the primary phellogen is of 
 deep origin (pericyclic in roots), whereas when it is of superficial 
 origin (e.g. epidermal or hypodermal phellogen in stem of Beech, 
 Hornbeam, Silver Fir, Cork-Oak, Cork -Elm), the primary phellogen 
 is frequently persistent. In the former case, however, when the 
 primary phellogen has passed over into some form of permanent 
 tissue, a new secondary phellogen, also of limited duration, is 
 developed internally to the first, and this process is repeated at 
 intervals ; hence the phellogen-layers become successively more and 
 more deeply seated, penetrating at length into the bast-tissue of the 
 stele. 
 
 The periderm, or secondary tegumentary tissue, the tissue formed 
 externally from the phellogen, consists of parenchymatous cells 
 more or less cubical in form, though sometimes somewhat elongated 
 tangentially (Fig. 118) ; the cell-walls may be thin or considerably 
 thickened ; generally speaking, the walls are completely suberised 
 (see p. 76), whence the tissue is often termed Cork; the cells 
 gradually lose their protoplasmic contents, and become filled with 
 air ; moreover, no intercellular spaces are formed in the tissue. 
 
 In view of its structure, it is clear that the periderm is a tissue
 
 152 
 
 PART II. ANATOMY AND HISTOLOGY. 
 
 35 
 
 which offers an obstacle to the passage of water ; hence all the 
 tissues, in a stem or root, lying externally to the periderm can receive 
 no supplies of water, and must dry up, and are eventually exfoli- 
 ated. The more deeply seated the phellogen, the greater is the 
 amount of primary tissue thrown off; thus, when the phellogen 
 arises in the inner layers of a heterogenous pericycle (see p. 119), 
 as in Berberis, Lonicera, etc., where the outer portion of the 
 pericycle is fibrous, the epidermis, the primary cortex, and the 
 outer portion of the pericycle are exfoliated. 
 
 The cells of the periderm are not always completely suberised. 
 In some cases (roots and stems of Onagracese, Hypericacese, some 
 
 Rosacese, etc.) some 
 layers of the peri- 
 derm consist of cells 
 with a suberised zone 
 like that of the cells 
 of the endodermis 
 (see p. 116), though 
 these cells usually 
 become completely 
 suberised eventually. 
 In other cases (e.g. 
 stem of Poteriiim, 
 Alchemilla, Agri- 
 monia, Epilobium) 
 the periderm con- 
 sists mainly of cells 
 with cellulose-walls, 
 
 FIG. 118.-Periderm of one-year's shoot of Ailanthus V + PAT1 w hir}i m- 
 
 glandulosa (trans, sect. ; x 350) : e the dead epidermis ; k cork ; D 
 
 the inner shaded layers are merismatic, the innermost being tercellular Spaces are 
 
 the phellogen, those external to it being young periderm f nrTnp ^ together 
 cells; r primary cortex. 
 
 with occasional com- 
 pact layers of cells with a suberised zone. 
 
 When the' primary periderm is of superficial origin, it forms for 
 many successive years the external investment of the branch ; it 
 may attain considerable thickness, as in the Cork-Oak, and at the 
 same time exhibit an alternation of dense and loose layers (e.g. the 
 Birch, in which the layers may be peeled off in thin white sheets) ; 
 sometimes (as in Acer campestre and the Cork-Elm) it forms wing- 
 like projections from the angles of the branches. In a few trees, as 
 the Silver Fir, the primary periderm persists for some years, or, as
 
 35] 
 
 CHAPTER II. THE TISSUES. 
 
 153 
 
 in the Beech, during the whole life of the tree ; the outer cork-cells 
 split off as the trunk of the tree increases in thickness, while the 
 phellogen, growing and extending in a tangential direction, gives 
 rise to new layers of cork. When, as in most cases, new layers of 
 phellogen arise after a few years in the deeper -tissues, leading to 
 the development of corresponding layers of periderm, an external 
 investment of a more or less complicated structure comes to be 
 formed. In consequence of the impermeability to water of these 
 secondary layers of periderm, all the tissues lying externally to them 
 become dried up. These dried-tip tissues, which may belong to 
 different tissue- 
 systems and include 
 the most various forms 
 of cells, constitute 
 what is known as 
 Bark. When the 
 primary periderm is 
 superficial, the new 
 secondary layers of 
 periderm are only arcs 
 of the circumference, 
 and as their margins- 
 are in contact with 
 the periderm which 
 has been previously 
 formed (Fig. 119), a 
 scaly bark is formed, 
 that is, isolated 
 patches of tissue are 
 transformed into bark. 
 This bark is stretched and torn by the increasing size of the 
 trunk, and the scales of it may be shed, as is the case in the Plane, 
 or they may adhere one upon the other, as in the Pines and Larches, 
 or remain connected by the bast-fibres in long strips as in Robinia. 
 When, on the other hand, the primary periderm has been formed in 
 the deeper layers of the cortex, the secondary periderm often forms 
 complete concentric rings ; thus hollow cylinders of the cortex are 
 transformed into bark (ringed bark). The longitudinal rupture of 
 this kind of bark is effected by the bast-fibres enclosed in it (e.g. 
 Vine, Clematis, and Thuja). 
 
 There are frequently in the periderm of both stems and roots 
 
 Fig; 119. Formation of Scaly Bark in a Larch, as 
 seen in a piece of the outer portion of the stem cut both 
 transversely and longitudinally (nat. size) ; r the 
 secondary cortex ; fe plates of cork ; b the scales of bark 
 cut off by the cork.
 
 154 PART II. ANATOMY AXD HISTOLOGY. [ 35 
 
 organs corresponding to the stomata of the epidermis, serving, like 
 them, to admit air to the living internal tissues ; these are the 
 Lenticels. They are usually circumscribed circular areas of the 
 periderm where the cork-cells formed in the course of the summer 
 are not arranged closely together, but are separated by intercellular 
 spaces. In winter the lenticels are closed by a layer of ordinary 
 periderm. They are most easily detected in branches of one year's 
 growth, where they are to be seen in the summer in the form of 
 brownish or whitish specks. When the periderm of the stem is 
 superficial, the lenticels are developed under the places where the 
 stomata occur in the epidermis, and these spots are commonly the 
 starting-points of the formation of the periderm; but this is not the 
 case in stems with a deep periderm, nor is it ever the case in roots. 
 
 In many trees, as the Birch, 
 the lenticels become much 
 extended in width by the 
 growth of the branch in 
 circumference. When the 
 periderm is very thick, as 
 in the Cork-Oak, the len- 
 ticels form deep canals 
 filled with a pulverulent 
 
 FIG. 120.-Lenticel in the transverse section of a aSS of cells. Sometimes 
 
 twig of Eider (x 300): c epidermis; q pheiiogen; i lenticels are not formed ; 
 
 cells, and pi the pheiiogen of the lenticel ; Ic cortical , , , 
 
 parenchyma containing chlorophyll. the y are not P reSent m 
 
 the stems of some plants 
 
 which have a pericyclic pheiiogen (e.g. Vitis, Clematis, Rubus, 
 Lonicera). 
 
 The phcllodcrm or secondary cortical tissue, the tissue formed 
 internally from the pheiiogen, consists of cells which have 
 essentially the same structure as those of the primary cortex : the 
 secondary cortex can, however, be distinguished from the primary 
 by the regular radial rows in which, like those of the periderm, its 
 cells are arranged. The cells have protoplasmic cell-contents, and, 
 when developed near the surface of aerial stems, they contain 
 chloroplastids ; their walls are usually thin and consist of cellulose, 
 but, like those of the cells of the primary cortex, they may become 
 more or less thickened and eventually lignified. 
 
 Just as the periderm replaces the disorganised epidermis as a 
 tegumentary tissue, sa the phelloderrn replaces the primary cortex 
 as a nutritive (metabolic) tissue when the primary cortex becomes 
 obliterated under the conditions explained on p. 149.
 
 3G] 
 
 CHAPTER II. THE TISSUES. 
 
 155 
 
 36. Formation of Tissue in consequence of Injury. 
 
 When the internal tissues of most parts of plants are laid bare by 
 injury, they are gradually covered by a formation of cork taking 
 place in the outermost layer of cells which remain uninjured and 
 capable of growth. This is easily seen in injured fruits, leaves, 
 and herbaceous stems, in which the wounds that have been covered 
 by a layer of cork are distinguished by a grey-brown colour. The 
 process is very easy to observe in potato-tubers, for each portion 
 of living tissue taken from one, if only prevented from drying too 
 quickly, will soon be covered 
 over the whole surface by a 
 layer of cork precisely similar 
 in structure to the ordinary 
 rind. In plants in which the 
 wood is well developed, cork 
 is not immediately formed 
 particularly when the cam- 
 bium is wounded or laid bare 
 but all the living cells 
 which border on the wound 
 become merismatic and give 
 rise to a homogenous j>aren- 
 chymatous tissue known as 
 tlic Callus. If the wound is 
 small, the callus-cells pro- 
 ceeding from the different 
 sides soon come into contact 
 and close up into a single 
 mass of tissue, which then 
 gives rise to cork on its outer 
 surface, and, joining the old 
 
 cambium at the margins, forms a new layer of cambium which 
 fills up the cavity. If the wound is a large one, cork and new 
 cambium are formed in the callus at the margins of the wound, and 
 it is not wholly closed till after repeated rupture of the approach- 
 ing cushions of callus. The wood exposed by the wound, which 
 usually assumes a dark colour tinder the influence of the air, does 
 not grow with that formed from the new cambium of the callus : 
 hence inscriptions, for instance, which are cut in the cortex so 
 as to reach the wood, though subsequently covered by a number 
 of annual layers of wood corresponding to the number of years, 
 
 FIG. 131. Diagrammatic longitudinal section 
 of a woody stem : A a short time after t.e 
 amputation of a lateral branch s; JB when the 
 wound is completely closed ; r cortex ; c cam- 
 bium ; 7i wood ; c' position of the cambium- 
 layer at the time of amputation ; fc' wood formed 
 since the amputation ; w the cushion of callus 
 formed over the surface of the wound.
 
 156 PART II. ANATOMY AND HISTOLOGY. [ 36 
 
 may easily be found. A similar explanation accounts for the fact 
 that the surfaces of the stumps of cut-off branches become over- 
 grown : the callus first appears as a ring from the cambium ex- 
 posed in the transverse section, and afterwards closes like a cap 
 over the old wood (Fig. 121). Foreign bodies nails, stones, and 
 stems of other plants may thus become enclosed in the wood of 
 a tree and be over-grown by it ; the cortex, being forced against 
 the foreign object by the pressure of the growing wood, splits, and 
 the callus formed in the rent grows round the object, enclosing it 
 and producing new cambium. 
 
 Steins of plants of the same species will grow together if they 
 are in close contact : the callus formed by the cortex of both, 
 coalesces and gives rise to a common cambium. On this depend 
 the various modes of artificial grafting, in which branches orjbuds 
 with a portion of the cortex are taken from a variety or an allied 
 species and placed so that their cambium is in contact with that 
 of a stem which serves as the stock, and subsequently they grow 
 together. 
 
 In conclusion, the mechanism by which deciduous members (see 
 p. 10). are detached has to be considered : the fall of the foliage- 
 leaf may be taken as the illustration. In some cases (e.g. Palms ; 
 some Ferns, as in the section Phegopteris ; the Oak) the leaves 
 simply wither on the stem, when they are non-articulated, and 
 are gradually destroyed and removed ; but in most cases they are 
 thrown off by a vital act before they wither, when they are said 
 to be articulated. The fall of the articulated leaf depends upon 
 the growth and division of all the living cells lying in a trans- 
 verse layer near its insertion ; by this means several (3 6) layers 
 of compact tissue are formed. A median layer of this tissue, the 
 abscission-layer, becomes disorganised, and then the leaf is held 
 in position only by the vascular tissue which enters it from the 
 stem. This soon breaks under the weight of the lamina, especially 
 if it be agitated by the wind, and the leaf falls. The disorgan- 
 isation of the median layer is often accelerated by the action of 
 -frost. The scar on the stem (leaf-scar, p. 10) either simply dries 
 up, or a layer of cork is formed over it by the merismatic tissue 
 which remains : in any case the vessels become sealed with mu- 
 cilage.
 
 PART III 
 PHYSIOLOGY 
 
 37. Introductory. The province of physiology is the study 
 of those phenomena which, taken together, constitute the life of 
 the plant ; in other words, whilst morphology is concerned with 
 what plants arc, and histology with their structure, physiology 
 deals with what they do. These phenomena may be classified, 
 according to their nature, into functions, or different kinds of 
 physiological work. 
 
 The body of the plant, whether it be unicellular or multicellular, 
 is one physiological whole. In the lower and simpler plants the 
 various functions are equally discharged by all parts of the body ; 
 but in more highly-organised plants the functions are distributed 
 among the members and tissues, that is, there is physiological 
 division of labour. In these higher plants each member, and 
 each tissue, is adapted to the performance of one or more functions, 
 and is the organ (p. 1) by which these special kinds of physio- 
 logical work are done. 
 
 The performance of their functions by the organs of the plant is, 
 however, materially affected by various external conditions. For 
 instance, the activity of the assimilatory function of green leaves is 
 altogether dependent upon exposure to light of adequate intensit3 r . 
 Hence the object of physiology is not only to distinguish and study 
 the various functions, and to demonstrate the relation between them 
 and the internal structure and the external form of the organs per- 
 forming them, but also to determine what are the external conditions 
 by which the performance of the various functions is affected, and 
 the modes in which these conditions exert their influence. 
 
 CHAPTER I 
 
 GENERAL PHYSIOLOGY 
 
 38. The Functions. In entering upon the consideration of 
 the vital phenomena of plants, it must be clearly understood that 
 these phenomena all depend upon the living protoplasm ; that the 
 
 157
 
 158 PART III. PHYSIOLOGY. [ 38 
 
 vital functions are performed by the protoplasm, though the other 
 cell-contents and the cell-walls are not without their physiological 
 importance. With regard to the functions themselves, it is 
 apparent, in the first place, that the outcome of the physiological 
 activity of the plant is the maintenance of itself, and the production 
 of new individuals resembling itself. Hence a distinction may 
 at once be drawn between the nutritive and the reproductive 
 properties of protoplasm. Moreover, during its life, the plant 
 responds, in a more or less marked manner, to the action of external 
 forces, such as light, gravity, etc. This is a manifestation of 
 another property of the protoplasm, namely irritability or 
 sensitiveness. Very commonly the response to the action of the 
 external forces is of the nature of movement ; but movements may 
 also be performed spontaneously. 
 
 It is clear that nutrition necessarily depends upon the absorption 
 of food from without ; hence the plant is capable of performing the 
 function of absorption. From the food absorbed, protoplasm is 
 ultimately formed; the building up of protoplasm out of the food is 
 termed assimilation, and the property by means of which this 
 function is performed is termed the metabolic property of proto- 
 plasm. But the metabolic processes going on in the protoplasm are 
 not only such as lead to its maintenance or increase in bulk ; on the 
 contrary, the protoplasm is continually undergoing decomposition. 
 It is to be clearly apprehended that there are two sets of chemical 
 processes continually and simultaneously going on in living proto- 
 plasm. Of these, which together constitute the metabolism of the 
 plant, one set includes those processes which lead to the formation 
 of more complex substances from simpler ones ; the other, those 
 processes which lead to the formation of simpler substances by the 
 decomposition of more complex ones. The former are designated 
 the constructive metabolism, or more shortly the anabolism, of the 
 protoplasm ; the latter are designated the destructive metabolism, 
 or the catabolism, of the protoplasm. It must also be clearly 
 understood that these two sets of processes affect not only the state 
 of the matter or substance of which the plant consists, but also the 
 state of the energy in the plant ; for the anabolism is accompanied 
 by a conversion of kinetic into potential or latent energy ; and the 
 catabolism, by a conversion of potential into kinetic energy. 
 
 The products of metabolism may be classified as plastic products 
 and waste-products : the former are such as can be further worked 
 up in anabolism ; the latter are not so used, but are withdrawn
 
 39] CHAPTER I. GENERAL PHYSIOLOGY. 159 
 
 from the sphere of the metabolic activity, by being either excreted, 
 6r~~iecreted in the insoluble form in special receptacles (see p. 
 96}7~ Of the products of catabolism, carbon dioxide is' the most 
 constant. 
 
 There is one property of living plant-cells which is of such funda- 
 mental importance, particularly in connexion with movement, that 
 it requires special mention. It is this, that the cells tend to take 
 up such large quantities of water, that a considerable pressure is 
 set up in the cell between the cell-sap, on the one hand, and the 
 elastic cell-wall on the other. This state of tension is known as 
 iuryidity or turgescence, and a cell in this state is said to be turgid. 
 The conditions upon which turgidity depends are three : first, the 
 presence of substances in the cell-sap which attract water ; second, 
 the presence of a layer of protoplasm lining the cell- wall ; third, the 
 presence of an elastic cell-wall. With regard to the first of these 
 conditions, the necessity for it is obvious. It appears that the 
 substances in question are especially the organic acids or acid salts, 
 which are abundantly produced in the metabolism of plants. The 
 significance of the second condition is, that the layer of protoplasm 
 prevents, at least within certain limits, the escape of the cell-sap 
 as the pressure in the cell increases, and it is on this account that 
 a high tension can be attained. Finally, the presence of an elastic 
 cell-wall is a necessary factor, for without resistance there can be 
 no tension . 
 
 39. The External Conditions. The functions of the plant 
 can only be carried on under a certain coincidence of favourable 
 external conditions. Thus, an ordinary green plant will onlv 
 flourish when the conditions are such that it is supplied with 
 appropriate food, with water, and with free oxygen for its respir- 
 ation, and is exposed to a suitable temperature and to sufficiently 
 intense light. 
 
 The importance of a supply of food and of water is sufficiently 
 obvious to need no further explanation here. The importance of a 
 supply of oxygen is that without it the normal catabolic processes 
 would either cease, or be SD far suppressed that the plant would no 
 longer manifest its vital phenomena ; for instance, it would cease 
 to grow, and would eventually die. 
 
 Inasmuch as the influence of heat and light is so comprehensive, 
 it may be generally considered now, the detailed consideration of 
 these and other external conditions being relegated to the discussion 
 of the functions which they especially affect.
 
 160 PART III. PHYSIOLOGY. [ 39 
 
 HEAT. Every function of the plant can only take place within 
 certain limits of temperature : that is, between a certain minimum 
 and a certain maximum degree. Between these limits there Js for 
 each function a degree of temperature, the optimum, at which that 
 function is carried on with the greatest activity ; any fall of 
 temperature from this optimum, or any rise above it, leads to a 
 diminished activity of the function. These general laws have been 
 arrived at by observation of such processes as movement, absorp- 
 tion by the roots, assimilation, etc. 
 
 It may be stated generally that all the functions of plants 
 inhabiting temperate climates begin to be carried on at a tempera- 
 ture a few degrees above the freezing-point ; as the temperature 
 rises to 25-30 C. the activity of the functions is increased and the 
 optimum attained ; with a further rise the activity of the functions 
 is diminished, and at 45-50 C. they commonly cease altogether. 
 In the case of plants which naturally grow in warmer climates, the 
 minimum-temperature is somewhat higher than that stated above. 
 Thus a pumpkin-seed will not germinate at a temperature below 
 13 C. 
 
 The power of withstanding the injurious effect of exposure to too 
 high a temperature depends mainly upon the proportion of water 
 which the plant, or any particular part of it, contains. Thus, dry 
 peas can withstand exposure for an hour to any temperature up to 
 70 C., whereas, when they have been soaked in water, exposure to 
 a temperature of 54 C. proves fatal. Most parts of plants are 
 killed by prolonged exposure to a temperature, in air, of about 
 50 C., and in water, of about 45 C. 
 
 Injury or death by exposure to cold, is only induced when the 
 temperature falls in some cases many degrees below freezing- 
 point. Some plants just those, namely, such as Lichens, and some 
 Fungi and Mosses, which can undergo dessication without injury 
 are not killed by exposure to low temperature. Here, also, the 
 liability to injury depends upon the amount of water contained in 
 the tissue. Thus, dry seeds and the winter-buds of trees can 
 readily withstand low temperatures ; but when they contain a 
 considerable quantity of water, as when the seeds are germinating 
 or the buds unfolding, they are very susceptible to injury. When 
 a part of a plant, which contains a large proportion of water, is ex- 
 posed to a low temperature, a portion of the water contained in the 
 cells escapes from them and becomes frozen on their surface, the 
 whole tissue at the same time contracting ; the water does not
 
 39] 
 
 CHAPTER I. GENERAL PHYSIOLOGY. 
 
 161 
 
 freeze in the interior of the cells. The water which has thus 
 escaped and frozen forms an incrustation (Fig. 122), consisting of a 
 number of elongated ice-crystals arranged side by side. This ice 
 is very pure, for the substances in solution in -the cell-sap remain 
 behind in a more concentrated form. 
 
 The effect on the trunks of trees of exposure to cold is to cause 
 radial splits, which close up again as the temperature rises, the 
 which actually heal only in the cortex. The splitting is due to 
 the unequal contraction of the wood, which is greater in the 
 external more watery portion, than in the interior. 
 
 JLiGHT. The influence of light may be considered under t_wp_ 
 heads : (1) the chemical effects, pro- 
 duced for the most part by the less 
 refrangible rays of the spectrum ; 
 (2) the mechanical effects, produced 
 mainly by the highly refrangible 
 rays. 
 
 The most conspicuous chemical 
 effects are manifested in plants which 
 normally contain chlorophyll. They 
 are : 
 
 a. The formation Of chlorophyll : Pls ' ^--Transverse section of a 
 
 *- frozen leaf-stalk of Cynara Scolymus: 
 
 in Phanerogams the Colouring-matter 6 the detached epidermis ; g the paren- 
 
 in which lie the transverse 
 sections of the vascnlar bundles (left 
 white) ; K K the incrustation of ice 
 Of Conifers and SOine Other plants), consisting of densely-crowded prisms 
 , , - v -,1 , .. ,. -, ' (the cavities of the ruptured tissue 
 
 but remains yellow (etiolm), unless are i e tt black in the figure), 
 exposed to light of not too great in- 
 tensity. This effect is not confined to the rays of low refrangi- 
 bility, but is produced (with equal intensity of light) also by those 
 of high refrangibility. The formation of chlorophyll is also de- 
 pendent on temperature, and will not take place if it be too low ; 
 hence the shoots of plants developed in the early spring remain 
 yellow if the weather is cold. 
 
 b. The assimilation of carbon dioxide by the chloroplastids will 
 only take place in the presence of light of considerable intensity ; 
 it is especially a function of the rays of low refrangibility, as will 
 be subsequently explained. This is also true of the first steps in 
 the assimilation of mineral nitrogenous food (nitrates). 
 
 The most conspicuous mechanical effects, exhibited by plants of 
 all kinds are : 
 
 of the chloroplastids cannot acquire cb5 [ r 
 its green hue (except in the seedlings
 
 162 PART III. PHYSIOLOGY. [ 40 
 
 a. The paratonic effect. All parts of plants grow more rapidly 
 in feeble than in strong light, as is shown by the excessive length 
 attained by the shoots of plants grown in the dark ; hence, light 
 exercises a retarding influence on the rate of growth ; it Jikewise 
 inhibits the spontaneous movements of motile leaves. 
 
 b. The phototonic effect. Dorsiventral leaves, when growing, 
 generally cease to grow, and when motile lose the power of move- 
 ment, if long kept in darkness ; but they_ soon regain the power 
 of growth and of movement on being again exposed to light ; this 
 condition of motility induced by light is known as phototonus. 
 
 c. The directive effect. The direction of the incident rays of 
 light effects the position of growing and other motile members : 
 these phenomena are designated by the general term heliotropism. 
 
 The various influences of light are well illustrated by plants 
 grown in darkness, or etiolated plants. For instance, an etiolated 
 potato-shoot has a stem with excessively long internodes, a result 
 of the absence of the paratonic effect of light ; very small leaves, 
 in consequence of the absence of the phototonic effect ; no chloro- 
 phyll, in consequence of the absence of the chemical action of 
 light. Etiolation can, however, be induced, not only in plants 
 which normally possess chlorophyll, but in others as well ; jor 
 instance, Fungi grown in darkness exhibit the characteristic 
 excessive elongation. Again, plants grown in light of low re- 
 frangibility (yellow or red) show the elongation characteristic of 
 etiolation ; chlorophyll is formed, and the leaves are fairly well 
 developed, but there is no heliotropic curvature : grown in light 
 of high refrangibility (blue), the stem is stunted and the leaves 
 very small, though chlorophyll is developed, and heliotropic 
 curvature is well marked ; they soon die. 
 
 40. The Functions of the Tissues. In dealing with this 
 subject, it is important to distinguish between the vital and the 
 physical functions; to distinguish, that is, the functions which 
 depend upon the activity of the living protoplasm, from those 
 which depend upon some chemical or mechanical property of the 
 cell-sap, or of the cell-wall, of the constituent cells. The following 
 remarks apply especially to the higher terrestrial plants. 
 
 a. The Tegumentary Tissue (pp. 106, 149), whether primary 
 
 (epidermis) or secondary (periderm), has as its primary function 
 
 : the mechanical protection of the underlying tissues : but it has 
 
 the further functions of absorption and of preventing excessive loss 
 
 of water by transpiration.
 
 40] CHAPTER I. GENERAL PHYSIOLOGY. 163 
 
 The absorptive function is confined to the primary tegumentary 
 tissue : it is by means of this tissue that absorption is carried 
 on by subterranean roots, either with or without root-hairs (see 
 pp. 109, 110), as also by the general surf ace- of submerged parts 
 of aquatic plants (p. 109). 
 
 The prevention of excessive transpiration is effected by the 
 more or less well-marked cuticularisation of the walls of the 
 epidermal and peridermal cells of sub-aerial parts. Since these 
 walls, though more or less pervious to gases, are almost or 
 altogether impervious to watery vapour, the watery vapour 
 evolved in the interior of the plant has to escape through special 
 apertures, namely the stomata and the lenticels : and the tran- 
 spiration is further regulated (see p. 108) by the opening and 
 closing of the stomata. The importance of the tegumentary tissue 
 in preventing desiccation is directly established by the fact that 
 parts of plants deprived of their tegumentary tissue quickly dry 
 up : and indirectly, by the relation between the degree of develop- 
 ment of this tissue and the conditions of life of the plant. Thus, 
 this tissue is highly developed in plants which grow in dry 
 situations, whereas in the submerged parts of aquatic plants it 
 is imperfectly differentiated, and there are usually no stomata 
 or lenticels : hence, the more the conditions of life tend to pro- 
 mote transpiration, the more highly-developed is the tegumentary 
 tissue. 
 
 b. The Parenchymatous Tissue (see p. 90), consisting as it i 
 typically does of cells which contain living protoplasm, is the 
 seat, not only of the metabolic processes, but also of the movements 
 and irritability of plants. 
 
 Different nutritive functions are discharged by various regions 
 of this tissue. For instance, the parenchymatous tissue of sub- 
 aerial parts, lying near the surface and exposed to light, contains 
 chlorophyll, and carries on the assimilation of carbon : this applies 
 especially to the leaves. Again, the cells of this tissue are 
 frequently glandular (see p. 96), containing or excreting various 
 waste-products : or they serve as depositories of reserve plastic 
 substances (e.g. starch, etc.), or as conducting-tissue for organic 
 substances. 
 
 Further, the cells of this tissue, having usually extensible 
 walls, are capable of becoming turgid and of varying in bulk : hence 
 they are the seat of the movements of those members, or parts of 
 them, in which movement is a mechanical possibility ; and when
 
 164 PART III. PHYSIOLOGY. [ 40 
 
 turgid, they give a considerable degree of rigidity to the member 
 of which they form part. 
 
 The intercellular spaces (p. 89) of this tissue, which are es- 
 pecially large in submerged parts of aquatic plants, are of great 
 importance in connection with transpiration and the distribution 
 of gases in the plant : they communicate with the interior by 
 means of the stomata and the lenticels. 
 
 c. The Sclerenchymatous Tissue (see p. 92), more especially the 
 prosenchymatous or fibrous form of it, has the purely mechanical 
 function of giving firmness to the members in which it is present. 
 Whilst it is true that a considerable degree of rigidity is afforded 
 by turgid parenchymatous tissue, and that many members con- 
 taining little or no sclerenchymatous tissue can grow erect (e.g. 
 conidiophores of Moulds, and succulent stems of herbaceous 
 annuals), yet this source of rigidity is precarious, as it is so 
 largely dependent upon external conditions, and is therefore insuf- 
 ficient in the case of perennial plants. In these plants rigid tissue 
 (stereom) is developed, and it is distributed in the body in just 
 such a manner as most adequately meets the mechanical require- 
 ments in each particular case (p. 120, Fig. 98). Stereom is most 
 perfectly developed in the stems of land-plants which grow erect 
 and have to support the weight of many leaves and branches ; 
 whereas in water-plants the development of stereom is rudi- 
 mentary, for their stems, being supported by the water, do not 
 need to be highly rigid. 
 
 When it is developed in the walls of fruits or in the seed-coats, 
 the sclerenchymatous tissue serves to protect the seed from being 
 eaten or digested by animals. 
 
 d. The Tracheal Tissue of the Xylem (see p. 93). It is clear 
 that when a plant-body is massive, partly subterranean and partly 
 sub-aerial, there must be some means for readily distributing the 
 water and other substances absorbed by the root. This distribu- 
 tion may take place by diffusion from cell to cell ; and, as a matter 
 of fact, this mode of distribution suffices in some plants in which 
 the seat of absorption is not far from that of consumption (e.g. 
 larger Fungi and Algae). But when these points are widely sepa- 
 rated, special conducting-tissue, in the form of the tracheal tissue 
 of the xylem, is differentiated. 
 
 The function of this tracheal tissue is demonstrated by the fol- 
 lowing experiment. If a cut be made all round the stem of a dico- 
 tyledonous tree, to such a depth as to penetrate far into the xylem,
 
 40] CHAPTER I. GENERAL, PHYSIOLOGY. 165 
 
 the effect is that the leaves borne on the stem and its branches 
 above the incision, will soon droop and wither. This is due to loss 
 of water, in consequence of which the cells of the leaves lose their 
 turgidity, and the leaf-blades and petioles are.no longer sufficiently 
 rigid to maintain their position of expansion." The loss of water 
 is the result of the continuance of transpiration in the absence of a 
 supply of water to meet it. The incision which has destroyed the 
 continuity of the young wood has also cut off the supply of water 
 from the root. The relation between the development of the xylem 
 and the activity of transpiration is well illustrated by the com- 
 parison of the vascular bundles of a land-plant with those of an 
 allied submerged aquatic species. The former transpires actively 
 and has well-developed xylem : the latter does not transpire at all, 
 and has quite rudimentary xylem. 
 
 Conduction takes place in dicotyledonous tree-trunks only 
 through so much of the peripheral portion of the wood as includes 
 living parenchymatous cells. The thickness of this conducting 
 region varies widely ; it is relatively small where the wood is 
 sharply differentiated into alburnum and duramen (see p. 143), and 
 in such trees (e.g. Oak) section of the alburnum is soon fol- 
 lowed by the withering of the leaves above the wound ; it is more 
 considerable in trees like the Beech, in which the transition from 
 alburnum to duramen is gradual ; and it is most extensive in those, 
 such as Birch and Maple, in which there is no differentiation of 
 alburnum and duramen. The dead portion of the wood does not 
 conduct, but at most only serves as a reservoir of water. 
 
 The tracheal tissue of the xylem discharges a purely mechanical 
 function in connexion with the conduction of water ; it is incapable 
 of any vital action inasmuch as it contains no protoplasm. 
 
 The liquid conducted from the roots to the leaves by the tracheal 
 tissue is not pure water, but holds in solution substances absorbed 
 by the roots from the soil ; hence this tissue plays an important 
 part in the distribution of food-materials in the plant. 
 
 e. The Sieve-Tissue (see p. 94). The function of the sieve-tubes 
 or phloem-vessels is to convey proteids from the organs in which 
 these substances are deposited or are being formed, to other parts 
 in which they are either being consumed or deposited as reserve 
 plastic material. This is demonstrated by the following experi- 
 ment : If a ring of tissue, extending inwards as far as the cam- 
 bium, be removed from the trunk of a young dicotyledonous tree, 
 the sieve-tubes will all be cut through, and their continuity inter-
 
 166 PART III. PHYSIOLOGY. [ 40 
 
 rupted. The effect of this upon the tree is that the portion of 
 the trunk below the wound, and the roots, cease to grow, and 
 slowly die, whei'eas the trunk and branches above the wound 
 remain healthy and continue to grow until the roots are no longer 
 able to absorb water, etc., from the soil with sufficient activity. 
 Inasmuch as the cortical tissue, through which the sugar travels, 
 is necessarily also cut through, the operation deprives the lower 
 parts of the body of the whole of their supply of organic plastic 
 material from the leaves, but does not interfere with the conduc- 
 tion of water from the roots to the leaves. 
 
 The sieve-tubes differ from the vessels of the xylem in that they 
 contain living protoplasm ; their function is therefore probably 
 not purely mechanical, but it is vital, though the relation of the 
 protoplasm to the conduction of proteids in the sieve-tubes is not 
 clear. 
 
 The companion-cells, and in their absence the cells of the bast- 
 parenchyma, which abut on the sieve-txibes, apparently serve in 
 the leaves as the means by which the nitrogenous products of 
 anabolism are brought to the sieve-tubes, and in other parts as 
 the means by which the proteids of the sieve-tubes are distributed 
 to the adjacent tissues ; there is some evidence to show that these 
 cells themselves actually carry on the formation of the proteids 
 which form the characteristic contents of the sieve-tubes. 
 
 /. The Glandular Tissue (p. 96). The essential function of the 
 glandular tissue is to secrete, and the secreta are either plastic 
 substances or waste-products. 
 
 It may be stated generally that the excretion of plastic sub- 
 stances on the surface of plants has special reference to their 
 relation with insects. Thus, the excretion of sugar by floral 
 nectaries is to attract insects to visit the flowers, and thus to 
 ensure the advantages of cross-pollination at a certain, though 
 relatively inconsiderable, cost. The excretion of sugar by extra- 
 floral nectaries is an expense incurred by the plant with the 
 object of attracting to it insects of a kind which will keep off 
 noxious insects or other animals ; these organs are especially char- 
 acteristic of mymnecopMlous (ant-loving) plants, which by this 
 means provide themselves with a police of ants to keep off either 
 other injurious (e.g. leaf-cutting) species of ants, or insects of other 
 kinds (e.g. boring bees, etc.), or even herbivorous mammals. 
 
 The secretion of waste-products has, as its immediate object, the 
 removal of these substances from the sphere of metabolism ; but
 
 41] CHAPTER I. GENERAL PHYSIOLOGY. 167 
 
 their deposit at or near the surface serves the purpose of protection 
 in various ways. For instance, the secretion of wax on the sur- 
 face is an obvious protection against wet. Similarly there can be 
 little doubt that when the system of resin-ducts, in plants which 
 contain them (e.g. most Conifers, etc.), is opened by a wound, the 
 resin serves to protect the raw surface both mechanically and 
 antiseptically ; and this doubtless also applies to the latex present 
 in many plants. Further, these waste-products, by their bitter, 
 acrid, or astringent taste, by their frequently poisonous properties 
 (e.g. alkaloids), or by their hardness, serve to protect the plants 
 from being eaten by animals ; for instance, the presence of raphides, 
 or of strongly acid sap, in the cells of leaves, etc., has been proved 
 to protect them against the attacks of snails. The secretion of 
 mucilage by the glandular hairs (colleters) often developed near 
 the growing-points of stems and leaves, serves to keep the young 
 tissues moist. 
 
 The special functional importance of the laticiferous tissue is not 
 fully understood. There is no doubt that it is, in the first place, 
 a reservoir of waste-products, since the latex generally consists 
 largely of such substances (e.g. caoutchouc, as in Siphonia elastica ; 
 alkaloids, as in the opium of the Poppy, etc.). But the latex has 
 also been found to contain plastic substances, such as proteids and 
 carbohydrates, and in one case (the Papaw) a proteolytic enzyme, 
 and it has hence been inferred that this tissue may serve to con- 
 duct plastic substances throughout the plant ; but this inference 
 has not been satisfactorily established. 
 
 41. The Functions of the Members. It has been pointed 
 out (p. 3) that, in its highest development, the plant-body con- 
 sists of the following members : root, stem, leaf. These members 
 will now be considered from the physiological point of view. 
 
 a. THE ROOT. The most general of the functions of the root 
 is that it absorbs the solid food of the plant in solution from the 
 substratum, whatever it may be, on which the plant is growing ; 
 and that, at the same time, it acts as an organ of attachment : in 
 submerged plants the latter is its main use. 
 
 In some few cases the plant is rootless (p. 44): under these circum- 
 stances other members become modified to perform the absorbent function 
 of the root ; in Salvinia, the aquatic leaves ; in Psilotum, the subterranean 
 shoots. In the " carnivorous " plants (e.g. Drosera, Dionsea, Nepenthes), 
 though they possess roots, the leaves are adapted for the absorption of 
 organic food in solution.
 
 168 
 
 PART III. PHYSIOLOGY. 
 
 [41 
 
 In a typical land-plant the development of the root-system is 
 such as to ensure an adequate supply of food from the soil, and a 
 supply of water sufficient to maintain the general turgidity of 
 the plant in spite of continued loss of water by transpiration. 
 
 The root of such a plant is adapted for the performance of its 
 functions both in its structure and in its properties. The most 
 striking structural adaptation is that the walls of the superficial 
 cells of the younger parts are not cuticularised, but remain per- 
 
 Fi. 123. A. Root-hairs (7i) on the primary root (ic) of a seedling grown in water of 
 Buckwheat (Polygonum Fagopyrum) ; he hypocotyl ; c cotyledons. B (after Sachs) Ends of 
 root-hairs showing their intimate connexion with particles of soil which adhere to the 
 mucilaginous external layer of the cell-walls. 
 
 vious to water. Generally speaking, the absorbent area of the 
 root is increased by branching ; and, in many cases, also by the 
 growing-out of the superficial cells of this region into root-hairs 
 (see p. 46). It appears that the development of root-hairs is de- 
 termined by the difficulty of obtaining water, on the one hand, 
 and by the relative activity of transpiration on the other : thus
 
 41] CHAPTER I. GEXERAL PHYSIOLOGY. 169 
 
 root-hairs are usually not developed by aquatic plants, the roots of 
 which, at least, are habitually immersed in water ; nor by plants 
 in which the transpiring surface is relatively small in proportion 
 to the root-system (e.g. small-leaved Conifers ; saprophytes, such 
 as Monotropa and Neottia). The root-hairs not only promote the 
 absorption of water, but also the absorption of salts from the soil, 
 coming, as they do, into very intimate relation with the minute 
 particles of the soil. They thus give the root a firmer hold on the 
 soil, and render it more serviceable as an organ of attachment. 
 
 In many cases the root becomes adapted to serve as a depository 
 of reserve plastic materials : such are the tuberous roots (p. 45) 
 of various plants, in which secondary growth in thickness (see 
 pp. 140, 143) produces a large amount of parenchymatous tissue, in 
 the cells of which the plastic substances (starch, etc.) are deposited. 
 
 The physiological adaptation of the root is even more remark- 
 able in its properties than in its structure, as is shown by its 
 irritability to the action of various stimuli. Thus the action of 
 the force of gravity causes roots (at least primary roots) to grow 
 towards the centre of the earth (positive geotropisni) : the action 
 of light, as a rule, causes the growing root to curve away from the 
 source of light (negative heliotropism) : a moist body causes the 
 root to curve towards it (positive hydrotropisni) : contact with hard 
 substances produces curvatures by which the direction of growth 
 of the root is altered. 
 
 These various kinds of irritability are of great importance in 
 ensuring the due performance of its functions by the subterranean 
 root. Positive geotropism causes it to penetrate into the soil, and 
 this is also promoted by negative heliotropism : positive hydro- 
 tropism causes it to grow towards the moister parts of the soil, 
 and thus tends to ensure an adequate supply of water. Its sen- 
 sitiveness to contact enables the root to get round obstacles which 
 it may meet with in the soil. 
 
 b. THE STEM. The function of the stem is essentially this : to 
 bear the foliage-leaves and the reproductive organs, and to bear 
 them in such a way that they shall occupy the most favourable 
 position for the performance of their respective functions. Further, 
 it is the means of communication between the roots and the leaves. 
 Occasionally it is specially modified to subserve other functions. 
 
 It has been already pointed out that the form of the stem varies 
 widely in plants, and the most characteristic forms have been de- 
 scribed (p. 27). The general physiological meaning of this variety
 
 ] 70 PART III. PHYSIOLOGY. [41 
 
 of form is that different plants attain the most favourable position 
 of their foliage-leaves and reproductive organs in different ways 
 which depend upon the particular combination of external condi- 
 tions under which they severally have existed. 
 
 The internal structure of the stem varies to some extent with its 
 general habit, and mainly in the arrangement and relative degree 
 of development of the sclerenchyma ; thus, the sclerenchyma is more 
 largely developed in an erect than in a trailing perennial stem. 
 
 There is one point in connexion with the relation of the vascular 
 tissue of the stem to the leaves which require special considera- 
 tion. It has been pointed out (p. 149) that vascular tissue is formed 
 secondarily in the stems (and roots) of most Dicotyledons and 
 Gymnosperms, whereas it is not so formed in those of most Mono- 
 cotyledons and Vascular Cryptogams. A consideration of the 
 general habit of the plants in question at once affords a clue to 
 this remarkable diversity. In the plants of the former groups, 
 the stem, as a rule, branches considerably, and consequently there 
 is every year an increase in the area of the leaf-surface of the 
 plant ; whereas in the plants of the latter groups, the stem 
 branches but little if at all, and the area of leaf-surface remains 
 approximately constant in the adult plant. It is clear that, in the 
 former case, the increase of leaf-surface necessitates an increase 
 in the conducting vascular tissue, a demand which is met by 
 the annual formation of an ever-widening ring of vascular tissue 
 by the cambium. Hence, in a plant of this kind, the vascular 
 bundles in the leaves of any one year are continuous, in the stem, 
 with the new vascular tissue formed in that year by the cambium. 
 
 Stems may be specially modified both in external form and 
 internal structure for the performance of special functions. Thus, 
 in leafless plants, in which the stem or its branches have to dis- 
 charge the functions of the leaf, they may become phylloid ; that 
 is, it may assume a flattened, leaf-like appearance (p. 28). The 
 cortical ground-tissue of the stems of such plants resembles the 
 mesophyll of foliage-leaves, not only in that the cells contain 
 chlorophyll-corpuscles in abundance, but also in the more or less 
 complete differentiation of a superficial palisade-layer from a more 
 deeply placed spongy tissue. 
 
 Again, stems may be specially modified to serve as depositories 
 of reserve materials (e.g. tubers of potato), or of water (e.g. stems 
 of Cactaceae), when they are much thickened by the development 
 of a large quantity of parenchymatous ground-tissue, in the cells
 
 41] CHAPTER I. GENERAL, PHYSIOLOGY. 171 
 
 of which the water or the reserve-materials are deposited. Or 
 they may be developed into thorns (p. 27) as a protection against 
 being eaten. 
 
 The physiological adaptation of stems is such that the move- 
 ments which they perform in response to the action of external 
 stimuli are always such as shall place the foliage-leaves and the 
 reproductive organs in the most favourable position. Most stems, 
 for instance, grow away from the centre of the earth (negative 
 geotropism) and towards the light (positive heliotropism) ; these 
 stems consequently grow up into the air, and take up such a posi- 
 tion with regard to the direction of the incident rays of light that 
 the leaves may be adequately exposed to them. Others, again, 
 grow horizontally under the influence of gravity (diageotropism) 
 and of light (diaheliotropism), and in this way spread out their 
 leaves to the sun's rays. 
 
 In some cases stems which tend to grow erect into the air are 
 unable to do .so in consequence of being insufficiently rigid to main- 
 tain their own weight, and that of their leaves, etc. Such stems 
 are enabled to obtain the necessary support by becoming attached 
 to foreign bodies, such as other plants, rocks, etc. This attach- 
 ment is sometimes purely accidental, as in the case of the hook- 
 climbers, such as the Bramble, where the stem is covered with 
 prickles which become fixed as the swaying shoot is blown about 
 by the wind. But in other cases the attachment is the result of 
 the mode of growth of the stem or its branches, in virtue of which 
 they twine round any suitable foreign body with which they may 
 come in contact. In some cases the stem and its branches are 
 sensitive to contact, e.g. Dodder ; in others, this sensitiveness is 
 restricted to certain specially modified branches, termed tendrils 
 (see p. 27, e.g. Vitis, Passiflora), and it is possessed by them in a 
 very high degree. 
 
 c. THE LEAF. In the discussion of the morphology of the leaf 
 it was pointed out that the forms of leaves are very various ; so 
 much so that it was necessary to classify them into a number of 
 categories. Each of these will now be briefly considered with 
 regard to its functions. 
 
 (1) Foliage-leaves. It may be stated generally with reference 
 to land-plants that the two great functions subserved by the leaf 
 are, first, the construction of organic substance from the raw 
 materials of the food ; and second, the exhalation of watery vapour, 
 or transpiration.
 
 172 
 
 PART III. PHYSIOLOGY. 
 
 [41 
 
 The internal structure of the leaf is in direct relation to these 
 two functions (see p. 114). The particular significance of the form 
 and arrangement of the cells of the mesophyll is made clear by the 
 following considerations. The palisade-layers occur always, be- 
 neath the epidermis, at those surfaces which are directly exposed 
 to the sun's rays. Further, if a plant which, when grown exposed 
 to sunlight, has well-marked palisade-layers in its leaves, be grown 
 in the shade, it will be found that the palisade-layers are imper- 
 fectly differentiated, even if they can be detected at all. The 
 development of the palisade-layers is clearly a peculiarity of leaves 
 which are exposed to sunlight. One explanation is this, that bright 
 light not only promotes the assimilatory function, but also pro- 
 motes the oxidation and decomposition of the chlorophyll. The 
 palisade-tissue affords a means of protection from the latter effect. 
 When a leaf-surface is exposed to diffuse daylight, the position of 
 
 the chlorophyll-corpuscles 
 in the palisade-cells is such 
 as to expose them as fully 
 as possible to the light ; 
 they are disposed on the 
 surface-w T alls, both upper 
 and lower, of the palisade- 
 cells (epistrophe). W T hen, 
 however, diffuse daylight 
 is replaced by direct sun- 
 light, the position of the 
 corpuscles is changed (see 
 Fig. 124) so that their 
 margin, and not their sur- 
 face, is presented to the 
 sun's rays ; they are removed to the lateral walls and towards the 
 inner end of the cell (apostrophe). It is clear that the elongated 
 form of the cells facilitates this withdrawal of the corpuscles from 
 too intense light, to light of a degree of intensity which promotes 
 the assimilatory function to the utmost extent compatible with a 
 due economy of the chlorophyll. 
 
 The spongy portion of the mesophyll is the tissue especially 
 adapted to the transpiratory function. By means of the large 
 intercellular spaces which form a system of channels throughout 
 this tissue communicating with the external air by means of the 
 stomata, a very large cell-surface, from which transpiration can 
 
 FIG. 121. (After Stahl). Sections of the thalloid 
 stem of LenvL tnsulca, illustrating epistrophe and 
 apostrophe of the chloroplastids : A position in dif- 
 
 B position in intense
 
 41] CHAPTER I. GENERAL PHYSIOLOGY. 173 
 
 readily take place, is brought into direct relation with the external 
 air. Transpiration takes place from the cells of the spongy 
 mesophyll into the intercellular spaces, and the watery vapour 
 then escapes from the leaf by the stomata. 
 
 Leaves are adapted not only structurally, but also by their 
 irritabilities, to the performances of their functions. They are 
 sensitive to the directive action of light and of gravity and, in 
 the course of their growth they take up a definite position termed, 
 on account of the predominating influence of light in determining 
 it, the fixed light-position. The response of the dorsiventral leaf 
 to the directive action of gravity, is generally one of diageotropism, 
 that is it places its blade horizontally, with the ventral surface 
 uppermost ; and similarly, its response to light is to expose the 
 upper surface of its blade at right angles to the direction of the 
 incident rays (diaheliotropism). The response of the isobilateral 
 and of the radial leaf to the action of gravity is one of negative 
 geotropism, so that they 
 grow erect ; and to light, 
 one of positive heliotropism, 
 as they tend to direct their 
 apices towards the source of 
 light. 
 
 Changes in the external 
 conditions act as stimuli, 
 which, in many cases, in- 
 duce a movement of the FIG. 125. -Leaf of Oxalis by day (T) and by 
 
 foliage-leaves involving ni ht <> Inthe lter,each leaflet is folded 
 inwards at right angles along its midrib, and is 
 Change of position : most also bent downwards. 
 
 frequently these movements 
 
 are performed by growing leaves, but also sometimes by adult leaves 
 with a permanent motile mechanism. They have been observed in 
 the growing leaves (and cotyledons) of many plants (e.g. Chenopo- 
 dium, Impatiens, Polygonum, Linum, etc.), and in the adult leaves 
 of many Oxalidacese and Leguminosae. The common feature of 
 these movements is that they serve to vary the area of surface 
 presented to the sky by the leaf. They are commonly known as 
 " sleep-movements," or nyctitropic movements, because they are 
 usually associated with the alternation of day and night. With a 
 falling temperature and a diminishing intensity of light the leaves 
 assume the "night-position," presenting a diminished surface, 
 generally only the edge, to the zenith, the leaflets of compound
 
 174 
 
 PART III. PHYSIOLOGY. 
 
 [41 
 
 leaves at the same time approaching each other, with the result 
 that they are protected from injury by cold in consequence of 
 excessive radiation of heat : with a rising temperature and an in- 
 creasing intensity of light, the leaves assume the "day-position," 
 presenting their upper surfaces to the zenith. But the day-position 
 is frequently liable to modification, with a view to the reduction 
 of transpiration and to the protection of the chlorophyll from the 
 action of too intense light, by movements which diminish the leaf- 
 area exposed to the direct rays of the sun ; and so, in some cases, 
 the edge, and not the upper surface, is presented to the sun : these 
 movements are designated "diurnal sleep" or parahcliotropism. 
 
 Some foliage-leaves, but only such as have a special motile 
 mechanism, respond by movement to the stimulus of a touch. 
 
 FIG. 126 (after Duchartre). Leaves of Mimosa pudtca: A normal diurnal position ; 
 B position assumed on stimulation. 
 
 This is the case in the " sensitive plants," such as Mimosa pudica 
 and some other species : the leaflets of the pinnate leaves of these 
 plants close together when touched, or when the plant is shaken, 
 and they are thus protected to some extent from injury by hail, 
 rain, or even wind. Other instances of movement in response to 
 touch are afforded by the "carnivorous" genera, Dionsea and 
 Aldrovanda, in which, when an insect alights on the upper sur- 
 face of the expanded leaf and touches the sensitive hairs, the two 
 lateral halves of the blade suddenly close together, like a hinge, 
 with the midrib as the axis. 
 
 Sensitiveness to long-continued contact is manifested by the
 
 41] 
 
 CHAPTER I. GENERAL PHYSIOLOGY. 
 
 175 
 
 petioles of various plants (e.g. Tropaeolum, Clematis) ; sometimes 
 by the whole phyllopodium (Lygodium) ; in many cases leaves 
 possessing this sensitiveness are modified into leaf-tendrils (see 
 p. 41 ; as in Cucurbitacese, etc.) ; leaves of this kind serve as 
 organs of attachment for climbing. 
 
 Foliage-leaves are sometimes modified into pitchers or ascidia 
 (p. 41) : these serve the purpose in some cases (e.g. Nepenthes) 
 of capturing insects and of digesting and absorbing them: in 
 other cases (e.g. Dischidia) they collect water and organic detritus ; 
 in Dischidia adventitious roots are developed, which lie in the 
 pitchers and absorb water, together with dissolved substances, 
 therefrom. 
 
 Leaf-spines, like stem-thorns, 
 appear to be exclusively protec- 
 tive against the attacks of her- 
 bivorous animals. 
 
 (2) Cataphyllary or Scaly 
 Leaves (p. 42) serve to protect 
 growing-points and young 
 leaves of buds, and in this they 
 are assisted by the secreting- 
 hairs (colleters, p. 101) which 
 they frequently bear : they 
 sometimes serve as depositories 
 of reserve plastic materials (e.g. 
 scales of Onion-bulb). 
 
 (3) Floral Leaves. 
 
 a. Hypsophyllary Leaves. 
 The leaves included under this 
 head are the bracts (and bracteoles) and the perianth-leaves 
 (p. 57). 
 
 When green, the bracts perform the ordinary functions of foliage- 
 leaves ; but when they are collected around a flower (epicalyx) or 
 an inflorescence (e.g. involucre of Compositse, Euphorbia, etc.) they 
 serve to protect the floral organs during their development. When 
 highly-coloured (e.g. in Aracese, Euphorbiacese, Nyctaginacese), 
 they serve to attract insects to visit the otherwise inconspicuous 
 flowers. 
 
 The sepals, like the bracts, are commonly green, and then they 
 perform the ordinary functions of foliage-leaves, and also serve to 
 protect the other floral organs : when petaloid (e.g. many Ranun- 
 
 FIG. 127 (after Darwin). Petiole of Solomon 
 jasminoides clasping a stick.
 
 176 PART III. PHYSIOLOGY. [ 41 
 
 culacese and Liliales), they attract insects for the purpose of cross- 
 pollination. 
 
 The petals are brightly-coloured in most flowers, and it is their 
 special function to attract insects. Not uncommonly they are 
 specially modified as nectaries (e.g. Helleborus), and thus further 
 contribute to ensure the visits of insects. 
 
 The perianth-leaves (and sometimes also the bracts), are often 
 capable of performing movements leading to the opening and 
 closing of the flower or inflorescence : thus the flowers of the 
 Crocus, Tulip, and Poppy, and the inflorescence of the Daisy, open 
 under the influence of rising temperature and increasing intensity 
 of light, closing under the contrary conditions : the closing is a 
 protection of the essential floral organs against cold and wet ; it 
 is essentially similar to the nyctitropic movements of foliage- 
 leaves. 
 
 b. Sporophyllary Leaves. As already stated (p. 55) the sporo- 
 phylls are the essential organs of the flower, when they are aggre- 
 gated on a special shoot, and have, in any case, the function of 
 asexually producing the spores. They are more or less generally 
 modified in form and structure in connexion with this function ; 
 and in the many different forms of flowers these leaves present 
 remarkable special adaptations which mainly refer to the process 
 of pollination, to the distribution of the seed, etc. It is impossible 
 to enter upon a further consideration of the biology of the flower, 
 but the phenomena of movement presented by the essential floral 
 organs deserve special mention. Thus the two lobes of the stigma 
 (e.g. Mimulus, Bignonia, Martynia), close together on being 
 touched : the movement doubtless ensures the adhesion of the 
 pollen brought by an insect. The stamens are irritable in many 
 plants. For instance, in Berberis, when an insect touches the 
 irritable base of one of the nearly horizontal stamens, the stamen 
 rises up on its point of attachment as on a hinge, and strikes the 
 insect with the anther, thus dusting it with pollen. Again, the 
 syngenesious stamens of Centaurea shorten on stimulation by 
 touch : the flower is protandrous ; consequently, as the filaments 
 contract, the pollen shed by the coherent anthers is pushed out of 
 the open end of the anther-tube by the style within, and is re- 
 moved by the insect.
 
 42] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 177 
 
 CHAPTER II. 
 SPECIAL PHYSIOLOGY OF THE NUTRITWE FUNCTIONS. 
 
 42. Absorption. The food of plants is absorbed, generally 
 speaking, either from the soil or from the air. 
 
 t Plants which do not possess chlorophyll (e.g. Fungi) usually 
 obtain the whole of their food from the soil ; whereas plants which 
 do possess chlorophyll absorb from the air one of the most im^ 
 portant constituents of their food, namely carbon dioxide, though 
 in exceptional cases it is obtained from other sources; for 
 instance, parasitic plants absorb their food from the hosts upon 
 which they live, and the " insectivorous " plants absorb a portion, 
 at least, of their food, from the insects which are caught by their 
 specially adapted leaves. Submerged aquatic plants absorb their 
 food entirely or mainly from the water in which they live. 
 
 The food of plants is always absorbed in the fluid form ; either 
 as a liquid or as a gas. The liquid food, consisting of a watery 
 solution of various substances, is absorbed from the soil most 
 commonly by the roots, or, in the absence of roots, by other 
 members (shoots, leaves) which have become specially adapted 
 for the performance of this function; the gaseous food (C0 2 ) is 
 absorbed from the air by the green parts of plants, and, in 
 the more highly differentiated forms, more especially by the 
 leaves. It not infrequently happens that chemical elements 
 are found in plants which are known to be present in the soil 
 in the form of compounds which are insoluble in water. These 
 compounds are brought into solution by various means. For 
 instance, the soil usually contains carbon dioxide, which is 
 evolved from the decomposing animal or vegetable matter which 
 is commonly present, and from the absorbent organs them- 
 selves ; and it is well known that various substances, such as cal- 
 cium carbonate and certain silicates, which are insoluble in pure 
 water, are soluble in water charged with carbon dioxide. Again, 
 the sap which fills the vacuoles and saturates the walls of root- 
 hairs, has an acid reaction, due to the presence of organic acid, and 
 this acid sap will dissolve many substances which are insoluble in 
 pure water. The solvent effect of this acid sap is well demonstrated 
 by means of the familiar experiment with a slab of marble. If a 
 highly-polished slab of marble be fixed in the bottom of a flower- 
 
 M.B. N
 
 178 PART in: PHYSIOLOGY. [ 42 
 
 pot, and a plant be grown in the soil above it, the roots will come 
 into contact with the slab and will apply themselves to its surface. 
 On subsequently examining the slab of marble, it will be found to 
 have become corroded where the roots had been in contact with it. 
 The corrosion is due to the solution, by the acid sap of the roots, 
 of particles of the marble. 
 
 Absorption of Liquids. The main idea connected with this 
 function is the taking up of water and other substances into the 
 plant from without ; but it must not be overlooked that, in a 
 multicellular plant, the cells absorb from each other. 
 
 In any case, the function of absorption depends upon the 
 physical process of diffusion through membrane of substances in 
 solution, or osmosis. Tor instance, supposing two adjacent cells, 
 one of which has its cell-sap charged with sugar, whereas that of 
 the other has none ; the sugar will diffuse through the intervening 
 cell-wall until the sap in both cells holds the same proportion in 
 solution. This being the mode of absorption, it is clear that the 
 food-materials can only be absorbed in the fluid form, either as 
 liquids or gases. 
 
 So far the function of absorption would appear to be a simply 
 physical process. It must, however, be borne in mind that the 
 cell-wall is lined by living protoplasm which modifies the purely 
 physical diffusion through the cell-wall, both as regards the nature 
 and the relative quantity of the substances which pass into or 
 out of the cell ; so that the physical laws of osmosis, as determined 
 by experiments with dead membrane, are not directly applicable 
 to the osmotic phenomena of a living cell. 
 
 Absorption of Gases. The absorption of gases depends, like the 
 absorption of water and substances in solution, upon diffusion. 
 Supposing an absorbent cell, the sap of which holds, to begin with, 
 no gases in solution, to be brought into relation with a mixture of 
 gases, these gases will be dissolved at the surface in proportion to 
 their solubility and to the amount of each gas present in the mix- 
 ture ; that is, the amount absorbed of each gas depends, in the first 
 instance, upon its solubility and its partial pressure. The relative 
 amount of each gas absorbed over a period of time will further 
 depend upon the extent to which it undergoes chemical alteration 
 after absorption. 
 
 Land-plants absorb gases, in the manner described above, at all 
 points of their surface ; by their shoots from the air, by their roots 
 from the gaseous mixture in the interstices of the soil ; the stomata
 
 43] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 179 
 
 of the sub-aerial parts are of great importance in connexion with 
 this process. Submerged water-plants absarb, in solution, the 
 gases dissolved in the water. 
 
 The absorbed gases remain in solution in t-he cell-sap, so that 
 living cells do not contain bubbles of gases. Moreover, gases 
 travel in the plant mainly by diffusion from cell to cell, though 
 their distribution may also be effected by means of the intercellular 
 spaces. 
 
 43. Transpiration. Every part of a plant which is exposed 
 to the air, except such as are covered by a thick layer of cork, is 
 continually exhaling watery vapour. This may be demonstrated 
 by placing a leafy branch under a cold bell-glass, when it will 
 shortly be observed that the internal surface becomes covered with 
 drops of water, the watery vapour exhaled by the branch having 
 condensed upon the cold glass. Again, the drooping of cut flowers 
 or herbaceous branches is due to the loss of water by transpira- 
 tion. 
 
 It must be clearly understood that transpiration is not simply 
 evaporation. If it were so, then clearly equal amounts of water 
 should be evaporated in a given time by equal areas of water- 
 surface and of living plant-surface. But this is not the case. 
 All observations show that the amount of water transpired from a 
 given area of living plant-surface in a given time, is only a small , 
 fraction of that evaporated in the same time from an equal surface 
 of water. On the other hand, the evaporation from dead plant- j 
 surface is as active, or even more so, than from a free surface I 
 of water. Transpiration, whilst ultimately depending upon the 
 purely physical process of evaporation, is essentially evaporation 
 modified by the living substance, protoplasm, from and through 
 which it takes place, and is therefore a vital function. 
 
 Inasmuch as most aerial leaves and stems have a more or less 
 well-developed and cuticularised tegumentary tissue, the transpira- 
 tion from the external surface is insignificant. In such cases the 
 transpiration takes place mainly through the thin uncuticularised 
 walls of the cells of the ground-tissue into the intercellular spaces, 
 and the watery vapour escapes from the intercellular spaces into 
 the external air by means of the stomata and the lenticels. The 
 stomata, especially, are organs for the regulation of transpiration. 
 As already mentioned (p. 163), the stomata open and close, their 
 opening and closing being dependent upon variations in the tur- 
 gidity (p. 159) of the guard-cells. When the guard-cells are highly
 
 180 PART III. PHYSIOLOGY. [ 43 
 
 turgid, that is, when they are tensely filled with cell-sap, they 
 curve so as to separate from each other in the middle line, thus 
 opening the stoma ; when they are flaccid, their free surfaces are 
 brought into contact, and the stoma is closed. The opening or 
 closing of the stomata is a function of transpiration as affected "by 
 the hygrometric condition of the air, and by the supply of water in 
 the plant : so that when the transpiration is normal, as determined 
 by a certain relation existing between the hygrometric condition of 
 the air and the supply of water to the transpiring leaf, the stomata 
 are open ; but when transpiration becomes excessive, by the air 
 becoming drier, or by a diminution in the supply of water to the 
 leaf, the stomata close, even before any trace of flagging is shown 
 by the leaf. Thus the stomata act as regulators of transpiration, 
 and their opening or closing depends partly on external and partly 
 on internal conditions. 
 
 The water lost by transpiration is supplied to the transpiring 
 organs from the roots. If the loss by transpiration is compensated 
 by the absorbent activity of the roots, the transpiring organs 
 remain fresh and turgid. But if, as is frequently the case on a 
 hot summer day, the loss of water by transpiration is greater than 
 the supply from the roots, the transpiring organs, more especially 
 the leaves, become flaccid and droop, and they are only restored to 
 the turgid condition in the evening when the temperature of the 
 air falls and the intensity of the light diminishes ; in a word, when 
 the external conditions become such as to lead to a diminution of 
 the transpiration. 
 
 There is, however, besides the flaccidity of the herbaceous 
 members of the plant, another means of observing the effect of 
 transpiration upon the amount of water contained in the tissues. 
 If the stem, or a branch, of an actively transpiring plant be cut 
 through under mercury or some other liquid, it will be observed 
 that the liquid will at once make its way for a considerable 
 distance into the woody tissue of the cut stem or branch. This is 
 due to the fact that, in consequence of the withdrawal of water 
 from them, the gases in the vessels are at a lower pressure than 
 that of the atmosphere. This is termed the negative pressure in 
 the vascular tissue. 
 
 These various points can be readily observed in low-growing 
 plants, such as the Cabbage. On a hot summer day the leaves 
 become flaccid, and the existence of a negative pressure in the 
 vessels of the stem can be ascertained. In the evening, when the
 
 44] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 181 
 
 activity of transpiration is diminished, but active absorption of 
 water from the warm soil by the roots continues, the leaves 
 become turgid, and water gradually accumulates in the vascular 
 tissue. During the night this accumulation of water in the 
 vascular tissue goes on until it becomes quite full, so that there 
 comes to be not only no negative pressure, but a positive 
 pressure. This positive pressure, were there no means of re- 
 lieving it, might become injurious to the tissues ; but it is re- 
 lieved by the filtering of drops out of the closed terminations of 
 the vascular bundles in the leaves, these drops making their way 
 to the surface through openings over the ends of the bundles, 
 which are either the ordinary stomata, or the specially-modified 
 water-stomata (p. 108). A row of such drops on the margin of the 
 leaves may be observed in many plants in the early morning. It : 
 appears, then, that during the day the loss of water by transpira- ; 
 tion is greater than the supply by absorption, whereas during the I 
 night the contrary is the case. 
 
 With regard to the physiological significance of transpiration, 
 it is important in that it causes a rapid current of liquid, the 
 transpiration-current, to flow through the plant from the roots to 
 the transpiring organs, more especially the leaves. This ensures 
 the distribution, not only of the absorbed water, but also of the 
 substances absorbed in solution from the soil. It will be noticed 
 that the conditions which promote transpiration, namely, light 
 and warmth, are just those which are most favourable to the per- 
 formance of their anabolic processes by the organs which contain 
 chlorophyll. Thus, when the leaves are actively producing organic 
 substance, they are actively transpiring, and they are therefore 
 constantly receiving supplies of the substances absorbed from the 
 soil, substances some at least of which are essential to the 
 chemical processes in operation. Transpiration has, then, an 
 important bearing upon nutrition. There seems to be, in fact, an 
 optimum activity of transpiration, that is to say, a certain activity 
 of transpiration which promotes to the utmost the formation of 
 organic substance ; so that if the average activity of transpiration 
 falls short of, or exceeds, this optimum, the nutrition of the plant 
 suffers, as shown by a diminished formation of organic sub- 
 stance. 
 
 44. Distribution of Water and other Substances. It is 
 clear that, when the plant-body is so far differentiated that only 
 certain parts of it are in a position to absorb water and substances
 
 182 PART III. PHYSIOLOGY. [. 44 
 
 in solution from without, there must be a distribution of the ab- 
 sorbed substances from the absorbent surfaces to the other parts. 
 Further, when the plant-body is differentiated into parts which do, 
 and others which do not, contain chlorophyll, there must be a 
 distribution of the produced organic substance from the former to 
 the latter. In plants of relatively low organisation, the distribu- 
 tion takes place entirely by diffusion through the cell-walls, 
 that is by osmosis, when the plant is multioellular : and even in 
 the highest plants diffusion plays an important part. 
 
 With regard to the distribution of water and substances 
 absorbed in solution from without in the more highly organised 
 plants there is a special conducting tissue, the wood or xylem of 
 the vascular bundles, extending from the roots, the absorbent 
 organs, to the leaves, the transpiring organs (see p. 164.) 
 
 The Root-Pressure. The existence of the root-pressure can be 
 easily ascertained. It is manifested spontaneously by that exuda- 
 tion of drops on the margin of the leaves of low-growing plants 
 during the night, to which allusion has already been made (p. 180). 
 An artificial manifestation of it is induced in stems which are cut 
 across at a time when, owing to active absorption and feeble 
 transpiration, the plants are rich in water ; drops exude from the 
 xylem-vessels at the cut surface of that part of a stem which is 
 still in connexion with the root. A familiar case of this is the 
 " bleeding " of certain shrubs and trees when pruned in the 
 spring. It is possible, in this way, to estimate both the activity 
 and the force of the root-pressure. By collecting the water which 
 exudes from the cut surface of the stem, the amount of water 
 absorbed by the root in a given time is determined ; and by 
 attaching a mercurial manometer to the cut surface of the stem 
 the force of the root-pressure can be measured. For instance, 
 3,025 cubic millimetres of liquid were collected from a Stinging 
 Nettle in 99 hours ; and the root-pressure required a column of 
 mercury 354 millimetres in height to counterbalance it : in other 
 words, the root-pressure of the Nettle was nearly half an atmos- 
 phere, and was capable of supporting a column of water about 
 15 feet high. 
 
 The essential point in the mechanism of the root-pressure is 
 the forcing of liquid by filtration under pressure from the paren- 
 chymatous cells into the xylem. The process is probably to 
 be explained somewhat in this way. When a certain degree of 
 turgidity is attained in the parenchymatous cells abutting on the
 
 44] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 183 
 
 xylem, their protoplasm undergoes a molecular change, in conse- 
 quence of which it becomes permeable and ceases to offer resistance 
 to the escape of the cell-sap ; consequently, under the elastic con- 
 traction of the distended cell- walls, a portion of the cell-sap is forced 
 out of the cell into the vascular tissue. From this point of view, 
 the root-pressure of a plant is simply the expression of the force of 
 the elastic contraction of the cell-walls of the parenchymatous cells 
 abutting on the xylem-bundles in the root. 
 
 With regard to the external conditions which affect the root- 
 pressure, the most important is the temperature of the soil ; a 
 rise of temperature up to the optimum increases the root-pressure, 
 bat any further rise causes it to diminish, and if the soil be 
 heated so as to kill the roots, the root-pressure altogether dis- 
 appears. 
 
 The liquid forced into the tracheal tissue is by no means pure 
 water; it holds various substances in solution, such as mineral 
 salts absorbed from the soil ; in the spring it is relatively rich 
 in organic substances, such as proteids, sugar, acids, colouring- 
 matters, etc., derived from the reserves stored in the parenchy- 
 matous cells of the root, which are being conveyed to the opening 
 buds. 
 
 The Transpiration-Current. The mechanism by which, after 
 the liquid has been forced into the xylem of the root, a sufficient 
 current is maintained through the stem of a lofty tree to supply 
 the actively transpiring leaves, is still one of the incompletely 
 solved problems of physiology. 
 
 It might be assumed that the transpiration-current is main- 
 tained simply by the root-pressure. There is no doubt that, in 
 low-growing plants (see p. 180), the root-pressure is sufficient to 
 force liquid to all parts of the plant ; and this is probably true 
 also of lofty trees. The objection is that no root-pressure can be 
 detected in any plant at the time when transpiration is active, 
 when, on the contrary, there is negative pressure (p. 180) in the 
 vessels. Moreover, a transpiration-current is maintained for a 
 time by entire plants whose roots have been killed by heat, as also 
 by cut-off shoots. 
 
 The present position of the question as to the mechanism of the 
 transpiration-current in lofty trees, may be stated as follows. In 
 the spring the wood is full of water forced into it by root-pressure. 
 When the leaves unfold and begin to transpire, water is gradually 
 withdrawn from the conducting tracheal tissue, and the tissue is
 
 184 PART III. PHYSIOLOGY. [ 44 
 
 at any rate for the most part, occupied by a system of short 
 columns of water with intervening gas-bubbles, the columns of 
 water being in communication by delicate films along the cell- 
 walls. If the whole of the tracheal tissue be in this state, it is 
 suggested that as water is withdrawn from the upper part of the 
 wood by the transpiration of the leaves, a current is set up, the 
 water travelling along the cell-walls, between them and the gas- 
 bubbles. But it may be that a continuous system of tracheids 
 completely filled with water is maintained, and that it is through 
 this that the current travels. The conducting-tissue is supplied 
 with water, in the first instance, from that which fills the non- 
 conducting tissue of the wood (and the old wood or duramen, if 
 present), and ultimately by the root. It may be thought that the 
 suction due to transpiration would be incapable of maintaining the 
 current ; but this difficiilty is met by the consideration that the 
 water is held in position by the capillarity and the cellular 
 structure of the tracheidal tissue, and that the system of columns 
 of water and gas-bubbles does not move as a whole, since the latter 
 cannot pass the pit-membranes of tracheids. Moreover the force of 
 transpiratory suction is considerable, thoxigh it has not been 
 accurately measured. 
 
 The Distribution of Organic Plastic Substances. These sub- 
 stances may be generally stated to consist of organic substances of 
 two kinds, nitrogenous and non-nitrogenous, and these are dis- 
 tributed through different channels. 
 
 1. The nitrogenous substances travel, in plants or in parts of 
 plants which are not supplied with vascular tissue, in the form 
 of amides (see p. 186) by osmosis from cell to cell. But in 
 vascular plants it is known that they also travel in the sieve- 
 tissue from one member of the plant to another, in the form of 
 indiffusible proteids. There is no evidence that the very slow 
 movement of the contents of the sieve-tubes is effected by any 
 special mechanism; it appears to be simply induced by the de- 
 mand for these substances at any point, and it is doubtless 
 promoted by the swaying of the stem and branches. 
 
 2. The non-nitrogenous substances travel through the plant in 
 the form of glucose and maltose (see p. 187), in solution ; they 
 travel by diffusion from cell to cell, and more especially in the 
 elongated parenchymatous cells, forming the conducting-sheath, 
 which, in the leaf, consists of mesophyll-cells closely investing the 
 vascular bundles, and, in the stem, belong to the inner cortex.
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 185 
 
 This layer is not the endodermis, but lies externally to it ; the 
 endodermis frequently contains starch-grains, and is sometimes 
 termed the starch-sheath, but it is rather a depository than a con- 
 ducting-tissue. 
 
 The direction in which organic substances travel in the plant 
 seems to be determined simply by the demand for them. Just as 
 the water and the substances in solution absorbed by the roots 
 travel to the transpiring and assimilating organs, so the organic 
 substances produced in the assimilating organs travel in the 
 plant to those parts in which organic substance is either being 
 used in growth, or is being stored up as reserve material. In a 
 Potato-plant, for example, part of the organic substance formed 
 in the leaves travels to the growing-points of the roots and of the 
 shoots, where it is required for the development of new leaves, 
 flowers, branches, etc., whilst the residue travels to the under- 
 ground shoots which are developing into tubers and are storing up 
 quantities of starch. Similarly, these organic substances travel 
 apparently by the same channels and in the form of the same 
 chemical compounds, from organs which serve as depositories of 
 reserve material, when these stores are drawn upon to supply the 
 growth of developing parts. For instance, when a Potato-tuber 
 begins to sprout, the starch, which is the principal reserve 
 material, is drawn upon, being gradually converted into sugar, 
 in which form it travels to the growing-points of the young shoots 
 and supplies a large proportion of the plastic material necessary 
 for their growth. 
 
 45. Metabolism. This subject will be subdivided into : 1, 
 Chemical Composition ; 2, Food of Plants ; 3, Anabolism ; 4, Cata- 
 bolism ; 5, Products of Metabolism. 
 
 1. Chemical Composition. As a preliminary, a general account 
 of the chemical composition of plants will be given. 
 
 All parts of living plants contain a considerable quantity of 
 water : this forms not merely the principal constituent of the cell- 
 sap, but also saturates the cell-walls, the protoplasm, in short, all 
 organised structures ; it is, in fact, one of the peculiarities of or- 
 ganised structures that minute particles of water are interposed 
 between the particles of solid matter of which they consist. By 
 heating to 100 or 110 C., all the water contained in any part of 
 a plant is expelled, and in consequence it will naturally lose 
 weight. The amount of this loss, that is, the quantity of contained 
 water, is very different in various plants ; ripe seeds dried in the
 
 186 PART III. PHYSIOLOGY. [ 45 
 
 air contain from 12 to 15 per cent, of water, herbaceous plants 60 
 to 80 per cent., and many water-plants and Fungi as much as 95 
 per cent, of their whole weight. 
 
 The residue, which gives off no more water at a heat of 100 C., 
 the dry solid, consists of a great variety of chemical compounds ; 
 these are partly organic, that is to say, combinations of carbon 
 w r ith other elements, and partly inorganic. The organic sub- 
 stances which occur in the living plant (with the exception of 
 salts of oxalic acid) all contain hydrogen. Some of them, such as 
 many oils, consist of these two elements only (carbon and hydro- 
 gen), but by iar the greater number, including cellulose, starch, 
 and sugar, as well as the vegetable acids and certain oils, contain 
 oxygen also. The proteid substances consist of carbon, hydrogen, 
 oxygen, nitrogen, sulphur, and sometimes phosphorus ; in other 
 bodies which contain nitrogen, as asparagin and many alkaloids, 
 there is no sulphur or phosphorus ; from certain other alkaloids, 
 for instance nicotin, oxygen is also absent. 
 
 The commoner organic substances of which the plant-body 
 consists may, in the first instance, be divided into those which 
 do and those which do not contain nitrogen in their molecule. 
 
 The most important nitrogenous substances may be classified as follows : 
 
 1. Proleids : these are substances with a large molecule of complex con- 
 stitution, to which no chemical formula has yet been assigned ; they may 
 be soluble or insoluble in water, and when soluble are mostly indiffusible ; 
 they are generally of a viscid nature (like white of egg) and are rai-eiy 
 crystal] isable. 
 
 2. Amides (or Amido-acids): these substances are soluble in water, not 
 coagulated on boiling, diffusible, and crystallisable. Those commonly 
 occurring in plants are Asparagin (C 4 H 8 N n O 3 ), Leucin (C 12 H 26 N 2 O 4 ), Tyrosin 
 (C 9 H n N0 3 ). 
 
 3. Alkaloids: these substances are, chemically, organic bases, occurring 
 in plants in combination with organic acids ; they are insoluble or but 
 slightly soluble in water, soluble in alcohol ; most of them are solid at 
 ordinary temperatures, and are crystalline, whilst others are liquid (Coniin, 
 Nicotin) ; they are generally poisonous. 
 
 The more familiar alkaloids are Coniin (C 8 H 15 N) from Conium ; Nicotin 
 (C IO H 14 N 2 ) from Tobacco ; Morphin (C 17 H 19 NO 3 ), and other opium-alkaloids 
 from the Poppy ; Strychnin (C 2 iH 22 N 2 O 2 ) from Strychnos Nux vomica; Quinin 
 (C2oH 24 N 2 O 2 ) from the Cinchona; Thein (C 8 Hi N 4 O 2 ) from Tea; Theobromin 
 (C 7 H 8 N 4 O 2 ) from Theobroma Cacao. 
 
 Some colouring-matters are also nitrogenous (e.g. chlorophyll, and indigo 
 C 8 H 5 NO), as also some glucosides (see below). 
 
 The principal non-nitrogenous substances are : 
 
 1. Carbohydrates : substances consisting of C, H, and O, the H and O be-
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 187 
 
 ing present in the same proportions as in water (H_,O) ; of these there are 
 the following classes : 
 
 a. Amyloses : general formula n (C 6 H 10 O 5 ) ; of these cellulose and starch are 
 
 the most common, the former entering largely into the composition 
 of cell-walls, the latter occurring as a reserve material in the form of 
 ' starch-grains; they are neither of them soluble in water under 
 ordinary circumstances : dextrin or amylin, a product of the action 
 of diastase on starch, is soluble in water but not crystallisable : 
 inulin (see p. 83) occurs in many Composites and all ied orders (Cam- 
 panulacese, Lobeliacese) in solution in the cell-sap; it is slightly 
 soluble in cold water and is crystallisable. The gums and mucilages 
 also belong to this group. 
 
 b. Sucroses: C^H^On : soluble in water and crystallisable: cane-sugar 
 
 occurs in many plants (esp. Sugar-cane and Beet-root) ; maltose is 
 the chief product of the action of diastase on starch. 
 
 c. Glucoses: C 6 H ]2 O 6 : soluble in water and crystallisable : they occur in 
 
 fruits (grape-sugar). 
 
 The sucroses and glucoses are commonly known as sugars. 
 
 A substance termed Mannite (C 6 H 14 O 6 ) occurs in the cell-sap of Fraxinus 
 Ornus and some other plants: though not a carbohydrate, it is closely 
 allied to this group ; crystallisable, but not readily soluble in water. 
 
 2. Organic Acids: these occur in the plant either free or, more commonly, 
 as neutral or acid salts in combination with organic or mineral bases ; 
 some are constituents of the fats and fixed oils (e.g. palmitic and oleic 
 acids ; see below) : the more common are oxalic acid (H 2 C 2 O 4 ) malic acid 
 (H 2 C 4 H 4 O 5 ), tartaric acid (H 2 C 4 H 4 O 6 ), citric acid (H 3 C 6 H 5 O 7 ). 
 
 3. Glucosides : substances of complex constitution which owe their name 
 to the fact that they give rise, on decomposition, to glucose among other 
 products : such are amyrjdalin, C 2> H 27 NO n (seeds, etc., of many Rosacese) ; 
 coniferin, Ci 6 H 22 O 8 (coniferous wood) ; myrosin, or myronate of potash, 
 KCjoH-sNS^o (seeds of Mustard); salicin, C 12 H 18 O 7 (in bark of Willows 
 and Poplars) ; yallo-fannin, C 34 H 28 O 22 (in Oak-bark). 
 
 Though some of these substances (e.g. amygdalin and myrosin) contain 
 nitrogen, it is more convenient to classify them with the more numerous 
 non-nitrogenous glucosides. 
 
 4. Fats and Fixed Oils : these substances, as they occur in the seeds and 
 fruits of plant?, are mixtures of free fatty acids with glycerin-compounds 
 (glycerides) of fatty acids ; thus palm-oil is a mixture of palmitic and oleic 
 acids with their glycerides palmitin, C 3 H 5 (Ci 6 H 31 O) 3 O 3 , which is a solid fat, 
 and olein, C 3 H 3 (C 18 H 33 O) C O 3 , which is a fluid fat or oil : olive-oil consists 
 chiefly of olein with some palmitin : castor-oil, of ricinolein (the glyceride of 
 ricinoleic acid) and stearin (the glyceride of stearic acid) : linseed-oil, of 
 linolein (the glyceride of linoleic acid) and palmitin. 
 
 The organic compounds can for the most part be resolved into 
 volatile products chiefly carbonic acid, water, and nitrogen by 
 exposure to great heat with free access of air, that is, by combus-
 
 188 
 
 PART III. PHYSIOLOGY. 
 
 [45 
 
 tion. The inorganic residue is a white, or, if the combustion is 
 imperfect, a grey powder, the ash. 
 
 As the result of chemical processes attending the .combustion, 
 the sulphur and phosphorus previously contained in the organic 
 compounds appear as sulphates and phosphates in the ash, and the 
 carbonic acid formed during combustion combines with some of 
 the inorganic substances. These, therefore, must not be included 
 in an accurate estimate of the constituents of the ash. 
 
 The ash usually constitutes but a small percentage of the whole 
 dry solid of the plant. The amount of ash increases with the age 
 of the plant, or of any part of it, inasmuch as there is no consider- 
 able excretion by the plant of the mineral substances absorbed. 
 The percentage of ash in the dry solid of the plant, or of any 
 organ, may vary widely at different times. The following analyses 
 of various portions of plants will give an idea of its amount and 
 composition : 
 
 1000 PAKTS OF DEY SOLID MATTER CONTAIN : 
 
 
 
 
 
 
 rf 
 
 
 g 
 
 c . 
 
 cS 
 
 a 
 
 
 4 
 
 < 
 
 1 
 
 | 
 
 1 
 
 1 
 
 11 
 
 |2 
 
 r 
 
 02 
 
 S 
 
 O 
 
 Clover, in bloom 
 
 68-3 
 
 21-96 
 
 1-39 
 
 24-06 
 
 7-44 
 
 0-72 
 
 6-74 
 
 2-06 
 
 1-62 
 
 2-66 
 
 Wheat, grain . 
 
 19-7 
 
 6 14 , 0-44 
 
 0-66 
 
 2-36 
 
 0-26 
 
 9-26 
 
 0-07 
 
 0-42 
 
 0-04 
 
 Wheat, straw . 
 
 53-7 
 
 7-33 0-74 
 
 3-Oa 
 
 1-33 
 
 0-33 
 
 2-58 
 
 1-32 
 
 36-25 
 
 090 
 
 Potato tubers . 
 
 37-7 
 
 22-76 0-99 
 
 0-97 
 
 1-77 
 
 0-45 
 
 653 
 
 245 
 
 0-80 
 
 1-17 
 
 Apples . . . 
 
 14-4 
 
 5-14 3-76 
 
 0.59 
 
 1-26 
 
 0-20 
 
 1-96 
 
 0-88 
 
 062 
 
 
 
 Peas (the seed) 
 
 273 
 
 11-41 0-26 
 
 1-36 
 
 2-17 
 
 0-16 
 
 9-95 
 
 0-95 
 
 0-24 
 
 0-42 
 
 2. The Food of Plants. The constituents of the ash do not 
 form a merely accidental mixture ; it has been proved by experi- 
 ment that certain inorganic compounds are absolutely necessary to 
 the life of the plant. Those chemical elements which the plant 
 requires for its nutrition, and which must therefore be regarded as 
 part of its food, are : 
 
 I. Non- metallic Elements : Carbon, hydrogen, oxygen, nitro- 
 gen, sulphur, phosphorus, and perhaps chlorine. These 
 elements exist in the plant, for the most part, as organic 
 compounds ; but they also occur to some extent as 
 inorganic compounds, carbonates, nitrates, phosphates, 
 sulphates, of the metals mentioned below. 
 II. Metallic Elements : Potassium, calcium, magnesium, iron.
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 189 
 
 Besides these we find in the ash of many plants though they 
 cannot be regarded as essential to nutrition the following ele- 
 ments : sodium, lithium, manganese, silicon, iodine, bromine, and 
 in rare cases, also aluminium, copper, zinc, cobalt, nickel, stron- 
 tium, and barium. Fluorine must also exist in vegetables, for it 
 is found in a perceptible quantity in the dentine of animals which 
 feed directly or indirectly on vegetables. 
 
 The essential elements of the food will now be severally dis- 
 cussed. 
 
 Carbon. Plants which possess chlorophyll obtain their carbon 
 mainly from the air (or, in the case of submerged plants, from the 
 water) in the form of carbon dioxide. The absorption of carbon 
 dioxide is, however, limited to those cells which actuall}' contain 
 chlorophyll, and it can only go on even in those cells so long as they 
 are exposed to sufficiently intense light. 
 
 Although plants possessing chlorophyll can and do use cai'bon dioxide 
 as carbonaceous food, yet there is reason to believe that they may supple- 
 ment this by absorbing more complex carbon-compounds. In certain cases 
 (e.g. Drosera, Dionsea, Utricularia, etc.), green plants are provided with a 
 special mechanism, in the form of modified leaves, for obtaining a supply 
 of organic carbon-compounds. Such plants are said to be insectivorous. 
 The case of Drosera may be selected for illustration. The upper surface 
 and the margin of a leaf of this plant bears numerous glandular appen- 
 dages, the tentacles (see Fig. 33, p. 48). The glands at the ends of the 
 tentacles continually excrete a viscid liquid. When an insect comes 
 into contact with one of the marginal glands, it sticks to it ; this stimu- 
 lates the tentacle, and it moves, curving inwards to the centre of the leaf, 
 and gradually the other marginal tentacles incurve over the insect (Fig. 
 33 B). The glands then secrete an acid liquid containing a digestive 
 enzyme which acts upon and dissolves the soft parts of the insect, and 
 the products of this digestion are absorbed. 
 
 Plants which do not possess chlorophyll are incapable of using 
 carbon dioxide as carbonaceous food, but require more complex 
 carbon-compounds. Such plants are, all Fungi, and among the 
 higher plants, Cuscuta (Dodder), Orobanche (Broomrape), Neottia, 
 etc., though in some of these latter, a small, but altogether insig- 
 nificant quantity of chlorophyll has been detected. These plants 
 absorb the complex carbon-compounds which they require, either 
 from living animals and plants, or from the organic substances formed 
 by animals or plants : in the former case they are termed parasites, 
 in the latter saprophytes. In some cases plants destitute of chloro- 
 phyll obtain their carbonaceous food from green plants, without^
 
 190 PART III. PHYSIOLOGY. [ 45 
 
 however, being strictly parasitic upon them since they do not 
 destroy or injure them. This association of two distinct plants is 
 termed symbiosis. The best instance of it is afforded by the 
 Lichens, where a Fungus and an Alga are associated symbiotically. 
 
 It is remarkable that certain plants which possess chlorophyll are never- 
 theless parasitic in habit; for instance, Viscum (the Mistletoe) which is 
 parasitic on various trees, Rhinanthus (the Eattle) and other Scrophu- 
 lariacete. also Thesium (Bastard Toad-flax,) which are attached to the roots 
 of other plants by their haustoria. The nutritive processes of these green 
 parasites are not yet fully understood, but it seems probable that they 
 absorb from their hosts the substances which they should normally obtain 
 from the soil, though in a somewhat modified form. 
 
 The great majority of the saprophytes are Fungi, such as the various 
 Agarics which grow in the soil of woods (humus) which is formed by de- 
 cayed leaves and is rich in organic matter ; the Moulds and Yeasts which 
 grow in saccharine juices, or fruits, etc. ; and Saprolegnia which attacks 
 the corpses of animals. Some of these Fungi, notably the Yeasts and the 
 various kinds of Bacteria (Schizomycetes), are peculiar in that they not 
 only decompose the amount of organic substance which they require for 
 their nutrition, but they give rise to widespread decompositions which are 
 known as fermentation and putrefaction. Amongst the higher plants there 
 are many saprophytes which grow in soils rich in humus : they may 
 be almost destitute of chlorophyll (e.g. Monotropa ; Neottia and some 
 other Orchids) : or they may possess it in considerable quantity 
 (e.g. some Orchids ; Pyrola ; Ericaceae), in which case they are probably 
 only partially saprophytic ; plants of this kind grow mostly in the leaf- 
 soil of forests, or in peat on moors. 
 
 Hydrogen. The hydrogen of the plant is mainly absorbed in the 
 form of water (H.,0), but it may also be absorbed in combination 
 with nitrogen as ammonia-compounds (NH 3 ), and also in combin- 
 ation with carbon when complex carbon-compounds are absorbed by 
 the plant. 
 
 Oxygen is absorbed in combination with carbon, as C0 2 , and 
 with hydrogen, as H.,0, and in many of the inorganic salts of the 
 food, such as sulphates, phosphates and nitrates, as well as in more 
 complex carbon-compounds. Oxygen is also absorbed uncombined, 
 in connexion with the catabolic processes, in respiration. 
 
 Nitrogen, which is an essential constituent of proteid substances, 
 is only exceptionally assimilated in the free form ; although it is 
 present in large quantities in the atmosphere, most plants perish 
 if the soil in which they grow contains no compounds of nitrogen. 
 Nitrates and compounds of ammonia are widely distributed, and it 
 is in this form that nitrogen is mainly taken up by plants ; it seems
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 191 
 
 probable that plants possessing chlorophyll absorb their nitrogen 
 in the form of nitrates only. 
 
 Nitrogen may be also absorbed, at any rate, by parasites, sapro- 
 phytes, and insectivorous plants, in the form of "nitrogenous carbon- 
 compounds. 
 
 Although it is generally true that plants cannot assimilate un- 
 combined nitrogen, nevertheless certain plants (Papilionese, such as 
 Peis, Beans, etc.) will grow and flourish in a soil from which all 
 traces of nitrogen-compounds have been carefully removed. The 
 nature of the means by which this result is attained is not yet 
 completely determined, but the principal facts are briefly as follows. 
 In the first place, the roots of these papilionaceous plants have been 
 found to bear peculiar gall-like outgrowths termed tubercles. The 
 tubercles are the result of the attack of a Fungus which penetrates 
 into the root through the root-hairs. The green plant and the Fun- 
 gus appear to exist in a state of symbiosis, with the result that the 
 green plant is adequately supplied with combined nitrogen although 
 growing in a soil from which such compounds are originally absent. 
 In explanation of these facts there can, first, be no doubt that 
 the supply of combined nitrogen obtained by the green plant is 
 ultimately derived from the free nitrogen of the atmosphere ; and, 
 secondly, that the supply is not obtained from the atmosphere 
 directly by the leaves, but indirectly by the roots through the soil. 
 Nor can there be much doubt that the tubercles are associated with 
 the process of the assimilation of the free nitrogen, and that it is 
 effected by the Fungus. 
 
 The tubercles are structures formed by the hypertrophy of the 
 cortex of the root : their cells are rich in sugar and starch : the 
 branches of the fungus-mycelium penetrate most of the cells, and 
 there bud off innumerable gemmules (sometimes called bacterioids). 
 The tubercle eventually becomes disorganised ; the gemmules are 
 then set free into the soil, and are doubtless the means by which 
 other roots become attacked by the Fungus. 
 
 Sulphur, which is a constituent of proteids and a few other sub- 
 stances occurring in plants, such as oil of Mustard, is derived from 
 the sulphates of the soil. 
 
 Phosphorus is absorbed from the soil in the form of phos- 
 phates, and enters into the composition of some of the proteid 
 substances ; phosphates constitute a large proportion of the ash of 
 seeds. 
 
 As regards Chlorine, it has been experimentally proved so far to
 
 192 PART III. PHYSIOLOGY. [ 45 
 
 be indispensable in the case of one plant only, the Buckwheat 
 (Polygonum Fagopyrum). 
 
 Iron, though it is met with in very small quantities, is absolutely 
 necessary for the formation of chlorophyll. The leaves produced 
 by plants which are not supplied with iron during their growth, 
 are white so soon as their own store of iron is exhausted ; 
 these leaves, which are said to be chlorotic, become green in con- 
 sequence of the formation of chlorophyll if the soil be supplied with 
 iron, or even if their surface is washed with a very weak solution 
 of iron. 
 
 Potassium. Unless the soil contains potassium-compounds, the 
 assimilation of carbon dioxide by plants possessing chlorophyll does 
 not go on, as is shown by the fact that, under these circumstances, 
 the plant does not increase in dry weight. Potassium-salts are 
 especially abundant in those parts of the plant which are rich in 
 carbohydrates such as starch and sugar, as in potatoes, beet-roots, 
 and fruits. 
 
 Calcium and Magnesium have been shown to be necessary to the 
 normal development of plants : they are absorbed as nitrates, phos- 
 phates and sulphates, and thus serve as bases for the absorption of 
 these other important elements. Little is known as to their direct 
 use : they may be of importance in neutralising the organic acids 
 (especially oxalic) formed in the plant. 
 
 The distinction of the essential from the non-essential elements 
 has been arrived at by the method of water-culture, which consists 
 in growing plants from the seed with their roots in a solution of 
 various salts in distilled water. By varying the salts in the 
 solution, and observing the effect of the change on the health of the 
 plant, the relative importance of the different elements can be 
 ascertained. The following are examples of solutions containing all 
 the essential elements : 
 
 1. 2. 
 
 Potassium nitrate Calcium nitrate 
 
 Calcium phosphate Potassium sulphate 
 
 Magnesium sulphate Magnesium phosphate 
 
 Ferric chloride Ferric chloride. 
 
 In these two mixtures, as well as in others of the same acids and 
 bases which might be formulated, all the essential elements are in- 
 cluded in forms suitable for absorption ; the proportion of mixed
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 193 
 
 salts should not, however, exceed about '3% by weight of the 
 liquid. 
 
 The following is a brief account of the non-essential mineral 
 constituents of the food. 
 
 Silicon, is absorbed from the soil as silica (Si0 2 ) or as silicates. 
 It cannot be regarded as of nutritive importance, since plants 
 which are usually rich in silica can be brought to an apparently 
 normal development under conditions which render the absorption 
 of silica impossible. It is usually deposited in the cell-walls, as in 
 Diatoms, Equisetum, many Grasses, etc. 
 
 Iodine and Bromine are found in the many marine plants, 
 especially in Algse, and are prepared from them ; it is not known 
 that they are of any value in the economy of the plant. 
 
 Sodium, being universally distributed, is found in plants. 
 
 Lithium occurs in the ash of several plants, particularly in 
 Tobacco. 
 
 Zinc, Copper, and other metals, though they are not commonly 
 present in the ash of plants, are nevertheless taken up by plants 
 from soils which are rich in them ; from this it appears that plants 
 may absorb substances which are not necessary and may be even 
 injurious. 
 
 3. Anabolism. Under this term are included all the chemical 
 processes going on in the plant which lead to the formation of 
 complex substances from simpler ones (p. 158). Of these, those 
 which are undergone by the food of the plant constitute assimila- 
 tion. 
 
 In the case of plants which contain chlorophyll, the first step in 
 the assimilation of the food is the construction from carbon dioxide 
 and water of an organic molecule which contains carbon, hydrogen 
 and oxygen. The process may be represented by the following 
 equation : 
 
 That some process of the kind takes place is proved by the fact 
 that when green plants are placed under the necessary conditions, 
 that is, when they are supplied with carbon dioxide, with water 
 and with salts from the soil, and are exposed to light, they gain in 
 weight in consequence of an increase in the amount of their dry 
 organic substance, and they give off oxygen. Moreover, the volume 
 of the free oxygen evolved is actually equal to that of the carbon 
 dioxide absorbed, as indicated in the equation. 
 
 There are three points connected with the performance of this 
 
 M.B. - O
 
 194 PART III. PHYSIOLOGY. [ 45 
 
 process which require special notice : the part played by the 
 mineral food, the action of light, the function of chlorophyll. 
 
 With regard to the first point, it appears that the process in 
 question cannot be performed unless potassium-salts are supplied 
 to the plant. There is no reason to believe that this metal takes 
 any direct part in the process ; but it has an indirect, though none 
 the less well-marked effect upon it (see p. 192). 
 
 The importance of exposure to light is briefly this. The chem- 
 ical process represented in the foregoing equation is one which 
 involves the doing of work ; for, from the simple and stable mole- 
 cules C0 2 and H 2 0, a more complex and less stable molecule CH 2 
 is produced. Work cannot be done without energy, and the plant 
 cannot evolve in itself the energy necessary. It avails itself, there- 
 fore, of the kinetic or radiant energy of the sun's rays. Hence 
 the importance of exposure to light is that the plant, by absorbing 
 the light-rays, obtains the energy required for the chemical work 
 which has to be done. 
 
 Next, as to the function of chlorophyll. The function of chloro- 
 phyll is to serve as the means by which the rays of light are 
 absorbed, and their energy made available for the performance of 
 the chemical work by the protoplasm with which the chlorophyll 
 is associated. When light which has passed through a solution of 
 chlorophyll is examined with a spectroscope, the spectrum is seen 
 to present certain dark bands, known as absorption-bands, in the 
 red, yellow, green, blue, and violet, the band in the red being the 
 most conspicuous. These bands indicate that certain of the rays 
 of the solar spectrum do not pass through the chlorophyll, but are 
 arrested and converted into another form of energy. It is this 
 energy which, in the living plant, the chlorophyll places at the 
 disposal of the protoplasm for the construction of an organic 
 molecule out of carbon dioxide and water, as expressed in the fore- 
 going equation. Protoplasm without chlorophyll is incapable of 
 making use of the kinetic energy of the rays of light for the per- 
 formance of this chemical work. 
 
 The product of this process of carbon-assimilation is (as indi- 
 cated in the foregoing equation) a non-nitrogenous organic sub- 
 stance having the composition of a carbohydrate. A leaf which 
 is actively assimilating carbon under the influence of light is 
 generally found to contain relatively large quantities of carbo- 
 hydrate, in the form either of sugar or starch. 
 
 The performance of this process can be readily demonstrated.
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 195 
 
 If a water-plant (e.g. a leaf of Potamogeton natans, or a portion of the 
 shoot of Elodca canadensis) be placed in water which holds carbon 
 dioxide in solution, and be exposed to sunshine, it will be seen that 
 from the cut surface of the leaf or stem bubbles" of gas are given off 
 at regular intervals (Fig. 128). These consist of oxygen. 
 
 The relation of light and of chlorophyll to the formation of 
 organic substance by a green plant can be demonstrated by the 
 starch-method. For instance, if a leaf of a starch-forming plant, 
 which has been exposed to bright light for some hours, be removed, 
 decolourised by alcohol and tested with iodine, it will assume a 
 dark blue colour, showing an abundant accumulation of starch. If 
 a leaf, still on the plant, be exposed, not to white light, but to a 
 spectrum, the starch will be found to have accumulated in those 
 portions of the leaf upon which have fallen the rays of light which 
 correspond to the principal absorption-bands of the chlorophyll- 
 spectrum. 
 
 It is, generally speaking, only 
 plants possessing chlorophyll 
 which can create organic sub- 
 stance. Inasmuch, therefore, as 
 organisms, whether plants or 
 animals, which do not possess 
 chlorophyll require for their nu- 
 trition more or less complex 
 
 . , Fie. 128. Evolution of oxygen from a 
 
 organic substances, they are water . plant (Elodea canadensis) : a the cut 
 
 entirely dependent for their food stem ; g a weight that keeps the stem in its 
 
 upon organisms which do pos- **"** 
 sess chlorophyll. 
 
 This process is also of great importance in another direction. 
 All living organisms, speaking generally, absorb free oxygen and 
 evolve carbon dioxide in respiration. Those organisms which 
 possess chlorophyll prevent the excessive accumulation of carbon 
 dioxide in the atmosphere, and keep up the supply of free oxygen, 
 in that, under the influence of light, they absorb the former gas 
 from the air, and replace it by an equal volume of the latter. 
 
 The characteristic difference between the anabolic capacity of 
 plants which do and of those which do not possess chlorophyll is 
 then this, that the former can produce, from carbon dioxide and 
 water, organic substances containing the elements C, H, and 0, 
 whereas the latter cannot produce these, but must be supplied 
 with them as food. From this point onwards the anabolic
 
 196 PART III. PHYSIOLOGY. [ 45 
 
 processes in the two cases are, as far as is known, identical. 
 From the simpler plastic substances containing C, H, and 0, 
 whether they have been formed from CO., and H 2 in the one case, 
 or have been absorbed as organic food from without in the other, 
 other more complex substances such as sugar, etc., are formed, 
 probably by the polymerisation or condensation of the simpler 
 molecules. Further, the nitrogen of the food, absorbed either as 
 nitrates or salts of ammonia, is worked into the anabolic processes, 
 so that nitrogenous organic substance is produced. Probably the 
 first formed nitrogenous substances are comparatively simple crys- 
 tallisable substances, such as asparagin and leucin, which belong 
 chemically to the amides (see p. 186). The next step is doubtless 
 the formation of those more complex nitrogenous substances, 
 the proteids, and here sulphur, and phosphorus in some cases, is 
 introduced into the molecule ; and finally the series of assimila- 
 tory processes concludes with the formation of molecules of 
 protoplasm. 
 
 These various assimilatory processes are not, however, carried 
 on simultaneously with equal activity. In plants which contain 
 chlorophyll, when under conditions favourable for carbon-assimi- 
 lation, the construction of non-nitrogenous organic substance from 
 C0;j and H 2 appears to be the most active process, for an accumu- 
 lation of non-nitrogenous organic substance can be detected in 
 the green parts of these plants when assimilation is being carried 
 on. Most commonly this excess of non-nitrogenous organic sub- 
 stance is accumulated in the form of starch-granules which are 
 formed in the chloroplastids ; less commonly in the form of sugar 
 which is held in solution in the cell- sap (e.g. leaves of Onion). 
 This excess of non-nitrogenous organic substance in the green 
 parts soon disappears, however, when, by withdrawal from the 
 influence of light, its further formation is arrested. For instance, 
 if a plant which has been exposed to light and whose leaves are 
 rich in starch, be placed in the dark for some hours, the starch 
 will then ba found to have almost or entirely disappeared. 
 
 The organic substance resulting from the anabolism of the 
 plant, is partly used in the growth of the plant, in forming new 
 protoplasm, cell-walls, etc., and is partly stored up, in various 
 organs, in the form of reserve materials which serve either for the 
 growth of the plant itself at a subsequent period (roots, tubers, 
 etc.), or for the nutrition of new individuals in the early stages of 
 their growth (spores, seeds, etc.).
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 197 
 
 4. Catabolism. Under this term are included all the chemical 
 processes going on in the plant which lead to the formation of 
 simple substances from more complex ones. 
 
 The chief physiological importance of the catabolic processes is 
 this : that, inasmuch as they consist in the decomposition of 
 relatively complex and unstable substances into others which are 
 relatively simple and stable, they necessarily involve a conversion 
 of potential into kinetic energy ; and it is by means of the kinetic 
 energy so evolved that the plant exhibits those phenomena, such as 
 growth, movement, etc., which characterise it as a living organism. 
 The degree of activity of life depends directly upon the degree of 
 catabolic activity ; when catabolism ceases, life ceases ; the organ- 
 ism is dead. A good illustration of this is afforded by the scarcely 
 perceptible catabolism of seeds, bulbs, etc., when quiescent, and 
 their very active catabolism when they begin to germinate. 
 
 The catabolic processes of the plant are carried on either by the 
 living protoplasm itself, or by means of certain substances formed 
 by the protoplasm, which are termed enzymes. 
 
 The catabolic processes carried on by the protoplasm are mainly 
 such as depend upon the absorption of free oxygen from without, 
 and are accompanied by an evolution of carbon dioxide ; in fact this 
 gaseous interchange between the plant and its environment, termed 
 Respiration, is the external manifestation of the performance of 
 these catabolic processes. The seat of these processes is the 
 protoplasm, and it is mainly the molecules of protoplasm that 
 are decomposed ; in other words, just as the construction of the 
 protoplasm-molecule is the ultimate result of anabolism, so the- 
 decomposition of the protoplasm-molecule is the central fact o 
 catabolism. 
 
 The reason, then, why most plants die when they are deprived 
 of free oxygen, is that they are unable to carry on, under these- 
 circumstances, those catabolic processes by which the energy 
 essential to the maintenance of life is evolved ; just as a fire goes 
 out, that is the oxidation of the coal stops, under the same con- 
 ditions. 
 
 Though it may be generally stated that living plants at all 
 times absorb free oxygen, and that the maintenance of life depends 
 upon a constant absorption of free oxygen, yet there are excep- 
 tions. There are, for instance, certain Fungi, such as Yeast and 
 Bacteria, which can live in the absence of free oxygen. Under 
 these conditions they carry on other processes of decomposition into
 
 198 PART III. PHYSIOLOGY. [ 45 
 
 which free oxygen does not enter, provided that suitable material 
 is accessible ; these processes are termed fermentations, and th6 
 plants organised ferments. Thus, Bacteria cause putrefaction and 
 other similar fermentations in the most various organic substances 
 with which they happen to come into contact. Similarly Yeast is 
 the cause of the alcoholic fermentation of sugar, which may be re- 
 presented by the equation 
 
 C 6 H 12 6 = 2C 2 H 6 + 2C0 2 . 
 
 The chief kinds of enzymes which have been found in plants 
 are: 
 
 1. Those that act on carbohydrates, converting the more complex 
 and less soluble carbohydrates into others of simpler composition 
 and greater solubility. 
 
 2. Those that act on fats, decomposing them into glycerin and 
 fatty acid. 
 
 3. Those that act on glucosides, glucose being a constant 
 product. 
 
 4. Those that act on the more complex and less soluble proteids, 
 converting them into others which are more soluble and probably 
 less complex, or decomposing them into non-proteid nitrogenous 
 substances (amides, etc.). 
 
 The chemical action of some of these enzymes are illustrated by the 
 following equations : 
 
 1. Conversion of starch into sugar (amylolytic enzyme, commonly termed 
 diastase) : 
 
 Starch. Maltose. Dextrin. 
 
 3 (C 6 H 10 5 ) + H 3 0= C 12 H 2 ,O n + C 6 H 10 5 
 
 2. Conversion of cane-sugar into grape-sugar (invert enzyme) : 
 
 Cane-sugar, Dextrose. Lsevulose. 
 C 18 H 22 U + H 2 0-C 6 H 12 6 + C 6 H 1S 6 
 8. Action of fat-enzyme : 
 
 OleYn. Oleic acid. Glycerin. 
 
 CjjH^Oe + SHsO- 3C 16 H 34 2 + C 3 H 8 O 3 
 
 It will be noted that, in every case, the action of the enzyme involves 
 the taking up of one or more molecules of water. 
 
 The action of the enzymes which act on proteids (protedytic enzymes) 
 cannot be represented by equations, inasmuch as no formulae for the 
 various proteids have at present been arrived at. It may be generally 
 stated that their effect is, like those of the other forms, to induce de- 
 composition with the assumption of water. The proteolytic enzymes, 
 acting some in an acid medium, others in an alkaline, convert the more 
 complex proteids, such as globulins, into simpler ones, such as peptone ;
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 199 
 
 and further cause the decomposition of peptone into amides, such as 
 asparagin, leucin, and tyrosin. 
 
 The chief importance of the enzymes in tb.e economy of the 
 plant is that by their means the reserve materials, which are 
 accumulated to such a large extent in the form of substances, 
 such as starch, fat, cellulose, proteids of aleuron-grains, which 
 are either not soluble in water, or if soluble are only slightly 
 diffusible, are converted into substances, such as amides and cer- 
 tain sugars, which are both readily soluble and diffusible, and 
 which can therefore travel osmotically from one part to another. 
 For instance, as mentioned above, the excess of carbohydrate 
 formed in the leaves when they are actively assimilating, is com- 
 monly stored up in the form of starch. This carbohydrate is 
 eventually conveyed to other parts of the plant ; but, since starch 
 is insoluble, it cannot be conveyed in that form ; it is, in fact, con- 
 verted into maltose by an amylolytic enzyme present in the leaves, 
 and it is in this form that non-nitrogenous organic substance is 
 conveyed away from the leaf where it has been produced. Other 
 striking illustrations of the importance of enzyme-action are to be 
 found in the chemical changes going on in germinating seeds, 
 bulbs, tubers, etc. When a starchy seed, or a starchy tuber like 
 the potato, germinates, the starch-grains are gradually dissolved, 
 the starch being converted into maltose. When the tuber of the 
 Dahlia or Artichoke, which contains inulin as the non-nitrogenous 
 reserve material, germinates, the inulin disappears and is 
 gradually replaced by grape-sugar. When an oily seed germinates, 
 the oil-drops become less and less apparent, as the oil is gradually 
 decomposed by enzyme-action into glycerin and fatty acids ; the 
 next step is the formation of carbohydrate (sugar or starch), pro- 
 bably from the products of the decomposition of the oil, a process 
 which involves the absorption and fixation of oxygen, since 
 carbohydrates contain a higher percentage of oxygen than does 
 any form of fat or oil ; and then, finally, any starch so formed is 
 converted into sugar. Similarly, the aleuron-grains in a germin- 
 ating seed gradually disappear, the indiffusible proteids composing 
 them being decomposed by the action of a proteolytic enzyme into 
 peptone, and then into amides, in which form they are conveyed 
 osmotically to the growing embryo. Finally, it is obvious that 
 the indiffusible proteids which are conveyed from part to part in 
 the sieve-tissue of vascular plants (see p. 165) must eventually be
 
 200 PART III. PHYSIOLOGY. [ 45 
 
 distributed osmotically in the form of diffusible compounds, pro- 
 bably amides, to the adjacent parenchyinatous tissues, and it is 
 probable, though not yet ascertained, that here again a proteolytic 
 enzyme is involved. 
 
 Respiration. This term is applied to the gaseous interchange, 
 consisting in the absorption of free oxygen and the evolution of 
 carbon dioxide, which takes place (with but few exceptions) be- 
 tween the living plant and the atmosphere, and which may be re- 
 garded as the external expression of the oxidative catabolic processes 
 going on in the tissue of the plant. This gaseous interchange goes 
 on over the whole surface of the body ; but in those parts jvvhich 
 possess stomata or lenticels, it is mainly conducted through these 
 apertures. 
 
 Respiration seems to be somewhat diminished under the in- 
 fluence of bright light ; but its activity is promoted by a rising 
 temperature, and to some extent by greater moistness of the air. 
 The relation to temperature is such that respiration takes place 
 at temperatures even slightly below 0C. ; that it increases in 
 intensity with a rise of temperature, but in greater proportion, up 
 to an optimum of 40-45 ; and then sinks as the temperature 
 further rises until the fatal degree is reached. 
 
 The relation of the volume of the gases absorbed and evolved in 
 respiration, that is, of oxygen and carbon dioxide, is a matter of 
 importance. It may be generally stated that the relation is de- 
 finite and constant for any given plant, or for any part of it, at a 
 given stage of development, all other conditions being constant : 
 the proportion 2? may be unity, or less or more than unity, ac- 
 cording to the nature of the plant under experiment, and is not 
 affected either by temperature or by light. 
 
 Respiration can be demonstrated by placing a quantity of germinating 
 seeds, or opening flower-buds, in an air-tight glass receiver (somewhat as 
 in Fig. 129), through which a current of air is drawn previously freed 
 from CO 2 by passing through solution of caustic potash. On examining 
 the gas drawn from the receiver, by passing it through a clear solution of 
 lime-water, it will be found that the lime-water becomes turbid in con- 
 sequence of the formation of calcium carbonate, the CO 2 in the gas with- 
 drawn combining with the lime. 
 
 5. The Products of Metabolism. The relation between the 
 anabolism and the catabolism of the plant may be generally stated 
 thus, that the construction of organic substance in the former is 
 greater than the decomposition of it in the latter, so that on the
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 201 
 
 whole there is an accumulation of organic substance in the body of 
 the plant. The organic substance is accumulated to some extent 
 in the actual structure or fabric of the plant, as protoplasm and 
 cell-wall, and to some extent in the form of "compounds which 
 may be present in some or all of the cells, but which do not 
 constitute any portion of the fabric. These compounds may or 
 may not be of nutritive value ; in the former case they are termed 
 jrtasfic products, in the latter icaste-products, of metabolism (see 
 p. 158). 
 
 The most important of the plastic products are enumerated be- 
 low. They are all found accumulated as reserve materials iu 
 various parts of plants. 
 
 Non-nitrogenous reserve mattriaJs: 
 
 a. Carbohydrates; in solid granules, starch; in many seeds, and 
 
 tubers, 
 
 in thickened cell-walls, cellulose ; as in Date- 
 seed, Coffee-seed, Vegetable Ivory, 
 
 dissolved in cell-sap ; grape-sugar, as in the Onion 
 and in fruits ; cane-sugar, as in the Sugar-cane 
 and the Beetroot ; inulin, as in the Jerusalem 
 Artichoke and Dahlia. 
 
 b. Fats ; in drops in many seeds (Rape, Linseed, Castor-oil, Palm. 
 etc.). 
 
 Nitrogenous reserve materials : 
 
 a. Proteids ; in solid granules (aleuron ; p. 80), in seeds, more espe- 
 cially oily seeds. 
 
 6. Amides; asparagin, etc., in solution in the cell-sap of bulbs, 
 tubers, bulbous roots, etc. 
 
 The icaste-products are most probably all formed as the result 
 of catabolic processes ; though their formation is often associated, 
 both as to time and place, with active anabolism. They may be 
 classified into nitrogenous and non-nitrogenous. 
 
 The principal nitrogenous waste-products appear to be the 
 alkaloids (see p. 186). They are probably products of the nitro- 
 genous catabolism of plants ; and it is suggestive that they prin- 
 cipally occur deposited in "the cells of deciduous parts, such as 
 leaves, seeds, bark, etc. 
 
 The principal non-nitrogenous waste-products are, water; free 
 oxygen (green plants in light) ; carbon dioxide, and some other 
 highly oxidised carbon-acids, such as the oxalic ; resins and ethereal 
 oils, tannins, aromatic substances, etc. 
 
 Of these waste-products, some are retained in the cells of the
 
 202 PART III. PHYSIOLOGY. [ 45 
 
 plant, whereas others are thrown off or excreted. The nitrogenous 
 waste -products are deposited either in cells or in the laticiferous 
 tissue : there is practically no excretion of such waste-products by 
 plants. Similarly, those of the non-nitrogenous waste-products 
 which are not gaseous at ordinary temperatures, are retained by 
 the plant. For instance, oxalic acid is deposited in the form of 
 crystals of calcium oxalate either in the cavities or in the walls of 
 the cells (see pp. 78, 81) : the crystals may have either six mole- 
 cules of water of crystallisation, when they are quadratic ; or two 
 molecules, when they are prismatic (raphides). The resins and 
 ethereal oils are usually excreted by the cells in which they are 
 formed, into intercellular spaces (resin-ducts, oil-glands, see p. 
 97) : the tannins are mostly stored in cells, dissolved in the cell- 
 sap. 
 
 The oxygen which is set free in connexion with the decomposi- 
 tion of C0 2 in the green parts under the influence of light, is 
 exhaled in the gaseous form ; this is also the case with the 
 carbon dioxide produced in catabolism. In some cases, however, 
 some portion of the carbon dioxide forms calcium carbonate, which 
 is either deposited in the solid form (e.g. cystoliths, see p. 78), or 
 is excreted by means of the chalk-glands (p. 96). 
 
 In some cases, substances of nutritive value are excreted by 
 plants, as for instance, the sugary liquid known as nectar by 
 special glands, the nectaries (see p. 26), of flowers, and the di- 
 gestive liquid poured out by the glands of the insectivorous plants. 
 This loss of substance is, however, compensated for by the advan- 
 tages gained by the excretion. The nectar attracts insects, and so 
 ensures cross-fertilisation, and the excretion of the insectivorous 
 plants results in the digestion of the entrapped insects (see p. 189). 
 
 The mechanism of excretion may be generally illustrated by 
 reference to two cases : to the nectaries, and to the chalk-glands. 
 The former afford an example of that mode of excretion in which 
 the necessary force is supplied by the excreting cells themselves : 
 the latter, of that mode in which the necessary force is derived 
 from another source. Excretion by nectaries can be well observed 
 in the case oiFritillaria imperialis (Fritillary, or Crown Imperial). 
 At the base of each of the petals of the flower, there is an 
 oval depression which is the gland or nectary and is seen to be 
 occupied by a large drop of nectar. If the flower be cut off, and 
 the drop be removed from the nectary by means of blotting-paper, 
 it will be shortly replaced by a fresh drop. It is therefore clear
 
 45] CHAP. II. PHYSIOLOGY OF NUTRITIVE FUNCTIONS. 203 
 
 that in this case the excretion of the liquid is effected, not by the 
 root-pressure, for the flower is no longer in connexion with the 
 root, but by the cells themselves. The mechanism of excretion 
 seems to be this, that the cells of the nectary become turgid, and 
 when a certain degree of turgidity has been attained, nitration 
 under pressure takes place, and liquid is pressed out. Excretion 
 by chalk-glands can be well observed in some of the Saxifrages. 
 The chalk-glands are here situated at the end of the finer vascular 
 bundles round the margin of the leaves, each gland being at the 
 bottom of a depression in the surface, and communicating with the 
 surface by two or three water-stotnata (see p. 109). So long as the 
 leaf is in connexion with the rest of the plant, and provided that 
 transpiration is not too active, drops of water holding chalk in 
 solution are poured out by these glands on to the surface through 
 the water-stomata. The excretion stops, however, directly the 
 leaf is removed, or the stem is cut through. In this case the 
 excretion clearly depends upon the root-pressure ; the gland itself 
 has no excreting power, but it simply accumulates the chalk which 
 is then washed out by the current of water forced through the 
 gland by the root-pressure. 
 
 In connexion with the catabolic processes there is an evolution 
 of energy constantly going on in the plant, which is for the most 
 part lost to the plant, or dissipated, most commonly in the form of 
 heat, in a few cases in the form of light, and also commonly in the 
 form of movement. The evolution of heat by plants is not usually 
 sufficient to cause the temperature of the plant-body to be higher 
 than that of the surrounding air. This is partly due to the fact 
 that the catabolic processes of plants are not generally very active, 
 and partly to the continual loss of heat by radiation and in con- 
 nexion with transpiration. It is however easy, under appropriate 
 conditions, to demonstrate the evolution of heat. If a quantity of 
 seeds be made to germinate in a heap, they will be found to be 
 distinctly warm (Fig. 129). This happens on a large scale in the 
 process of malting barley. When a large quantity of barley -grains 
 are germinating on a malting-floor, they become quite hot : they 
 have, in fact, to be continually turned to prevent overheating. 
 The conditions are here most favourable : for the catabolic pro- 
 cesses are extremely active in germinating seeds, and there is but 
 little loss of heat by radiation and transpiration. Similar observa- 
 tions may be made with opening flower-buds, the opening of the 
 bud being also a period of great catabolic activity. In some cases,
 
 204 
 
 PART III. PHYSIOLOGY. 
 
 [ 45 
 
 as in the Aracese, where the inflorescence consists of a great num- 
 ber of flowers which open simultaneously, and which are protected 
 by a large leaf, the spathe, a rise of temperature as much as 18 O 
 has been observed. 
 
 The few plants in which an evolution of energy in the form of 
 light has been clearly established are 
 all Fungi. It is commonly termed 
 phosphorescence. The so-called phos- 
 phorescence of decaying wood is due to 
 the presence of the mycelium of Agar- 
 icus melons, and that of putrefying 
 meat and vegetables to Schizornycetes 
 of the nature of Micrococci. Various 
 other species of Agaricus have been 
 found to be luminous. 
 
 Movement of some kind is manifested 
 by all plants. All plants exhibit that 
 slow movement which is termed 
 growth : in many, there is a more or 
 less well-marked movement of the pro- 
 toplasm in the cell or cells of which the 
 plant-body consists, which is known as 
 cydosis, circulation, or rotation :. some 
 are capable of locomotion during the 
 whole or a portion of their life, a 
 peculiarity which is shared by many 
 reproductive cells, such, as zoospores 
 and spermatozoids : in some cases, the 
 floral or the foliage-leaves of the plant 
 can perform movements, as the foliage- 
 leaves of the Sensitive Plant, of the 
 Telegraph-plant, of Dioncea muscipiila 
 (Venus' Fly-trap), the stamens of Ber- 
 beris and of the Cynareae, or portions 
 of leaves as the tentacles of Drosera 
 (Sun-dew, see p. 189). These movements 
 are considered in detail in the next 
 chapter. 
 
 The connexion between these various 
 forms of dissipation of energy and the 
 catabolic processes, is clearly demon- 
 
 Fio. 129. Apparatus for de- 
 tecting the rise of temperature 
 in 8mp.ll opening flowers or ger- 
 minating seeds. The seeds are 
 heaped as closely as possible in 
 the funnel r which is inserted 
 into the mouth of a bottle con- 
 taining a solution of caustic 
 potash. This absorbs the car- 
 bon dioxide produced by respi- 
 ration. The whole is enclosed 
 in a glass vessel, and a delicate 
 therm oraeter is inserted through 
 the cotton wool which closes 
 the mouth. The bulb of the 
 thermometer is plunged in 
 among the seeds. The tempera- 
 ture in this apparatus will be 
 higher than in another arranged 
 in the same way forcompnrison, 
 and in which the flowers or 
 seeds have previously been 
 Ic.lled.
 
 46] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 205 
 
 strated by the fact that any change which prejudicially affects 
 the activity of catabolism, similarly affects the dissipation of 
 energy. For instance, in the absence of free oxygen, a condition 
 which" diminishes catabolic activity in most cases, germinating 
 seeds or opening flowers cease to evolve heat ; the luminous Fungi 
 cease to emit light ; growth, and the other more conspicuous 
 movements are arrested : similar effects are produced by exposure 
 to a low temperature. 
 
 CHAPTER III. 
 
 SPECIAL PHYSIOLOGY OF MOVEMENT. 
 
 46. Introductory. The movements to be specially con- 
 sidered here are such as may be characterized as vital ; that is, 
 they are essentially manifestations of the life of the protoplasm. 
 This statement is rendered necessary by the fact that movements 
 do occur in plants which are dependent upon purely physical 
 causes ; instances of these are afforded by the rupture of pollen- 
 sacs and other sporangia, the twisting and untwisting of awns (as 
 in the fruits of Erodium and Stipa), the bursting of fruits (as 
 in the Balsam, Impatiens Noli-me-tangere, and the Squirting 
 Cucumbers, such as Ecbalium, Momordica, and Elaterium). These 
 movements may be due, in the simpler cases, either to expansion 
 and contraction of hygroscopic cell-walls resulting from variations 
 in the moisture of the air, or to the imbibition with water and the 
 consequent swelling-up of mucilaginous substances in the cells ; 
 in the more complicated cases the movement depends upon tensions 
 set up between different layers of tissue in consequence of unequal 
 expansion. 
 
 The vital movements are either spontaneous or induced. In the 
 former case they are the result of causes operating in the organism 
 itself ; in the latter, they are the result of causes acting upon 
 the organism from without. 
 
 The following are the principal phenomena of movement ex- 
 hibited by plants ; the streaming movement of protoplasm 
 (cyclosis) ; the expansion and contraction of contractile vacuoles ; 
 the locomotion of entire organisms ; the movements of cellular 
 members.
 
 206 PART III. PHYSIOLOGY. [ 47 
 
 47. The Spontaneous Movements may be conveniently 
 considered under the two heads of movements of protoplasm, and 
 movements of cellular members. 
 
 A. Movements of Protoplasm. Under this head are included 
 such spontaneous movements as can be directly observed in the 
 protoplasm. The first to be noted is the streaming movement, 
 which can be frequently observed either in naked protoplasm (e.g. 
 plasrnodia of Myxomycetes), or in the protoplasm of ccenocytes 
 clothed by a cell-wall (e.g. hyphse of Fungi), or in that of cells 
 (e.g. leaf of Elodea and Vallisneria, internodal cells of Characeae, 
 root-hairs of Trianea bogotensis, hairs of the stamens of Trades- 
 cantia, etc.). The movement takes place in the more fluid por- 
 tion of the protoplasm, and is made evident by the granules of 
 various kinds which are carried along by the current. The 
 direction of the movement varies somewhat according to circum- 
 stances : the current travels in one direction, and this simple 
 longitudinal movement is all that can be observed in plasmodia 
 and in hyphse ; but in cells, owing to their shortness, it can be 
 observed to travel up one long side, across the end, and down the 
 other side ; and when the cytoplasm forms not merely a parietal 
 layer, but forms strands traversing the vacuole (e.g. Fig. 36 Z>), 
 currents can be observed in these strands also. 
 
 The contractile vacuoles are small, more or less nearly spherical, 
 cavities which make their appearance in the protoplasm and 
 then suddenly disappear. In their relatively slow expansion 
 (diastole), they become filled with cell-sap, which is forced out 
 on the sudden contraction (systole). They have been exclusively 
 found in motile organisms, such as the Volvocineae, the plasmodia 
 of Myxomycetes, the zoospores of many Algae and of some Fungi. 
 
 In the second place the protoplasmic movements which involve 
 locomotion have to be considered. The simplest case of this is the 
 amoeboid movement exhibited, among plants, by the zoospores of 
 the Myxomycetes and of some Algae, and by the naked masses of 
 protoplasm which constitute the plasmodia of the Myxomycetes. 
 There is here no specialised motile organ, but any part of the 
 protoplasm may be protruded as a pseudopodium into which the 
 remainder of the protoplasm gradually flows, and thus locomotion 
 of the whole is effected. 
 
 The locomotory movements of most zoospores, of spermatozoids, 
 and of entire organisms such as Volvox, Pandorina, etc., is effected 
 by means of specialised motile organs, which are delicate proto-
 
 47] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 207 
 
 plasmic filaments termed cilia (see p. 51) ; each cell may have 
 one, two, four, or many cilia (see Figs. 1, 62, 63). 
 
 Locpmotion is also exhibited by other Algae, such as Diatoms, Oscil- 
 latorias, etc., but the mechanism is not fully understood. 
 
 B. Movements of Cellular Members. Instances of the move- 
 ment of parts of plants consisting of one or more cells having a 
 cell-wall, are afforded by all growing members, and by some 
 specially modified mature members ; the movements of the latter 
 are termed movements of variation, those of the former, movements 
 of growth. 
 
 These two kinds of movements can be readily distinguished 
 from each other, inasmuch as the movements of variation are 
 rapid and can be easily observed, whereas the movements of 
 growth are slow and can only be followed by means of special 
 apparatus. 
 
 a. Movements of Variation. The majority of the movements of 
 variation are induced, a few only being spontaneous. An instance 
 of spontaneous movement is afforded by the rising and falling of 
 the lateral leaflets of the trifoliolate leaf of Desmodium gyrans, the 
 Telegraph-plant. It must, however, be pointed out that the power 
 of spontaneous movement may be possessed by plants though they 
 do not manifest it under ordinary circumstances. Thus the leaves 
 of the Sensitive Plant (Mimosa pudicd) move spontaneously in 
 darkness, but they will not do so in the light. This is also true 
 of various Leguminosce and Oxalidacese. 
 
 b. Movements of Growth. Before entering upon a description 
 of the movements of growth, a clear idea must be formed of what 
 growth really is. By growth is meant change of external form, 
 which is usually, though not necessarily, accompanied by increase 
 in bulk ; the change of form being rendered permanent by the 
 deposition of new substance : it is a function of embryonic proto- 
 plasm (see p. 8). 
 
 The growth of the plant-body takes place to a greater or less 
 extent in all three dimensions of space. For instance, when it 
 takes place equally in all three dimensions, a spherical body is 
 produced, as in Protococcus and Volvox. Occasionally it takes 
 place especially in two dimensions, the result being a flattened 
 body, such as a Fern-prothallus or an Ulva. More commonly, 
 however, it takes place especially in one direction, so that the 
 plant-body assumes an elongated form. An extreme case of this
 
 208 
 
 PART III. PHYSIOLOGY. 
 
 47 
 
 is afforded by Spirogyra and other filamentous Algae. It is this 
 growth in length which has been more especially studied physio- 
 logically, and in what follows, " growth " may be taken to mean 
 " growth in length," unless there is some definite statement to the 
 contrary. 
 
 The growth in length of the plant-body takes place at first 
 throughout its whole extent ; but at a later period it is limited, as 
 a rule, to particular regions (see p. 8). In the growing portion 
 of any member two regions may be distinguished : the formative 
 region, which is the growing-point proper: and the region of 
 elongation adjacent to it (Fig. 130). In the formative region the 
 construction of the new tissue from plastic substances takes place, 
 as is specially manifested in the formation of cell-walls accom- 
 panying the cell-division going on in this region of a multicellular 
 growing-point; but the amount of elonga- 
 tion is slight. In the region of elongation, 
 the formative processes have ceased : in 
 multicellular plants little or no cell-division 
 takes place in this region ; the cells are 
 here fully formed, and they simply require 
 to increase in bulk, to grow in fact, in 
 order to attain the mature form. Beyond 
 the region of elongation comes the portion 
 of the member which has already ceased to 
 grow. It must be clearly understood that 
 each portion of the growing-point passes 
 through these three phases. For instance, 
 in a multicellular apical growing-point, 
 each cell is produced in the formative re- 
 gion ; and as in consequence of the con- 
 tinued formation of younger cells in front 
 of it at the apex, it comes to lie at an 
 increasing distance from the apex, it passes 
 through the stage of growth, to become an 
 adult tissue-element. 
 
 The movement of growth in length is 
 altogether spontaneous. It may be generally described as the 
 travelling of the organic apex in a line which is the continuation 
 of the longitudinal axis of the growing member. Both the rate 
 and the direction of growth are liable to variation. 
 
 Variations in the Rate of Growth. When a member begins to 
 
 KIG. 130. The growing 
 primary root of the Pea in 
 two stages. .4 The root is 
 marked by lines atequal dis- 
 tances. In B the differences 
 in rapidity of growth are 
 perceptible : the uppermost 
 lines have not been sepa- 
 rated ; the root has ceased 
 to grow here. The lowest 
 likewise are still close toge- 
 ther ; at the apex elonga- 
 tion has not taken place. 
 In the intermediate zones 
 the elongation has been 
 very great.
 
 CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 209 
 
 grow, its rate of growth is at first slow ; it then accelerates, until 
 a maximum rapidity is attained ; after which it diminishes until 
 growth ceases altogether. This gradual rise -and fall in the rate 
 of growth, extending over the whole of one period of growth, is 
 termed the grand period of growth. 
 
 This periodicity is manifested also in each cell of the growing 
 region. A young cell grows but slowly ; as it becomes older, 
 and is gradually removed from the growing-point, its rate of 
 growth increases up to a maximum ; as it becomes still older 
 and is still more remote, the rate of growth sinks, until finally 
 the adult stage is reached, and growth ceases. 
 
 Careful observation of growing members has shown that, in 
 addition to the spontaneous variation constituting the grand 
 period of growth, small irregular variations are constantly taking 
 place, which, since they are apparently spontaneous, are termed 
 irregular spontaneous variations. 
 
 Another point which must be taken into account is the energy 
 of groicth ; that is, the relative capacity of different members for 
 growth in length. The differences in the energy of growth in 
 growing members manifest themselves in differences either in the 
 length of the grand period, or in the rate of growth ; in other 
 words, members may grow for a longer or shorter time, or they 
 may grow more or less rapidly. In any case the result is that 
 members attain different lengths. Tor instance, it is easy to 
 observe that the lower internodes of most stems remain short; 
 that those above them are longer ; that those of a certain part of 
 the stem are the longest ; and that the upper ones again are short. 
 In the same way the size of the leaves attached to these various 
 parts of the stem increases from below to about the middle, and 
 then diminishes. 
 
 Variations in the Direction of Growth. Although it is true, as 
 stated above, that the result of growth is, generally speaking, that 
 the apex of the growing member is moved onwards in a line which 
 is the continuation of the axis of the growing organ ; yet, during 
 the actual process of growth, this relation of position is not 
 maintained, because the rate of growth is at no time uniform 
 throughout the transverse section of the region of elongation. 
 Suppose a radial stem rising vertically from the soil ; the longi- 
 tudinal axis of the fully grown portion of this stem is vertical, 
 but this is not true of the growing portion. If the apex be looked 
 down upon from above it will be seen to travel in an orbit round 
 
 M.B. P
 
 210 
 
 PART III. PHYSIOLOGY. 
 
 [47 
 
 the prolongation of the longitudinal axis of the fully grown 
 portion. "When the stem is radially symmetrical, the orbit is 
 approximately circular ; but in cases in which the member tends 
 to be bilaterally symmetrical, one diameter of the orbit becomes 
 proportionally elongated, the orbit being then oval, or elliptic, 
 until, finally, when the bilateral symmetry is strongly marked, 
 the orbit becomes a straight line, the growing-point simply oscil- 
 lating from side to side. Whilst the growing-point is travelling 
 
 Fie. 131. Illustration of the epinastic growth of the leaves of the Sunflower (Helianthus 
 animus). A represents the position of the leaves when the plant is exposed to light; J5 
 represents the position of the leaves when the plant has been kept in darkness for twenty- 
 four hours. In A the leaves are expanded in consequence of the directive (diaheliotropic) 
 action of the incident rays of light. In B the leaves, in the absence of light, have become 
 recurved in virtue of their inherent epinastic growth. 
 
 in its orbit, it is at the same time being raised upwards ; so that 
 it describes a path which is, according to the form of the orbit, a 
 circular spiral, an elliptical spiral, or a zig-zag. These changes 
 of position are, however, not permanent ; for example, though the 
 growing-point may be travelling upwards in a spiral, the fully- 
 grown stem does not resemble a corkscrew, but is straight.
 
 48] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 211 
 
 These spontaneous changes in position of growing-points are 
 designated generally by the term Nutation. 
 
 All growing members nutate in a more or less marked manner ; 
 but the most conspicuous instances are afforded by slender struc- 
 tures, such as tendrils, and the internodes of twining stems. 
 
 A peculiar form of nutation is commonly exhibited by dorsiventral 
 members, such as leaves. In the early stages the one surface of the leaf 
 grows much faster than the other, thus leading to certain peculiar forms 
 of vernation and aestivation (see p. 43) ; in the later stages the other side 
 grows the faster, and so the expansion of the leaf is brought about. 
 When it is the upper surface which is growing the faster, whether 
 along the transverse or the longitudinal axis of the leaf, it is said to be a 
 case of ejrinasty (Fig. 131) ; when the lower surface, it is said to be a case 
 of hyponasty. A striking example is afforded by leaves having circinate 
 vernation, as many Ferns, Drosera, etc. ; this form of vernation is due to 
 the growth of the leaf being at first longitudinally hyponastic. The 
 convolute, involute, and conduplicate forms are all the result of trans- 
 verse hyponastic growth in the early stages of development of the leaf, 
 whereas the revolute form is the result of transverse epinastic growth. 
 
 48. Induced Movements. All parts of plants which can 
 exhibit movement are also irritable ; that is, they respond to the 
 action of external agents either by a movement or by a change 
 in the rate or the direction of their movement. The following 
 are the principal causes, or stimuli, of movement, or change of 
 movement : 
 
 a. Mechanical ; contact or pressure ; 
 
 b. Variations of temperature ; 
 
 c. Variations in the intensity of light ; 
 
 d. Changes in the direction of incidence of the rays of light ; 
 
 e. Changes of position with regard to the line of action of 
 
 gravity (vertical); 
 /. Differences of degree of moisture in the surrounding medium. 
 
 a. Irritability to Mechanical Stimuli. This form of irritability 
 is most strikingly manifested by motile mature members, and less 
 markedly by certain growing members. 
 
 The following are instances of irritability to contact manifested 
 by mature motile members : by the leaves of the sensitive plants 
 (see p. 174), and by those of Dion sea and Drosera ; by the stamens 
 of Berberis, Mahonia, the Cynarese, and the Cistaceae ; by the lobes 
 of the stigma of Miinulus, Martynia, and Bignonia (p. 176).
 
 212 PART III. PHYSIOLOGY. [ 48 
 
 The most familiar case is that of Mimosa, pudica, the Sensitive Plant. 
 The leaf of this plant is bipinnate, consisting of a primary petiole bearing 
 at its free end four secondary petioles, upon which the leaflets or pinnae 
 are inserted (see Fig. 126). The primary petiole is articulated to the 
 stem; each secondary petiole to the primary petiole ; and each pinna to 
 the secoridar3- petiole, by a pulvinus. When stimulated, the pinnae fold 
 together forwards and upwards : the secondary petioles move sideways so 
 as to come closer together and to lie almost parallel; and the primary 
 petiole sinks downwards ; the pulvini act as hinges upon which the 
 various parts move. 
 
 It is only a few growing members which react perceptibly to 
 mechanical stimulation ; such are tendrils, the petioles of leaf- 
 climbers (e.g. Tropseolum, Clematis, Solanum jasminoides], the 
 stem of at least one stem-climber, namely that of Cuscuta 
 (Dodder), and roots. In these cases the contact must be of 
 relatively long duration, becoming, in fact, pressure. 
 
 The irritability of growing members to mechanical stimulation 
 is, however, less marked than that of the mature motile members 
 mentioned above. Even in the most sensitive growing members, 
 such as tendrils, the resulting movement is comparatively slow. 
 The movement induced in these members is that they tend to 
 curve round -the object with which they have come into contact. 
 The result of this is that fresh portions of the member come into 
 contact and are stimulated to curve, so that the member forms 
 coils round the object, and thus becomes firmly attached to it. In 
 the case of roots, when the growing-point is more or less injured 
 by pressure or otherwise, a curvature is induced of such a kind 
 that the injured side becomes convex, with the result that the 
 growing-point, and consequently the direction of growth, is de- 
 flected from the obstacle or other cause of injury. 
 
 1). Irritability to Variations of Temperature. Movement, like 
 the other functions (see p. 160), is affected by temperature, but 
 this influence is not stimulating but tonic : it does not induce 
 movement, but merely modifies the activity of movement. A 
 sudden variation of temperature may, however, act as a stimulus 
 and induce a movement. This kind of irritability has been de- 
 tected in various leaves : for instance, a rise of temperature causes 
 certain flowers (e.g. Tulip, Crocus) to open, and a fall of tempera- 
 ture causes them to close : similarly a fall of temperature causes 
 the leaves of such plants as the Sensitive Plant and the Wood- 
 Sorrel (Oxalis Acetosetta) to fold up, whereas a rise of temperature 
 causes them to expand (see Tigs. 125, 126).
 
 48] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 213 
 
 c. Irritability to Variations in the Intensity of Light (Paratonic 
 Effect of Light ; p. 162). This is exhibited in a marked manner 
 by the majority of motile members, more especially leaves. When, 
 for instance, the intensity of the light is diminished, the perianth- 
 leaves of many flowers and the foliage-leaves and cotyledons of 
 many plants perform movements which are termed nyctitropic or 
 sleep-movements (see p. 173). Thus, the flowers close; and the 
 foliage-leaves change their position in various ways, assuming 
 what is known as the nocturnal position, so that thsy no longer 
 present the surface, but the margin of the blade to the sky. Con- 
 versely, when flowers or leaves which have assumed the nocturnal 
 position are exposed to light, or to brighter light than before, they 
 resume their normal expanded (diurnal) position. 
 
 Another remarkable manifestation of this irritability is that 
 movements of variation in some cases, and movements of growth 
 in most cases, are retarded or arrested by exposure to light of a 
 sufficient intensity. 
 
 In illustration of the effect of light upon movements of varia- 
 tion, it may be stated that certain members, such as the leaves 
 of the Sensitive Plant, which perform spontaneous movements of 
 variation, are unable to do so when exposed to bright light : 
 under this condition the leaves become fixed, as it were, in the 
 diurnal position. This is not, however, the case with all mature 
 motile members : for instance, the movement of the lateral leaf- 
 lets of the Telegraph-plant (Desmodium gyrans) continues even in 
 bright sunlight. 
 
 The paratonic action of light on movements of growth is strik- 
 ingly exhibited in various ways. It is well demonstrated by etio- 
 lated plants (see p. 162), that is, by plants which have been kept 
 in darkness for some considerable time. A characteristic feature of 
 etiolated shoots is the excessive length of their internodes, as com- 
 pared with those of a shoot which has been growing for the same 
 period exposed to the normal alternation of day and night. This ex- 
 cessive elongation in darkness which occurs as a rule in all radial 
 and isobilateral members which usually grow exposed to light is 
 the result of the absence of the retarding paratonic action of light. 
 
 The effect of the paratonic action of light can also be estimated 
 by direct measurement of the growing member. As the result of 
 a great number of comparative measurements, it has been found, 
 in regard to members of all kinds, that the rate of growth is more 
 rapid in darkness than in light.
 
 214 PART III. PHYSIOLOGY. [ 48 
 
 An interesting demonstration of the relation of the rate of 
 growth to light is afforded by the observation of the growth of 
 any member at given intervals every hour, or every two or three 
 hours daring an entire day of twenty-four hours. By this means 
 it has been ascertained that a growing member exhibits a regular 
 daily periodicity in the variations in its rate of growth, which 
 has a direct relation to the alternation of day and night. 
 
 The paratonic action of light varies with its intensity : the more 
 intense the light the more marked the paratonic action. Exposure 
 to very intense light may entirely arrest growth for the time 
 being.' 
 
 It has been found that the different rays of the spectrum are 
 not equally active ; the paratonic effect of the more highly refran- 
 gible rays (violet, indigo, blue) is far greater than that of the 
 rays of lower refrangibility. 
 
 d. Irritability to the Direction of Incidence of the rays of Light 
 (Heliotropism). This kind of irritability is extremely common, 
 and generally manifests itself in the most striking manner. The 
 most active rays of light are those of high refrangibility (violet, 
 indigo, blue). 
 
 A remarkable example of this is afforded by the zoospores of 
 various plants (e.g. Ulothrix, Hsematococcus, Botrydium, etc.). 
 When light falls obliquely upon them, these zoospores arrange 
 themselves in the water so that their long axes are parallel to the 
 direction of incidence of the rays ; this phenomenon is termed Photo- 
 taxis. Moreover, the direction of their movement is also determined 
 by the direction of incidence of the light. They move in the line 
 of incidence, but they may move either towards or away from the 
 source of light ; the direction depending partly on the intensity of 
 the light, and partly on the degree of irritability of the zoospore. 
 When a zoospore moves towards a source of light, it is said to be 
 positively phototactic ; when away from it, negatively phototactic. 
 Another important case is the change of position of the chlorophyll- 
 corpuscles in the cells (see p. 172). 
 
 Motile cellular members, whether mature or growing, are, as a 
 rule, sensitive to the directive influence of the incident rays of 
 light. Among mature motile members, foliage-leaves are those 
 which most markedly respond to the directive or heliotropic influ- 
 ence of light ; among growing members, it is more especially stems 
 and leaves which are sensitive, but roots have in many cases been 
 found to be so. All these irritable members take up a definite
 
 48] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 215 
 
 position, the light-position (p. 173), with reference to the direction 
 of incidence of the rays of light. Members capable of performing 
 movements of variation can, if necessary, change their light- 
 position, whereas the light-position of other members can only be 
 changed so long as they are growing. 
 
 The particular position which the member assumes under the 
 heliotropic influence of light, depends upon its organisation. Three 
 classes of members, namely the dorsiventral, the isobilateral, and 
 the radial, have therefore to be considered. 
 
 It may be generally stated of dorsiventral members, that, for a 
 certain mean intensity of light, their light-position is such that 
 the morphologically upper surface is directed towards the source 
 of light, and lies in a plane perpendicular to the direction of 
 incidence of the rays : that is, they are diaheliotropic. 
 
 The case of motile foliage-leaves may be taken first in illustra- 
 tion, such as those of the Sensitive Plant, Robinia, Scarlet Runner, 
 etc. When these leaves are exposed to light of sufficient intensity 
 to cause them to assume the diurnal position (see p. 174), their 
 upper (ventral) surfaces are at right angles to the direction of 
 incidence of the rays. If, on the one hand, the light to which 
 they are exposed becomes less intense than this, they will manifest 
 no sensibility to its direction of incidence, but will merely assume 
 the nocturnal position. If, on the other hand, the light becomes 
 more intense, then the leaves will alter their position so that the 
 blades will present their edge, instead of their ventral surface, to 
 the incident rays (paraheliotropism, see p. 174). 
 
 In the case of foliage-leaves and other dorsiventral members 
 which cannot execute movements of variation, the light-position is- 
 assumed in the course of development, and is fixed. Since it 
 cannot be altered in relation to variations in the intensity of the- 
 incident rays, the position assumed is determined by the most 
 frequent direction of incidence of the rays of suitable intensity. 
 Tor instance, the fixed light-position of the foliage-leaves of plants 
 growing free in the open, is usually not such that the upper sur- 
 face is horizontal, facing the zenith ; but such that it is directed 
 towards that quarter of the sky from which, not the brightest 
 sunlight, but the brightest diffuse daylight, falls perpendicularly 
 upon it. In fact, it is not unusual to find that the fixed light- 
 position of leaves, when the light is of high average intensity, is 
 such that the surfaces are vertical, so that the margin is presented 
 to the zenith. Under these circumstances both surfaces are equally
 
 216 PART III. PHYSIOLOGY. [ 48 
 
 exposed to light, and the structure of the leaf becomes more or 
 less isobilateral (see p. 114). 
 
 The fact that the ultimate position of dorsiventral leaves is 
 mainly determined by light, is demonstrated by removing them 
 whilst still growing, and therefore capable of a change of posi- 
 tion from its influence. In darkness these leaves take up an 
 altogether different position (see Fig. 131), becoming curved in 
 various ways ; when again exposed to light they resume their 
 previous diaheliotropic position. 
 
 With reference now to radial members, it may be generally 
 stated that the essential feature of their response to the directive 
 influence of light is that they tend to place their long axes in the 
 direction of incidence of the brightest light falling upon them. 
 Whereas in the case of dorsiventral members the important point 
 is the relation of the morphologically upper surface to the direc- 
 tion of the incident rays ; in the case of radial members the im- 
 portant point is the relation of the long axis to the direction of the 
 incident rays. 
 
 An exact coincidence between the direction of the long axis of the mem- 
 ber and that of the incident rays is, however, not always attained in 
 .nature, on account of the antagonistic action of other directive influences. 
 This point is more fully discussed on p. 222. 
 
 It must be mentioned that, inasmuch as there are no radial 
 members which are both heliotropically irritable and capable of 
 performing movements of variation, all that is here said refers to 
 growing radial members. 
 
 In illustration, the case of a radial member which has been 
 grown in the dark may be taken, and it may be assumed to be 
 vertical. Light is allowed to fall upon it from one side ; the effect 
 is a gradual curvature of the member, as it continues to grow, so 
 that its long axis comes to coincide more or less nearly with the 
 direction of the incident rays. 
 
 But the curvature may be in one of two directions ; it may be 
 .either such that the apex of the member comes to point towards 
 the source of light, or such that it points in the opposite direction. 
 When the former is the case the member is said to be positively 
 heliotropic ; when the latter, it is said to be negatively heliotropic. 
 
 The nature of the curvature, whether positive or negative, 
 depends upon the specific irritability of the member. Thus, gene- 
 rally speaking, primary shoots, including such forms as the stems
 
 48] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 217 
 
 of Chara and Nitella, the peduncles of flowers, the stipes of the 
 larger Fungi, and the conidiophores of Moulds, as also radial 
 leaves such as those of the Onion, are positively heliotropic. 
 Negative heliotropism has been observed in many roots, especially 
 aerial roots, and in the root-hairs of Marchantia. With regard to 
 shoots, the hypocotyl of Viscum, the Mistletoe, is negatively helio- 
 tropic. 
 
 Although the relation between the external symmetry of the 
 member and its heliotropic irritability is generally that indicated 
 above, yet there are exceptions : all dorsiventral members are dia- 
 heliotropic ; but not all radial members are positively or negatively 
 heliotropic, for some of them are diaheliotropic. It seems that 
 continual exposure to intense light falling on one side induces at 
 least physiological dorsiventrality in some radial members (e.g. 
 shoots of Ivy and Tropseolum). 
 
 The flattened, typically isobilateral, leaves of various Monocoty- 
 ledons, such as those of Iris, appear to be positively heliotropic. 
 
 e. Irritability to the Directive Influence of Gravity (Geotro- 
 pism). 
 
 The effects of the stimulating directive action of gravity must 
 be clearly distinguished from those which are due to the mere 
 weight of the parts. It is only the former which are referred to 
 by the term geotropism. The geotropic curvatures are effected 
 with considerable force, and will take place even against consider- 
 able resistance ; for instance, it has been observed that the primary 
 roots of seedlings will curve downward into mercury. 
 
 Geotropic irritability is manifested by various members, such as 
 stems, leaves, and roots. The phenomena of geotropism in the 
 three categories of members, the dorsiventral, the radial, and the 
 isobilateral, will now be studied. 
 
 With regard to dorsiventral members, it appears that many 
 leaves, both growing and motile, lateral shoots of Conifers and of 
 many dicotyledonous shrubs, runners, etc., which are dorsiventral, 
 take up such a position, when acted upon solely by gravity, that 
 their longitudinal axis is horizontal that is, at right angles to the 
 line of action of gravity, the vertical and that their morphologi- 
 cally superior surface is directed upwards. If these members are 
 moved out of this position so that their long axis is not horizontal, 
 the}- curve until it is so ; or if they be so moved that the normally 
 upper surface faces downwards, they twist until it faces upwards. 
 These members behave in respect to the line of action of gravity
 
 218 PART III. PHYSIOLOGY. [ 48 
 
 just as they do to the direction of the incident rays of light. They 
 are diageotropic, just as they are diaheliotropic. 
 
 It is a familiar fact that at all points of the earth's surface typi- 
 cal radial members, such as primary shoots and roots, grow with 
 their long axes vertical, but with this difference, that the direction 
 of growth of the primary shoots is away from the centre of the 
 earth, whereas that of the primary roots is towards the centre of 
 the earth. It can be readily demonstrated (by Knight's machine) 
 that this vertical direction of growth is due to the force of gravity, 
 that it is, in fact, a phenomenon of geotropism. But the effect 
 produced is precisely opposite in the two cases ; primary shoots 
 grow in a direction opposed to that of the action of gravity, they 
 are negatively geotropic ; primaiy roots grow in the same direc- 
 tion as that of the action of gravity, they are positively geotropic. 
 If these members be moved out of their normal position, they will 
 return to it by performing geotropic curvature. 
 
 The principle of Knight's 
 machine is to expose growing 
 plants to the action of centri- 
 fugal force, either alone or 
 together with gravity. The 
 object of it is to demonstrate 
 that gravity is the directive 
 force which determines the re- 
 
 _ . lative directions of growth of 
 
 Fie. 132. Geotropic curvature of a Pea-seedling e 
 
 placed horizontally. The thicker outline indicates shoots and roots. When seed 
 the original positions of the primary shoot and lings are grown on a rapidly 
 root ; the shoot s has curbed upwards in the rotating vertical wheel, in 
 course of its growth, the root v> has curved con sequence of the continuous 
 downwards. The bud at the apex of the shoot . . . . , 
 
 is nutating. change in position with re- 
 
 gard to the vertical, it is 
 
 obvious that the directive action of gravity is eliminated, for all parts 
 of the seedlings are acted upon by gravity for successive equal times 
 in opposite directions: the only force in action is the centrifugal force. 
 The result is that the primary roots grow towards the centre of the 
 wheel, in a direction contrary to that of the line of action of the cen- 
 trifugal force, whilst the primary shoots grow outwards, away from 
 the centre of the wheel, in the same direction as the action of the cen- 
 trifugal force. It is clear from these facts (1) that a purely physical 
 force can determine the direction of growth of roots and shoots : (2) that 
 the physical force employed (centrifugal force) affects primary roots and 
 shoots in a precisely contrary manner : and it may be concluded that 
 since the phenomena produced by the action of centrifugal force in these 
 experiments are quite analogous to those observable in nature, the cause
 
 48] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 219 
 
 of the natural phenomena is also a purely physical force, and the force 
 of gravity is the one which meets all the necessary conditions. 
 
 The geotropic influence of gravity is greatest when the radial 
 member is in a horizontal position ; that is, the curvature into the 
 normal position then takes place with the greatest rapidity. But 
 the visible effect is the more marked, the further the member is 
 removed from its normal position ; for instance, when a primary 
 shoot is turned upside down, a curvature of 180 has to be per- 
 formed in order that the apex may again point upwards. 
 
 In addition to the primary shoots of seedlings, the following radial 
 members are negatively geotropic ; the stipes of Mushrooms, the conidio- 
 phores of Moulds, the stems of Characese, the stalks of the receptacles of 
 Liverworts, the peduncles of many flowers, the setse of Mosses, etc. Also 
 isobilateral leaves, such as those of Iris ; when placed horizontally in 
 darkness, whether flat or edgeways, they curve upwards. 
 
 In addition to the primary roots of seedlings, the following radial mem- 
 bers are positively geotropic ; the hyphse of Fungi which penetrate into 
 the substratum, the root-like filaments of Vaucheria and other Algse, the 
 rhizoids of Muscinese, the rhizomes of Yucca filamentosa and of Cordyline 
 rubra, etc. 
 
 An instance of the absence of geotropic irritability in a growing member 
 is afforded by the hypocotyl of the Mistletoe. 
 
 The degree of geotropic irritability is not the same in all radial 
 members. It may be generally stated that the lateral branches 
 both of shoots and roots are less irritable than primary shoots and 
 roots. For instance, the secondary branches of roots grow, not 
 vertically downwards, but obliquely outwards and downwards, in 
 the soil. 
 
 It has been observed in some cases that the nature of the geo- 
 tropic irritability of a member may change in the course of its 
 development. For instance, the peduncle of the Poppy is posi- 
 tively geotropic whilst the flower is in the bud, but negatively 
 geotropic during flowering and fruiting. Again, the flowers of 
 the Daffodil are negatively geotropic when in the bud, but they 
 become diageotropic as they open. 
 
 /. Irritability to Differences in the degree of Moisture in the 
 surrounding Medium (Hydrotropisrn}. 
 
 Irritability of this kind is especially characteristic of earth-roots 
 which possess it in a high degree. It can be readily demonstrated 
 by a well-known experiment. Peas or Beans are made to ger- 
 minate in a sieve full of damp sawdust, the sieve being suspended
 
 220 PART III. PHYSIOLOGY. [ 49 
 
 in a slanting position. The primary roots grow downwards through 
 the sawdust, and escape into the air (which is kept moist). At 
 first they grow vertically downwards in consequence of their 
 positive geotropism, but they soon curve upwards towards the 
 moist surface. They do this in virtue of their hydrotropic irrita- 
 bility, and it is clear that they are positively hydrotropic. 
 
 g. Irritability of other kinds. It has been ascertained by ex- 
 periment that members of various kinds may be stimulated to 
 curvature by other causes, such as differences of temperature on 
 the two sides, galvanic currents, the flowing of currents of water, 
 and by the presentation of various chemical substances ; but these 
 various phenomena are not of such immediate importance to the 
 well-being of the plant as those which have been described above 
 in detail. 
 
 The stimulating action of certain chemical substances (cheinio- 
 tajcis) is, however, of some importance in connexion with the re- 
 productive processes. It had been frequently observed that the 
 motile male cells (spermatozoids) of plants possessing them appeared 
 to be attracted to the female organ, fertilisation being thus en- 
 sured, but the cause of this has only recently been ascertained, 
 and only in certain cases. It appears that the female organ, when 
 it is fit for fertilisation, excretes into the surrounding water a 
 substance which attracts the male cells. In Ferns and Selaginella 
 this substance is a compound of malic acid ; in Mosses it is cane- 
 sugar. 
 
 49. Localisation of Irritability. Among members which 
 perform movements of variation, there are many instances of well- 
 defined localisation of irritability. Thus, in the Sensitive Plant, 
 no movement ensues when the upper side of the pulvinus of the 
 primary petiole is touched, but only when the sensitive hairs on 
 the under side of the pulvinus are touched ; and, in the leaflets, 
 it is the upper side of the pulvinus which is sensitive. In Drosera, 
 the irritability of the tentacles is localised in the terminal gland, 
 In Diona3a, movement only ensues when the irritable hairs on the 
 upper surface of the leaf are touched. 
 
 Among growing organs, tendrils offer well-marked localisation 
 of irritability. In most tendrils the lower or basal part is either 
 not at all sensitive, or is sensitive only to prolonged contact. 
 Most tendrils have their tips slightly hooked, and their irritability 
 is localised in the concavity of this curvature. The tendrils of 
 Cobcea scandens and of Cissus discolor are irritable on all sides ;
 
 50] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 221 
 
 in those of Mutisia the inferior and lateral surfaces are irritable, 
 but not the superior. The irritability of the root to the pressure 
 of obstacles (see pp. 169, 212) is localised in the.tip. 
 
 The foregoing examples sufficiently prove the localisation of 
 irritability to mechanical stimulation : and the question arises 
 whether or not irritability to other stimuli is also localised. It 
 has been ascertained that this is the case, in connexion with 
 heliotropism and geotropism, at least in certain plants. Thus, the 
 heliotropic irritability (i.e. sensitiveness to the directive influence 
 of light) of the cotyledons of certain Grasses, though not abso- 
 lutely confined to the tip, has been found to reside especially in 
 that part, and the same is the case with the primary shoot of 
 many dicotyledonous seedlings and with young shoots of. various 
 plants. The geotropic irritability of roots also resides in the tip, 
 and this appears to be also true of other members. 
 
 50. Transmission of Stimuli. The most striking in- 
 stances of this are offered by motile leaves, such as those of the 
 Sensitive plant and of Drosera. If the terminal pair of leaflets of 
 a pinna of the leaf of the Sensitive Plant be irritated, not only will 
 they fold up, but each of the other pairs of leaflets of the same 
 pinna will fold up in succession ; if the stimulus is sufficiently 
 strong, its effect may extend to other pinnae causing their leaflets 
 to fold up, or to the secondary petioles causing them to converge, or 
 even to the main petiole which then sinks downward (see Fig. 126). 
 Stimulation of one leaf, if sufficiently powerful, will cause move- 
 ment in another. In the case of Drosera, stimulation of the central 
 tentacles of a leaf causes the inflexion of the marginal tentacles 
 (p. 48). 
 
 In so far as heliotropic and geotropic irritability is localised in 
 the tips of growing members, these must also afford instances of 
 transmission of stimuli. The stimulus acts upon the irritable tip 
 and the impulse is transmitted to the region in which the curva- 
 ture takes place. 
 
 The means by which stimuli are transmitted is a matter which 
 is still under discussion ; but it appears that the means of trans- 
 mission is not the same in all cases. Whilst in some, such as ten- 
 drils and the leaves of Drosera, the stimulus is probably transmit- 
 ted by means of the delicate protoplasmic filaments which connect 
 the protoplasm of adjacent cells (see p. 65) ; in others, for instance 
 Mimosa pudica^ the stimulus is transmitted as a disturbance of the 
 hydrostatic equilibrium of the cells : it would, in fact, appear that
 
 222 PART III. PHYSIOLOGY. [ 51 
 
 whilst the former means of transmission suffices for a short distance, 
 the latter is necessary when the distance to be traversed is 
 considerable. In Mimosa pudica there appears to be a special 
 tissue along which the stimulus is conducted : it belongs to the 
 bast, and consists of large elongated cells with pitted cellulose 
 walls. 
 
 51. Combined Effects of different Stimuli. Inasmuch 
 as it is commonly the case that the motile members, whether 
 growing or mature, are irritable to stimuli of various kinds, it is 
 clear that the assumption by them of any particular position is the 
 resultant effect of the stimuli which may be acting simultaneously. 
 The phenomena in question are strikingly manifested by growing 
 members, and it is to these that the following account especially 
 refers. 
 
 According to the position assumed in the course of their growth 
 under the influence of various external directive influences, plant- 
 members may be conveniently classified into those which have their 
 long axis vertical, and those which have their long axis oblique or 
 horizontal, the former are distinguished as orthotropic, the latter 
 as plagiotropic. Most radial and isobilateral members are ortho- 
 tropic ; all dorsiventral, and some radial members are plagiotropic. 
 For instance, radial primary shoots and roots are orthotropic ; all 
 dorsiventral leaves, etc., are plagiotropic ; lateral branches of shoots 
 and roots, even though radial, are plagiotropic. 
 
 The directive influences which mainly determine the direction of 
 growth of radial primary shoots are gravity and the direction of the 
 incident rays of light, and the shoots themselves are negatively 
 geotropic and positively heliotropic. If only the conditions are such 
 that each side of the shoot receives an equal amount of light, as 
 when the plant grows quite in the open, no heliotropic curvature 
 takes place, and the shoot grows erect. But when one side of the 
 plant is shaded, as when it grows by the side of a hedge, the shoot 
 in most cases curves heliotropically out of the vertical. This 
 curvature is the resultant effect of the negative geotropism of the 
 shoot which tends to keep it straight, and its positive heliotropism 
 which tends to make it curve more than it actually does. Uni- 
 lateral illumination usually causes some degree of curvature in 
 shoots, because, as a rule, their heliotropic irritability is higher 
 than their geotropic irritability. Exceptions to this rule have been 
 found in the inflorescences of Verbascum and Dipsacus, which 
 remain erect even when one side is shaded.
 
 52] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 223 
 
 Similarly, the influences which ordinarily determine the direction 
 of growth of radial primary roots, are gravity and the distribution 
 of moisture in the soil. If the soil is uniformly moist, the root 
 grows vertically downwards under the influence of gravity ; but if 
 the soil is not uniformly moist, the root will curve out of the vertical 
 towards the moister area, because its hydrotropic is greater than 
 its geotropic irritability. 
 
 The conditions which determine the plagiotropic position of most 
 radial lateral branches of shoots are these : they are negatively 
 geotropic, and they are diaheliotropic, at least in intense light. In 
 darkness they grow erect, in virtue of their negative geotropism. 
 Some radial subterranean rhizomes are, however, diageotropic. The 
 oblique growth of lateral roots is simply due to their feeble 
 geotropic irritability. 
 
 The conditions which determine the plagiotropic position of 
 dorsiventral members are these : they are both diageotropic and 
 diaheliotropic. But inasmuch as their heliotropic is higher than 
 their geotropic irritability, their ultimate position is that in which 
 the incident rays of appropriate intensity fall nearly or exactly at 
 right angles upon the upper surface. 
 
 It will be observed that, as a rule, in growing members w r hich 
 are heliotropically irritable, this irritabilit}' is higher than any 
 other ; consequently the ultimate position assumed by the member 
 is mainly determined by the direction of the incident rays of light, 
 and it is termed, therefore, a light-position (see p. 215), although 
 other directive influences may have contributed to its assumption. 
 
 The most remarkable case of combined effects is afforded by the 
 growth of twining stems. A twining stem, at its first development, 
 is straight, but after it has come to consist of two or three inter- 
 nodes its apex hangs over to one side, for the stem is not sufficiently 
 rigid to support its own weight. It then exhibits circumnutation 
 in a marked manner. If once it comes into contact with a more or 
 less vertical support of appropriate thickness, it twines round it. 
 
 The commonly accepted explanation of twining is that it is due 
 to the negative geotropism of the stem, combined with its circum- 
 nutation modified by contact with the support ; but it is doubtful 
 if this explanation is adequate. It has been suggested, with some 
 show of reason, that twining stems may be irritable, like tendrils, 
 though in a less degree, to continuous contact with a support. 
 
 52. Conditions of Movement. Inasmuch as the move- 
 ments under consideration are vital, they can only take place when
 
 224 PART III. PHYSIOLOGY. [ 53 
 
 the external conditions are favourable to the life of the plant. The 
 following conditions are essential ; a moderate temperature, extremes 
 of heat and cold arrest movement ; a supply of water, all move- 
 ments are arrested by drought ; a supply of free oxygen, in the case 
 of most plants (p. 197) ; and, in some cases, exposure to light of a 
 certain intensity. 
 
 The importance of exposure to light as a condition of movement 
 requires special consideration. It has been ascertained to be 
 essential to movements of the most different kind. For instance, a 
 Bacterium (Bacterium photometricutn) has been found to be motile 
 only when exposed to light. Again, various movements of vari- 
 ation, such as those of the foliage-leaves of Mimosa, etc., do not 
 take place unless the plant either is, or recently has been, exposed 
 to light. But the most important case is the arrest of growth of 
 dorsiventral members when kept in darkness. For example, if a 
 potato-tuber sprouts in a dark chamber, the produced shoots have 
 excessively elongated internodes (see p. 162), but very small leaves ; 
 the growth of the leaves is arrested in darkness. On the other 
 hand, intense light retards movement (e.g. its action on growth) or 
 altogether arrests it (e.g. arrest of spontaneous movement of the 
 leaves of the Sensitive Plant). 
 
 What is exactly the influence of light in promoting movement is 
 not understood, but it is termed the pholotonic influence (p. 162) : it 
 induces, that is, a particular condition, the condition of phototonus, 
 in the protoplasm, without which movement is impossible. It 
 appears that the rays of low refrangibility (red-yellow) are most 
 favourable for the phototonic condition. 
 
 Irritability also depends upon the above essential conditions : in 
 fact, induced movements are more rapidly arrested by unfavourable 
 conditions than are spontaneous movements. For instance, when a 
 Sensitive Plant is kept in continuous darkness, the leaves first lose 
 their power of responding to stimuli, and later their spontaneous 
 movements cease. 
 
 Irritability may also be abolished by special means. For in- 
 stance, exposure to the vapour of chloroform or ether destroys the 
 irritability of the leaves of the Sensitive Plant. Again, it may be 
 abolished by repeated stimulation, the interval between the stimu- 
 lations being very short. This has been observed in the case of 
 the leaves of the Sensitive Plant and of Dionsea. 
 
 53. Mechanism of the Movements. The ultimate factor 
 in the mechanism of the vital movements of plants, whether spon-
 
 53] CHAPTER III. SPECIAL PHYSIOLOGY OF MOVEMENT. 225 
 
 taneous or induced, is the motility of the protoplasm. With re- 
 gard to the streaming movement of the protoplasm, it is probably 
 due to wave-like contractions and expansions- ^of the protoplasm. 
 The mechanism of the movements of the contractile vacuoles 
 appears to be this : the systole of the vacuole is due to the sudden 
 active contraction of the protoplasm, the contained liquid being 
 expelled ; the diastole, to the active but gradual expansion of the 
 protoplasm, the cavity of the vacuole, as it enlarges, being filled 
 with liquid. The protrusion and retraction of pseudopodia in 
 amoeboid movement may be accounted for in the same way ; the 
 protrusion is probably analogous to the diastole .of the contractile 
 vacuole, the retraction to the systole. A similar explanation may 
 be offered of ciliary movement. 
 
 The movements of cellular members take place in a definite 
 region, which may be distinguished as the motile region ; this is, 
 in growing members, the region of elongation (see p. 208) ; and, in 
 mature members, is a more or less well-marked region of motile 
 tissue which may constitute a distinct motile organ (e.g. pulvinus 
 of a motile leaf). The movements depend essentially upon varia- 
 tions in bulk of the cells, and these, in turn, upon variations in 
 turgidity. It is clear that if the turgidity, that is the hydrostatic 
 pressure of the cell-contents, increases, the cell will expand pro- 
 vided that the wall be extensible ; and conversely, that if the 
 turgidity diminishes, the cell will shrink, provided the wall be 
 elastic. Movement can only take place when the cell-walls possess 
 these physical properties: hence, the pulvinus of mature motile 
 leaves consists mainly of parenchymatous cells with unlignified 
 walls, the lignified tissue being reduced as much as possible : 
 similarly, in the elongating region of growing-members the cell- 
 walls are thin and unlignified. But whilst the movements of 
 variation (p. 207) are the result of a sudden loss of turgidity, 
 which is either spontaneous or the effect of stimulation, the move- 
 ment of growth depends upon the maintenance of turgidity, and 
 the variations in the rate of growth (see p. 208) are the expression 
 of variations in the degree of turgidity. 
 
 The following instances will serve to illustrate the foregoing 
 considerations. 
 
 A simple case is offered by the induced movement of the stamens 
 of the Cynarese (p. 176). When at rest, the cells of the filaments 
 are expanded in the direction of their length, and are turgid ; on 
 stimulation, the cells suddenly shorten and become flaccid, having 
 
 M.B. Q
 
 226 PART III. PHYSIOLOGY. [ 53 
 
 lost a portion of their cell-sap. The expanded state is regained by 
 the gradual expansion of the cells, tiu*gidity being restored by the 
 absorption of water. 
 
 In the foregoing case, all the cells of the motile portion are 
 affected ; but in many cases some only of the cells are affected. 
 Thus, in the case of the leaf of the Sensitive Plant, the primary 
 petiole, when at rest, stands out nearly at right angles to the stem 
 (Fig. 126, p. 174) : on stimulation, it sinks downwards so as to 
 form an acute angle with the internode below its insertion. The 
 mechanism is this : when at rest, the cells of the pulvinus are all 
 turgid, and they support the petiole in its normal position : on 
 stimulation, the cells of the lower portion of the pulvinus lose 
 their turgidity, water escaping from them into the intercellular 
 spaces ; these cells, being flaccid, are unable to counteract the 
 downward pressure of the still turgid cells of the upper half of the 
 pulvinus, and to support the weight of the leaf ; consequently the 
 primary petiole sinks downwards. The same mechanism obtains 
 in the movements of the leaflets and of the secondary petioles ; the 
 only difference being that, in the pulvinus of a leaflet, it is the 
 cells of the upper half of the pulvinus which lose their turgidity 
 on stimulation, so the leaflet is raised upwards ; and, in the pul- 
 vinus of the secondary petiole, it is the cells of the inner half 
 which lose their turgidity, so the secondary petioles approach the 
 middle line. This account is also applicable to all side-to-side 
 movements, such as that of the leaf of Dionsea, and that of the 
 stamens of Berberis and Mahonia. 
 
 The heliotropic or other curvatures taking place in the elonga- 
 ting region of growing cellular members, are due to the shortening 
 of the cells on the side becoming concave, and to the elongation of 
 the cells on the side becoming convex. The mechanism of the 
 curvature seems to depend in this case not so much upon a differ- 
 ence of turgidity between the cells of the two sides as upon a 
 difference in its effect : whereas turgidity induces the usual longi- 
 tudinal elongation of the cells of the convex side, it induces longi- 
 tudinal shortening in the cells of the concave side in consequence 
 of extension in the other dimensions. 
 
 Turgidity is then the main factor in the mechanism of the move- 
 ments of cellular members ; its mechanical importance is further 
 strikingly illustrated by the great rigidity of turgid members, and 
 by the great force, equivalent in some cases to twenty times the 
 atmospheric pressure, which they develope in opposition to ex-
 
 54] CHAP. IV. SPECIAL PHYSIOLOGY OF REPRODUCTION. 227 
 
 ternal resistance, as when the roots of tree cause the splitting of 
 walls or of pavements. Although one essential factor in turgidity 
 (see p. 159) is the purely physical osmotic activity of substances 
 in the cell-sap, it must not be forgotten that it also depends upon 
 the resistance offered by the protoplasm to filtration under pres- 
 sure : so that the maintenance of turgidity is after all a vital act. 
 The maintenance of turgidity appears, in fact, to depend upon a 
 certain state of molecular aggregation of the protoplasm lining 
 the cell-wall, in which it offers resistance to the escape of the 
 cell-sap ; whereas in the flaccid condition the state of molecular 
 aggregation of the protoplasm is such that it readily permits the 
 escape of the cell-sap under the elastic pressure of the cell-wall. 
 
 Whilst the fundamental mechanism of the movement of mature 
 motile members and that of growing members is essentially the 
 same, there is this secondary difference between the two cases. 
 The change of position which is the result of the movement of 
 mature members, is reversible ; they can return to their former 
 position : the change of position, curvature for instance, of growing 
 members is reversible only so long as it has not been rendered 
 permanent by actual deposition of substance. Thus the changes of 
 position due to the nutation (p. 211) of growing members are only 
 temporary, for they are of brief duration ; but changes of position 
 due to some directive influence acting for a considerable time 
 become permanent, for instance, the light-positions (p. 223) assumed 
 by growing members. 
 
 CHAPTER IV. 
 
 SPECIAL PHYSIOLOGY OF REPRODCUTION. 
 
 54. Introductory. It has been already stated (see p. 49) 
 that reproduction consists essentially in the throwing off by the 
 individual of a portion of its protoplasm which does not merely 
 grow but developes into a new organism ; and that two modes of 
 reproduction, vegetative multiplication and spore-reproduction 
 may be conveniently distinguished, though they are not absolutely 
 distinct. 
 
 Reproduction has been considered so far mainly from the 
 morphological standpoint, and it now remains to discuss it from 
 the physiological point of view. The most important general 
 consideration is that reproduction is a function of embryonic, as
 
 228 PART III. PHYSIOLOGY. [ 55 
 
 distinguished from adult, protoplasm. But it must not be over- 
 looked that all embryonic protoplasm is not necessarily reproduc- 
 tive : and it is interesting to trace the differences in this respect, 
 presented by various kinds of embryonic protoplasm. To begin 
 with, there is no doubt that the merismatic cells of the cambium 
 are embryonic : but they are not at all reproductive, for they 
 cannot give rise to a new member, still less to a new organism ; 
 they can only add to the bulk of the body of which they form 
 part, by the development of new tissue. Again, the protoplasm 
 of a growing-point is embryonic, but it is only imperfectly repro- 
 ductive ; it possesses this property to the extent that it not only 
 contributes to the increase of the member to which it belongs, 
 but also developes new members. Finally, the protoplasm of a 
 reproductive cell, such as a spore, is embryonic and is completely 
 reproductive ; for it does not in any degree contribute to the bulk 
 of the parent-organism, but gives rise to a new individual. 
 
 55. Vegetative Multiplication. This mode of reproduc- 
 tion is distinguished as vegetative, because it is carried on by the 
 vegetative organs of the plant, and, in the simpler cases, it is not 
 distinguishable from the ordinary processes of growth ; though, 
 in its higher forms it approximates to reproduction by spores. 
 The simpler cases referred to are those of unicellular organisms : 
 these, when they have reached by growth their characteristic 
 limit of size, undergo cell-division, with the result that each new 
 cell constitutes a new individual : here, multiplication is effected 
 by a purely vegetative process, which, in a multicellular plant, 
 would merely result in an increase in the number of the cells of 
 which the individual consists. Much the same thing occurs in 
 higher plants when (as in many Bryophyta, and in rhizomatous 
 Pteridophyta and Phanerogamia) the main shoots die away, and 
 the isolated lateral branches constitute new independent in- 
 dividuals. Something of a similar kind also takes place in the 
 artificial multiplication of plants by means of cuttings : in many 
 plants, but by no means all, if a shoot be cut off and be kept under 
 favourable circumstances with its cut end in suitable soil, the 
 cutting will complete its segmentation by the development of 
 roots, and will then be a new individual. Not uncommonly, 
 certain parts of the body may become more or less specially 
 modified to effect vegetative propagation : for instance buds be- 
 come developed into bulbs or into bulbils (see p. 25), or portions 
 of the stem or the root become tuberous. But the specialisation
 
 55] CHAP. IV. SPECIAL PHYSIOLOGY OF REPRODUCTION. 229 
 
 which may be regarded as the highest of all, because it approaches 
 most nearly to spore-reproduction, and involves the entire develop- 
 ment of all the new members, is that of gemmae in which the 
 vegetative reproductive body is not merely a modified member of 
 the parent, but is a special development consisting in some cases 
 of only a single cell (e.g. gemmae of some Algae and Liverworts ; 
 oidium-cells of Fungi). Something of the same kind occurs 
 amongst the higher plants, such as some Ferns, Bryophyllum, etc., 
 where an entirely new structure, a bud, is developed on the leaf, 
 and produces stem, leaves and roots ; it is in this way that Bego- 
 nias are artificially propagated (see p. 136). 
 
 An interesting artificial mode of vegetative propagation is that known 
 as grafting or budding, in which a young shoot or a bud, termed the 
 scion, of one plant is inserted into the stem of another, though allied 
 plant, the stock (see p. 156) , the scion and the stock grow together so as to 
 form one plant, the scion retaining its own peculiar characters (e.g. graft- 
 ing of fruit-trees, budding of roses). 
 
 An important fact connected with vegetative reproduction is 
 that it is associated with a rejuvenescence of the protoplasm. For 
 example, when an adult cell of a unicellular plant, such as Pleuro- 
 coccus (Fig. 137), divides, it gives rise, not to adult cells, but to 
 young ones : and a cutting produces a young plant, not an old one. 
 
 The relation of vegetative reproduction to the alternation of 
 generations is of importance. In the lower plants (e.g. Bryophyta) 
 where the gametophyte is the conspicuous generation, it is 
 this generation which multiplies itself vegetatively, although 
 vegetative reproduction of a somewhat different kind has been 
 artificially induced in the sporophyte of some Mosses ; but in the 
 Phanerogamia it is exclusively the sporophyte which thus multi- 
 plies itself. In the Pteridophyta, whilst vegetative multiplication 
 of the sporophyte is common, the gametophyte still retains this 
 capacity in certain cases (some Ferns ; Lycopodium). Vegetative 
 multiplication does not, as a rule, affect the alternation of genera- 
 tions, each generation producing its like : the exceptions are 
 afforded by cases in which the one generation is developed vegeta- 
 tively from the other; that is, where vegetative propagation 
 replaces spore-formation. For instance, in some Ferns, the pro- 
 thallium is developed vegetatively from the Fern-plant, without 
 the intervention of spores (apospory) ; and the Fern-plant vegeta- 
 tively from the prothallium, without the intervention of sexual 
 organs (apogamy}.
 
 230 PART III. PHYSIOLOGY. [ 56 
 
 56. SpOKe-Reproduction (see p. 50). The highest degree 
 of reproductive capacity is that possessed by spores. Though 
 they are single cells, they are nevertheless capable, each by it- 
 self, of giving rise to a plant-body which, as in the higher plants, 
 may present complete morphological and histological differentiation. 
 
 The advantages gained by the development of spores are, first, 
 that they are readily scattered, so that the plants developed from 
 them grow at a distance from each other ; this is, for instance, 
 the meaning of the development of free swimming zoospores by 
 plants (Algae) living in water. Secondly, spores, especially in the 
 lower plants, are highly resistent to unfavourable conditions, such 
 as drought and extremes of temperature ; so that they serve to 
 maintain the species under conditions which would be fatal to the 
 plant itself. 
 
 In Phanerogams the function of maintaining the species through a 
 period of unfavourable conditions, as also the dissemination of the new 
 plants, is transferred to the seeds which, like the spores of lower plants, 
 have a great capacity for endurance. 
 
 Most plants, and probably all, produce spores ; and from the 
 physiological point of view there are two modes of origin of 
 spores : they are developed either asexually or sexually. In the 
 lowest plants (e.g. Cyanophyceae, Schizomycetes, etc.), as also in 
 others which have become sexually degenerate (Fungi, such as 
 the J^cidiomycetes and Basidiomycetes), spores are only produced 
 asexually : whereas in some sexual plants there is an exclusively 
 sexual formation of spores (some Algae, such as the Conjugates, the 
 Fucacese, and the Charoideae). In the higher plants (Bryophyta, 
 Pteridophyta, Phanerogamia) spores are produced both sexually 
 and asexually. 
 
 Sexual Spore-formation. The sexual process consists typi- 
 cally in the fusion of two gametes, that is, of two sexual reproduc- 
 tive cells, neither of which is capable, by itself, of developing into 
 a new individual. 
 
 The first question which naturally arises is as to the nature of 
 sexuality ; the question, namely, as to what difference, if any, can 
 be observed between a gamete and an asexually-produced spore. 
 To this question no answer can at present be given ; no difference 
 can be detected between a gamete and a spore. It must not, 
 however, be concluded that because there is no observable differ- 
 ence between a gamete and an asexually-produced spore, there is 
 no difference whatever between them; on the contrary it is clear
 
 56] CHAP. IV. SPECIAL PHYSIOLOGY OF REPRODUCTION. 231 
 
 that they differ widely, since the former cannot (except in 
 rare cases), whilst the latter can, develope -by itself into a new 
 organism. 
 
 The second question is as to the nature of sex : what is the 
 difference, if any, between a male and a female gamete ? In 
 some cases there is a marked external difference ; for instance, in 
 the Pteridophyta, Bryophyta, and many Algae, the female gamete- 
 is a large motionless oosphere, whilst the male gamete is a small- 
 actively-swimming sperrnatozoid. But this marked difference is 
 not essential, it is merely adaptive ; it is an adaptation to a more 
 or less aquatic mode of life or, at least, of fertilisation. Moreover, 
 it is obviously inapplicable in explanation of the many cases in 
 which the two conjugating gametes are externally quite similar. 
 Nor has minute microscopic investigation brought to light any 
 distinguishing criterion. But it must not be concluded on this 
 account that there is no difference between a male and a female 
 gamete ; it is obvious that there is an essential physiological' 
 difference between them. For, were it otherwise, it would be- 
 impossible to account for such a fact, for instance, as that even 
 where, as in many Algae, the gametes are all extruded into the- 
 water, fusion never takes place between two male or two female- 
 gametes, but only between a male and a female. 
 
 Brief allusion may be made to the means by which the sexual' 
 process is ensured. It might be thought that the most effectual' 
 means would be the development of the male and female organs- 
 in close propinquity on the same individual. No doubt this is- 
 the case, but the result is to ensure the less advantageous mode 
 of the process, the mode of self-fertilisation ; in fact, in many 
 cases in which the male and female organs are thus developed close 
 together, as in moncBcious plants (p. 61), self-fertilisation is pre- 
 vented by the male and female organs maturing at different times. 
 The real problem is, then, to ensure a sexual process between two 
 gametes derived from distinct individuals. The end is attained 
 either directly, by bringing the diverse gametes together ; or 
 indirectly, by bringing the spores together, and consequently also 
 the gametophytes. 
 
 The method of bringing the two gametes together is essenti- 
 ally connected with the aquatic mode of fertilisation. It has 
 been observed and investigated in plants in which, whilst the 
 oosphere is motionless and remains in the female organ, the 
 spermatozoids are free-swimming ; and it is among the most
 
 232 PART III. PHYSIOLOGY. [ 56 
 
 striking phenomena of chemiotaxis (see p. 220). In various 
 Mosses and Ferns it has been ascertained that, on the opening of 
 the archegoninm, the mucilage which is extruded includes some 
 substance which diffuses into the water and attracts to the 
 archegonium any spermatozoid that may be present ; in Mosses 
 the substance in question is cane-sugar; in the Ferns, a salt of 
 malic acid. 
 
 The method of bringing the spores together, so that they may 
 germinate near each other, is especially characteristic of hetero- 
 sporous plants, and more particularly of those which grow erect 
 on dry land. It is thus most strikingly exhibited in the pollination 
 of the Phanerogams, where the microspores are carried by the wind 
 or by insects into such a position that they germinate in proximity 
 to the macrospores. 
 
 In order that a sexual process may take place between them, a 
 certain relationship must exist between any two gametes of oppo- 
 site sex ; when the limit is overstepped in the direction of either 
 a too close or a too remote relationship, the process will either not 
 take place at all, or the offspring will be few and feeble. 
 
 The most fertile sexual process is that taking place between the 
 gametes of different individuals of the same species. It has been 
 proved that the offspring of such cross-fertilisation have the 
 advantage in vigour and fertility over the progeny of one of the 
 Bame plants when self -fertilised. , It has, in fact, been proved 
 that in many Phanerogams the pollen of a flower is incapable 
 of fertilising the oospheres of its own ovules ; and that the pollen 
 from another flower of the same plant is only slightly, if at all, 
 more potent. 
 
 A sexual process may also take place between varieties of the 
 same species ; between distinct species of the same genus ; and 
 even between species belonging to different genera. Such a process 
 is known as hybridisation, and the progeny as hybrids, the hybrid 
 being distinguished as a variety- hybrid, species-hybrid, or genus- 
 hybrid, according to circumstances. 
 
 Effects of the Sexual Process. The sexual process is not always 
 limited in its effect to the production of a spore which will give 
 rise to a new individual. For instance, when the female cell is 
 borne by the parent at the time of fertilisation, the act of fertili- 
 sation induces a more or less marked growth and change in the 
 adjacent organs and tissues of the parent, leading to the formation 
 of & fruit (see p. 61).
 
 PART IV. 
 CLASSIFICATION. 
 
 Introductory. A systematic classification of plants may be 
 arrived at by either of two methods. In the first, the different 
 forms of plants are arranged according to some one given prin- 
 ciple ; by this means order is established, and a definite position 
 in the system is assigned to each plant. Many such systems have 
 been devised, and are known as artificial systems. The principle 
 of classification in such a case must be determined more or less 
 arbitrarily and without considering whether or not, in the resulting 
 arrangement, the plants which are nearly allied are always brought 
 together, and those which are less nearly allied are kept apart. 
 The best known of these artificial systems is that of Linnseus, 
 called the sexual system, which classifies plants by the number 
 and mode of arrangement of the floral organs. This system is, 
 however, only applicable to Phanerogams. 
 
 The natural system, to the gradual development of which a more 
 exact knowledge of the reproduction of Cryptogams has largely 
 contributed, has for its object the classification of plants according 
 to their fundamental relationships ; and as these are established 
 once for all by Nature itself, the natural system is not based upon 
 any arbitrary principle of classification, but depends upon the 
 state of our knowledge of these fundamental relationships. These 
 find their chief expression in the structure and other characteristics 
 of the reproductive organs, as well as in the peculiarities of poly- 
 morphism presented by the life-history (see p. 2). This is more 
 particularly true with regard to the definition of the larger groups 
 of the Vegetable Kingdom ; within these groups relationships may 
 be exhibited sometimes in one way and sometimes in another, so 
 that it is not possible to lay down any universal rules for deter- 
 mining closS affinities. 
 
 As the investigation of this subject is still far from complete
 
 234 
 
 PART IV. CLASSIFICATION. 
 
 the natural system cannot be regarded as being perfectly evolved ; 
 the various general sketches which have hitherto been given are 
 therefore no more than approximations to the truth. 
 
 The following are the main divisions of the Vegetable King- 
 dom : 
 
 IST GROUP. Thallophyta. 
 
 Class 1. Algse. 
 
 Class 2. Fungi. 
 2xD GROUP. Bryophyta. 
 
 Class 3. Hepatic*. Sub-kingdom 
 
 Class 4. Musci. ( Cryptogamia. 
 
 3RD GROUP. Pteridophyta. 
 
 Class 5. Filicinae. 
 
 Class 6. Equisetinaa. 
 
 Class 7. Lycopodinee. 
 4TH GROUP. Gymnospermae. 
 
 Class 8. Gymnospermae. Sub-kingdom 
 
 STH GROUP. Angiospermae. Phanerogamia. 
 
 Class 9. Monocotyledones. (Spermaphyta). 
 
 Class 10. Dicotyledones. 
 
 In considering the distinguishing characteristics of these great 
 groups, it may be pointed out, in the first place, that whereas in 
 the Bryophyta, Pteridophyta, and Phanerogamia, without excep- 
 tion, the life-history presents a regular alternation of generations, 
 in the Thallophyta the alternation is generally irregular and is, 
 in many cases, altogether wanting. The Bryophyta differ from 
 the Pteridophyta and the Phanerogamia, in that (a) in their life- 
 history, " the plant " that is, the form to which the name is 
 attached (see p. 2) is the gametophyte, whereas in the two latter 
 groups it is the sporophyte ; and in (fe) the relatively rudimentary 
 differentiation, both morphological and histological, of the sporo- 
 phyte, whereas their gametophyte is more highly differentiated 
 than that of the two latter groups. Finally, though resembling 
 them in many respects, the Gymnospermae and the Angiospermse 
 differ from the Pteridophyta in that they produce seeds : in fact, 
 the Phanerogamia may be contrasted, as seed-bearing plants 
 (Spermaphyta), with the three groups (Thallophyta, Bryophyta, 
 Pteridophyta) of plants which do not bear seeds, and which are 
 collectively termed Cryptogamia.
 
 INTRODUCTORY. 235 
 
 Furthermore, the Thallophyta are characterised by the fact that 
 the female organ is never an archegonium, whereas in the other 
 three groups it is never anything else than an archegonium, though 
 it may present variations of form and structure (see p. 61). 
 
 Considered with reference to plants now actually living, the 
 above-mentioned Classes are of very unequal extent ; for while 
 certain of them, as the Equisetinse, include few forms, and those 
 for the most part very closely allied, others, as the Dicotyledones 
 and the Fungi, include an enormous number of very different 
 forms. These discrepancies arise from the very nature of the 
 natural system, for a great diversity does not necessarily display 
 itself within the limits of a single Class ; and it must not be for- 
 gotten that when the living representatives of a Class, for instance 
 the Equisetinae or the Lycopodinae, are few, they are but the sur- 
 viving remnant of once various and numerous forms which have 
 become in great measure extinct. 
 
 Those Classes which include a sufficiently large number of forms 
 are subdivided into subordinate divisions, as (1) Sub-classes, (2) 
 Series, (3) Cohorts, (4) Orders, and these again, if necessary, into 
 Sub-orders, etc. ; but these names are applied in the most arbitrary 
 manner to the different sub-divisions. The two narrowest system- 
 atic conceptions, viz., Genus and Species, are used to indicate an 
 individual plant. Under the term Species are included all in- 
 dividuals which possess in common such a number of constant 
 characters that they may be considered to be descended from a 
 common ancestral form. New peculiarities may arise in the 
 course of multiplication : the individuals characterised by these 
 new peculiarities are regarded in classification as varieties of the 
 species. When several species resemble each other so distinctly 
 that their general characters indicate a relationship, they are 
 grouped together in a Genus. The limits of genera are conse- 
 quently by no means fixed, but vary according to the views of 
 individual botanists. In the larger genera the species are grouped 
 into Sub-genera. 
 
 The scientific name of every plant consists on the plan intro- 
 duced by Linnaeus of two words, the first indicating the name of 
 the genus, and the second that of the species. Thus, for instance, 
 the greater Plantain, Plantago major, and the Ribwort, Plantago 
 lanccolata, are two species of the genus Plantago. Since in early 
 times the same plants were often described under different names, 
 and as different plants were often designated by the same name, it
 
 236 PART IV. CLASSIFICATION. 
 
 is necessary in systematic works, in order to avoid confusion, to 
 append to the name of the plant the name of the botanist who is 
 the authority for it. Thus Plantago lanceolata L., indicates that 
 Linupeus gave the plant this name, and at the same time that the 
 plant meant is the one which Linnseus described and to which he 
 gave the name. Again, the Spruce Fir is called Picea excelsa 
 Link, while the same plant was placed by Linnaeus in the genus 
 Pinus under the name Pinus Abies L., and by De Candolle in the 
 genus Abies (Don) as Abies excelsa DC. ; hence these names are 
 synonymous : but Pinus Abies Duroi, or Abies excelsa Link, is 
 another plant altogether, the Silver Fir (Abies pectinata DC). 
 
 The method by which each plant has its place assigned to it in 
 the natural system is exhibited in the two following examples 
 I. Plantago major ; II. Agaricus muscarius : 
 
 I. Sub-kingdom : Phanerogamia. 
 
 Group : Angiospermse. 
 Class : Dicotyledones. 
 Sub-class : Gamopetalse. 
 Series : Hypogynse. 
 Cohort: Lamiales. 
 
 Order : Plantaginaceas. 
 Genus : Plantago. 
 Species : major. 
 
 II. Group: Thallophyta. 
 
 Class : Fungi. 
 
 Sub-class : Basidiomycetes. 
 Series : Autobasidiomycetes. 
 Order : Hymenomycetes. 
 Family: Agaricinse. 
 Genus : Agaricus. 
 
 Sub-genus : Amanita. 
 Species : muscarius.
 
 GROUP I. THALLOPHYTA : ALG.E. 237 
 
 GROUP I. 
 
 THALLOPHYTA 
 
 THIS group includes the more lowly-organised plants. As already 
 mentioned, the alternation of generations is here either irregular 
 or wanting. The morphology of these plants is such that the body 
 is generally a thallus, though in certain cases there are more or 
 less distinct indications of that differentiation of the body into 
 root, stem, and leaf, which is so familiar in the sporophyte of the 
 Pteridophyta and Phanerogamia. In those forms in which the 
 sexual organs are differentiated, the female organ may be an 
 oogonium, or a procarp, or an archicarp, but it is never an arche- 
 gonium. 
 
 These plants are further characterised by the simplicity of their 
 structure : the body may be unicellular, ccenocytic and unseptate 
 or incompletely septate (see p. 63), or it may be multicellular. 
 One conspicuous structural feature (shared, however, with the 
 Bryophyta), is the absence of lignified cell-walls, the cell-walls 
 consisting generally of some form of cellulose, and being frequently 
 mucilaginous. In the lower forms, vegetative reproduction by 
 some mode of cell-division is not uncommon. 
 
 The division of the group into the two classes Algse and Fungi 
 appears to be artificial, inasmuch as it is based upon a single 
 character, the presence (Algse) or absence (Fungi) of chlorophyll. 
 But the division is really natural, since this one character is 
 correlated with various others. It is, indeed, becoming usual to 
 regard the Algse and the Fungi as altogether distinct groups : but 
 it appears to be preferable to continue to regard them as classes 
 of the group Thallophyta, inasmuch as the Fungi have doubtless 
 arisen from the Algse, and since they possess many features in 
 common. 
 
 CLASS I.ALGM. 
 
 Many of these are plants of the simplest structure, which either 
 live in water in the form of green, blue-green, red, or brownish 
 filaments or masses of cells, or clothe damp surfaces, such as rocks, 
 walls, or the bark of trees, with a covering of one or other of these 
 colours. In the sea they attain often a very considerable bulk ; 
 some of them are of a very beautiful red or brown colour, and
 
 238 PART IV. CLASSIFICATION. 
 
 attract the attention of the observer, partly by their considerable 
 size, and partly by the elegance of their form. 
 
 The most important feature in which the plants of this Class 
 differ from the Fungi is the presence of chlorophyll and the con- 
 sequent mode of life. The Algae are able to form the organic siib- 
 stances necessary for their nutrition, whereas the Fungi are obliged 
 to obtain them from other organisms (p. 195). The presence of 
 chlorophyll is obvious enough in the green Algae, but it exists also, 
 though less evidently, in Algae which have a bluish-green, olive- 
 green, brown, or red colouring-matter in addition in their chroma- 
 tophores. The nature of this additional colouring-matter is usually 
 the same throughout whole families which also resemble each 
 other in their modes of reproduction. Hence this characteristic 
 affords a trustworthy basis for classification, on which the Algae 
 are divided into the following sub-classes : 
 
 Sub-class 1 : CYANOPHYCEJS (or Phycochromaceae), blue-green 
 Algae, containing a blue colouring -matter 
 phycocyanin ; 
 ., 2 : CHLOROPHYCEJE, green Algae, containing only 
 
 chlorophyll and its derivatives ; 
 3 : PELEOPHYCE.E, brown Algae, containing a yellow 
 
 or brown colouring-matter phycophcein ; 
 4 : RHODOPHYCE.E, red Algae, containing a red or 
 purple colouring-matter phyc.oerythrin. 
 
 The colouring-matters phycocyanin, phycophsein, and phycoerythrin, 
 can be extracted by means of water; they thus differ from chlorophyll, 
 which is insoluble in water. The presence of chlorophyll in the 
 Cyanophyceae, Phaeophycese, and Rhodophyceae, can be proved by ex- 
 tracting the other colouring-matters with water ; the plants then assume 
 a green colour. 
 
 Structure. The body may be unicellular ; or coenocytic and 
 unseptate (as in the Siphonaceae), or incompletely septate (Clado- 
 phoraceae) ; or multicellular. The unicellular forms either exist 
 singly, or a number may be held together in a colony by a mucila- 
 ginous common cell- wall, either as a filament (e.g. some Desmidiese) 
 or a mass (palmelloid Protococcaceae, Chroococcaceae). In some of 
 the multicellular forms (e.g. Spirogyra, Pandorina, Ulva) all the 
 cells of the body are quite similar; at first vegetative, they 
 eventually become reproductive, so that there is no distinction 
 between nutritive and reproductive cells: in these histologically
 
 GROUP I. THALLOPHYTA : ALG^E. 
 
 239 
 
 uudifferentiated forms the body is termed a ccenobium. Even 
 the most highly organised forms attain but a low degree of his- 
 tological differentiation, amounting (as e.g. 'in the Fucacese) 
 only to a distinction between peripheral assimilatory tissue and 
 central conducting tissue : in some of the Laminariacese the con- 
 ductiug-tissue has the form of sieve-tubes. 
 
 Morphology. The body may be entirely undifferentiated ; this 
 condition is most common in the unicellular forms, but it also 
 occurs among the multicellular (e.g. Volvox) ; or it may present 
 a distinction of base and apex (e.g. Rivularia) ; or it may be 
 differentiated into root and thalloid shoot (e.g. Botrydium, Fucus) ; 
 or into root, stem, and leaf (e.g. Cladostephus, Chara, Polysiphonia). 
 
 The undifferentiated body (thallus), as also the thalloid shoot, 
 
 A 
 
 xjy. 
 e. 
 
 FIG. 133. Growing-points of Algae. A Apical growing-point, with apical cell, of 
 StypoeauloTi rcoparium ( x 30). B Intercalary growing-point (where the transverse lines are 
 close together) of Desmarestia ligulata in longitudinal section (x 60). C Apical growing- 
 point, with apical cll, of Cltaitopteris plumosa (x 40: afterFaulkenberg). 
 
 presents great variety of form: it may be spherical, or filamentous, 
 or a flattened expansion, and its symmetry may be multilateral, 
 isobilateral, or dorsiventral. 
 
 The growth in length of the thallus or of the shoot is effected in a 
 variety of ways. It may be either apical or intercalary (Fig. 133.) 
 In cellular plants the apical growth is effected either by a single 
 apical cell (e.g. Characese, Sphacelariese, Fucacese, Dictyota, Fig. 
 106, most Rhodophycese) ; or by a marginal series of apical cells 
 (e.g. Coleochseteae, some flattened Rhodophyceae) ; whereas in those 
 coenocytic plants (Siphonoidese) w r hich grow apically, there is no 
 apical cell, but an apical mass of embryonic protoplasm. In some 
 .cases of intercalary growth there is no growing-point, all the cells
 
 240 PART IV. CLASSIFICATION. 
 
 of the body being merismatic (e.g. Spirogyra, Ulothrix, Ulva). In 
 some few cases (e.g. Volvocoideae, Botrydium) there is no growth 
 after the embryo-stage. 
 
 The primary root is never developed in due proportion to the 
 shoot ; consequently, in order to ensure the attachment of the 
 plant, adventitious roots are very commonly formed on the shoot, 
 and when the shoot is dorsiventral unicellular root-hairs are 
 commonly developed on the surface in contact with the substratum. 
 In some cases special organs of attachment (haptera, see p. 48), 
 are developed on the shoot ; they may be adhesive discs borne on 
 on the ends of branches of the shoot (e.g. Plocamium coccineum), 
 or root-like out-growths as in Laminaria bulbosa, where at the 
 base of the shoot, a large umbrella-shaped out-growth is formed, 
 bearing numerous haptera on its upper and outer surface. 
 
 The leaves vary in form. In a few cases they somewhat 
 resemble the foliage-leaves of the higher plants : in others (e.g. 
 Cladostephus, Chara) they resemble the stem and its branches, 
 but are distinguished by their limited growth ; in others again 
 (e.g. Polysiphonia and other Rhodophyceae), they are filamentous 
 and hair-like. 
 
 The Reproduction of the Algae is effected in various ways. 
 Vegetative multiplication takes place in the unicellular forms 
 (e.g. Cyanophyceae, Protococcoideae, Desmidieae, etc.) by cell-division, 
 in some of the higher forms (e.g. Sphacelaria, Chara, Melobesia) by 
 means of multicellular gemmae (see p. 49). Non-motile cells, with 
 a cell- wall, which are probably gemmae, are thrown off by Vaucheria 
 gcminata, and sometimes by other species of Vaucheria (Chloro- 
 phyceae). Reproduction by means of asexually-produced spores 
 occurs with but few exceptions (e.g. Conjugatse, Fucaceae, Characeae). 
 Sexual reproduction is general throughout the class, though it has 
 not yet been observed in all forms ; it appears to be definitely 
 absent in the Cyanophyceae, and in some of the lower Chlorophyceae 
 (e.g. some unicellular Protococcoideae). 
 
 There are various modes of sexual reproduction in the group. 
 The following is an enumeration of them (see also p. 58) : 
 
 I. Isoyamy : the sexual cells are similar gametes ; process, 
 conjugation ; product, a zygospore. 
 
 (a) Gametes ciliated (planogametes) ; set free ; e.g. Ulothrix, 
 Pandorina, Ectocarpus, Cutleria. 
 
 (6) Gametes not ciliated (aplanogametes) ; not set free in the 
 Conjugates ; set free in the Diatomacese.
 
 GROUP I. THALLOPHYTA : ALG.E. 241 
 
 II. Hcterogamy : 
 
 (a) Oogamy : the female organ is an oogonium ; the sexual 
 cells are spermatozoids and oospheres, the former ciliated and 
 free-swimming, the latter not ciliated but sometimes free-floating; 
 process, fertilisation ; product, an oospore ; (e.g. Volvox, Vaucheria, 
 (Edogonium, Coleochsete, Characese, Fucacese). 
 
 (b) Carpogamy ; the female organ is a procarp in which no 
 female cell is differentiated ; male cell free, not ciliated, a sperma- 
 tium ; process, fertilisation ; product, a fructification termed a 
 cystocarp (Rhodophycese). 
 
 The sexual cells are aplanogametes, planogametes, oospheres, 
 spermatozoids and spennatia ; though they differ widely in various 
 respects, they agree in being nucleated masses of protoplasm 
 destitute of a proper cell-wall. 
 
 The aplanogametes are characterised by the absence of cilia 
 and of any defined form ; they are confined to the Conjugates and 
 Diatomacese. 
 
 The planogametes are somewhat pear-shaped, the anterior more 
 pointed end being destitute of the chromatophores which are pre- 
 sent in the more rounded portion. They have two cilia which 
 are inserted, in the isogamous Chlorophyceee, at the pointed end 
 of the cell ; in the isogamous Phseophycese, laterally at the junction 
 of the anterior colourless portion with the posterior coloured por- 
 tion of the cell. In conjugation, the planogametes first come into 
 contact by their colourless anterior ends. 
 
 The oospheres are spherical cells, usually containing chroma- 
 tophores either throughout their whole substance, or leaving a 
 colourless area on one side, the receptive spot, at which the sper- 
 matozoid enters in the process of fertilisation (e.g. (Edogonium, 
 Vaucheria, Sphaeroplea). 
 
 The spermatozoids may be somewhat pear-shaded, resembling 
 the zoospores of the plant, but smaller (e.g. Coleochsete, (Edogo- 
 nium) ; or they may be more elongated and club-shaped (e.g. 
 Sphseroplea, Volvox) ; or still more elongated and spirally twisted 
 (Characeae). They usually bear two cilia at the pointed end ; but 
 in Vaucheria, Volvox, and the Fucacese, they are inserted laterally ; 
 in (Eiogonium there is a circlet of cilia round the pointed colour- 
 less end. They are faintly coloured, in the Chlorophycese usually 
 yellow. 
 
 The male cells of the Rhodophycese are peculiar on account of 
 the absence of cilia, and are distinguished by the special name 
 
 M.B. R
 
 242 PART IV. CLASSIFICATION. 
 
 spcrmatium : the spermatia surround themselves with a proper 
 wall at the time of fertilisation. 
 
 The sexual organs. In those Algse in which the sexual cells are 
 similar, and the sexual process is isogamous, the sexual organs are 
 gametangia. In many cases they are unicellular and undifferen- 
 tiated : thus, when the gametophyte is unicellular (e.g. Desmidiese, 
 Diatomacese) the cell itself constitutes the gametangium ; and in 
 some multicellular or coenocvtic forms (e.g. Zygnemeee, Hydrodic- 
 tyon, Confervoidese) the gametangia are simply ordinary vegetative 
 cells or coenocytes. In some isogamous Algse, however, the game- 
 tangia are differentiated as lateral appendages, and are multi- 
 cellular, as in the Phseosporese ; in Cutleria it is even possible to 
 distinguish the male from the female gametangium. 
 
 When the gametangium is unicellular or coenocytic, it usually 
 gives rise to a number of gametes ; but in the Conjugates a single 
 gamete is formed. When the gametangium. is multicellular, 
 each cell usually gives rise to a single gamete ; but in the male 
 gametangium of Cutleria 2-8 gametes are developed in each cell. 
 
 The female organ, the oogonium, is in all cases unicellular or a 
 coenocyte ; in Sphseroplea it is undifferentiated, retaining the form 
 of a vegetative segment of the incompletely septate plant ; in 
 most cases it is more or less spherical in form, and in some species 
 of Coleochsebe it is prolonged at the apex into a delicate tube, the 
 trichogyne. It opens, in most cases, by the absorption of the wall, 
 at a point opposite the receptive spot of the oosphere when that 
 is present; but in others (e.g. Volvox, Chara) it remains closed. 
 In the former case the spermatozoid enters by the aperture : in 
 the latter, it bores its way through the wall of the oogonium which 
 becomes mucilaginous at its exposed surface. The oogonium of 
 the Fucacese ruptures and sets free the contained female cell or 
 cells. Usually a single female cell (oosphere) is formed in an 
 oogonium, by the rejuvenescence of its protoplasmic contents ; but 
 in various Fucaceae, the protoplasm divides to form two, four, 
 or eight oospheres, and in the coenocytic oogonium of Sphaeroplea 
 there are several oospheres. 
 
 The female organ of the Rhodophycese, the procarp, is some- 
 times unicellular (e.g. Nemaliese), but more commonly multi- 
 cellular. It is in nearly all cases prolonged into a trichogyne, the 
 basal portion being termed the carpogonium. The trichogyne re- 
 mains closed. The protoplasm of the procarp does not undergo
 
 GROUP I. THALLOPHYTA : ALG^E. 243 
 
 differentiation into a female cell comparable with the oosphere of 
 the oogonium. 
 
 The male organ, the anther idium, is with few exceptions (e.g. 
 Sphaeroplaea) more or less differentiated in form, attaining its 
 highest development in the Characeae. It is usually unicellular ; 
 but in (Edogonium it consists of two cells, and of many cells in 
 the Characese where its structure is highly complex. When the 
 antheridium is unicellular, it usually gives rise to a number of 
 male cells, but in Coleochaete and most Rhodophyceae only to one. 
 When it is multicellular, each fertile cell gives rise to a single 
 spermatozoid. 
 
 Sexual organs are not known in the following forms : Cyano- 
 phyceae, some Protococcoideae, some Siphonaceae, some Phaeosporese 
 (e.g. Desmarestia ; Laminariaceae, except Chorda). 
 
 The asexual reproductive cells of the Algae are formed either 
 sexually or asexually : the former are either zygospores, or oospores ; 
 the latter are spores. 
 
 The zygospores and oospores occur exclusively in the Chloro- 
 phycese and Phaeophyceae : they are spherical nucleated cells with 
 a cell-wall. The differentiation of the cell-wall varies with the 
 nature of the spores and of the conditions to which they are 
 likely to be exposed. In the Phaeophyceae the zygospore or the 
 oospore germinates at once on its formation, and its wall remains 
 thin, and consists only of a single layer. In the Chlorophyeeae, the 
 sexually produced spore usually undergoes a period of quiescence 
 before it germinates, and except in marine forms (e.g. Acetabularia), 
 it is exposed during this period to the danger of desiccation. As a 
 protection, its wall consists of two layers, a delicate endospore, and 
 a hard cuticularised exospore which often grows out into promin- 
 ences, giving to the spore a stellate appearance. 
 
 The spores produced asexually may be resting-spores with a 
 thick wall, which may consist of two layers as described above 
 (e.g. many Cyanophyceae) : or cells destitute of a cell-wall, either 
 ciliated (e.g. zoospores of (Edogonium, Coleochaete, Sphaeroplaea, 
 Pandorina), or not ciliated (e.g. tetraspores and carpospores of the 
 Rhodophyceae). 
 
 The asexual reproductive organs are sporangia. In the simple 
 unicellular forms, the whole body may become a sporangium (e.g. 
 Hsematoccoccus) : in some coenobitic multicellular plants there are 
 no definite asexual reproductive organs, but any of the cells of 
 the body may act as such (e.g. Ulothrix, Pandorina, Coleochaete,
 
 244 PART IV. CLASSIFICATION. 
 
 Ulva) without any special morphological differentiation ; this is 
 true likewise of the coanocytic Algse Siphonoidese, such as Botry- 
 dium, Vaucheria, Sphseroplea, Cladophora, where the whole or 
 part of the body may act as a sporangium. Specially differen- 
 tiated sporangia occur only in some Phseosporese, and in the 
 Rhodophycese where they usually produce each four spores (tetra- 
 .spores) and are hence termed tetrasporangia : specially differenti- 
 ated sporangia are also developed in the cystocarp of the Rhodo- 
 phycese where they are termed carposporangia : these organs are 
 in all cases unicellular. 
 
 In the Cyanophycese the formation of spores is effected without 
 any sporangium, for in these plants a cell of the body is converted 
 into a spore by simple encystment. 
 
 As a rule a sporangium gives rise to a number of spores ; 
 but only one is formed in the sporangium of Vaucheria and 
 of (Edogonium (see p. 85), and in the carposporangium of the 
 Rhcdophycese. 
 
 Sub-Class I. CYANOPHYCESE (also called Phycochromacese), or 
 blue-green Algse. The body consists of a single, more or less nearly 
 spherical cell, as in most of the Chroococcacese (e.g. Gloeocapsa, 
 Fig. 134) ; or it is a multicellular layer one cell thick (e.g. Meris- 
 mopedia); or it is filamentous, consisting of a row of cells (e.g. 
 Oscillaria, Nostoc, Rivularia, Scytonema). When the body is 
 filamentous, it sometimes presents a distinction of base and apex 
 (e.g. Rivularia) ; and it is frequently branched. In most cases 
 growth and cell-division go on in all the cells of the body, but 
 in the Scytonemacese only at the apex. The plant is usually 
 free, but it grows attached in some species of Rivulariacese and 
 Sytonemaceae. A characteristic feature of the sub-class is the 
 more or less bulky mucilaginous cell-wall which invests the cells 
 and filaments. The filaments of the Oscillariacese exhibit a glid- 
 ing, oscillating movement, but the mechanism of it is not fully 
 understood. 
 
 Reproduction is mainly effected in a purely vegetative manner. 
 In the unicellular forms (Fig. 134) each cell-division necessarily 
 leads to the formation of new individuals. In the flattened forms 
 (e.g. Merismopedia), when the body reaches a certain limit of size, 
 it simply breaks up into a number of portions each of which 
 becomes a new individual. In the filamentous forms, vegetative 
 propagation is effected by the breaking up of the filament into 
 lengths, each such portion being termed a hormogonium ; in most
 
 GROUP I. THALLOPHYTA : ALGLE. 
 
 245- 
 
 of them (except Oscillariacese) the limits of the hormogonia are 
 indicated by large inert cells, heterocysts (Fig. 135 ^4), which differ 
 both in size and colour from the living cells to the filament. The 
 
 Pis. 131. Gkeocapsa (x 300) in 
 various stages : A becomes H CD E 
 by repeated division. (From Sachs.) 
 
 PIG. 135. A Filament of Nostoc ; the large 
 unshaded cell is a heterocyst. B Portion of 
 a filament of Oscillaria (+ 300). 
 
 hormogonia are motile, though the mechanism of their movements : 
 is not understood ; they eventually separate, and escaping from 
 the common mucilaginous cell-wall of the filament, they develope 
 by growth and cell-division into new filaments (Fig. 136 A B}. 
 
 In many cases special reproductive cells, spores, are produced. 
 Each spore is formed from a single cell of the body, which sur- 
 rounds itself with a thick firm exospore ; the spore germinates 
 
 s* t ~ ** 
 
 PIG. 136. (After Thuret : x 330). A and B Development of a filament from a hormo- 
 gonium of Nostoc vesicarium. A Cells of hormogonium dividing at right angles to its long 
 axis; B rows of cells formed as B uniting at alternate ends, so as to constitute a Nostoc- 
 filament ; z heterocysts. C Germinating spores of Anabcena licheniformis. 
 
 under favourable conditions, the exospore being ruptured (Fig. 
 136 C). 
 
 It is possible that zoospores are produced in some forms, but
 
 246 PART IV. CLASSIFICATION. 
 
 the evidence is at present inconclusive. No form of sexual repro- 
 duction has been observed in any member of this sub-class. 
 
 The cells of the Cyanophycese contain nuclear substance, but 
 the nucleus is not well-defined ; and the chlorophyll and the phy- 
 cocyanin appear to be diffused throughout the cytoplasm, and not 
 to be aggregated in special plastids. 
 
 The Cyanophycese resemble the Schizomycetes, among the Fungi, 
 in many respects ; as, for instance, in their general form and struc- 
 ture, in their vegetative multiplication, in their spore formation, 
 in the absence of sexual reproduction, in the formation of a bulky 
 mucilaginous cell-wall, and in their polymorphism. On these 
 grounds they are frequently placed, along with the Schizomycetes, 
 in a distant class Schizophyta. But this arrangement does not 
 seem to secure any special advantage. It is more natural to regard 
 the Cyanophycese and the Schizomycetes as parallel groups, the 
 one belonging to the Algse, the other to the Fungi. 
 
 The Cyanophycese are both marine and fresh -water : many grow 
 on damp walls, rocks, etc. 
 
 Sub-Class IL CHLOROPHYCE.E, or Green Algae. In the simpler 
 forms the plant consists of a single cell (e.g. Protococcoidese, some 
 Desmidiese): or it is coenocytic, as in the Siphonoidese, either 
 unseptate (Siphonacese) or incompletely septate (Cladophoracese, 
 Hydrodictyacese) ; it is, in fact, only in this sub-class that the 
 coanocytic structure occurs among the Algse : or the body is mul- 
 ticellular, with essentially similar cells and therefore coenobitic 
 (e.g. Spirogyra, Pandorina, Ulva), or exhibiting at least a dis- 
 tinction between vegetative and reproductive cells (e.g. Volvox). 
 The only members of the sub-class in which there is any appreci- 
 able differentiation of the vegetative cells are the Characese. 
 
 The body presents all degrees of morphological differentiation ; 
 it may be a thallus, either spherical (e.g. Hsematococcus, Volvox), 
 or filamentous (e.g. Spirogyra, Ulothrix), or a flattened expansion 
 (e.g. Diva, Coleochsete) ; or a filament with rudimentary differen- 
 tiation into root and shoot (e.g. (Edogonium) ; or it may present 
 differentiation into stem, leaf, and root (e.g. Characese). It may 
 be free or attached. Growth and cell-division commonly go on in 
 all the cells of ,the body, so that the growth is intercalary (e.g. 
 Spirogyra, (Edogonium, Ulva) ; it is but rarely that there is a 
 definite growing-point, and then it is apical (Coleochsete, Characese, 
 -some Siphonoidese) ; and in the cellular plants which have an 
 apical growing-point, there is a single apical celL
 
 GROUP I. THALLOPHYTA : ALG.^. 247 
 
 Vegetative multiplication by division occurs in some of the lower 
 forms (e.g. Protococcoidese) of this sub-class. Reproduction by 
 zoospores is general (absent in Pleurococcacese, Conjugate, most 
 Volvocoidese, Characeae) ; they are formed, not in specialised re- 
 productive organs, but in any cell or part of the body. A sexual 
 process has been observed in members of every division of this 
 sub-class : it is either isogamous, consisting in the fusion of piano- 
 gametes or aplanogametes (Conjugatse), with the formation of a 
 zygospore ; or oogamous, consisting in the fertilisation of an 
 oosphere, which is in no case extruded from the female organ, 
 by a spermatozoid, with the formation of an oospore. The sexual 
 organs are either gametangia, or antheridia and oogonia ; they are 
 unicellular in all the cellular forms (except the antheridium of 
 Characese and that of some species of (Edogonium), and present 
 various degrees of specialisation. A gametangium gives rise to 
 many planogametes, but to not more than one aplanogamete ; the 
 oogonium produces but a single oosphere, except in the coenocytic 
 Sphaeroplea ; the unicellular (as also the coenocytic) antheridium 
 gives rise to numerous spermatozoids, except in Coleochsete and in 
 some species of (Edogonium where it forms only one ; in the multi- 
 cellular antheridium of the Characese, numerous spermatozoids 
 are developed singly in distinct mother-cells. 
 
 There is considerable polymorphism in many members of this 
 sub-class, so that various forms which were considered to be inde- 
 pendent members of the simpler families are now known to be 
 merely phases in the life-history of more complex forms ; for in- 
 stance, various unicellular forms, such as Protococcus, Palmella, 
 Grlceocystis, etc., formerly classed among the Protococcacese, are 
 now known to be stages in the life-history of other Protococcoidese, 
 Confervoidese, Siphonoidese, etc. 
 
 The Chlorophyceae may be classified as follows : - 
 
 Series I. Protococcoidese : plants unicellular, isolated or held together by 
 mucilaginous cell-walls into colonies; non-motile; the body is a 
 thallus, and has no apical growth; reproduction, vegetative by 
 division, asexual by zoospores, rarely sexual and then isogamous with 
 conjugation of planogametes. 
 
 Series II. Volvocoidese : plants unicellular or multicellular, and when 
 multicellular not filamentous ; not attached, motile by means of cilia ; 
 the body is a thallus, with limited growth ; reproduction, vegetative 
 by division, asexual rarely by zoospores, sexual, either isogamous 
 with conjugation of planogametes, or oogamous.
 
 248 PART IV. CLASSIFICATION. 
 
 Series III. Siphonoidese : plants ccenocytic, unseptate or incompletely 
 septate ; non-motile ; the body may be a thalJus or may be differen- 
 tiated into stem, leaf, and root ; with or without apical growth ; 
 reproduction, asexual by zoospores ; sexual, either isogamous (plano- 
 gainetes), or oogamous. 
 
 Series IV. Confervoideae : plants generally multicellular, filamentous, 
 branched or unbranched ; growth frequently intercalary, rarely 
 apical ; body attached or floating, a thallus, or sometimes with rudi- 
 mentary differentiation into root and shoot ; reproduction, asexual 
 by zoospores, in some cases ; sexual, isogamous (either planogametes 
 or aplanogametes), or oogamous. 
 
 Series V. Charoidese : plants multicellular ; body attached, differentiated 
 into stem (with apical growth), leaf, and root ; reproduction, vegeta- 
 tive by gemmse, no zoospores ; sexual, oogamous, with multicellular 
 antheridium of complex structure. 
 
 Series I. PROTOCOCCOIDE^E. The forms included in this series are very 
 various, and, inasmuch as their life-history is for the most part imper- 
 fectly known, it is uncertain to what extent they are independent, or are 
 only phases in the life-history of each other or of higher Chlorophycese. 
 It appears, however, that they may be fairly 
 classified into two orders : 
 
 Order 1. Pleurococcaceae : cells isolated, or 
 aggregated into colonies of more or less definite 
 form ; multiply only by "cell-division ; no other 
 mode of reproduction. 
 
 To this order belong such isolated forms as 
 Pleurococcus and Oocystis ; and such aggregate 
 FIG. l37.-Pl<mroeoccus forms as Palmophyllum, Palmodictyon, Scene- 
 vulgaris (x 640) : cells desmus. They generally grow in fresh water ; 
 dividing. but Pleurococcus grows on damp trees, stones, 
 
 etc., and Palmophyllum is marine. 
 
 Order 2. Protococcaceae : cells isolated, or aggregated into colonies of 
 more or less definite form ; multiplication by cell-division is not general ; 
 reproduction, asexual by zoospores, or, less commonly, sexual isogamous 
 (planogametes). 
 
 This order includes (1) isolated unicellular forms, either free, such as 
 Chlorococcum, Halosphsera ; or attached at one end, such as Sciadium, 
 Characium ; or inhabiting the tissues of higher plants, such as Chloi-o- 
 ch3'trium, Phyllobium, Endosphaera ; (2) cells aggregated into mucila- 
 ginous masses of indeterminate form, e.g. Chlorosphsera which lies in or 
 on submerged fresh-water plants ; (3) cells aggregated into mucilaginous 
 masses of determinate form, the whole colony being generally attached at 
 some definite point (e.g. Apiocystis, Tetraspora), or free-floating (e.g. 
 Dictyosphserium, Botryococcus). 
 
 In some of these forms there is what is termed a Palmel la-stage, in 
 which the cells multiply by division, surrounded by mucilage (e.g. Hor- 
 motila, Characium). 
 Isogamous reproduction by means of planogametes is known in some
 
 GROUP I. THALLOPHYTA : ALG.E. 
 
 249 
 
 forms (e.g. Tetraspora, Chlorochytrium). The zygospore, on germination, 
 usually gives rise to one or two zoospores. 
 
 Series II. VOLVOCOIDE.E. The body, in this series, is free-swimming 
 for at least a considerable portion of its life, and consists of one or more 
 cells clothed with a somewhat mucilaginous cell- wall, through which 
 the cilia (usually two from each cell) project into the water. According 
 to the unicellular or multicellular structure of the body, two orders may 
 be distinguished : 
 
 Order 1. Chlamydomonadaceae : body a single cell, resembling in 
 many cases a zoospore in appearance, but differing essentially from it in 
 possessing a cell-wall ; some forms have a resting Palmella-stage, in 
 which they multiply by division ; sexual process, generally isogamous 
 with fusion of planogametes, but sometimes in Chlamydomonas it is really 
 oogamous, consisting in the fusion of a small (male) aplanogamete with a 
 larger (female) aplanogamete ; the reproductive cells (planogametes or 
 aplanogametes) are formed by division ; the zygospore generally gives 
 rise, on germination, to two or four motile or non-motile individuals. 
 
 The principal genera are Chlamydomonas, Hsematococcus (or Sphae- 
 rella), Phacotus. 
 
 Order 2. Volvocaceae : body 
 multicellular, consisting of a 
 definite or indefinite number of 
 cells, which may be all alike 
 (coenobium), as in Pandorina 
 (Fig. 138), which consists of 
 16 cells ; or there may be a 
 distinction between vegetative 
 and reproductive cells (Volvox). 
 Vegetative reproduction is ef- 
 fected by division of any or all 
 of the cells of the body (Pandor- 
 ina), or of certain non-motile 
 gonidial cells (Volvox), from 
 each of which a new individual 
 is formed; sexual reproduction, 
 isogamous by planogametes 
 (Pandorina), or oogamous (Vol- 
 vox). 
 
 In Pandorina any cell may divide to form a new individual, or to forni 
 planogametes ; the zygospore sets free one or two zoospores on germi- 
 nation. 
 
 Volvox is sometimes monoecious, sometimes dioecious. The contents of 
 the oospore undergo repeated bipartition until the requisite number of 
 cells to form a new individual is attained. The vegetative development 
 of new individuals from the gonidial cells of Volvox, takes place in pre- 
 cisely the same way as the development from the oospore : the small 
 individuals formed vegetatively from the gonidial cells are set free into 
 the cavity o.f the parent, where they remain until it dies, when they are 
 
 Pis. 138. Pandorma Morum ( x400) : A vege- 
 tative stage ; B two planogametes in process of 
 conjugation.
 
 250 
 
 PART IV. CLASSIFICATION. 
 
 set free. 
 
 ~b 
 
 The spermatozoids of Volvox are club-shaped, yellow, and 
 
 bear two cilia, inserted 
 ' . laterally. 
 
 Series III. SIPHO- 
 NOIDEJE. The forms in- 
 cluded in this series 
 may be arranged in 
 the three following 
 orders : Siphonacese, 
 Cladophoracese, Hy- 
 drodictyacese. 
 
 Order 1. Siphona- 
 ceae. The body is an 
 unseptate coenocyte, 
 septa being only 
 formed in connexion 
 with the development 
 of reproductive or- 
 gans , it is usually 
 attached, and presents 
 a considerable variety 
 FIG. 139. Volvox Globator (after Cohn: *x about 100), of form; it may be 
 monoecious, with antheridia a, and oogonia b. thalloid and then be 
 
 FIG. 140. Vaucheria smttix (x30): A sp a newly-formed zoogonidium; B a resting 
 zoospore ; C, the commencement, D and E more advanced stages, of germination ; 
 sj> zoospore ; apex of the green filament ; ic a colourless adventitious root ; F filament 
 with sexual organs; og oogonium ; h autheridium after rupture. (After Sachs.)
 
 GROUP I. THALLOPHYTA : 
 
 251 
 
 tubular and much, branched (usually in Vaucheria, Fig. 140) ; or it may 
 be differentiated into root and shoot, the shoot assuming various forms, 
 such as a rounded cushion ((Jodium Bursa), or a simple vesicle (Botrydium, 
 Fig. 142) ; or the shoot may be differentiated into stem and leaf (Acetabu- 
 laria, Fig. 141); it has sometimes continuous apical growth (e.g. Vaucheria) ; 
 the wall is sometimes impregnated with chalk (e.g. Acetabularia). 
 
 Asexual reproduction is known to take place in only a few forms ; it is 
 effected by zoospores, which are uniciliate in Botrydium, or multiciliate, 
 as in Vaucheria, where they are sometimes non-motile. In Vaucheria 
 the spores are formed singly in simple sporangia formed by septation of 
 branches of the body ; in Botrydium they are formed in large numbers 
 from the protoplasm of the tubular body. 
 
 Sexual reproduction is generally isogamous by planogametes : Vau- 
 
 FIG. 141. -Acetabularia crenulata (after Kutz- 
 ing ; nat. size) : the terminal circular disc con- 
 sists of a whorl of coherent leaves ; in these 
 the gametangia are formed. 
 
 FIG. 142. Botrydium granulatum 
 ( x 6) : s the green shoot ; w the 
 colourless root. 
 
 cheria is the only known oogamous form. Isogamy is known in Botry- 
 dium, Acetabularia, and others. In Botrydium and Acetabularia the 
 gametangia are formed by the aggregation of the protoplasm (in the 
 coherent leaves of the latter) into rounded masses which become sur- 
 rounded by a wall, and are set free by the rupture of the parent organism; 
 their contents undergo frequent division to produce the planogametes 
 which are eventually set free. In Botrydium and Acetabularia the con- 
 jugating gametes are quite similar. 
 
 In Vaucheria, the sexual organs are unilocular antheridia and oogonia, 
 and are developed as lateral branches which become shut off by a septum 
 (Fig. 140); each antheridium gives rise to a number of biciliate sperma- 
 tozoids ; each oogonium gives rise to a single oosphere which is not
 
 252 
 
 PART IV. CLASSIFICATION. 
 
 extruded, and has a hyaline receptive spot directed towards the opening 
 of the oogonium. 
 
 Vaucheria forms the green felt which covers the soil in damp flower- 
 pots or other moist situations. Aquatic species occur in ditches, etc., 
 often forming a thick scum on the surface. 
 
 Order 2. Cladophoraceae. The body is incompletely septate and the 
 segments are coenocytic ; it is filamentous, branched or unbranched, some- 
 times differentiated into root and thalloid shoot, attached or free-floating, 
 the shoot with or without apical growth : 
 reproduction, asexual by zoospores ; sex- 
 ual, isogamous, or oogamous. 
 
 Fam. 1. SphceropJece : the body consists 
 of floating unbranched filaments, without 
 distinction of base and apex, and with 
 intercalary growth. Each segment con- 
 tains numerous small chloroplastids. 
 Any segment of the body may become 
 a sexual reproductive organ, either an 
 oogonium or an antheridium, without 
 any change of form; in the oogonium 
 several oospheres are formed by free cell- 
 formation (see p. 87), and likewise in the 
 antheridium, after repeated nuclear divi- 
 sion, a great number of sperm atozoids ; 
 the oospheres are not extruded, but are 
 fertilised in the oogonium by spermato- 
 zoids which enter through an opening 
 formed in the wall ; the oospore, at first 
 green, assumes a bright red colour, and 
 on germination sets free 2-8 zoospores, 
 each of which gives rise to a new fila- 
 ment. Sphseroplea is the only genus, and 
 it comprises but one species S. annutina : 
 it inhabits fresh water. 
 
 Fam. 2. Cladophorece : body filamentous, 
 generally attached by a basal root-seg- 
 ment, branched (e.g. Cladophora) or un- 
 branehed (e.</.Chaetomorpha), with usually 
 intercalary growth (though it is apical 
 in Cladophora) ; each segment contains a 
 peripheral layer of chloroplastids (Fig. 
 143), Continuous or interrupted, in which 
 are scattered pyrenoids ; reproduction, 
 asexual by zoospores in some forms (e.g. 
 Cladophora), or vegetatively (e.g. Pitho- 
 phora); an isogamous sexual process be- 
 tween planogametes has been observed in 
 Gladophora: reproductive cells formed in 
 
 FIG. 143. Cladophora glomerata 
 (after Btrasburger: x 540). A 
 coenocyte of the filament (chromic 
 acid and carmine preparation) : 
 n a nucleus ; ch a chloroplastid ; the 
 polygonal chloroplastids form a 
 continuous layer, the outlines of 
 the individual plastids remaining 
 visible; p pyrenoids; v starch- 
 grains.
 
 GROUP i. THALLOPHYTA: ALG^E. 253 
 
 all or any of the segments of the body without special modification ; the 
 zygospore appears to develope directly into a new plant (Cladophora). 
 
 Cladophora and Chaetomorpha oocur in both salt and fresh water ; 
 Pithophora exclusively in fresh water ; Urospora' exclusively in salt 
 water ; Rhizoclonium occurs both in fresh and salt water, and also on 
 damp soil. Cladophora is to be found attached to stones in ditches. 
 
 Order 3. Hydrodictyaceae : body thalloid. a non-motile unattached 
 c^nobium, formed by the aggregation of originally distinct cells, of 
 limited growth ; a net (Hydrodictyon), or a flat plate (Pediastrum) : 
 reproduction, asexual by zoospores ; sexual, isogamous by planogametes. 
 These plants are confined to fresh water. 
 
 The following is a brief sketch of the life-history of Hydrodictyon. 
 The asexual reproduction of this plant consists in the formation of a 
 large number (7,000-20,000) of zoospores in any one of the segments of the 
 coenobium ; the zoospores do not escape from the segment, but swim 
 actively within it for a time, when they come to rest, cohering, as they 
 do so, to form a small net-like coenobium, which is eventually set free by 
 the disorganisation of the wall of the sporangium, and then grows to 
 the full size. The sexual reproduction consists in the formation in a 
 segment (gametangium) of the coenobium, of a very large number 
 (30,000-100,000) of small planogametes ; these are set free into the water, 
 and conjugate to form zygospores. The zygospore, which has a thick 
 wall and is angular in form, undergoes a period of quiescence ; on germi- 
 nation its contents divide into two or more cells which are set free as 
 zoospores, and, after a brief period of motility, come to rest. Each then 
 surrounds itself with a thick cell-wall, and assumes a peculiar angular 
 form, on account of which it has been termed the polyhedron-istage. The 
 polyhedron grows and its contents divide into a number of zoospores ; the 
 outer coat of the polyhedron then ruptures, and the contents, surrounded 
 by the thin inner coat, are extruded ; the zoospores then arrange them- 
 selves into a small Hydrodictyon-plant. 
 
 The life-history of Pediastrum is essentially the same as that of Hydro- 
 dictyon ; but in Pediastrum the zoospores are set free, surrounded by a 
 delicate membrane within which they come to rest and cohere to form a 
 Pediastrum plant. 
 Series IV. CONFERVOIDE.S:. The principal forms included in this series 
 
 may be arranged in the following orders : 
 Sub-series A, Azoosporese : no zoospores. 
 
 Order 1. Conjugatse : sexual reproduction by aplanogametes. 
 Sub-series B. Zoosporese ; asexual reproduction by zoospores. 
 Itiogamous Orders : 
 
 Order 2. U lothrichaceae : body filamentous, unbranched. 
 Order 3. Ulvaceae : body a flat or tubular cellular expansion. 
 Oogamous Orders : 
 
 Order 4. CEdogoniaceae : body filamentous, unbranched (except Bulbo- 
 chsete). 
 
 Order 5. Coleochsetacae : body filamentous, branched ; oogonium with 
 a trichogyne.
 
 254 PART IV. CLASSIFICATION. 
 
 An asexual formation of spores takes place in all the Confervoideae 
 except the Conjugatse. A sexual formation of spores takes place in all 
 the Confervoidese ; in the isogamous forms the product of conjugation is a 
 zygospore ; in the oogamous forms it is an oospore. In the isogamous 
 forms the sexual organs, or gametangia, are not differentiated ; any or all 
 of the cells of the body may act as gametangia ; the sexual cells are 
 (except in the Conjugatse) free-swimming similar planogametes ; in the 
 Conjugatse the gametes are not set free into the water and they are not 
 ciliated. In the oogamous forms the sexual organs are antheridia and 
 oogonia ; they are more or less markedly differentiated. The sexual cells 
 are oospheres and spermatozoids. The oospheres are formed singly in the 
 oogonium. The spermatozoids are formed singly in the mother-cell ; they 
 resemble the zoospores of the respective plants, but are smaller and are 
 not green. 
 
 In Ulothrix and (Edogonium, the contents of the spore, whether zygo- 
 spore or oospore, undergo division giving rise to two or more zoospores 
 which are set free and, after a longer or shorter period of movement, come 
 to rest and germinate, each developing into a plant. In Coleochsete, the 
 contents of the oospore likewise undergo division, but the product is not 
 several zoospores ; it is a small multicellular body, each cell of which 
 eventually sets free its contents as a single zoospore which, on coming to 
 rest, develops into a plant. 
 
 The following is a brief account of the orders of the Confervoidese : 
 
 Order 1. Conjugates ; the characteristics of this sub-order have been 
 already stated ; it need only be added that the plants are usually not 
 attached. It includes the families Desmidiese and Zygnemeae ; all fresh- 
 water. 
 
 Family 1. Desmidiece. These are unicellular organisms, either solitary 
 or connected into filaments ; they possess some power of locomotion. 
 Each cell consists of a mass of protoplasm with a central nucleus, and 
 contains two or more chloroplastids in which lie conspicuous pyrenoids. 
 The cell-contents are arranged symmetrically in the two halves of the 
 cell, and in many forms this bilateral symmetry is emphasised by a 
 deep constriction in the median plane. 
 
 The Desmids multiply to a large extent by division ; the cell is divided 
 into two by the formation of a cell-wall in the median plane, and then 
 each half produces a new half corresponding to itself ; hence the two 
 halves of a cell are of different ages. The only other mode of repro- 
 duction is by means of zygospores formed by the conjugation of two 
 individuals. On germination the contents of the zygospore divide into 
 two halves, each of which becomes an individual. 
 
 Among the commoner forms of the Desmidiese are Closterium (Fig. 144), 
 Staurastrum, Euastf urn (Fig. 144 (7). They can best be found in pools of 
 peaty water 011 moors and bogs. 
 
 Family 2. Zygnemece. These plants, consisting of long, delicate, un- 
 branched filaments composed of cylindrical cells, occur as floating green 
 masses in ponds and springs. Each cell contains a peripheral layer of 
 protoplasm in close contact with the cell-wall, enclosing a large central
 
 GROUP I. THALLOPHYTA : ALOE. 
 
 255 
 
 vacuole in which the nucleus is situated in a mass of protoplasm con- 
 nected with the peripheral layer by several delicate protoplasmic 
 filaments. The chloroplastids are the most conspicuous feature of the 
 cell ; in Spirogyra (Fig. 
 
 145) the chloroplastids, of ^ 
 which there may be from /,! \ 
 one to four, lie in the & ^**r*. --.- . .:..-^-^. \oEJ^ 
 parietal protoplasm ; they 
 
 are spirally twisted in 
 Spirogyra, but are nearly 
 straight in Sirogonium : 
 like those of the Desmids, 
 these chloroplastids con- 
 tain several pyrenoids 
 with associated starch- 
 grains ; in Zygnema (Fig. 
 144 A) each cell contains 
 two chloroplastids, sus- 
 pended in the middle line, 
 each containing a pyrenoid with starch-grains. 
 
 The filaments elongate by the growth and division of all the constitu- 
 ent cells, and readily break up into segments, consisting of one or more 
 cells, which grow into new filaments. 
 
 The sexual organs (gametangia) are quite undifferentiated ; any or all 
 of the cells of a filament may act as sexual organs, the whole of its con- 
 tents being converted into a single non-oil iate gamete. The sexual process 
 (conjugation) consists in the fusion of the gametes derived from two cells 
 belonging generally to two filaments, but sometimes to the same filament. 
 It is effected, in most cases, by the development of a lateral outgrowth 
 from the middle of each gametangium ; the two outgrowths meet (Fig. 
 
 146) and their walls become absorbed at the point of contact so that the 
 cavities of the two gametangia are continuous. The protoplasmic con- 
 tents of each cell contract away from the wall of each gametangium to 
 
 FIG. 144. .4 Fragment of a filament of Zypnenia ; 
 in each cell are two star-shaped chloroplastids con- 
 nected by a colourless mass of protoplasm in which lies 
 the nucleus. B Closterium. C Eaastrnm, two Desmids 
 with chloroplastids; in B there is a vacuole at each 
 end in which a number of granules may be seen in 
 motion. 
 
 FIG. 145. Conjugation in Spirogyra ( x 400). At A two cells of adjacent filaments are 
 about to conjugate, and are putting out protuberances (a) towards each other; ct chlcro- 
 plastid ; fc nucleus. At B the gamete p of the one cell is passing over and fusing with 
 that of the other (p). At C the process of conjugation is completed, the zygospore Z being 
 the product.
 
 256 
 
 PART IV. CLASSIFICATION'. 
 
 form the gamete. The formation of the gamete takes place earlier in one 
 gametangium than in the other, and the first formed gamete travels 
 across the connecting channel into the cavity of the other gametangium 
 when it fuses with the other gamete ; the resulting cell surrounds itself 
 with a wall, and constitutes a zygospore. Since the first-formed gamete 
 is the more active in the process of conjugation, it may be regarded as a 
 male cell, the other as a female cell, so that there is a rudimentary differ- 
 entiation of sex. Further, since the cells of any one filament all behave 
 alike in the process of conjugation, it is possible to speak of male and 
 female filaments or individuals. In Zygogonium, however, the gametes 
 are similar, both as regards the time of their formation and their share 
 in conjugation ; in this form the gametes meet in the connecting channel 
 and there fuse to form the zygospore. 
 
 After a period of rest, the zygospore germinates ; the outer coat is 
 ruptured, and the contents, covered by a thin cell-wall, protrude as a 
 filament which is divided by a transverse septum into two cells ; of these, 
 the one becomes elongated and remains narrow in the cavity of the spore, 
 undergoes no further division, and contains little or no chlorophj'll, 
 whereas the other becomes broader, contains one or more chloroplastids 
 and, by repeated division, forms a filament. Thus there is at first a 
 differentiation of the body into root and shoot, but this soon ceases to be 
 apparent. It is most clearly marked in Spirogyra. Principal genera : 
 Zygnema, Spirogyra. 
 
 Spirogyra occurs as floating masses in ponds or slowly running water 
 during the warmer parts of the year, but only where the water is pure. 
 It may be found in conjugation about May or June. 
 Order 2. Ulothrichaceae. The unbranched filament is attached by a 
 
 narrow elongated, frequently 
 
 colourless, root-cell ; the growth 
 
 in length of the filament is 
 
 intercalary, that is, each cell 
 
 elongates and divides by a 
 
 transverse wall into two. 
 
 The reproductive organs are 
 
 quite undifferentiated ; any cell 
 
 of the filament may become an 
 
 asexual reproductive organ, or 
 
 a sexual organ, a gametangium. 
 
 In the former case the proto- 
 plasmic contents of the cell 
 
 divide into two or four parts 
 
 which are set free as zoospores ; 
 
 in the latter case the contents 
 
 divide into eight or sixteen 
 
 which are set free as planoga- 
 
 metes. The zoospores are some- 
 what pear-shaped in form, the 
 
 more pointed end being colourless 
 
 Fio. 146. Ulollirix zonota : A part of a fila- 
 ment from a cell of which planogametes are 
 escaping, the other cells having already emptied 
 themselves; B planogametes; C the process 
 of conjugation; D young zygospores; E mature 
 zygospore ; F germinating zygospore with 
 hyaline root ; G the contents of the embryonic 
 shoot dividing to form zoospores.
 
 GROUP i. THALLOPHYTA: ALGLE. 257 
 
 and bearing four cilia and a pigment-spot : the planogametes resemble the 
 zoospores but are proportionately smaller and have only two cilia. When 
 the zoospores come to rest, they secrete a cell-wall, and become attached by 
 the colourless end which forms the root-cell of the developing filament. 
 The planogametes conjugate to form zygospores, but if they fail to con- 
 jugate they may germinate independently, and they do so in the same 
 manner as the zoospores, only the resulting filament is smaller. The 
 zygospore grows and attaches itself by its hyaline portion which de- 
 velopes into a root ; after a period of quiescence its contents divide and 
 are set free as 2-8 zoospores Fresh water and marine. Principal genera : 
 Ulothrix, Conferva. 
 
 Order 3. Ulvaceae. The membranous body consists of a single flat 
 layer of cells (Monostroma), or of a single tubular layer of cells enclosing 
 a cavity (Enteromorpha). or of two layers in close contact (Ulva) ; the 
 body is attached, at least when young, by a root, and is sometimes 
 branched (esp. Enteromorpha) ; the growth of the body is intercalary, all 
 the cells being concerned in it. 
 
 Any cell of the body may become a sporangium or a gametangium ; the 
 zoospores have four cilia, the planogametes two ; conjugation of piano- 
 gametes has been observed in the three above-mentioned genera; the 
 zygospore, on germination, develops directly into a new plant, producing 
 basally the root and distally a cellular filament which becomes the 
 thalloid shoot. Inhabit both fresh and salt water. 
 
 Order 4. QEdogoniaceae. Filaments unbranched (except Bulbochsete), 
 attached by a root ; growth intercalai - y. The mode of growth of the 
 individual cells of (Edogonium is peculiar ; in the plane of division a ring 
 of cellulose is formed round the cell- wall ; the cell- wall then ruptures, 
 and the cellulose-ring is stretched so as to form a membrane across the 
 rent ; as this process takes place repeatedly near the upper end of the cell, 
 the projecting edges of the repeatedly ruptured cell-wall form a series of 
 caps; the transverse septa, dividing the elongated cells into two, are 
 always formed toward the lower end of the cells. 
 
 Any cell of the body may be a zoosporangium, setting free its proto- 
 plasmic contents as a single zoospore with a circlet of cilia round its more 
 pointed colourless end. On coming to rest, the zoospore attaches itself by 
 its colourless end, surrounds itself with a cell-wall, and grows into a 
 filament ; the colourless portion becomes the root-cell (see Fig. 62). 
 
 The sexual organs are differentiated. Some cells of a filament increase 
 in size and become rounded in form, each constituting an oogonium. The 
 protoplasm in each oogonium contracts away from the wall to constitute 
 the single oosphere. Access to the oosphere is afforded either by the per- 
 foration of the oogonium-wall, or by the partial breaking-away of the cell 
 immediately above the oogonium in the filament. The oosphere has a 
 well-marked receptive spot. The antheridia are formed, either in the 
 same or another filament as the species is monoecious or dioecious, by the 
 repeated transverse division of a cell of the filament ; in some species the 
 antheridium gives rise to a single spermatozoid, but in most it undergoes 
 division into two cells each of which produces a spermatozoid. The sper- 
 
 M.B. S
 
 258 
 
 PART IV. CLASSIFICATION. 
 
 \ 
 
 matozoids resemble the zoospores, but are smaller and are yellow instead 
 of green; they are set free, and finding their way to the oogonia, one 
 enters an oogonium and fertilises the oosphere, penetrating into it at the 
 receptive spot (Fig. 147). 
 
 In some species, termed gynandrosporous, the filaments produce no 
 antheridia, but only oogonia. Some of the cells of such a filament under- 
 go transverse division to form short cells which somewhat resemble 
 
 antheridia. The con- 
 tents of each of these 
 cells are set free as a 
 single zoospore, termed 
 an androspore, interme- 
 diate in size and colour 
 between the ordinary 
 zoospores and the sper- 
 matozoids, and resem- 
 bling them in form. 
 The androspore comes 
 to rest, attaching itself 
 to the wall of an oogon- 
 ium (Fig. 147), and ger- 
 minates, forming a 
 small filament, known 
 as a dwarf-male, which 
 consists of a root-cell 
 and two or three cells 
 above it; each of these 
 upper cells is an aiither- 
 idium, and its contents 
 are set free as a single 
 spermatozoid. 
 
 On germination, the 
 contents of the oospore 
 are set free as four 
 zoospores, each of which 
 develops into an (Edo- 
 gonium- plant. Fresh- 
 water plants : genera 
 CEdogonium, Bulbo- 
 chsete. 
 
 Order 5. Coleochae- 
 taceae. Body filamen- 
 tous, branched, forming 
 hemispherical or disc- 
 shaped cushions on sub- 
 merged stones or parts 
 of water - plants ; the 
 mode of growth is es- 
 
 FIG. 147. A (Eclogonium ciliatum (x 250). A Middle 
 part of a sexual filament with three oogonia (og) fertilised 
 by the dwarf-male plants (m), developed from androspores 
 formed in the cell TO at the upper part of the filament. 
 B Oogonium at the moment of fertilisation : o the 
 oosphere ; og the oogoninm ; z the spermatozoid in the 
 act of forcing its way in ; m dwarf-male plant. C Ripe 
 oospore. D Piece of the male filament of (Ed. gemelli- 
 porum, z spermatozoids. E Branch of a Bulbochcete, with 
 one oogoninm still containiog an oospore, another in the 
 net of allowing it to escape; in the lower part an empty 
 oojronium. F The four zoosporea formed from an oospore. 
 G Zoospore come to rest. (After Pringsheim.)
 
 GROUP I. THALLOPHYTA : ALG.E. 
 
 259 
 
 sentially apical, though in the discoid forms the apical cells consti- 
 tute a marginal series ; most of the cells eventually develop the peculiar 
 sheathing hairs which have suggested the name of the family. Fresh- 
 water : Coleochaete, the sole genus. 
 
 Any cell may set free its protoplasmic contents as a zoospore with two 
 cilia. 
 
 The sexual organs, oogonia and antheridia, are differentiated, especially 
 in the more distinctly filamentous forms. In the filamentous forms (e.g. 
 C. pulvinata, Fig. 148) the oogonia and antheridia are borne at the ends of 
 the branches ; the terminal cell of a branch enlarges to form an oogonium, 
 becoming spherical, and growing out into a long filament, the trichogyne ; 
 the antheridia are developed as small flask-shaped cells from the terminal 
 
 Fre. 113. Coleoc'KBte pidvinita (x.350: after Pringsheim). A Part of a sexual plant 
 bearing oogonia og (with trichogynes tr) and antheridia OH ; h hair?. B portion of 
 a plant in which a mnlticellnlar structure has been developed in each fertilized oogoninm. 
 C the isolated structure the investment of which is ruptured prior to the setting free of 
 zoospores. 
 
 cells of a filament. In the discoid forms (e.g. C. scutate), the oogonia and 
 antheridia are not terminal ; the oogonium is simply an enlarged 
 spherical cell and has no trichogyne ; the antheridium is simply a small 
 cell formed, in a group of four, by the division of one of the vegetative 
 
 ('(Us. 
 
 A single oosphere is formed in each oogonium, and a single spermatozoid 
 in each antheridium. The spermatozoids, on being set free, find their 
 way to the oogonia, and, entering by an opening in the wall (in the 
 trichogyne when it is present), reach the oospheres and fertilise them. 
 
 The effect of fertilisation is not only to cause the oosphere to become an
 
 260 
 
 PART IV. CLASSIFICATION. 
 
 oospore by clothing itself with a proper wall, but also to cause the neigh- 
 bouring cells to grow round the oogonium and form a compact cellular 
 investment for it. Surrounded by this investment, the oospore falls to 
 the bottom of the water, as the plant dies down, and undergoes a period 
 of quiescence. On germination it grows, splitting the investment, and 
 divides to form a small multicellular body, the existence of which shortly 
 comes to an end by the escape of the whole of the protoplasmic contents 
 of all the cells as zoospores, one from each cell (Fig. 148 6'). 
 
 Series V. CHAROIDE.E. The forms included in this series constitute but 
 a single order, the Characese. 
 
 Order I. Characeae. The stem is distinctly segmented into nodes and 
 internodes, the nodes being marked by the whorls of leaves which they 
 bear. It consists of a longitudinal series of elongated cylindrical cells, 
 each of which constitutes an internode, separated from each other by 
 transverse plates of small cells which are the nodes. In Chara, there is, 
 
 in addition, a cortex consist- 
 ing of rows of cells, sometimes 
 spirally twisted, produced by 
 a growth of the peripheral 
 cells of each node, both up- 
 wards and downwards, over 
 the internodes above and 
 below it. 
 
 All the cells contain small 
 discoid chloroplastids which 
 lie imbedded in the proto- 
 plasm immediately beneath 
 the cell-wall. The more in- 
 ternal portion of the proto- 
 plasmic layer shows the 
 movement known as cyclosis ; 
 the central portion of the 
 cell-cavity, when the cell is 
 fully grown, is occupied by a 
 large vacuole filled with cell-sap. Each cell contains a single nucleus 
 when young; but the long internodal cells, when old, are found to 
 contain many nuclei produced by the fragmentation of the original 
 nucleus. 
 
 The growth in length of the stem is unlimited, and is effected by means 
 of a hemispherical apical cell (Fig. 149). This cell undergoes repeated 
 division, a series of segments being cut off by transverse walls ; after a 
 segment has been cut off, the apical cell regains its normal size by 
 growth, then another segment is cut off, followed by renewed growth, and 
 so on. Each segment is immediately divided into two cells by a trans- 
 verse wall ; of these two cells the upper, in all cases, becomes a node, 
 dividing by vertical walls into the small cells, central and peripheral, of 
 which the node consists ; the lower, in all cases, becomes an internode ; it 
 does not divide, but simply grows in length. In Chara the young peri- 
 
 FIG. U9. Diagram of growing-point of stem of 
 Chara fragilis (x500, after Sachs): a apical cell; 
 segment lately cut off ; n 1 n 2 n 3 successive nodes ; 
 in 1 in 2 in 3 successive internodes ; I leaves ; c cortical 
 cells growing down over in 3 from n 3 .
 
 GROUP I. THALLOPHYTA : AUGJE. 261 
 
 pheral nodal cells keep pace with the growth of the internodal cells, 
 forming the cortex over them. 
 
 The leaves and branches of the stem are all developed from the cells of 
 the nodes ; the leaves spring in a whorl, one from each of the peripheral 
 cells of the node, and the branches are developed as buds in the axils of 
 one or more of the leaves of each whorl. 
 
 The mode of growth and general morphology of the leaf is essentially 
 the same as that of the main stem or one of its branches ; it grows by 
 means of an apical cell resembling that of the stem, and from the seg- 
 ments are formed nodes and internodes in regular succession ; from the 
 nodal cells of the leaf arise whorls of leaf-branches or leaflets. The only 
 fundamental difference between the leaf and the stem of the Characese is 
 that, whereas the apical growth of the latter is unlimited, that of the 
 former is limited ; the apical cell of the leaf at length ceases to' divide, 
 assuming a somewhat cylindrical form with a pointed tip. 
 
 The roots, with the exception of the first root of the embryo, are all 
 adventitious, being developed from the lower nodal cells of the stem. 
 They are simpler in structure than the stem or leaf, each consisting of a 
 colourless filament of long, narrow cells; the growth is apical, though the 
 apical cell is not specially differentiated as in the stem; the cells of the 
 root are connected in a peculiar manner, the contiguous ends of the two 
 cells having each somewhat the shape of the sole of a human foot ; root- 
 branches are developed from that portion of the cell, just above the articu- 
 lation, which corresponds to the heel ~>f the foot. 
 
 The sexual organs (Fig. 150) are in all cases borne on the leaves ; the 
 antheridium is developed from the terminal cell of a leaf or of a leaflet ; 
 the oogonium replaces a leaflet. The plant may be either monoecious or 
 dioecious. 
 
 The antheridium is a spherical body, of a green colour when young, but 
 orange when mature, borne on a stalk. Its wall consists of eight cells, 
 each of which is termed a shield, presenting marginal infoldings of the 
 wall ; the wall of the upper half of the antheridium consists of four tri- 
 angular shields ; that of the lower half consists likewise of four triangular 
 shields, each of which has its lower angle truncated to admit of the 
 passage of the stalk-cell. On the inner surface of each shield, at its 
 centre, is attached a cylindrical cell, the manubrium, which extends to 
 near the centre of the antheridium. Each manubrium bears at its inner 
 end a somewhat spherical cell, the capitulum. To each capitulum are 
 attached usually six rounded cells, the secondary capitula. Connected with 
 each secondary capitulum are two cells, each of which bears a pair of long 
 filaments, each filament consisting of about two hundred cells. The cells 
 of the filaments are the mother-cells of the spermatozoids, each cell giving 
 rise to a single spermatozoid. 
 
 The male cell or spermatozoid consists of a club-shaped spirally-wound 
 mass of protoplasm bearing two long cilia at its pointed anterior end. 
 When the antheridium is mature the shields separate, the spermatozoids 
 are set free from their mother-cells and escape into the water. 
 
 The oogonium is the enlarged terminal cell of the leaflet which it repre-
 
 262 
 
 PART IV. CLASSIFICATION. 
 
 sents. Beneath, the oogonium proper is a node, the central cell of which 
 constitutes the stalk-cell of the oogonium, whilst the five peripheral cells 
 of the node grow out into filaments which gradually become spirally 
 twisted and enclose the oogonium ; the tips of these filaments project at 
 the free end of the oogonium, constituting the crown or corona, and are cut 
 off from the rest of the filaments either by one transverse wall, so that the 
 
 FIG. 150. CTiarafragilis, reproductive organs (after Strasburger). A Median longitu- 
 dinal section through a leaf (gametophyll) r, and the sexual organs which it bears; a an- 
 theridium, borne on a nodal cell na by the stalk-cell p ; m the manubria ; ob an oogonium, 
 borne on a nodal cell no and an internodal stalk-cell po ; c corona (all x 90). B spermato- 
 zoids(x540).
 
 GROUP I. THALLOPHYTA : ALG.E. 
 
 crown consists of five cells as in the Chareae, or by two transverse walls, 
 so that the crown consists of ten cells as in the Nitelleae. Each oogonium 
 contains a single oosphere, a nucleated mass of protoplasm containing 
 starch-granules, with a well-marked clear area, the" receptive spot, at the 
 apical end. 
 
 At the time of fertilisation, the cells of the crown separate so as to form 
 a channel leading to the apex of the oogonium. The wall of the oogonium 
 is not ruptured, but it becomes mucilaginous. The spermatozoids enter 
 the channel and reach the apex of the oogonium; one of them makes its 
 way through the mucilaginous cell-wall, and, entering the oosphere at 
 the receptive spot, fertilises it. 
 
 After fertilisation, the oosphere becomes 
 an oospore, surrounding itself with a 
 proper wall. The more internal walls of 
 the investing filaments become thickened, 
 and assume a dark brown colour. The 
 whole organ falls off and undergoes a 
 period of quiescence. 
 
 On germination, the oospore does not at 
 once give rise to an ordinary Chara plant. 
 It produces, in the first instance, an em- 
 bryo, consisting of a filamentous root and 
 a shoot of limited growth. The adult 
 form is developed upon the embryo by the 
 development of a lateral growing-point at 
 the node of the embryonic shoot (see Fig. 
 151). Fresh water. 
 
 Sub- Class III. PILEOPHYCE.E, or 
 Brown Algae. The body may consist 
 of a single cell (e.g. Diatomaceae), but 
 is generally multicellular. When 
 multicellular, it presents various de- 
 grees of morphological differentiation, 
 being usually differentiated into shoot 
 and root, and in some cases (e.g. 
 Cladostephus, Sargassum) into stem, 
 root, and leaf. 
 
 Vegetative multiplication is com- 
 mon in the unicellular forms, in which 
 
 it is effected by division ; in a few forms (e.g. species of Sphace- 
 laria) it is effected by means of gemmae. 
 
 In all but the lowest forms there is a distinction between re- 
 productive and vegetative cells, the former developing into more 
 or less highly differentiated reproductive organs. 
 
 I'iG. 161. Chara frag His (after 
 Pringsheim: x 4). Embryogeny: 
 ap apical portion of shoot of the 
 embryo ; r primary root of embryo, 
 springing from the oospore ; tr 
 adventitious roote,; I leaves, 
 amongst which lies the growing- 
 point of the adult shoot; i inter- 
 mediate cell.
 
 264 PART IV. CLASSIFICATION. 
 
 Asexual reproduction is effected by means of spores, either zoo- 
 spores (as in the Phseosporese), or non-motile spores (as in some 
 Phseogamte). The spores are developed either singly, or more 
 commonly several together, in unicellular (and also necessarily 
 unilocular) sporangia. 
 
 Sexual reproduction is either isogamous or oogamous : when 
 isogamous, it may be effected by aplanogametes (Diatomacese), 
 but more commonly by planogametes (Phseosporese) which usually 
 resemble each other ; but in some cases (e.g. species of Ectocarpus, 
 Cntleriacese) they are of two kinds, differing in size and in the 
 duration of their movement, the one which is smaller and more 
 active being the male ; when oogamous, it is effected by means of 
 spermatozoids and oospheres, and is peculiar in that the oospheres, 
 though not ciliated, are extruded from the female organ before 
 fertilisation takes place. The sexual plants may be monoecious 
 or dioecious. The sexual organs, in the isogamous forms, are 
 gametangia, sometimes unicellular (Diatomacese) but more com- 
 monly multicellular (Phseosporese) : in the latter case each cell of 
 the gametangium gives rise either to a single planogamete or 
 to several : they are in most cases all alike, though some (e.g. in 
 species of Ectocarpus, Cutleriacese) consist of smaller and more 
 numerous cells than the others and give rise to the smaller 
 planogametes. In the oogamous forms, the oogonium is unicel- 
 lular, giving rise to one or more (2-8) oospheres : the antheridium 
 is sometimes multicellular, but it is unicellular in the Fucacese ; 
 in the former case each cell gives rise to a single spermatozoid, in 
 the latter several spermatozoids are developed in the one cell. 
 
 Of the motile reproductive cells of this sub-class, the zoospores 
 and the planogametes contain chromatophores, and have two cilia 
 inserted laterally ; the spermatozoids, however, have no chromato- 
 phores, nor have the smaller planogametes in those cases in which 
 the conjugating planogametes differ in size ; the oosphere has no 
 receptive spot. 
 
 The following groups of the Phseophycese will be considered : 
 Unicellular Forms : 
 
 Order Diatomaceae: sexual reproduction isogamous by aplanoga- 
 metes. 
 
 Multicellular Forms : 
 
 Series (a) PHJEOSPORE^E : sexual reproduction isogamous by planoga- 
 metes ; asexual by zoospores. 
 Order Ectocarpaceae (Ectocarpus, Sphacelaria, Cladostephus, etc.).
 
 GROUP I. THALLOPHYTA : ALG.E. 
 
 265 
 
 Order Laminariacese (Laminaria, Alaria, Chorda, etc.). 
 Order Cutleriacese (Cutleria Zanardinia). 
 
 Series (l>) PH^OGAM^E : sexual reproduction oogamous; asexual, want- 
 ing, or by non-motile spores. 
 Order Fucacese. 
 
 Order Diatomaceae. Unicellular plants, either free, or connected into 
 filaments or masses by mucilage; sometimes attached. Reproduction, 
 vegetative by division; or by means of asexual ly produced spores; or 
 sexual isogamous by the conjugation of aplanogametes. The cell-wall is 
 impregnated with silica. Both fresh-water and marine. 
 
 The Diatomaceae resemble the Desmidiese in many respects; the two 
 orders are, in fact, corresponding forms in the Phseophycese and the 
 Chlorophycese respectively ; but, besides their colour, the Diatoms differ 
 from the Desmids in the presence of silica in their cell-wall. 
 
 The cell, or frustule, as it is called, is enclosed by a rigid wall. The 
 wall, like that of the Desmids, consists of two 
 halves, called valves, of different ages ? whiph 
 are not directly continuous, but are related to 
 each other as the two parts of a pill-box, the 
 one overlapping the other (Fig. 152). The 
 cell-contents consist of a more or less vacuo- 
 lated mass of protoplasm, which forms a laj-er 
 in close contact with the inner surface of the 
 cell-wall ; in this there is a nucleus, sometimes 
 parietal sometimes central, and chromato- 
 phores which may be very numerous and 
 small, or few in number (sometimes only one) 
 in the form of relatively large plates. 
 
 Vegetative multiplication by division takes 
 place by the division of the protoplasm into 
 two cells; each of these cells has one of the 
 two valves of the parent frustule on one side 
 of it ; it then secretes a new valve on its naked 
 side, which is smaller than the older valve and 
 fits inside its rim; thus two new individuals 
 are formed. 
 
 It will be noted that this process of multiplication is accompanied by a 
 decrease in size ; and, were it repeated indefinitely, the cells would become 
 very small. This process of diminution is interrupted by the formation 
 of auxospores, either asexually or sexually. In the former case the pro- 
 toplasmic contents of a cell escape from the separated valves, as an auxo- 
 spore, which, after growing considerably, secretes two new valves forming 
 a n.-w and larger frustule. In the latter case, two naked cells which have 
 thus escaped, conjugate to form an auxospore which becomes a new 
 frustule. This process of conjugation differs, however, from that of the 
 Desmidiese, in that no resting zygospore is formed, but simply a new 
 individual. 
 
 Series PH^EOSPOEE^. The multicellular body is attached; it some- 
 
 FiG.162. Pinnularia, a Dia- 
 tom (mug. and diag.); lateral 
 view, showing the mode of 
 connection of the two halves 
 of the frnstule; s surface view.
 
 PART IV. CLASSIFICATION. 
 
 times consists of a flattened dorsiventral branched filament, the branches 
 of which are often coherent into a disc which adheres to the substratum 
 by the ventral surface and bears vertical shoots on its dorsal surface (e.g. 
 Ectocarpus, Myrionema, Pylaiella) ; the body is frequently more or less 
 clearly differentiated into root and shoot, and in some cases (e.g. Clado- 
 stephus, Cheetopteris) the shoot is differentiated into stem and leaf ; adven- 
 titious roots are very generally developed. 
 
 The body presents a considerable variety of structure. In the simplest 
 forms (e.g. Ectocarpus, etc.) it is filamentous and branched, the filament con- 
 sisting of a single row of cells (monosiphonous) ; in others it is filamentous, 
 consisting of several coherent longitudinal rows of cells (poly$iplionous}\ 
 in the most highly developed forms it consists of parenchymatous tissue 
 frequently differentiated into a small-celled cortex and a medulla of large 
 
 cells elongated parallel to 
 the long axis of the plant 
 (e.g. Laminariacese). 
 
 Growth in length may 
 be effected without a de- 
 finite growing-point, all 
 the cells being merismatic 
 (e.g. generally in Ectocar- 
 pacese) ; or there may be 
 a definite growing-point, 
 which may be apical, with 
 an apical cell (e.g. Sphace- 
 lariese) ; or the growing- 
 point may be intercalary, 
 either sub - apical (e.g. 
 Chordaria), or more or 
 less basal (e.g. Laminari- 
 acese). The division of 
 the apical cell, or of the 
 initial cells, of the grow- 
 ing-point takes place only 
 
 Fia. 153. - Longitudinal section through three inter- 
 nodes of a sexual plant of Cladostephus verticillatus 
 (Ectocarpaceae) : a gametophyll ; the larger appendages 
 are foliage-leaves. (x60: after Pringsheim.) 
 
 in one plane, the transverse. The segments thus formed undergo division 
 either only transversely (monosiphonous forms), or longitudinally (poly- 
 siphonous), or in several planes. 
 
 The sporangia are in all cases unicellular. In the simple filamentous 
 forms they are somewhat enlarged and rounded cells, either intercalary in 
 position (e.g. Pylaiella), or terminal, occupying the place of a lateral 
 branch, and generally sessile (e.g. Ectocarpus, etc.). In the more bulky 
 thalloid forms, the sporangia may be merely developments of single 
 superficial cells (e.g. Laminariacese) scattered singly or in groups (sori) 
 over the whole surface. In others again they are borne as lateral branches 
 on hair-like outgrowths from the superficial cells. In certain cases, where 
 the shoot presents differentiation into stem and leaf (e.g. Cladostephus), 
 the sporangia are borne on specialised leaves, sporophylls (Fig. 154). 
 
 The gametangia are in all cases multicellular. each cell constituting a
 
 GROUP 1. THALLOPHYTA : ALG.E. 
 
 267 
 
 loculus which gives rise to one or more planogametes. In their distribu- 
 tion and general morphology they resemble the sporangia. The game- 
 tangia of any one species are, as a rule, all exactly alike, but in some few 
 cases they present two forms which differ in the size, "and consequently in 
 the number, of their constituent cells (e.g. Ectocarpus fenestratus and E. 
 secundus, Cutleriacese) ; the small-celled gametangia are considered to be 
 the male, and the large-celled the female organs. The plants may be 
 monoecious or dioecious (Cutleria). 
 
 The zoospores and the planogametes are generally all very much alike : 
 in Cutleria, however, and in those species of Ectocarpus which have two 
 kinds of gametangia, the one kind of planogamete (female) is considerably 
 
 PIG. 151. Fertile leaves of Cladostephus vertivillatus: A sporopbyll ; one of the uni- 
 cellular sporangia has discharged its zoospores with a mass of mucilage ; B gametophyll, 
 bearing the multicellular gametangia. (x280: after Pringsheim.) 
 
 larger than the other (male), and has a shorter period of motility ; the 
 smaller planogametes are developed in the small-celled gametangia. A 
 sexual process has been observed in but few cases (Ectocarpus silicuiosus, 
 Scytosiphon lamentariiis, Cutleria). In the two former the planogametes 
 are externally similar, but they behave differently in the process of con- 
 jugation, some coming to rest earlier than others, thus indicating that 
 they are female. When the female plauogamete is at rest, it is approached
 
 208 
 
 PART IV. CLASSIFICATION. 
 
 by a number of the still motile male planogametes (Fig. 155), one of which 
 fuses with it. In Cutleria the larger planogamete soon comes to rest, and 
 then one of the smaller planogametes fuses with it. In Ectocarpus silicu- 
 losus the zygospore gives rise to a plant which resembles its parents : it 
 has been observed that, if the planogametes fail to conjugate, they are 
 capable of germinating independently. 
 
 The Phseosporese are almost exclusively marine, the only fresh-water 
 forms being the genus Pleurooladia (Ectocarpacese) and two species of the 
 genus Lithoderma. The size of the plants included in this series varies 
 widely, from microscopic Ectocarpacese to gigantic tree-like Laminariacese, 
 such as Macrocystis, Nereocystis, etc., which may attain a length of 
 geveral hundred feet. In some of the 
 Laminarias, which have cylindrical 
 stalk-like region in their thalloid 
 shoot, secondary growth in thickness 
 takes place by means of a merismatic 
 layer. In these large forms too, the 
 conducting tissue is sometimes so far 
 developed as to form sieve-tubes; 
 though no woody tissue is developed, 
 nor is it required in view of the fact 
 that these plants live submerged. 
 
 Series PH^EOGAM^E. The orders 
 comprised in this group are character- 
 ised by the oogamous sexual process. 
 
 Order Fucaceae. Body differ- 
 entiated into root and shoot; shoot 
 usually thalloid, either cylindrical or 
 flattened ; differentiated into stem and 
 leaves in Sargassum ; growth in length 
 by a single apical cell; branching 
 generally dichotomous. No asexual 
 production of spores. Sexual organs, 
 unicellular antheridia and oogonia; 
 spermatozoids, ciliated, formed several 
 together in the antheridium : odspheres, 
 set free but not ciliated; one (Py- 
 cnophycus, Himanthalia), two (Pel- 
 vetia), four (Ascophyllum), or eight 
 (Fucus) formed in each oogonium. 
 Marine. 
 
 The body consists of what may be termed cortical and medullary tissue. 
 The cortical tissue consists of closely-packed parenchymatous cells, the 
 external layer of which, the limiting layer, is for a time merismatic, and 
 plays an important part in the growth of the body. The medullary tissue 
 consists of filamentous rows of cells the walls of which are mucilaginous 
 and much swollen. The cortex is essentially the assimilatory tissue and 
 the medulla the conducting tissue. 
 
 Fio. 155. Sexual process in Ecto- 
 carpus siliculosus : I a-/, female piano- 
 gamete coming to rest: II resting 
 female planogamete suspended from 
 the surface of the water, with numerous 
 motile male planogametes : III con- 
 jugation of a male and a female 
 planogamete. (x790: after Berthold.)
 
 GROUP I. THALLOPHYTA : ALG.E. 
 
 269 
 
 In some of these plants (e.g. Fucus vesiculosus, Ascophyllum, Halidrys, 
 Cystoseira, Sargassum) there are large intercellular spaces, filled with air, 
 which project on the surface, and are known as air-bladders ; they serve as 
 floats. In Halidrys and Sargassum the air-bladders -are borne on special 
 branches. 
 
 The sexual organs are in all cases borne in depressions of the surface 
 known as concepfades (Fig. 157). The conceptacles are commonly confined 
 to special portions of the thallus ; either to the tips of the branches (e.g. 
 
 FIG. 166. Pucus vetieulosMS, about half nat. size : b air-bladders j / fertile branch. 
 
 Fucus, Cystoseira) or to special branches, the gametophores (e.g. Himau- 
 thalia, Ascophyllum). From the inner surface of the conceptacle there 
 arise a number of hairs (pqraphyses) among which the sexual organs 
 are borne. The oogonia (Fig. IBS) are nearly spherical, and are borne on a 
 short stalk consisting of a single cell ; the antheridia (Fig. 158) are the 
 lateral branches of some of the hairs. The plants may be monoecious 
 (e.g. Fucus piatgcarptu, Halidrys, Pelvetia, Cystoseira), or dioecious (e.g. 
 Himanthalia, Ascophyllum, Fucus vesiculosus and serratus); in the former 
 case each conceptacle contains both antheridia and oogonia.
 
 270 
 
 PART IV. CLASSIFICATION. 
 
 The oospore, which is the product of the fertilisation of an oosphere, 
 germinates without any period of quiescence. It first becomes somewhat 
 pear-shaped ; it is then divided into two by a transverse wall ; the more 
 pointed of the two cells forms the primary root, whilst the other gives 
 rise to the shoot (Fig. 158 d). 
 
 FIG. 157. Section of a female conceptacle, with surrounding tissue, of Fucus tjesicutosus. 
 (x50: after Thuret.) 
 
 FIG. 163. Fucus vesiculosus. a Paraphysis, from male conceptacle, bearing antheridia ; 
 b an oogonium (with paraphyses), showing division of its contents to form eight oospheres ; 
 c process of fertilisation, an extruded oosphere surrounded by spermatozoids; d develop- 
 ing embryo. (x!60: after Thuret.)
 
 GROUP I. THALLOPHYTA : ALG.E. 271 
 
 Sub-Class IV. RHODOPHYCE.E (FLORIDELE) or Red Algae. Multi- 
 cellular plants ; body, generally differentiated into shoot and root ; 
 shoot, sometimes differentiated into stem and leaf ; flattened or 
 filamentous ; when filamentous, consisting of a single longitu- 
 dinal row of cells (monosiphonous} or of several rows (polysi- 
 phonous") with or without a small-celled cortex , the filamentous 
 forms grow by means of a single apical cell from which segments 
 are cut off either by transverse walls, or by oblique walls alter- 
 nately right and left ; the flattened forms grow by means of a 
 marginal series of initial cells ; but in the Bangiacese there is 
 no growing-point, all the cells being merismatic : branching, 
 generally monopodial, but sometimes sympodial (eg. Plocamium, 
 Dasya) ; adventitious roots common. 
 
 Vegetative reproduction by gemmae (e.g. Monospora, Melobesia) 
 is rare. 
 
 The plant, as a rule, produces tetrasporcs asexually, but they are 
 usually not borne on individuals which produce sexual organs, 
 but on distinct individuals, though there are exceptions to this 
 rule (e.g. Lomentaria kaliformis, Callithamnion corymbosum, 
 Polysiphonia variegata, etc.). 
 
 The spores are produced in unilocular sporangia, either singly, 
 or two together, or sometimes as many as eight, but most commonly 
 in fours; hence they are generally termed tctraspores. They 
 may be formed t etrahedrally ; or by transverse divisions, when 
 they are said to be zonate ; or by two divisions at right angles 
 to each other, when they are said to be cruciate. 
 
 The arrangement of the sporangia on the shoot is various. In 
 simple monosiphonous forms (e.g. Callithamnion) the terminal 
 cells of short lateral branches become sporangia. In forms of 
 more complex structure the sporangia are developed internally, 
 within the superficial layer of tissue. The sporangia may be 
 scattered over the surface of the shoot, or collected into special 
 receptacles of various forms. In some cases (e.g. some Rhodome- 
 lacese, such as Polysiphonia) the sporangia are confined to certain 
 specially modified branches which are termed sticliidia. The tetra- 
 sporas are set free as spherical unciliated cells without a cell- wall. 
 
 The sexual organs are antheridia and procarps ; they are usually 
 borne by distinct individuals, but in some cases on the same (e.g. 
 Grateloupia, Halymenia, Halarachnion, Xemastoma, Dudresnaya 
 ciccinea &n& purpurifcra, Glceosiplionia capillaris, ITelminthora 
 dicaricata}.
 
 272 
 
 PART IV. CLASSIFICATION. 
 
 The antheridia are small and unicellular ; in the simple fila- 
 mentous forms they occur singly or in groups at the ends of the 
 branches ; in others of more complex structure, they are produced 
 in special receptacles (e.g. Corallinacese) ; in the flattened paren- 
 chymatous forms they occur in groups on the surface ; in those 
 forms in which the shoot is differentiated into stem and leaf (e.g. 
 some Rhodomelacese such as Polysiplionia fastigiata and nigre- 
 scens, Chondriopsis tcnuissima) the antheridia are confined to 
 the leaves, the whole or part of the leaf being specially modified 
 for this purpose. The male cells (spermatia) are formed singly 
 in the antheridia, and are set free as 
 small, spherical or oval, unciliated cells 
 destitute of a cell-wall ; they acquire a 
 cell-wall at the time of fertilisation ; 
 they contain no chromatophores, except 
 in Bangiacese. 
 
 The procarp presents considerable 
 variety of form and structure. It may 
 be unicellular (e.g. Bangiacese, Chan- 
 transia, Batrachospermum, Lemanea, 
 Nemalion), or multicellular, as is more 
 commonly the case. The unicellular 
 procarp consists simply of a carpo- 
 gonium prolonged (except perhaps in 
 Bangia) into a filament termed the tri- 
 chogync. Various descriptions are given 
 of the structure of the multicellular pro- 
 carp ; however, it appears to consist 
 essentially of a unicellular carpogonium 
 (with a trichogyne) together with one or 
 more specially differentiated auxiliary 
 cells. In some cases (e.g. Dudresnaya 
 coccinea, Squamariacese), the carpogonium and the auxiliary cells 
 are not developed in the same procarp, but in distinct organs. 
 
 Whether the procarps be unicellular or multicellular, the carpo- 
 gonia agree in that the trichogyne remains closed, and further, 
 in that the protoplasm of the carpogonium does not undergo re- 
 juvenescence to form a distinct female cell (oosphere) as is the 
 case in the oogamous Algae (see p. 241). 
 
 The carpogonium is (except in the Bangiacese) developed from 
 the terminal cell of a lateral appendage; in some cases (e.g. 
 
 FIG. 159. Portion of a branch 
 of Dosya elegans, bearing a 
 slichidium (), with tetrahedral 
 tetrasporangia (t); V empty 
 tetrasporangium. (x 25 ; 
 after Kutzing.)
 
 GROUP I. THALLOPHTTA : ALG^E. 273 
 
 Polysiplionia fastigiata and nigrcscens) the lateral appendage is a 
 leaf, the whole or part of which goes to form the procarp ; in the 
 Corallinacese the procarps are aggregated in receptacles. 
 
 The sexual process consists in the fusion of the protoplasmic con- 
 tents of a spermatium with those of a trichogyne. The sperina- 
 tium is brought by the water into contact with the projecting 
 trichogyne to which it adheres, the spermatium being at this 
 time covered with a cell-wall; the intervening cell- walls are 
 absorbed at the point of contact, and the protoplasm of the sper- 
 matium enters the trichogyne. 
 
 The product of fertilisation is a fructification termed a cysto- 
 carp, consisting of a number of 
 carposporangia. The cystocarp 
 is developed either directly or 
 indirectly from the carpogonium : 
 directly, when the procarp is uni- 
 cellular ; indirectly, when it is de- 
 veloped from both carpogonial and 
 auxiliary cells : the trichogyne 
 takes no part in the development 
 of the cystocarp, being shut off by 
 a septum. 
 
 The simplest mode of direct 
 formation of the cystocarp occurs 
 in the Bangiacese ; the cavity of the 
 carpogonium becomes chambered, 
 by the formation of cell- walls, into 
 usually eight cells, each of which 
 is a sporangium, giving rise to a 
 carpospore : only a single spore is 
 formed in the genus Erythrotrichia. 
 In other cases of direct formation 
 (e.g. Nemalion, Batrachospermum), 
 the carpogonium gives rise to a 
 number of filaments, termed oo- 
 blastema-filaments, which bear a 
 cluster of sporangia (Fig. 160). 
 
 In the indirect formation of the cystocarp, the carpogonium 
 fuses with one or more of the auxiliary cells. In the simplest 
 case (e.g. G-igartinacese, Rhodymeniaceae), the carpogonium fuses 
 directly with the auxiliary cell (or cells), and from the latter the 
 
 M.B. T 
 
 FIG. 160. Sexual organs of Nemalion 
 ( x 300). A. lends of branches bearing a 
 unicellular procavp t-o, and a group of 
 antheridia s ; the trichogyne (t) of the 
 procarp has two spermatia () adhering 
 to it. B early stage in the development 
 of the cystocarp ; the fertilised carpo- 
 gonium is undergoing growth and 
 division. C nearly mature cystocarp, 
 consisting of a number of short fila- 
 ments each terminating in a carpospo- 
 rangium. The development of the 
 cystocarp is direct.
 
 274 
 
 PART IV. CLASSIFICATION. 
 
 sporangia, or filaments bearing sporangia, are formed. In other 
 cases the carpogonium gives rise to one or more elongated, branched, 
 ooblastema-filaments which fuse with one or more auxiliary cells, 
 and the sporangia are produced either from the ooblastema- 
 filaments (e.g. Gelidiacese) or from the auxiliary cells (e.g. Squama- 
 riacese and other Cryptoneminse). 
 
 In the Corallinacese, where the procarps are aggregated in re- 
 ceptacles, only a single cystocarp is formed from the whole group 
 of procarps. Some of the procarps appear to be altogether abor- 
 tive, and only those toward the centre of the group have tricho- 
 gynes, whilst others seem to have only auxiliary cells : after 
 
 Fio. 161. Sexual organs of Spermothamnion Hennaphro&itwn. A Male and female organs ; 
 c multicellular procarp ; t trichogyne ; V trichophore ; on terminal cluster of antheridia. 
 B cystocarp developing from the fertilised procarp ; a cluster of carposporangia is 
 springing from each of the two opposite lateral auxiliary cells. The development of the 
 cystocarp is indirect ( x 300 ; after Naegeli). 
 
 fertilisation, the carpogonia of the central procarps fuse with 
 each other, and with the auxiliary cells of the other procarps, 
 forming a large cell from the periphery of which the corpo- 
 sporangia, constituting the cystocarp, are developed. 
 
 In many cases the cystocarp consists merely of the cluster of 
 sporangia (e.g. Bangia, Chantransia, Callithamnion, Dudresnaya) ; 
 in other cases the cluster of sporangia is surrounded by a cellular 
 investment, termed the pericarp, formed by the growth of adjacent 
 sterile cells. 
 
 Each sporangium always gives rise to a single carpospore, which
 
 GROUP I. THALLOPHYTA : FUXGI. 275 
 
 is set free as a somewhat spherical unciliated cell destitute of a 
 cell- wall, and germinates without any quiescent period. 
 
 The germination of the tetraspores and of- the carpospores has 
 only been followed in a few cases. Generally speaking the spore 
 becomes elongated in form, and is attached by the more pointed 
 end which is almost colourless ; division by a transverse wall then 
 takes place ; the elongated attached cell developes into the root, 
 the other into the shoot. 
 
 The Rhodophyceae are almost exclusively marine ; the only 
 fresh-water forms are Batrachospermum, Lemanea, and species of 
 Chantransia, Bangia, and Hildenbrandtia. 
 
 CLASS II.-FUNGI. 
 
 This class, like the preceding, includes many very simple 
 organisms, as well as others of tolerably high development. None 
 of them contain chlorophyll ; hence they cannot assimilate so 
 simple a carbon-compound as carbon dioxide, but must take up 
 their carbonaceous food in the form of rather complex compounds, 
 and their structure and mode of life are correlated with this 
 peculiarity (see p. 189). Some are parasites, such as the Rusts and 
 Smuts, and absorb these complex carbon-compounds from other liv- 
 ing organisms, whether plants or animals. Others are saprophytes, 
 absorbing these compounds from the remains of dead organisms, 
 or from organic substance formed by living organisms ; the numer- 
 ous and often large Fungi which grow on humus or leaf-soil in 
 forests, or on the bark of trees, are examples of the former case ; 
 the Yeasts and Moulds which make their appearance on juicy 
 fruits, saccharine liquids, etc., are examples of the latter. Some 
 Fungi are symbiotic ; that is, they live in intimate relation 
 (symbiosis) with plants which possess chlorophyll, and obtain 
 from them the necessary carbonaceous food, but without destroy- 
 ing, or apparently injuring them. They commonly live with 
 Algae, forming Lichens ; or in connexion with the roots of trees 
 (esp. Cupuliferae) and of Orchids, Leguminosae, and other plants, 
 or with prothallia (e.g. Lycopodium), forming what is known as 
 Mycorhiza. 
 
 The vegetative body may be unicellular, or coenocytic. In the 
 former case it is small and rounded or rod-shaped in form. In 
 the latter case the body is always a mycelium, consisting of more 
 or less branched filaments, termed hyphce. The mycelium may be
 
 276 PART IV. CLASSIFICATION. 
 
 unseptate, as in the Phycomycetes, in which case the body re- 
 sembles in structure that of the Siphonaceae among the Green Algae 
 (see p. 250 1. Or the mycelium may be septate, as in the higher 
 Fungi, in which case it appears to be always incompletely septate ; 
 that is to say, the segments of the hyphae which are marked out by 
 the transverse septa, are not cells, each with a nucleus, but contain 
 several nuclei, and are coenocytes (as in the Cladophoraceae among 
 the Chlorophyceae). The hyphae grow in length at the apex in 
 the manner of such Algae as Vaucheria and Cladophora (see 
 p. 239). 
 
 In some of the more complex forms, the hyphae of the repro- 
 ductive organs form compact masses of tissue of a somewhat 
 parenchymatous appearance, in which there is no differentiation 
 of tissue-systems, but the superficial layers of hyphae form a kind 
 of tegumentary tissue, termed generally cortex. Considerable 
 differences in the nature of the cell-wall may obtain in different 
 parts of such organs, some walls being soft and mucilaginous, 
 whilst others are relatively hard without, however, ever being lig- 
 nified. In a few Mushrooms (e.g, Lactarius) some of the hyphae 
 form a system of laticiferous tissue, and in others glandular struc- 
 tures occur. 
 
 Except in the simplest forms, the body is generally more or less 
 clearly differentiated into root and shoot. These members can be 
 distinguished partly by their relative position, the root-hyphae 
 growing into the substratum, and the shoot-hyphae into the air ; 
 and partly by the fact that the shoot-hyphse bear the reproductive 
 organs. Some parasitic forms have root-like organs, termed 
 haustoria, which penetrate into the cells of the host ; similar 
 organs occur in some saprophytes, and in others (e.g. crustaceous 
 Lichens) the roots (sometimes called rhizines) consist of bundles of 
 hyphae. There is in no case any differentiation of the shoot into 
 stem and leaf. 
 
 The foregoing account does not apply to the body of the Myxomycetes, 
 which consists of a multinucleate mass of protoplasm, termed a plas- 
 modium, without any cell-wall. It is formed by the cohesion of a 
 number of small, originally independent amoeboid cells, like that of the 
 Hydrodictyacese among the Algae (see p. 253). 
 
 Vegetative propagation is common among the Fungi. The 
 simplest form of it is simple cell-division (e.g. Schizomycetes), or 
 that form of cell-division known as budding or sprouting (gemm-
 
 GROUP I. THALLOPHYTA : FUNGI. 277 
 
 at ion) (e.g. the Yeast-forms of various Fungi). It is effected in 
 some cases (e.g. in some Zygomycetes, Ascomycetds, and Basi- 
 diomycetes) by unicellular gcmmce of various .sizes (termed chlamy- 
 dospores when they are relatively large and thick -walled; and 
 are adapted for a period of quiescence ; oidium-cells, when they are 
 small and thin-walled and capable of immediate germination) 
 which are formed by the segmentation of a hypha by transverse 
 septa into short cells which become somewhat rounded and separate 
 from each other ; on germination, each may give rise to a mycelium. 
 In other cases (e.g. many Ascomycetes, such as the Sclerotiniese, 
 Pezizese, Claviceps, etc. ; some Basidiomycetes, such as Coprinus 
 stcrcorarius, species of Typhula and Agaricus), it is effected by 
 bodies termed sclcrotia ; each sclerotium consists of a compact 
 mass of hyphge, filled with reserve materials, covered by a cortex 
 of one or more layers of tissue, which are thick- walled and of a 
 dark colour. They become detached from the mycelium on which 
 they are formed, and are capable of retaining their vitality during 
 a long dormant period ; on germination they give rise to shoots 
 bearing reproductive organs. A form of sclerotium is found also in 
 the Myxomycetes. Here it consists of a plasmodium, or a part of 
 a plasmodium, which has surrounded itself with a membrane, and 
 remains for a longer or shorter time in a dormant condition : 
 the individual amoeboid cells may also surround themselves with 
 a membrane and remain dormant, in the form of microcysts. 
 
 Reproduction is effected sexually or asexually. A sexual process 
 takes place in the Zygomycetes, in the Peronosporacese, and in 
 some Ascomycetes. 
 
 The modes of the sexual process are the following : 
 
 I. Isogamy : sexual cells, similar aplanogametes which are not 
 set free ; process, conjugation ; product, a zygospore ; Zygomy- 
 cetes. 
 
 II. Heterogamy: 
 
 a. Oogamy : sexual cells, oospheres and undifferentiated male 
 
 cells ; process, fertilisation ; product, an o'ospore ; Peron'o- 
 sporacese. 
 
 b. Carpogamy : no differentiated female cell ; female orga'ri 
 
 fertilised by the undifferentiated contents of the male organ 
 or by differentiated male cells, spermatia : product, a fructifi- 
 cation termed an ascocarp : all the forms in which this 
 mode occurs belong to the Ascomycetes.
 
 278 PART IV. CLASSIFICATION. 
 
 There is no sexual process in the Schizomycetes, the Myxomy- 
 cetes, in some of the Phycomycetes (Saprolegniacese), the great 
 majority of the Ascomycetes, the vEcidiomycetes, and the Basidi- 
 omycetes. In the Schizomycetes and Myxomycetes, the absence 
 of a sexual process may be attributed to their rudimentary charac- 
 ter ; in the higher groups it is due to sexual degeneration. In 
 the Saprolegniacese, female and, generally, male organs are deve- 
 loped, but the male organs are functionless ; still the female organs 
 produce oospores. In the majority of the apparently sexual 
 Ascomycetes, even when both kinds of sexual organs are present 
 (e.g. Erysiphese, Penicillium, Sordaria) it is a question if any sexual 
 process takes place : yet in all these cases an ascocarp is pro- 
 duced, either from the female organ or from the mycelium. 
 
 The sexual organs, with the exception of those of some Ascomy- 
 cetes, are unicellular. They are either quite similar to each other, 
 as in the Zygomycetes and some Ascomycetes (e.g. Eremascus), 
 when they may be termed gainetangia ; or they may be more or 
 less differentiated, as in the Oomycetes, and in some Ascomycetes 
 (e.g. Erysiphese, etc.), as male and female. 
 
 The male organ is a pollinodium in the Oomycetes and in some 
 Ascomycetes (e.g. Pyronema, Erysiphese, Ascobolus) ; it is generally 
 unicellular but sometimes multicellular (e.g. Ascobolus). As it is 
 developed in close proximity to the female organ, fertilisation is 
 effected, in these forms, by absorption of the cell- walls at the 
 point of contact of the two organs, or the development of a tube 
 placing their cavities in communication. 
 
 In some Ascomycetes (the Laboulbeniacese) non-motile male 
 cells (spermatia} are formed in unicellular antheridia. Spermatia 
 occur in other Ascomycetes, as also in the ^Ecidiomycetes, but 
 their sexuality has not been established in these cases. 
 
 The female organ is either a unicellular closed oogonium (Oomy- 
 cetes), or a unicellular or multicellular archicarp (Ascomycetes). 
 The archicarp may consist (like the procarp of the Rhodophycese) 
 of two parts : a receptive portion, the trichogyne, which is a more 
 or less elongated multicellular filament, and a sporogenous portion, 
 the ascogoniuntj from which, after fertilisation has taken place, the 
 one or more sporangia (asci) of the ascocarp are developed. 
 
 Sexual cells are only clearly differentiated in the case of the 
 female cells of the Oomycetes and of the spermatia of some 
 Ascomycetes. The female cells of the Oomycetes are oospJieres,
 
 GROUP I. THALLOPHYTA : FUNGI. 279 
 
 spherical cells destitute of a proper wall : the spermatia generally 
 have a cell- wall. 
 
 In all other cases the protoplasmic contents jof the sexual organs 
 are not differentiated into cells of definite form ; but the fusing 
 masses of protoplasm of the Zygomycetes may be regarded as 
 aplanogametes ; and that portion of the protoplasmic contents of 
 the pollinodium of the Peronosporacese which enters the oogonium 
 and fertilises the oosphere, may be regarded as a male cell. 
 
 An asexual formation of spores is of general occurrence. In the 
 Schizomycetes there are no special spore-bearing organs, but the 
 protoplasm of the cells surrounds itself with a proper cell-wall, and 
 becomes a spore. 
 
 In the Myxomycetes sporangia are formed, attaining, in some 
 forms, a high degree of complexity of structure. 
 
 In the higher Fungi, the spores are formed, speaking generally, 
 either in the interior of unilocular sporangia (e.g. Phycomycetes), 
 or by abstriction, either singly or a number in succession, from 
 certain special hyphse (as in the Ascomycetes, JScidiomycetes, and 
 Basidiomycetes) ; in the latter case the spores are often distin- 
 guished as conidia. 
 
 In either case, the spores are borne upon an organ, a special 
 branch of the mycelium, termed a sporophore or conidiophore. 
 This may consist of a single hypha (e.g. Mucor, Peronospora, 
 Penicillium, Puccinia), when it is said to be simple ; or of a 
 number of coherent hyphse (e.g. the Mushroom, and the fructifica- 
 tions of other Basidiomycetes ; the ascocarp of the Ascomycetes ; 
 the secidium of the ^Ecidiomycetes) when it is said to be com- 
 pound. The conidiophores may be scattered over the mycelium, 
 or they may be collected into receptacles termed pycnidia. 
 
 The asexually-formed spores are but rarely motile (e.g. ciliated 
 zoospores of Myxomycetes and Oomycetes) ; in all other Fungi they 
 are non-motile and have a cell-wall. There is considerable variety 
 in their form, colour, etc. In some cases the spores are compound ; 
 that is, they appear to consist of two or more cells (e.g. teleuto- 
 spores of Puccinia Graminis and other vEcidiomycetes ; ascospores 
 of some Ascomycetes such as Pleospora, Hysterium, Cordyceps, 
 etc.) ; each cell, however, germinates independently and is there- 
 fore itself a spore. These compound spores are formed by the 
 division of a primary mother-cell. 
 
 The Life-History of the Fungi is generally very much compli- 
 cated by . polymorphism. In most of the Schizomycetes there is
 
 280 PART IV. CLASSIFICATION. 
 
 remarkable polymorphism especially in the higher forms which 
 pass through several distinct phases in the course of their life. 
 Again, in some Ascomycetes and ^Ecidiomycetes there may be two 
 or three forms bearing different kinds of reproductive organs, the 
 different forms being parasitic on different hosts (hctercecisiri). 
 The Fungi may be classified as follows : 
 
 Sub-Class I. SCHIZOMYCETES : Body unicellular, or multi- 
 cellular and filamentous ; no special spore- 
 bearing organs ; no sexual reproduction. 
 
 Sub-Class II. MYXOMYCETES : Body a plasmodium ; spores 
 formed in more or less well-developed spor- 
 angia ; zoospores ; no sexual reproduction. 
 
 Sub-Class III. PHYCOMYCETES : Body generally a coenocytic 
 unseptate mycelium ; sexual reproduction 
 general ; zoospores present in most orders. 
 
 Section A. Zygomycetes: sexual process 
 isogamous ; product, a zygospore. 
 
 Section B. Oomycetes : sexual process 
 oogamous ; product, an oospore. 
 
 Sub-Class IV. ASCOMYCETES : Body usually an incompletely 
 septate mycelium; sexual process carpoga- 
 mous ; the product is an ascocarp. 
 
 Sub-Class V. JEciDiOMYCETES : Body an incompletely septate 
 mycelium ; no sexual process. 
 
 Sub-Class VI. BASIDIOMYCETES : Body an incompletely septate 
 mycelium; no sexual process; compound 
 sporophores are always formed. 
 
 Sub-Class I. SCHIZOMYCETES. These organisms are either uni- 
 cellular or multicellular ; most of the unicellular forms are very 
 minute. The cell consists of a mass of protoplasm, with a rudimen- 
 tary nucleus, surrounded by a cell- wall which consists in some cases 
 of cellulose, and in others of a proteid substance. In some cases 
 the cells are coloured red, green, blue, etc. ' a starchy substance, 
 turning blue with iodine, is found in the cells of some forms 
 (e.g. Bacillus Amylobacter). 
 
 The forms presented are extremely various. The individuals 
 may be spherical, the Coccus-form (Fig. 162, a) ; or rod-shaped, the 
 Bacterium-form (Fig. 162, &) ; or spirally-wound, the Spirillum- 
 and Spirochsete-forms (Fig. 162, d) ; or straight free filaments, the 
 Bacillus-form ; or straight filaments attached by one end, the Cre-
 
 GROUP i. THALLOPHYTA: FUNGI. 
 
 281 
 
 
 
 nothrix-form ; or the individuals may form cubical masses, as in 
 Sarcina Ventriculi. Some forms (e.g. Bacillus, Spirillum, and 
 some Coccus-forms) are capable of locomotion";- they are provided 
 with one (Coccus-form) or more 
 (one or more at each end in Bac- 
 illus and Spirillum-forms) vibratile 
 cilia, by means of which movement 
 is effected. 
 
 A remarkable phase, common to 
 the life-history of nearly all forms, 
 more especially the unicellular, is 
 the zoogloea-stage. It consists of 
 great numbers of cells held toge'ther 
 by bulky mucilage, to form either 
 a membrane (e.g. the scum on 
 putrefying liquids) or masses of the most various form. A striking 
 zoogloea-stage is that known as Leucoriostoc mesenterioideSj which 
 consists of wavy chains of cocci imbedded in a mass of mucilage, 
 the whole resembling the structure of Nostoc ini the Cyanophycese 
 (Fig. 136, A, B). 
 
 Although a special name has been given to each of the multi- 
 farious forms assumed by the Schizomycetes, it must not be 
 assumed that each form to which a name has been given con- 
 
 FIG. 162. pifferent forms of Schizo- 
 mycetes : a Micrococcus ; b Bacterium ; 
 c Bacillus with spores; d Spirillum 
 (diag.: x600). 
 
 FIG. 163. Bacillus subtilts: A zooglcea-stage; B motile stage; C zooglcea-stage, with 
 spore-formation. After Strasburger : x 800.) 
 
 stitutes a distinct species. On the contrary, the Schizomycetes 
 are highly polymorphic, and the various simpldr forms are, for
 
 282 PART IV. CLASSIFICATION. 
 
 the most part, merely phases in the life-history of the more com- 
 plex forms. 
 
 The Schizomycetes multiply mainly by cell-division (whence 
 their name), and they do so with great rapidity under favourable 
 conditions. In many forms reproduction is also effected by means 
 of spores (e.g. Bacillus subtilis, Bacillus Anthracis, Clostridium 
 butyricum). Each spore is formed from a cell, the protoplasmic 
 contents contracting from the cell-wall and surrounding them- 
 selves with a thick proper wall ; the spore is set free by the decay 
 of the old cell-wall. Spore-formation generally takes place in 
 the zooglo3a-stage, and is promoted by conditions which are un- 
 favourable to growth and multiplication by division. The vitality 
 of the spores is remarkable, being retained under conditions, such 
 as extremes of temperature, desiccation, etc., which would prove 
 fatal to the organisms themselves. 
 
 A comparatively simple life-history is that of Bacillus subtilis, which 
 makes its appearance in infusions of hay when allowed to stand. The in- 
 fusion gradually becomes turbid, owing to the rapid multiplication of the 
 Bacillus. At first the organisms move actively by means of cilia (Fig. 
 163, B), the motile form: after this the cells cease to be motile, and 
 remain connected into filaments, the bacillus-form: then a membranous 
 scum forms on the surface of the liquid, the zoogloea-form : at this stage 
 spore-formation begins (Fig. 163, C) and the life-cycle is at an end. The 
 spores give rise, on germination, to the motile form, and so the cycle is 
 repeated. 
 
 The most conspicuous feature in the physiolog}- of the Schizomy- 
 cetes is their capacity for decomposing organic compounds, indu- 
 cing various fermentative processes, such as the lactic and the 
 butyric fermentation of various kinds of sugars, etc. (but never 
 the alcoholic fermentation), and the putrefactive fermentation of 
 complex nitrogenous organic substances, such as proteids, etc. 
 Some are parasitic in the bodies of animals, such as Sarcina Ven- 
 triculi, Leptothrix buccalis which causes decay of the teeth, and 
 the various forms of Bacteria which cause Phthisis, Cholera, An- 
 thrax, and other diseases. 
 
 The particular form presented, and the degree of the physiolo- 
 gical activity manifested, at any given time, is determined by the 
 external conditions, such as the nature of the obtainable food, the 
 temperature, the presence or absence of oxygen, etc. ; important 
 variations in any of these conditions may induce change from one
 
 GROUP I. THALLOPHYTA : FUNGI. 283 
 
 form of the organism to another, and may modify its physiological 
 activity. 
 
 There is a general resemblance in organisation and reproduction 
 between the Schizomycetes and the Cyanophycese, as well as a 
 remarkable correspondence between individual forms belonging to 
 the two groups. On this ground they are sometimes placed to- 
 gether in a distinct group, the Schizophyta. It is, however, pre- 
 ferable to place them respectively in the classes Fungi and Algae 
 as corresponding sub-cltiesee. 
 
 Sub-Class II. MYXOMYCETES. These organisms are character- 
 istically saprophytic, living on decaying organic substances, such 
 as spent tan, decaying leaves, tree-stumps, etc. 
 
 Their life-history is, in most cases (Endosporese), as follows : 
 On the germination of the spores, the contents of each spore escape 
 as a zoospore, a naked mass of protoplasm, enclosing a nucleus 
 and a contractile vacuole, provided with a single cilium ; this con- 
 stitutes the mastigopod stage, and in this stage the cells multiply 
 by division. After a period of active swimming, the zoospore 
 draws in its cilium, and now creeps about by means of temporary 
 protrusions of its protoplasm termed pseudopodia ; this is the 
 amceboid or myxopod stage, and in this stage also multiplication 
 by division takes place. The amoebae then collect together, cohering 
 into a plasmodium ; the protoplasm of the amoebse in some cases 
 fuses completely so that the plasmodium presents no cellular 
 structure, whereas in others (pscudoplasmodium} the outlines of 
 the coherent amoebse persist ; but, in any case, there is no fusion 
 of the nuclei of the constituent amoebae,, so that the plasmodium is 
 multinucleate and syncytic. 
 
 The plasmodium creeps about, like a gigantic amoeba, by means 
 of pseudopodia, until spore-formation begins. At this time the 
 plasmodium comes to rest ; and it either forms a single sporangium, 
 or divides into several portions each of which forms a sporangium. 
 The mass of protoplasm then assumes the form of the future 
 sporangium ; the external portion of it hardens to form the wall ; 
 while the internal portion, after rapid nuclear division, separates 
 into cells each of which secretes a proper wall and becomes a 
 spore. In most forms a portion of the internal protoplasm goes 
 to form a number of filaments, generally tubular, either free or 
 connected into a net-work, which constitute the capillitium. 
 The wall dries, and eventually ruptures, and' the spores are 
 scattered by the expansion and hygroscopic movements of the
 
 284 
 
 PART IV. CLASSIFICATION. 
 
 elastic capillitium. In many cases the sporangium has a stalk, 
 (sporophore) which is sometimes continued into the cavity of the 
 sporangium as a columella. 
 
 In the Exosporese the spores are not formed in the interior of 
 a sporangium, but by abstriction from the ends of filaments de- 
 veloped from the surface of the sporophore. 
 
 In some forms (e.g. Fuligo vdridns) a compound sporangium is 
 
 II 
 
 Fie. 164J A Part of a plasmodium of ZKdt/mium leucopu* (x 300). J? A closed sporangium 
 of Arcyria incarmito. C The same after the rupture of its wall (p) and expansion of the 
 capillitium cp ( x 20) . (After SachsO 
 
 formed, termed ^Ethalium, by the combination of a number of 
 plasmodia. 
 
 The sporangium : wall and capillitium give the reactions of 
 cuticularised cell-wall. 
 
 The life-history, as sketched above, varies somewhat in different 
 forms'. In some (e.g. Dictyosteliacese, Gruttulinese) the mastigopod 
 stage is wanting; the spores" giving rise directly to amoebae. 
 Again, the mastigo pods' or the amoebae may surround themselves
 
 GROUP I. THALLOPHYTA : FUNGI. 
 
 285 
 
 with a membrane and go through a resting-stage as microcysts ; or 
 the whole or part of a plasmodium may do the same as a sclerotium. 
 
 Sub-Class III. PHYCOMYCETES. Section A : 'Zygomycetes. 
 
 The section Zygomycetes includes several orders of which, how- 
 ever, only the characteristic order Mucorinse will be considered. 
 
 Order Mucorinae. Body an unseptate mycelium, septa being only 
 developed in connection with the formation of reproductive organs ; repro- 
 duction by spores, and by zygospores formed by conjugation; mostly 
 saprophytic, but some are parasitic on other Fungi. 
 
 The mycelium ramifies in the substratum (Fig. 165). The asexual repro- 
 ductive organs are developed as simple sporophores which grow erect into 
 the air. In the Mucoracese the simple sporophores are unbranched, and each 
 
 FIG. 165. Mucor Mucedo : m a mycelium bearing a simple sporophore with a terminal 
 sporangium s ; S a sporangium much magnified; t the end of the sporophore dilated into 
 the columella c ; ic the wall of the sporangium ; gp the spores ; z zygospore formed by the 
 fusion of the contents of two gametangia. 
 
 bears at its apex a single sporangium ; the sporophore projects into the 
 cavity of the sporangium as a columella (Fig. 165). In the Chaetocladieae 
 and the Piptocephalideae the sporophore is branched and more or less 
 septate ; it produces a number of spores by abstriction from the tips of its 
 branches. On germination, the spore gives rise to a mycelium similar to 
 that from which it was derived. 
 
 The gametophores are short swollen hyphse; by the formation of a 
 septum near the tip of the gametophore, a terminal cell is produced, which 
 is the sexual organ or gametangium; the protoplasmic contents of the 
 gametangium constitute the gamete. Two gametophores from adjacent 
 vegetative hyphse come into contact at their tips ; the walls of the two
 
 286 
 
 PART IV. CLASSIFICATION. 
 
 gametangia are absorbed at the point of contact ; the protoplasmic con- 
 tents (gametes) of the gametangia fuse to form the cell which surrounds 
 itself with a coat of two layers and becomes a zygospore (Fig. 166). 
 
 In many cases the zygospore, on germination, gives rise to a small 
 branched or unbranched mycelium, which bears a single simple sporo- 
 
 phore. The spores 
 derived from this 
 sporophore give 
 rise, on germina- 
 tion, to the ordin- 
 ary mycelium. In 
 other cases, how- 
 ever, the zygo- 
 spore gives rise 
 directly to a my- 
 celium bearing 
 sexual organs. 
 
 The mycelium, 
 when under un- 
 favourable con- 
 ditions, gives rise 
 to unicellular 
 gemmae, either 
 c h 1 a m y d ospores 
 or oidium - cells : 
 the latter multi- 
 ply by gemmation 
 in a yeast -like 
 manner (e.g. Mu- 
 cor racemosus) and, 
 like Yeast, have 
 the power of caus- 
 ing alcoholic fer- 
 mentation ; this 
 takes -place espe- 
 cially when the 
 hyphse are im- 
 mersed in liquid. 
 The hyphse be- 
 come segmented 
 into a row of cells 
 by the formation 
 of transverse 
 septa, and the 
 cells then sepa- 
 rate and become 
 free. The chla- 
 mydospores are 
 
 FIG. 166 Mucor Mucedo: A diagram of sexual process: two 
 gametophores in contact ; at the end of each gametophore a cell, 
 the gametangium, has been cut off by a septum ; B commencing 
 development of the zygospore from the fused gametangia; C ripe 
 eygospore, still connected with the gametophores; D free zygo- 
 spore, showing one point of attachment ; E germinating zygo- 
 spore, bearing a small ,'promycelium with a single sporangium 
 (after Brefeld).
 
 GROUP I. THALLOPHYTA : FUNGI. 287 
 
 thick- walled and large; the oidium-cells are smaller and thin-walled 
 (see p. 277). 
 
 Mucor Mucedo may be obtained by keeping fresh horse-dung under a 
 bell-jar in a warm room: it may be further cultivated by sowing the 
 spores on slices of bread moistened and kept under a bell-jar. 
 
 Section B. Oomycetes. 
 
 This section of the Phycomycetes includes the following orders : 
 Order 1. Peronosporaceae: body branched; oogonia terminal 
 
 or intercalary ; pollinodium functional. 
 
 Order 2. Saprolegniacese : body branched ; oogonia generally 
 terminal, rarely intercalary ; pollinodium absent, 
 or, if present, functionless. 
 
 Order 1. Peronosporaceae. The forms comprised in this order are 
 mostly parasitic, chiefly on Phanerogams, but some species of Pythium 
 inhabit the dead bodies of plants and animals. 
 
 The asexual reproduction of the plant is effected, in most forms, by 
 sporangia developed at the ends of the branches of the simple sporophores 
 (Fig. 168 A): no such organs have, however, been 
 observed as yet in Pythium vexans or P. Artotrogus. 
 In some forms the sporangium gives rise to zoo- 
 spores either before or after, it has fallen off the 
 sporophore (Fig. 168 B, C) ; whilst in other forms 
 it falls off and germinates as if it were itself a 
 spore, growing out into a hypha, and so into a p IG- 167- _ 
 mycelium. phthora omnivora. An 
 
 The oogonium is spherical, and remains closed oogonium (Og), contain- 
 
 (Fig. 167). The protoplasmic contents undergo *** an spore ( 'f ' a 
 \" . . . ' . . a pollinodium which has 
 
 differentiation into a single oosphere which is fert iii 8e d the oosphere. 
 surrounded by the remainder of the protoplasm, (x400.) 
 the peripi-asm. 
 
 The pollinodium is developed terminally, either on a hypha springing 
 from beneath the 'oogonium, or on an adjacent hypha, and is club-shaped- 
 Its protoplasmic contents undergo differentiation into a male cell (aplano- 
 gamete) and into periplasm. 
 
 At the time of fertilisation, the pollinodium is closely applied to the 
 oogonium and sends out a delicate tube which penetrates through the 
 wall of the oogonium and reaches the oosphere. The tube then opens, and 
 the male cell passes out of the pollinodium into the oosphere and fertilises 
 it. The oosphere then surrounds itself with a proper wall and becomes 
 the oospore. In some genera (Peronospora, Cystopus) an external coat, 
 the episporium or perinium, is formed round the oospore from the peri- 
 plasm. 
 
 The germination of the oospore takes place in different ways in different 
 species. In Phytopltthora omnieora and Pythium proliferum it gives rise 
 to a small mycelium (promycelium) which produces a few spores, from
 
 288 
 
 PART IV. CLASSIFICATION. 
 
 which, sexual plants are developed. In other species (e.g. Cystopus candidus) 
 the contents of the oospore are set free as a number of zoospores. In yet 
 other species (e.g. Pythium de-Baryanum, Pythium Artotrogus, Peronospora 
 Valerianellce), the oospore directly gives rise to a sexual plant. 
 
 Pythium can be obtained by sowing cress in a pan of earth. When the 
 seedlings spring up, they should be well watered and be kept covered with 
 a bell-jar so as to keep them moist. Some of them will be seen to fall 
 
 owing to the failure of the 
 stem just above the surface 
 of the soil ; these are infected 
 with Pythium. If an in- 
 fected stem be kept in a drop 
 of water on a slide for a day 
 or so, and be examined from 
 time to time, hyphse bearing 
 the reproductive organs of the 
 Fungus will be seen to be de- 
 veloped at the surface. 
 
 In the genus Peronospora, 
 which is represented by 
 many species (P. parasitica 
 on Capsella, P. calotheca on 
 Rubiacese, etc.), only one 
 sporangium is borne by each 
 branch of the sporophore 
 which protrudes through a 
 stoma. In Phytophthora 
 the sporangia are displaced 
 laterally by branches which 
 arise from the hyphte bearing 
 the sporangia, at their points 
 of origin. To this genus 
 belongs P. infestans, which 
 produces the potato-disease. 
 The tissues of the host un- 
 dergo decomposition in the 
 infected parts and turn 
 black : the mycelium of the 
 Fungus extends from the 
 circumference of these spots, 
 and throws up sporophores 
 through the stomata (Fig. 
 
 FIG. 168. .4 Surface-view of the epidermis of a 
 Potato-leaf with the sporophores of Phytophthora 
 infestant projecting out of the stomata ( x 90). B A 
 ripe sporangium. C Another undergoing division. 
 
 D A zoospore. ( x 540 : after Strasburger.) 168). The sporangia of the 
 
 parasite are carried by the 
 
 wind to healthy plants and infect them : the zoospores also penetrate 
 through the soil to the tubers, and the mycelium which is developed from 
 them extends into the young Potato-plant which grows from the tuber. 
 No sexual reproductive organs have been observed in this Fungus as yet.
 
 GROUP I. THALLOPHYTA : FUNGI. 
 
 PhytopJtthora omnivora infects and destroys the seedlings of the Beech and 
 other plants. In Cystopus (C. Candidas on Capsella and other Crucifers, 
 C. cubicus on Compositse) sporophores bearing numerous sporangia are 
 formed in great numbers close together under the epidermis, and 
 cause its rupture. 
 
 Order 2. Saprolegniaceae. The Saprolegniacese all live in water, and 
 are mostly saprophytic, though some are parasitic ; one species causes the 
 Salmon-disease. 
 
 Asexual reproduction is effected entirely 
 by zoospores ; they are formed in terminal 
 but not otherwise especially differentiated 
 sporangia (Fig. 169). On coming to rest 
 they germinate to form a mycelium. They 
 are, in some forms, surrounded by a thin 
 cell-wall at their first formation. 
 
 The oogonia and pollinodia (when pre- 
 sent) resemble those of the Peronosporaceae. 
 The number of oospheres in the oogonium 
 varies widely in different individuals ; 
 sometimes there is only one (Leptolegnia, 
 Aphanomyces) ; but as a rule there are 
 many, as many as 30-40 ; in either case 
 they are developed from the whole of the 
 protoplasm of the oogonium. 
 
 The male and female sexual organs are 
 commonly borne on the same hypha, but 
 in some cases (e.g. Saproleynia dioica and 
 anisospora) this is not the case ; however, it 
 is not clear that these species are actually 
 dioecious. In some species (Saprolegnia 
 Thureti, (orulosa, monilifera, and Achlya 
 stellata) no male organs are developed as a 
 rule; in others (Saprolegnia mixta, Achlya 
 spinosa) they are as often absent as present ; 
 in others they are frequently absent 
 (Aphanomyces stellatus, Saprolegnia hypogyna, 
 Aplanes BrauniY); in others, finally, they 
 are always present (Achlya racemosa and 
 polyandra, Saprolegnia monoica). 
 
 When pollinodia are present, they are 
 closely applied to the oogonium ; sometimes 
 several are applied to one oogonium. In 
 some forms (e.g. Saprolegnia asterophora) the 
 pollinodium undergoes no change, or it 
 sends out a short tube which enters the oogonium but does not touch the 
 oospheres. In most others the pollinodium sends out one or more tubes 
 which enter the oogonium and come into close contact with the oospheres. 
 But in all cases the tubes remain closed, and no act of fertilisation has 
 M.B. U 
 
 FIG. 169. Zooeporangmm of 
 an Achlya : A closed ; B the zoo- 
 spores are escaping ; c a lateral 
 branch ; a zoospores just escaped ; 
 b empty membranes ; e swarming 
 zoospores. ( x 550 : after Sachs. )
 
 290 PART IV. CLASSIFICATION. 
 
 been observed: the oospheres, however, all become oospores. The ger- 
 mination of the oospores presents the same variations as in the Perono- 
 sporacese. 
 
 Saprolegnia can be obtained by placing dead flies in water from a ditch 
 or pond: in a day or two the flies will be found covered with mycelium, 
 if the temperature has been sufficiently maintained. 
 
 Sub-Class IV. ASCOMYCETES. This sub-class includes a 
 vast number of forms, both saprophytes and parasites. Some of 
 them (e.g. Penicillium glauctim, Eurotium Aspergillus) are fami- 
 liar as the blue or green moulds appearing on jam, damp boots, etc. ; 
 others (Erysiphese) as mildew on roses, etc. : Cordyceps infests the 
 larvse of insects. 
 
 In some cases the life-history is complicated by polymorphism, 
 including one or more entirely asexual conidia-bearing forms. 
 These various life-histories are briefly illustrated by the following 
 examples. 
 
 In some cases (e.g. Eremascus albus, Gymnoascus, most Asco- 
 mycetous Lichen-fungi, Ascobolus furfuraceus, Pyronema) the 
 life-history is perfectly simple, presenting only the plant bearing 
 sexual organs, and, subsequently, the ascocarp. On germination 
 the spores (ascospores) produced in the ascocarp give rise to the 
 plant. 
 
 In other cases (e.g. Erysiphese, Eurotium, Penicillium) the plant 
 reproduces itself by means of conidia ; in the Erysiphese and Euro- 
 tium it generally produces sexual organs eventually ; but in 
 Penicillium the formation of sexual organs takes place only excep- 
 tionally under special conditions, so that many successive genera- 
 tions may be produced by means of conidia before a sexual plant 
 makes its appearance. This may occur also in the Erysiphese. 
 
 A more complicated life-history can be clearly traced in Clavi- 
 ceps purpurea, the Ergot of Rye. The mycelium is developed 
 in the ovary of the Rye-flower, and forms a continuous layer 
 of hyphse, a compound conidiophore, at the surface, from which 
 immense numbers of conidia are formed by abstriction, imbedded 
 in a mucilaginous substance known as Honey-dew. This substance 
 is eaten by insects, and thus the conidia are carried to other 
 flowers and there reproduce the fungus. This is the Sphacelia- 
 form. When the rye is ripening, the mycelium forms a dense 
 sclerotium (see p. 277), fusiform, about an inch long, of a dark purple 
 colour at the surface. This is the Ergot, and it remains dormant 
 until the following spring. On germination the sclerotium gives
 
 GROUP I. THALLOPHYTA : FUNGI. 
 
 291 
 
 rise to several filaments termed stromata, about an inch long, each 
 composed of a strand of hyphse, which bear a swollen knob at their 
 apices (Fig. 176). All over the surface of the 'knob are a number 
 of depressions, in each of which there is an ascocarp (perithecium) 
 containing a number of asci, and in each ascus there are eight 
 filiform ascospores. The ascospores are carried by the wind to the 
 Rye-fbwers and there give rise to the Sphacelia-fonn. 
 
 In some cases only conidia-bearing forms are known (e.g. Asper- 
 gillus clavatus, Botrytis Bassii, species of Isaria, Cladosporium 
 Iferbarum, etc.). 
 
 The Reproductive Organs are asexual and sexual. 
 
 The asexual organs are conidiophores, either simple or compound 
 (see Figs. 170, 175), branched or un- 
 branched ; the conidia are formed 
 by abstriction from short tubular 
 outgrowths of the unbranched, or 
 of the terminal cells of branches 
 of the branched, conidiophore, 
 termed sterigmata. In many cases 
 the conidiophores are collected into 
 special receptacles termed pycni- 
 dia. 
 
 The sexual organs are modified 
 hyphse. They may be unseptate 
 (e.g. Eremascus, Eurotium Asper- 
 gillus, Pyronema), or septate (e.g. 
 Ascobolus, Laboulbeniacese) ; they 
 may be quite similar (e.g. Eremas- 
 cus) or more or less differentiated ; 
 they may come into close contact 
 (e.g. Eremascus, Eurotium, Pyronema). 
 
 When, as in Eremascus, the sexual organs are undifferentiated, 
 no special names are given to them ; but when they are differen- 
 tiated the female organ is termed an archicarp, and the male 
 organ a pollinodium, when its contents do not undergo differen- 
 tiation into cells, or an antheridium when (as in the Laboul- 
 beniaceee) male cells are formed in it. 
 
 In some forms (e.g. Laboulbeniacese, Pyronema) the archicarp 
 consists of two parts ; a receptive portion, filamentous in form, the 
 trichogyne; a fertile portion, the ascogonium (compare Rhodo- 
 phycese, p. -272). In the simpler forms, the trichogyne is absent 
 
 FIG. 170. Conidiophore of Penieil- 
 lium j/lnucnm : s a row of conidia on a 
 sterigma ; m hypha of the mycelium 
 (x!50.)
 
 292 PART IV. CLASSIFICATION. 
 
 (e.g. Eurotitim, E^sipheae, Ascobolus), the archicarp consisting 
 solely of the ascogonium. The form of the ascogonium is either 
 filamentous, sometimes spirally coiled (e.g. Eurotium, Fig. 175) ; 
 or, it is dilated, and spherical or oval (e.g. Pyronema, Fig. 172, 
 Erysiphese). 
 
 The pollinodium may be filamentous (e.g. Eurotium), or dilated 
 and club-shaped (e.g. Pyronema, Erysiphese). The antheridium 
 of the Laboulbeniacese is unilocular, and produces several non- 
 motile male cells (spermatia) within it. 
 
 Some of these plants bear receptacles termed spermogonia. 
 The spermogonium consists of a wall formed of coherent hyphse 
 from which a number of free hyphse, the sterigmata, grow into 
 the interior and produce, by repeated abstriction at their apices, 
 a number of small, rod-shaped cells, the spermatia, with a cell- 
 wall, as to the nature of which there is some doubt. These cells 
 reach the surface through the small opening of the spermogonium. 
 
 A process of fertilisation has not been observed in all forms in 
 which sexual organs are present j but it has been observed in the 
 
 c. 
 
 FIG. 171. Sexual reproduction of Eremascus albus. A Sexual organs in contact. B 
 Fusion of the organs at the apex, with developing ascocarp. C Mature ascocarp, consist- 
 ing of a single ascus containing eight ascospores. ( x 1000 : after Eidam.) 
 
 following cases which are representative of the various modes in 
 which it may take place. 
 
 In Eremascus (Fig. 171) the apices of the undifferentiated sexual 
 organs come into contact, and, the cell-walls being absorbed at the 
 point of contact, the protoplasmic contents fuse. 
 
 In Pyronema the trichogyne comes into close contact with an 
 adjacent pollinodium ; the cell-walls become absorbed at the point 
 where the apex of the trichogyne presses against the pollinodium, 
 and the contents of the two organs fuse (Fig. 172). 
 
 In the Laboulbeniacese it appears that the male cells spermatia
 
 GROUP I. THALLOPHYTA : FUNGI. 
 
 293 
 
 are brought by means of water into contact with the projecting 
 trichogyne. One of them adheres to the trichogyne ; the cell-walls 
 are absorbed at the point of contact, and the protoplasm of the 
 spermatium enters the trichogyne, with the result that the 
 ascogonium developes into an ascocarp. 
 
 It is probable that, in consequence of sexual degeneration, the 
 sexual organs are f unctionless in the majority of those Ascomycetes 
 in which both kinds of them are present. 
 
 The Ascocarp. In those Ascomycetes in which there is an 
 archicarp, the ascocarp is developed directly or indirectly from 
 that organ : when no archicarp is present, the ascocarp is developed 
 directly from the mycelium. 
 
 The simplest form of ascocarp is found in Ereinascus (Fig. 171). 
 After the sexual process has taken 
 place, a large spherical cell is formed 
 at the point of junction of the two 
 sexual organs. This cell is an ascus, 
 and produces within it eight ascospores. 
 Here the whole ascocarp consists of a 
 single naked ascus. 
 
 The ascocarp of some of the Ery- 
 sipheae (e.g. Sphserotheca) is but little 
 more complex than that of Eremascus. 
 Here likewise the archicarp gives rise 
 directly to a single ascus ; but an in- 
 vestment is formed round the develop- 
 ing ascus by the growth round it of 
 hyphae from the adjacent mycelium, 
 which cohere to form a layer of paren- 
 chymatous tissue. 
 
 In the majority of forms the development of the ascocarp is 
 indirect. The archicarp gives rise to a greater or smaller number 
 of filaments, branched or unbranched, the ascogenous hyphce 
 (which closely correspond to the ooblastema-filaments of the 
 Rhodophycese, see p. 273), from which the asci are formed as 
 branches, and which together form a compound sporophore. The 
 asci are developed close together, forming a hymenial layer or 
 group, and may or may not be enclosed, either completely or 
 partially, by an investment formed from the surrounding myce- 
 lium. In the latter case, vegetative hyphae grow in among the 
 ascogenous hyphae and terminate in a number of sterile filaments, 
 
 PIG. 172. Sexual reproduc- 
 tion in Pyronema confluent : e 
 archicarp with trichogyne () 
 which has fused with the 
 pollinodium a. ( x 300 : after 
 Kihlman.)
 
 294 PART IV. CLASSIFICATION. 
 
 the paraplujses, which are situate in the hymenial layer between 
 the asci. 
 
 The following forms of ascocarp may be distinguished amongst 
 those which have a cellular investment : the cleistothecium ; the 
 investment remains closed until it decays and ruptures to permit 
 of the escape of the ascospores (see Figs. 173, 175): ihe> pcrithe- 
 cium; a narrow aperture is developed opposite to the hymenial 
 layer (see Fig. 176) : the apothecium ; the investment is somewhat 
 saucer-shaped, so that the hymenial layer is fully exposed (see 
 Fig. 177). 
 
 The ascus is in all cases unicellular. It may be either spherical 
 (e.g. Eremascus, Eurotium), or oval, or club-shaped (e.g. Peziza) in 
 form. In some cases the ascospores are ejected with considerable 
 force ; in others they are set free on the mucilaginous degeneration 
 of the wall of the ascus. 
 
 The ascopores are formed by free 
 cell-formation (see Fig. 64, p. 86) 
 from a portion only of the proto- 
 plasmic contents of the ascus, pre- 
 ceded by nuclear division. The 
 unused portion of the protoplasm 
 is termed the cpiplasm, and is rich 
 in a carbohydrate called glycogen. 
 In nearly all cases eight ascospores 
 
 Fro. 173. A Ascocarp of UnetrmZa It- , , 
 
 oroi. (Erysipheie), slightly magnified: are formed ; m some cases each of 
 
 m mycelium; / cleistothecium; ft, in- the eight Spore-rudiments under- 
 vesting filaments. B An ascus from tho -,? . . , , 
 cleistothecium. containing eight asco- & oes dlvision to form a compound 
 snores (more highly magnified). Spore (e.g. Hysterium, Pleospora, 
 
 etc.), the cells of which may either 
 
 separate or remain coherent. The form of the ascospore is spherical, 
 or oval, or rarely filamentous (e.g. Claviceps, Fig. 176). The wall 
 generally consists of exospore and endospore: the protoplasm 
 generally contains oil-drops. 
 
 The germinating ascospore usually gives rise directly to the 
 ordinary mycelium. 
 
 The Ascomycetes may be classified as follows: 
 
 Order L Gymnoasceae : asci withqut any investment, or with only a 
 rudimentary investment, either solitary, or forming a hymenial layer. 
 
 The typical members of this group are Eremascus (Fig. 171), Gymnoas- 
 cus, and Exoascus parasitic on various trees. 
 
 It is now customary to place in this order the family of the SACCHA-
 
 GROUP I. THALLOPHYTA : FUNGI. 295 
 
 ROMYCETES, or Yeast-Fungi, which is familiar on account of the alcoholic 
 fermentation of saccharine solutions which some of its members excite (e.g. 
 Saccharomyces Cerevisice used in brewing, and S. eHipsoideun which causes 
 the fermentation of the grape-juice in the manufacture of wine: see p. 198). 
 The plant is usually a single small spherical or oval nucleate cell, and 
 multiplies rapidly by gemmation (Fig. 174: see p. 149). When budding is 
 proceeding very rapidly, the successive cells may remain coherent for a 
 time; but a true mycelium is only rarely found, as in S. Mycoderma, 
 which forms a scum on decomposing wine and beer. 
 
 Under certain conditions, particularly the absence of a sufficient supply 
 of food, the plant forms spores. Usually four spores are formed in a cell, 
 by free cell-formation, from a portion of the protoplasm, the rest remain- 
 ing as a parietal layer of epiplasm. The spores surround themselves with 
 a membrane, and are set free by the disorganisation of the wall of the 
 cell. The spores retain their vitality under conditions, such as desicca- 
 tion, absence of food, extremes of temperature, etc., which would prove 
 fatal to the Yeast-plants. The spores germinate, on attaining appropriate 
 conditions of moisture and temperature, and give rise to Yeast-cells by 
 budding. 
 
 Inasmuch as the formation of the spores in a Yeast-cell takes place in 
 the same manner as the formation of spores in 
 an ascus, the Yeast-cell may be regarded as an 
 ascus. It is on this account that the Saccharo- 
 mycetes are included in the Ascomycetes, and in 
 the Gymnoascese on account of their naked asci. 
 They are, however, reduced and sexually de- 
 generate forms. 
 
 It must be borne in mind that cells very Fio. 174,-BuddinR cells 
 
 similar to those of the true Saccharomycetes, of Yea8t J*^***"**" 
 
 ..-.., if Cerevisue) ; the clear spaces 
 
 multiplying in the same manner, and often in thfl ce]lg are vacuo ] es> 
 
 capable of exciting the alcoholic fermentation (x300.) 
 of sugar, may be formed by gemmation from 
 
 the conidia of various kinds of higher Fungi (e.g. Mucor racemosus, Peni- 
 cillium glaucum, some Ustilaginese and Basidiomycetes) under special 
 conditions. These Yeast-like cells, however, grow into mycelia -under 
 appropriate treatment. However, it is still a question whether all the 
 forms of Saccharomycetes may not be merely secondary cpnidial forms of 
 gernmse of mycelial Fungi. 
 
 Order II. Pyrenomycetes : asci forming a hymenial layer, with an 
 investment; the ascocarp is either a cleistothecium or a perithecium; a 
 stroma is present in some families. 
 
 The ascocarp is a cleistothecium in the sub-order Perisporiacese, includ- 
 ing the families Erysipheae (the Mildews) and Perisporieae (e.g. Eurotium 
 and Penicillium) ; in these families there is no stroma. 
 
 Eurotium Aspergilhis is the greenish Mould which so often attacks jam. 
 It can be well cultivated for study on stewed prunes, by sowing conidia 
 obtained from infected jam. The prunes soon become covered with a 
 white, dowjiy substance, which is the vegetative mycelium ; this grad-
 
 296 
 
 PART IV. CLASSIFICATION. 
 
 ually assumes an olive-green colour as the conidiophores are developed ; 
 and finally bright yellow patches appear, indicating the formation of the 
 ascocarps. 
 
 Specimens of Mildews can generally be obtained, in a wet summer, from 
 the leaves of the Rose or of the Hop. 
 
 The ascocarp is a perithecium in the sub-order Hypocreacese, Sphseria- 
 cese, and Dothideacese (e.g. Claviceps, Cordyceps) : a stroma, which varies 
 much in form, is frequently present. 
 
 FIG. 176. Eurolium repens. A A portion of the mycelium with a simple conidiophore 
 (c) bearing conidia; the conidia have already fallen off from the sterigmata (st) ; at, a 
 young ascogonium. B Ascos;onium (as) with a pollmodium(p). C Another, with hyphse 
 growing up round it. L> A cleistothecium seen on the exterior. E F Sections of unripe 
 cleistothecia ; 10 the investment; / ascogenous hyphffl arising from the ascogonium, 
 which subsequently bear the asci. 0? An ascus. H A ripe ascospore. (Magnified : after 
 Sachs.) 
 
 Order III. Discomycetes : the ascoearp is an apothecium of various 
 form ; a stroma sometimes present; 
 
 The order may be divided, according to the form of the apothecium, 
 into the two sub-orders Pezizaceae and Helvellacese. In the former the 
 apothecium is cup-shaped, the hymenium covering the concave surface
 
 GROUP I. THALLOPHYTA : FUNGI. 
 
 297 
 
 and is closed in the early stages of its development ; in the latter the 
 apothecium is borne on the convex, smooth, or reticulate surface of an 
 erect strorna. 
 
 A 
 
 FIG. 176. Clainceps purpurea. A A sclerotium (c) bearing stromata (x2). B Section 
 of a stroma ; cp the perithecia. C A perithecium more highly magnified. D An ascus 
 ruptured ; the elongated spores (sp) are escaping. (After Sachs.) 
 
 The sub-order Pezizacese includes several families, the Phacidiese, 
 Pezizese, Bulgarieee, etc. As representative may be mentioned Rhytisma 
 Acerinum, the mycelium of which infests the leaves of the Maple, but the 
 development of the apothecium 
 does not take place until after the 
 leaves have fallen ; and other 
 similar forms which inhabit the 
 leaves of the Silver Fir, Spruce, 
 and other trees : Ascobolus, which 
 grows on dung : the various 
 species of Peziza, with brightly- 
 coloured apothecia, growing on 
 rotting wood, etc. : Bulgaria, with Fl - !?7. Longitudinal section of the 
 a gelatinous apothecium, growing a Pt h ecimn of Peziza convexula -. h the hy- 
 
 menium. (After Sachs.) 
 on dead branches of the Oak. 
 
 The sub-order Helvellaceae includes the genera Morchella (the Morell, 
 esculent), Gyromitra, Helvella, etc.
 
 298 PART IV. CLASSIFICATION. 
 
 Sub-Class V. ^ECIDIOMYCETES. This sub-class includes a con- 
 siderable number of parasitic plants known as Rusts and Smuts. 
 They are characterised by their remarkably complex life-history, 
 due to polymorphism, presenting two or more spore-bearing forms : 
 and by the fact that the spores are not developed in the interior 
 of a sporangium, but are formed by abstriction. 
 
 FIG. 178. Puccmta Graminis. I Transverse section of a leaf of Barberry, with secidia 
 (a) ; p the wall of the aeculiuin ; u lower, o upper surface of the leaf, which has become 
 thickened at u, y, in consequence of the presence of the parasite ; on the upper surface are 
 spermogonia (sp). A A young secidium which has not yet opened. II Sorus of teleuto- 
 spores (t) on the leaf of Triticum repens ; e its epidermis. HI Part of a sorus of uredo- 
 spores on the same plant ; ur the uredospores; t a teleutospore. (After Sachs.) 
 
 The sub-class is divisible into two orders : 
 
 Order 1. Uredineae : have an secidium-form, as a rule. 
 
 Order 2. Ustilaginese : never have an secidium-form.
 
 GROUP I. THALLOPHYTA : FUNGI. 
 
 299 
 
 Order I. Uredineae. This order comprises those parasites which are 
 generally known as Busts, on account of the rusty appearance which 
 they give to their host-plants at a certain stage of their life-history, when 
 they bear at the surface a great number of orange-coloured spores. 
 
 Puccinia G-raminis affords an example of the most complex life-history 
 with heteroecism : that is, that the different forms inhabit different hosts. 
 It infests Wheat, Rye, and other Grasses, and developes its mycelium in 
 the tissues of the young plants. During the summer it produces groups of 
 simple sporophores, at the apex of each of which a single oval spore, 
 termed a uredospore, of en orange colour, is formed by abstriction (Fig. 
 178, III) in consequence of the grea,t development of cells at these points 
 the epidermis of the host is 
 ruptured, and the groups of 
 uredospores are visible on the 
 surface as rusty spots. These 
 uredospores are scattered by the 
 wind, and infect other Grass- 
 plants ; on reaching a leaf, the 
 uredospore germinates at once, 
 forming a hypha which enters 
 through a stoma into the in- 
 terior of the leaf, where it de- 
 velopes into a mycelium bearing 
 uredospores. This stage in the 
 life-history is termed the Uredo- 
 form. 
 
 Later in the season, when the 
 tissues of the hosts are becoming 
 hard and dry, the Uredo-form 
 no longer produces uredospores, 
 but dark-coloured often com- 
 pound spores, known as teleuto- 
 spores (Fig. 178, 77), developed in 
 the same way as the uredospores. 
 The teleutospores remain qui- 
 escent during the winter. When 
 they germinate in the following 
 spring, one or both of the cells 
 gives rise to a small, free, non- 
 parasitic mycelium (promycel- 
 ium), from each of the cells of which a delicate conidiophore is produced, 
 which developes a small conidium (termed a sporidium) by abstriction at 
 its apex (Fig. 179). 
 
 The sporidia are scattered by the wind, and if they fall on the leaves of 
 the Barberry they germinate, giving rise to a hypha which pierces the 
 epidermis of the leaf, and then forms a dense mycelium in the inter- 
 cellular spaces of the mesophyll. At certain points the tissue of the leaf 
 is hypertrophied, forming cushions which project on the under surface. 
 
 c. 
 
 A. 
 
 FIG. 179. Germination of teleutospores of 
 various Uredineae : A of Puccinia Graminis ( x 
 40C) ; B of Melampsora ( x 300) ; C of Coleo- 
 sporium ( x 230) ; t teleutospore ; pm promy- 
 celium ; sp sporidia.
 
 300 
 
 PART IV. CLASSIFICATION. 
 
 Towards the upper surface of the cushion there are formed on the my- 
 celium small receptacles, the spermogonia (Fig. 178 sp\ each of which con- 
 tains a number of uuseptate hyphse, radiating from the wall towards the 
 centre, which are termed sterigmata ; each of these produces at its apex by 
 abstriction a small cell, the spermatium, which escapes from the spermo- 
 gonium ; spermogonia are formed, though less frequently, on the under 
 surface : the significance of the spermogonia and spermatia is not known. 
 Large spherical structures are formed on the under surface of the cushion 
 (Fig. 178) ; these are the aicidia. This form of the fungus is known as 
 sEcidium Berberidis. Each secidium consists of a hymenial layer of simple 
 unseptate sporophores at its base, from the apices of which a number of 
 spores (cKcidiospores) are formed by successive abstriction; the secidium 
 has a definite wall which ruptures at the surface to set free the spores. 
 
 JJ. 
 
 FIG. 180. Transverse section of a Willow-leaf FIG. 181. Germinating resting. 
 
 infested by Melampsora salicina -. par mesophyll 
 of leaf: eo upper, eu lower epidermis. On the 
 under side a gorus of uredospores (st) with para- 
 physes (p) has broken through the epidermis ; 
 beneath the upper epidermis is a sorus of young 
 teleutospores (t). (x 260.) 
 
 spores: A of Vstilago receptaculorum ; 
 B of Tilletia Caries ( x 460) : sp the 
 spore ; pm the promycelium ; d the 
 sporidia : in B the sporidia have 
 coalesced in pairs at e. 
 
 The secidiospores are conveyed by the wind to Grass-plants, on the leaves 
 of which they germinate, putting out hyphse which penetrate into the 
 interior through the stomata, giving rise to the mycelium which bears 
 the uredospores, and subsequently the teleutospores. 
 
 Order 2. Ustllagineae. This order comprises those parasites which are 
 known as Smuts. The life-history of most of the members of this order 
 is briefly as follows. The plant produces numerous thick-walled, often 
 black (Smut) resting-spores, the development of which is usually inter- 
 calary (resembling that of chlamydospores) on more or less specialised 
 mycelial branches (conidiophores). On germination, the resting-spore
 
 GROUP i. THALLOPHYTA: FUNGI. 
 
 301 
 
 forms a number of reproductive cells, sporidia, of various form ; the 
 sporidia are usually developed on a small promycelium, which may be 
 either multicellular (Fig. 181 A), or unicellular (Fig. 181 B). In most 
 forms these sporidia then coalesce in pairs ; but in any case they germin- 
 ate, either producing at once the mycelium which will bear the resting- 
 spores (e.fj. Protomyces), or a second promycelium bearing secondary 
 sporidia. from which the mycelium bearing resting-spores is developed 
 (e.g. Tilletia Caries). 
 
 In some species (e.g. Entyloma Ranunculi, Tuburc.inia Trientalis) the my- 
 celium, before it produces the resting-spores, developes conidia ; these are 
 small, thin-walled, somewhat spindle-shaped cells, developed by abstric- 
 tion from the ends of unbranched simple conidiophores. 
 
 The sporidia, when cultivated in nutrient solutions, may be made to 
 multiply actively by gemmation, producing a number of yeast-like cells. 
 
 The most important and the inost common species are Ustilago Carbo, 
 which especially attacks Oats, but other Cereals and Grasses as well : U. 
 Maidis, which produces large tumours in the Maize, filled with resting- 
 spores : Urocystis occulta, which fructifies in the leaves and haulms of 
 the Eye : Tilletia Caries, the Smut of Wheat ; this is dangerous because 
 the grains filled with resting-spores remain closed, and are therefore 
 harvested with the sound ones. Many other species and genera infest 
 wild plants. 
 
 Sub-Class VI. BASIDIOMYCETES. This sub-class includes 
 
 a large number of plants, both, saprophytes and parasites, the 
 
 fructifications of 
 
 which are well 
 
 known as Mush- 
 rooms, Toad -stools, 
 
 and Puff-Balls; they 
 
 are the most highly 
 
 organised of the 
 
 Fungi. 
 
 The body is a 
 
 branched septate 
 
 mycelium, growing 
 in the substratum, 
 and bearing the re- 
 productive organs 
 which come to the 
 surface. That of 
 the common edible 
 Mushroom is gener- 
 ally termed " mush- 
 room-spa wn." 
 
 FIG. 182. A Section of young compound sporopbore of 
 Agarieus (Amanita) vaginatui: v the velum universale; 
 st the stipe; h the pileus ; I the lamella: B the same 
 Romewhat older; the velum v is ruptured. C Agarieus 
 nwlleiis: m the mycelium (Rhizomorpha) ; in the smaller 
 specimen to the right the hymenophore is still covered 
 by the velum partiale o ; in the larger specimen the velum 
 is almost completely ruptured, and remains attached to the 
 stipe as the ring, a. (i nat. size.)
 
 302 
 
 PART IV. CLASSIFICATION. 
 
 The reproductive organs are of two kinds, compound and simple. 
 Of these the compound sporophore is universal, and is character- 
 istic of the sub-class ; it constitutes the fructification commonly 
 known as a Mushroom, a Toadstool, etc. The structure of this 
 fructification may be illustrated by reference to the common Mush- 
 room (Agaricus campestris). It consists of a stalk, termed the 
 
 stipe, bearing at its 
 apex a large circu- 
 lar, somewhat um- 
 brella-shaped expan- 
 sion, the pileus. 
 On the underside of 
 the pileus are a 
 number of radiating 
 plates of tissue, the 
 lamella* (Fig. 183), 
 covered with the 
 spore-bearing layer 
 of cells, called the 
 hymenial layer or 
 hymenium. The 
 lamellae collectively 
 constitute the hy- 
 menophore. To- 
 wards the upper end 
 of the stipe is a 
 ring of tissue, the 
 annulus, the torn 
 remains of a mem- 
 brane (the velum) 
 which extended from 
 the stipe to the 
 margin of the pileus, 
 
 FIG. 183. Agaticus campestris. A Tangential section of 
 the pileus, showing the lamellae (1) of the hymenophore. 
 B A similar section of a lamella more highly mag nifled 
 hy the hymenium; t the central tissue called the trarta. 
 C A portion of the same section more highly magnified 
 (x 650): q young basidia and paraphyses; ' the first 
 formation of spores on a basidium ; s" more advanced 
 stages ; at "" the spores have fallen off. (Alter Sachs.) 
 
 enclosing the hy- 
 menial cavity (Fig. 
 182). 
 
 The stipe consists 
 of a number of close- 
 ly-packed branching 
 hyphse, which, at its apex, spreads out to form the tissue of the 
 pileus. In the pileus the hyphse branch repeatedly, the hyphae
 
 GROUP I. THALLOPHYTA : FUNGI. 303 
 
 towards the lower surface forming the lamellae. Each lamella 
 (Fig. 183 B) consists of a mass of hyphae, constitxiting the trama ; 
 as the hyphae approach the surface of the lamella, the cells become 
 shorter. The last cells, before reaching the hymenial laj'er, are 
 very short, and constitute a definite layer, known as the sub- 
 hy menial layer (Fig. 183 B, C, sh}. The terminal cells of the 
 hyphae constitute the hymenial layer (Fig. 183 B hy). This con- 
 sists of somewhat elongated club-shaped cells, some of which bear 
 spores, and are termed basidia, whilst the others are sterile, and 
 are termed paraphyses (Fig 183 C q}. Each basidium developes at 
 its apex 2-4 delicate outgrowths, the sterigmata, and at the apex 
 of each sterigma a single small spore (C s' s") is formed. These 
 spores are termed basidiospores, with reference to their mode of 
 origin. 
 
 The form of the compound sporophore, as 
 also the relation of its different parts, varies 
 widely in the orders and families of the sub- 
 class. In some families (e.g., Auricularieae, 
 Tremellineae, Clavariese Hydneae, most 
 Polyporeee, and some Agaricinae), the hymen- 
 ium is exposed from its first development, 
 and the sporophore is consequently said to 
 be gymnocarpous. In Polyporus volvatus, 
 species of Boletus, and in some Agaricinae 
 (e.g. sub-genera Armillaria, Psalliota, of the 
 genus Agaricus, etc.) the hymenium is covered FIQ ]gl _ Multicellular 
 for some time by a membrane, termed a basidium of Tremeiia : 
 velum partiale. as described above (see Fig. 8 sterigma ; p basidio- 
 
 spores. (x 350.) 
 
 182); the sporophore is then termed hemi- 
 
 angiocarpous. Finally, the whole sporophore may be surrounded 
 by a membrane, which is dehiscent or indehiscent, and is then 
 said to be angiocarpous. This is due to the fact that the sporo- 
 phore is developed from the internal portion of the primitive mass 
 of hyphal tissue, the external portion constituting the enveloping 
 membrane. This arrangement obtains in various genera of Agari- 
 cinae, such as Agaricus (sub-genera Amanita, Fig. 182, Lepiota) 
 and Coprmus, and generally in the order Gasteromycetes. This 
 membrane is termed, in the case of the Agaricinae, a velum uni- 
 versale ; in that of the Grasteromycetes, a peridium. When it is 
 dehiscent, and the sporophore is stipitate, a portion of it remains 
 surrounding the base of the stipe as a volva.
 
 304 PART IV. CLASSIFICATION. 
 
 In the higher Basidiomycetes (Autobasidiomycetes) the basidia 
 are unicellular, but in the lower forms (Protobasidiomycetes) they 
 are multicellular, either with transverse septa (Pilacrese, Auricu- 
 lariese), or with longitudinal septa (Tremellinese, Fig. 184). 
 
 The number of spores borne by a unicellular basidium is usually 
 four ; but it may be one (species of Hymenogaster), or two (Calo- 
 cera, Dacryomyces, species of Octaviana and Hymenogaster), or 
 4-8 (Phalloidese). In the case of the multicellular basidium, each 
 cell bears one basidiospore. 
 
 Simple conidiophores have been discovered in several forms (e.g. 
 Pilacre Petersii, Auricularia sambucina, Exidia, Trcmella 
 mesenterica and lutcscens. In these forms the basidiospore gives 
 rise, on germination, to a mycelium, sometimes small and un- 
 branched, which is either itself the simple conidiophore, or bears 
 simple conidiophores, on which conidia are formed by abstriction. 
 The same mycelium may subsequently bear the compound sporo- 
 phores ; or the conidia-bearing form may reproduce itself through 
 successive generations until at length, under appropriate con- 
 ditions, the form bearing the compound sporophores occurs. 
 
 The conidia of Tremella, cultivated in nutrient solution, mul- 
 tiply rapidly by budding, producing yeast-like cells which have 
 not, however, the power of exciting alcoholic fermentation. 
 
 The formation of unicellular gemmae (see p. 277) is of common 
 occurrence in the Basidiomycetes ; either in the form of chlamydo- 
 spores (e.g. Nyctalis, Oligoporus, Fistulina) ; or, more commonly 
 (e.g. species of Coprinus, Clavariese, Polyporus, Cyathus, etc.) in 
 the form of oidium-cells. The chlamydospores are especially de- 
 veloped in the basidial fructifications of the plants in which they 
 occur : the oidium-cells are generally developed from the vegeta- 
 tive mycelium, either the whole of it or individual hyphse, forming 
 sometimes a more or less definite fructification. In some Agaricinse 
 (e.g. Coprinus, Clavariese) the oidium-cells appear to be incapable 
 of germinating. 
 
 Sclerotia (see p. 277) are known in some cases. The mycelium 
 (e.g. species of Typhula, Coprinus stercorariuSj Tulostoma) pro- 
 duces sclerotia as an antecedent to the formation of the compound 
 sporophores; the sclerotia become quite free from the mycelium, 
 and may be kept for months without losing their vitality. On 
 germination each sclerotium gives rise to one or more compound 
 sporophores. The most remai'kable sclerotia are those of Agaricus 
 mclleus, a Fungus which is very destructive to timber. The
 
 GROUP I. THALLOPHYTA : LICHENTS. 
 
 305 
 
 mycelium gives rise to dark-coloured compact strands of hyphse, 
 of the pseudo-parenchymatous structure characteristic of sclerotia ; 
 but they are peculiar in possessing continued apical growth, and 
 by this means they soon become long filaments, known as Rhizo- 
 morpha. It is in this way that the Fungus spreads from tree to 
 tree : the Rhizomorpha-filaments grow underground from the roots 
 of an infected tree to those of a healthy tree (usually a Conifer) ; 
 it penetrates into them and spreads in the tissues external to the 
 wood in the form of a white fan-shaped mycelium. The compound 
 sporophores (Agaricus melleus) are borne either on the subter- 
 ranean Rhizomorpha-filaments, or on the parasitic mycelium ; in 
 either case they come to the surface. 
 
 The Basidiomycetes are classified as follows : 
 
 Series I. PROTOBASIDIOMYCETES : basidia multicellular. four-celled, each 
 cell bearing a spore ; simple conidiophores generally present. Principal 
 genera 5 Pilacre, Auricularia, Tremella, Exidia. 
 
 Series II. Autobasidiomycetes : basidia unicellular ; simple conidio- 
 phores in some forms. 
 
 This series consists of the two orders Hymenomycetes and Gasteromy- 
 cetes, which are distinguished by the facb that in the former the hymenium 
 is exposed before the maturity of the lasidiospores, whereas in the latter, 
 the hymenium either remains altogether enclosed in the tissue, or is 
 exposed only after the spores are ripe. 
 
 The principal genera of Hymenomycetes are, Clavaria, Hydnum, Poly- 
 porus, Agaricus (Mushrooms) 5 and of Gasteromycetes, Lycoperdon (Puff- 
 ball), Ehizopogon, Cyathus, Geaster, Phallus. 
 
 Subsidiary Group. LICHENES. A Lichen consists of a Fungus 
 and an Alga, living in intimate connexion^ and both contributing to 
 their mutual welfare that 
 is,symbiotically (see p. 275). 
 
 The Lichen-Fungus has al- 
 ways a mycelioid body, and 
 is the constituent of the 
 Lichen which bears the re- 
 productive organs. From 
 the nature of these organs 
 the Lichen-Fungi have been 
 found to belong chiefly to 
 the discomycetous and py- 
 renomycetous Ascomycetes, 
 
 but a few are basidiomy- 
 
 , , . FIG. 185. Section of a spermogonium of Ana- 
 
 cetous, belonging to the ptMcWa Cl ,^ 8: sp the ape P rtnre K at the 8urface ; 
 
 orders Hymenomycetes and c cortex> and TO medullary portion, of the thallus ; 
 
 Gasteromycetas. g layer of algal cells. (After Strasburger.) 
 
 M.B. X
 
 306 
 
 PART IV. CLASSIFICATION. 
 
 The reproductive organs of the Ascolichenes are sterigmata, producing 
 spermatia, contained in spermogonia (Fig. 185) ; archicarps (in the order 
 Collemacese), differentiated into a coiled ascogonium and a multicellular 
 
 projecting trichogyne ; and 
 ascocarps, which are either 
 apothecia (discomycetous) or 
 perithecia (pyrenomycetous) ; 
 the archicarp, apparently 
 after fertilisation by means 
 of spermatia, gives rise to 
 filaments which form the 
 hymenial layer (consisting 
 of asci and paraphyses) of 
 the apothecium, and out- 
 growths from the adjacent 
 FIG. 186. A-D Soredia of Usnea barbata. A A. 
 
 simple soredium , consisting of an algal cell covered vegetative hyph 
 with a web of hyphse. B A soredium, in which the 
 algal cell has multiplied by division. C A group 
 of simple soredia, resulting from the penetration of 
 the hyphffi between the algal cells. D K Germin- 
 ating soredia : the hyphae are forming a growing- 
 point, and the algal cells are multiplying. (Alter 
 Bachs.) 
 
 wall of the apothecium. 
 In the fructification of the 
 Basidiolichenes there is a 
 hymenial layer consisting of 
 paraphyses and basidia, the 
 latter bearing apical sterig- 
 mata, on each of which a 
 basidiospore is produced by terminal abstriction. 
 
 Lichens are also reproduced by gemmse, termed soredia, which consist 
 of one or more algal cells invested by hyphse ; they are budded off from 
 the surface of the thallus, and grow into new plants (Fig. 186). 
 
 The Lichen- Algse belong either to the Cyanophycese or to the Chloro- 
 phycese. The algal cells or filaments may be distributed throughout the 
 thallus, when it is said to be homoiomerous ; this is usually the case in 
 gelatinous Liphens (such as the Collemacese), in which the Alga belongs 
 to the Cyanophyceae, but also in some non-gelatinous forms in which the 
 Alga belongs to the Chlorophycese (such as Coenogonium, Eacodium, and 
 others, in which the Alga is Trentepohlia) : or they may be arranged in 
 a definite layer near the surface of the thallus, when it is said to be 
 heleromerous (Fig. 188), as in the case of nearly all those Lichens of which 
 the Algae belong to the Chlorophycese, and 
 some in which the Algse belong to the 
 Cyanophyceee (e.g. Peltigera, Pannaria). 
 In some heteromerous forms (e.g. Theli- 
 dium) the Algse are quite on the surface. 
 Occasionally (e.g. Endocarpon) algal cells 
 are present in the hymenium. 
 
 It may be generally stated that the form 
 of the thallus is determined in the homoio- 
 merous Lichens by the Alga, in the hetero- 
 merous Lichens by the Fungus. In the latter 
 case three main forms are distinguished: 
 
 FIG. 18". A gelatinous Lichen, 
 Cnllema jiulposum, slightly magni- 
 fied. It is homoiomerous, and the 
 Alga is Xostoc. (After Sachs.)
 
 GROUP I. THALLOPHYTA : LICHENES. 
 
 307 
 
 (a) frulicose Lichen*, in which the thallus grows erect, branching in 
 a shrub-like manner. Of this form are the various species of Usnea 
 (Fig. 189 .4), and allied genera with a cylindrical thallus, which grow on 
 trees : Roccella tinctoria grows on rocks in regions bordering on the 
 Mediterranean ; from it and other allied Lichens litmus is prepared : 
 Ramalina and Evernia, with a ribbon-shaped flattened thallus, occur on 
 trees and wooden fences: Cetraria islandica is the Iceland Moss, which 
 forms a mucilaginous fluid when boiled with water : Cladonia, the Cup 
 Moss, has a scaly decumbent thallus, from which erect branches spring 
 bearing the apothecia ; Cladonia fimbriata is common ; Cladonia rangiferina, 
 the Reindeer Moss, occurs on moors. 
 
 (i) foliaceous Lichens, in 
 which the thallus is flat- 
 tened and adheres to the 
 substratum: the green 
 (rarely bluish-green) algal 
 cells form a single layer 
 beneath the upper surface 
 (Fig. 188). The margin of 
 the thallus is usually lobed. 
 
 Parmeiia (or Physcia) pa- 
 rietina occurs, with its 
 bright yellow thallus bear- 
 ing apothecia, on tree- 
 'trunks and walls, together 
 with other species of a grey 
 colour ; Sticta pulmonacea 
 (Fig. 189 B) has a reticu- 
 lated yellowish thallus, and 
 grows on tree-trunks : Pel- 
 tigera is represented by 
 several species which grow 
 on mossy banks in woods ; 
 the apothecia are borne on 
 the margin of the lobes of 
 the thallus. 
 
 (c) crustaceous Lichens, in 
 which the thallus is usually 
 indefinite in outline, and 
 can often be scarcely dis- 
 tinguished from the substratum, the fructification alone being con- 
 spicuous. 
 
 The Lichens of this form are extremely numerous. Among them may 
 be mentioned the Lecanorese. of which Lecanora subfusca occurs on the 
 trunks of trees : the Lecideaceae, which occur mainly on earth and rocks, 
 Lecidea geographica forming bright yellow incrustations of considerable 
 extent on silicious rocks : the Graphideae, of which Graphis scripta is 
 common on the trunks of Beeches and other trees. 
 
 FIG. 188. Transverse section of the heteromerous 
 thallus of Sticta fuliginnsa (x 500). o Cortex of the 
 npper surface ; tt under surface ; m network of 
 hyphse forming the medullary layer ; g algal cells ; 
 r root-like outgrowths (rhizines) of the under sur- 
 face. (After Sachs.)
 
 308 
 
 PART IV. CLASSIFICATION. 
 
 FIG. 189. jl A fruticosa Lichen, TJsnea larbata, with apothecia. a. B A foliaceous Lichen, 
 Sticta pulmonacea, with apothecia, a (nat. size). (After Sachs.) 
 
 Many species of crustaceous 
 Lichens inhabit the highest 
 peaks of the Alps, and other 
 lofty mountains, on which there 
 is no other vegetation, and they 
 contribute materially to the 
 weathering of the rocks and to 
 the formation of a vegetable 
 soil. When they grow on the 
 trunks of trees, they occur more 
 especially upon those which 
 have a smooth surface ; the 
 formation of a rough bark seems 
 to interfere with their growth. 
 Lichens may become completely 
 dried up without losing their 
 vitality. 
 
 FIG. 190. Crustaceous Lichens. A and B 
 Qraphit elegans : B slightly magnified. C Per- 
 tusaria, Wulfeni, slightly magnified. (After 
 Sachs.)
 
 GROUP II. BRYOPHYTA. 309 
 
 GROUP II. 
 BRYOPHYTA (Muscinese). 
 
 The plants forming this group, that is the Liverworts (Hepa- 
 ticae) and the Mosses (Musci), are characterised by the following 
 distinctive features. Their life-history presents a regular and well- 
 marked alternation of generations : the gametophyte is the more 
 conspicuous form, constituting " the plant " : the sporophyte is a 
 sporogontum, presenting indications of differentiation into root and 
 shoot, but not of the shoot into stem and leaves ; it never becomes 
 an independent individual, but remains attached to the game- 
 tophyte, from which it derives all or much of its nutriment. In 
 some of the Mosses there is an indication, in both the sporophyte 
 and the gametophyte, of a differentiation of vascular tissue. 
 
 The GAMETOPHYTE. The germinating spore does not at once 
 give rise to what is known as the " Moss-plant," but produces an 
 embryonic body, the protonema, which consists generally of a 
 branched filament, but occasionally of a flat layer, of cells which 
 contain numerous chloroplastids. The protonema is generally in- 
 conspicuous and short-lived in the Hepaticse, whilst in the Musci 
 it is more amply developed and may, either wholly or in part, 
 persist from year to year. 
 
 The "Moss-plant " is the adult sexual form. It does not possess 
 any true roots, but is attached to the soil either by unicellular 
 root-hairs (Hepaticse), or by multicellular protonematoid filaments 
 termed rhizoids (Musci). The body of the " Moss-plant " is essen- 
 tially a shoot, which is highly developed and specialised in con- 
 nexion with the functions which it performs the development of 
 the sexual reproductive organs and, in the case of the shoots 
 bearing female reproductive organs, the nourishment of the at- 
 tached sporophyte developed in consequence of fertilisation. The 
 adult shoot arises as a lateral (rarely terminal) bud on the proto- 
 nema : the protonema may give rise to a single shoot (Hepaticae) 
 or to several (generally in Musci). In the latter cases, the adult 
 shoots may become distinct " plants " by the complete or partial 
 dying away of the protonema. The symmetry of the shoot is, 
 almost uniformly, dorsiventral in the Hepaticse and radial in the 
 Musci. It is either thalloid, as in most Hepaticae ; or it is 
 differentiated into stem and leaf, as in the higher Hepaticae 
 (foliose Jungermanniaceae) and in the Musci.
 
 310 
 
 PART IV. CLASSIFICATION. 
 
 The sexual organs are borne on the adult shoot, and are an- 
 theridia and archegonia. They are rarely borne singly or scat- 
 tered, but more commonly in groups (sori) surrounded by some 
 kind of protective investment to which the general term involucre 
 may be applied. In some cases the portion of the shoot which 
 immediately bears the sexual organs is more or less specialised as 
 a receptacle, and in others special reproductive branches, gameto- 
 phores, are differentiated, and may be either antheridiophores or 
 archegoniophores. In the lower Hepaticse the sexual organs are 
 generally borne on the upper (dorsal) surface of the shoot, whilst 
 in the higher Hepaticse (Jungermanniacese acrogynse) and in the 
 Mosses they are borne at the apex. 
 
 PIG. 191. Funaria hygrometrica (Moss). A Germinating spores : u rhizoid; s exospore. 
 H Part of a protonema, about three weeks after the germination of the spore : 7i a pro- 
 cumbent primary shoot with brown wall and oblique septa, out of which arise the 
 ascending branches with limited growth : K rudiment of a leaf-bearing axis with rhizoid 
 (tc). (A x 550 : B about 93.) 
 
 The distribution of the sexual organs is various : the male and 
 female organs may be borne on distinct shoots, when they are 
 dio3Cious ; or on different branches of the same shoot, when they 
 are moncc.cious but diclinous ; or together in the same sorus, when 
 they are monoclinous. In Mosses it appears to be the rule, in 
 dicecious forms, that a protonema always bears both male and 
 female shoots. 
 
 The sexual organs are always multicellular. The antheridium 
 (Figs. 192, 193) is a capsule of various shape, having a longer or
 
 GROUP II. BRYOPHYTA. 
 
 311 
 
 shorter stalk ; its wall consists of a 
 single layer of cells which contain 
 chloroplastids when young ; internally 
 it consists of very numerous small cells, 
 each of which eventually gives rise to 
 a single spermatozoid. 
 
 The spermatozoid is a cell, consisting 
 of a naked filament of protoplasm, spir- 
 ally twisted, thickened at the posterior 
 end where lies the nucleus, tapering at 
 the anterior end where it terminates in 
 two long cilia by means of which it 
 swims (Figs. 192, 193) ; the spermatozoids 
 are set free by the rupture of the an- 
 theridial wall, which usually takes place 
 at the apex of the antheridiuni. 
 
 The archegonium is flask-shaped and 
 shortly stalked (Figs. 194, 195) ; it con- 
 sists of a slightly dilated basal portion, 
 the venter, and of a long slender neck. 
 The axis of the archegonium, when 
 young, is occupied by a central row of 
 cells ; the basal cell of this row, lying 
 in the venter, is the central cell of the 
 archegonium ; it grows considerably, and 
 eventually divides into two unequal parts, an upper and smaller, 
 the ventral canal- 
 cell, and a lower 
 and larger which 
 is the female re- 
 productive cell or 
 oospJiere : the upper 
 cells of the central 
 row constitute the 
 neck - canal - cells. 
 At maturity the 
 terminal cells, lid- 
 cells, of the neck 
 separate ; the neck- 
 canal -cells and the FlG - 193 --^ Antheridium of if arclwntia polymarplia ( Liver. 
 , , wort) iu optical longitudinal section: p parapbyses (x 90). 
 Ventral Canal-cell B Sparmatozoids ( x 600) : (after Strasburger). 
 
 FIG. 192. Fitnaria hygromet- 
 rica (Moss). A Anantberidium 
 bursting -. a the spermatozoids 
 (x 350). B Spermatozoids 
 (x 800); bin the mother-cell: 
 c free spermatozoid of Poly- 
 trichutn.
 
 312 
 
 PART IV. CLASSIFICATION. 
 
 become mucilaginous and disorganised, so that the oosphere is 
 placed in communication with the exterior by the canal of the 
 neck. Fertilisation takes place when the plants are more or less 
 covered with water from rain or dew. Then the antheridia dehisce, 
 the spermatozoids are set free, and, since the male and female 
 organs are at no great distance, they, swimming by means of their 
 cilia, come into the neighbourhood of the archegonia ; they are 
 
 attracted to enter 
 the necks of 
 archegonia by the 
 escaping mucilage 
 formed by the 
 disorganisation of 
 the canal - cells, 
 which contains 
 cane-sugar which 
 substance has been 
 shown to be 
 especially attrac- 
 tive to them (see 
 p. 220). One of 
 the entering sper- 
 matozoids travels 
 down the canal 
 to the oosphere, 
 which it pene- 
 trates, the nu- 
 cleus of the sper- 
 matozoid fusing 
 with that of the 
 oosphere. Fer- 
 tilisation is now 
 complete ; the 
 fertilised oosphere 
 surrounds itself with a cell- wall and becomes the oospore, which 
 begins to divide and to develope into the sporophyte. 
 
 The effect of fertilisation is not confined to the oosphere. The 
 adjacent tissue of the shoot is stimulated to growth, and in some 
 forms (Sphagnaceae) it grows out into a long leafless stalk, the 
 pseudopodium, which carries up the fertilised archegonium on its 
 apex. The venter of the archegonium also grows, forming, either 
 
 FIG. 194. Marchantia ^olymorpha. A young ; -B mature, but 
 unfertilised, archegonium. C Fertilised archegonium, with 
 dividing ooepore. fc' Neck-canal-cells ; fc" ventral canal-cell ; 
 o oosphere ; pr perigynium. (x 640 : after Strasburger.)
 
 GROUP II. BRYOPHYTA. 
 
 313 
 
 by itself or together with the adjacent tissue of the shoot (as 
 commonly in the Hepaticse), an investment, termed the calyptra, 
 which surrounds the developing embryo within and, for a longer 
 or shorter time, keeps pace with its growth. 
 
 The gametophyte has a remarkable power, especially in the 
 Musci, of reproducing itself vegetatively. This is effected fre- 
 quently by the gemmce, formed from various parts of the body : 
 the leaves, for instance, in the foliose Hepaticse ; or in distinct 
 receptacles termed cupules, as in 
 the Marchantiese and some Musci. n 
 
 The gemmae are either unicellular 
 or multicellular, and, in the latter 
 case, may be either spherical or 
 flattened in form. In the branched 
 forms vegetative propagation is 
 effected by the dying away of 
 the main shoot or of the larger 
 branches, the smaller branches be- 
 coming isolated and constituting 
 independent plants. In the Musci 
 almost any part is capable, under 
 favourable conditions, of growing 
 out into protonemal filaments on 
 which new adult shoots are de- 
 veloped. 
 
 With regard to the histology of 
 the adult shoot, it need only be 
 pointed out that rudimentary vas- 
 cular tissue, absent in the Hepa- 
 ticae, is to be found in the stems 
 and the midribs of the leaves of 
 many Musci ; and, further, that 
 the epidermis is not clearly differ- 
 entiated as a tissue- system, and is 
 destitute of stomata. It is true 
 that in some Hepaticse (e.g. Antho- 
 ceros, Marchantia, etc., Fig. 199) 
 there are structures in the super- 
 ficial layer which are erroneously 
 called stomata ; these are merely 
 pores, and differ altogether in 
 
 FIG. 195. Futiaria hygrometriea. A 
 Longitudinal section of the summit of a 
 weak female plant (x 100) raarchegonia ; 
 b leaves. B An archegoninm ( x 550) : 
 b ventral portion with the oosphere ; 
 neck ; m mouth still closed ; the cells of 
 the axile row are beginning to be con- 
 verted into mucilage. C The part near 
 the mouth of the neck of a fertilised 
 archegonium with dark red cell-walls. 
 (After Sachs.)
 
 314 
 
 PART IV. CLASSIFICATION. 
 
 structure and development from the true stomata which are to be 
 found on the sporophyte of Anthoceros and of most Musci, as well 
 as on the sporophyte of the higher plants. 
 
 The SPOROPHYTE, the asexual spore-producing form, is developed 
 from the oospore within the venter of the archegonium (Fig. 196). 
 The oospore divides first into two cells by a transverse wall, the 
 basal u-allj at right angles or obliquely to the long axis of the 
 
 archegonium ; the upper cell, 
 the one next the neck, is 
 termed the epibasal cell, 
 the lower the hypobasal 
 cell. This is followed in 
 some Hepaticse (Marchan- 
 tiaceae, Anthocerotacese) by 
 the formation of two walls, 
 at right angles to the basal 
 wall and to each other, 
 which are known as the 
 quadrant and octant walls, 
 since they respectively seg- 
 ment the oospore into quad- 
 rants and octants of a 
 sphere. In other Hepaticse, 
 and generally in the Musci, 
 the segmentation into oc- 
 tants is confined to the 
 epibasal cell, the hypobasal 
 cell either remaining un- 
 divided, or dividing irregu- 
 larly. With the exception 
 of some of the lower Hepa- 
 ticae (Riccieae), where epi- 
 basal and hypobasal cells 
 alike contribute to the 
 formation of the capsule in 
 which the spores are de- 
 veloped, the epibasal cells 
 alone give rise to the cap- 
 sule. The hypobasal cell gives rise to the foot, which is well- 
 developed in the lower forms of both Hepaticae and Musci, but 
 is rudimentary in the higher. The foot is essentially an em- 
 
 FIG. 196. Funaria hygrometrica. A Develop- 
 ment of the sporogonium (/ /) in the ventral 
 portion (6 I) of the archegonium (longitudinal 
 section x 600). B C Different farther stiiges of 
 development of the sporogonium (/) and of 
 the calyptra (c) ; 7i neck of the archegonium. 
 ( x about 40.)
 
 GROUP II. BRYOPHYTA. 315 
 
 bryonic organ ; but it persists, acting, when sufficiently developed, 
 as the organ of absorption and attachment, throughout the life of 
 the Moss-sporophyte, because the sporophyte, since it does not 
 become free and independent, does not altogether develope beyond 
 the embryonic stage. In most forms the epibasal half of the 
 oospore also gives rise to a longer or shorter stalk, the seta, by the 
 elongation of which the capsule is raised up out of the calyptra. 
 In those Hepaticse which have a seta, its elongation, and the 
 consequent rupture of the calyptra, takes place suddenly when the 
 capsule is already mature and the spores fully developed ; in the 
 Musci its elongation is gradual, whilst the capsule is still rudi- 
 mentary, and the rupture of the calyptra takes place relatively 
 early. In the Hepaticse and some Musci (Sphagnaceae, Phascum, 
 Ephemerum) the whole of the ruptured calyptra remains as a 
 sheath, the vaginula, round the base of the seta : but in the 
 higher Musci (most Bryineae) the calyptra is ruptured trans- 
 versely into an upper and a lower half ; the latter constitutes the 
 vaginula, whereas the former is carried up as a cap on the top of 
 the capsule. In some forms, where the true hypobasal foot is 
 rudimentary (some Jungermanniaceae and Bryinese) and is function- 
 less, the base of the seta becomes dilated to form a false foot 
 (epibasal), which performs the functions of attachment and ab- 
 sorption. 
 
 The body developed from the oospore, which constitutes the 
 asexual generation or sporophyte of the Bryophyta, is termed the 
 sporogonium. With regard to its general morphology it may be 
 considered (except in Ricciese) to present differentiation into root 
 and shoot ; the foot, however rudimentary, developed from the 
 hypobasal half of the oospore, represents the root ; the capsule and 
 the seta (when present), developed from the epibasal half of the 
 oospore, represent the shoot. The shoot is in no case differentiated 
 into stem and leaf. In the Riccieae the products of the hypobasal 
 and epibasal cells are quite similar, so that the whole thalloid 
 sporogonium consists only of a capsule. Hence, whilst it is the 
 rule in the Bryophyta that sporogenous cells are only developed in 
 the shoot-portion of the sporophyte, that is, are derived only from 
 the epibasal cell, in the Ricciese the derivatives of the hypobasal 
 cells are also sporogenous. 
 
 The sporogonium is not an independent sporophyte, but remains 
 attached to the gametophyte, obtaining from it either the whole 
 or a portion of its food. It must, however, be clearly understood
 
 316 
 
 PART IV. CLASSIFICATION. 
 
 that there is no continuity of tissue between the two generations ; 
 the sporophyte is simply inserted into the tissue of the gameto- 
 phyte. In the Hepaticse (except Anthoceros) the sporophyte is 
 short-lived, and is entirely dependent upon the gametophyte for its 
 nutrition. In Anthoceros, and in most of the Musci, the capsule 
 possesses more or less well-developed assimilatory tissue, and its 
 epidermis is provided with stomata, so that the sporophyte is 
 capable of using the carbon dioxide of the air as its carbonaceous 
 food, and is dependent upon the gametophyte only for its supply 
 of water and salts. In many of these forms the seta has a central 
 strand of rudimentary vascular tissue through which the water 
 and salts, absorbed from the gametophyte, can travel to the region 
 of the capsule where assimilation and transpiration are carried on. 
 
 FIG. 197. Comparative morphology of the sperogonium in the Bryophyta : diagram- 
 matic transverse sections of the young capsule. A Sphserocarpus (typical Liverwort) ; B 
 Ceratodon (typical Moss) ; C Anthoceros (aberrant Liverwort). E Endothecium : 9-9 
 primary divisions (quadrant and octant walls) ; s (shaded) archesporium ; C columel'.a. 
 (A and C after Leitgeb ; B after Kienitz-Gerioff.) 
 
 The tissue of the developing capsule becomes differentiated into 
 an external layer (or layers) of cells, termed the amphithecium, 
 which, in nearly all cases (except Anthocerotacese and Sphagnacese) 
 forms only the wall of the capsule ; and an internal solid mass of 
 cells, the cndothecium. The spores are developed from a mass or 
 a layer of cells termed the archesporium. In the Hepaticae the 
 archesporium (Fig. 197 .4) includes the whole of the endothecium 
 (except in Anthocerotacese, Fig. 197 (7), and the archesporial cells are 
 either all sporogenous (Ricciese) or, as is more frequently the case, 
 some of them are sterile and generally become spirally thickened 
 and elongated in form when they are termed elaters. In the Antho-
 
 GROUP II. BRYOPHYTA. 317 
 
 cerotaceae and in nearly all Musci the archesporium is a layer of 
 cells : it is generally the external layer of the endothecium, but 
 in most of the Anthocerotaceae and in the Sphagnacese it is the 
 innermost layer of the amphithecium. In those forms where the 
 archesporium is a layer of cells, the internal sterile tissue of the 
 endothecium constitutes what is termed the columella. The arche- 
 sporial cells are either themselves the mother-cells of the spores, 
 or they undergo division to form these cells. Each mother-cell 
 gives rise to four spores ; the nucleus divides into two, and each 
 of these divides again ; the protoplasm aggregates round the four 
 nuclei, constituting four cells which surround themselves with a 
 proper wall and which are the spores. They do not usually all 
 lie in one plane, but are placed tetrahedrally. The mature spore 
 is a cell, consisting of a mass of protoplasm, with a nucleus, and 
 containing chloroplastids, starch-grains and oil-drops ; the wall 
 consists of two layers of the usual structure (see p. 50). During 
 the formation of the spores the mother-cells become isolated from 
 each other, floating freely in a mucilaginous liquid in the interior 
 of the capsule. 
 
 The escape of the spores from the capsule is effected in various 
 ways. In some cases the wall of the capsule simply decays (e.g. 
 Riccieae, Phascum) ; or it splits into valves (e.g. Jungermanniaceae) ; 
 or the upper part is thrown off as a lid or operculum (e.g. some 
 Marchantieae, Sphagnaceae, most Bryineae). 
 
 On being set free, the spores germinate, when the conditions 
 are favourable, giving rise to the protonema. The brittle exo- 
 spore being ruptured, the contents, covered by the endospore, 
 then generally grow out in the form of a filament, which is the 
 beginning of the protonema. In some rare cases (e.g. Pellia) cell- 
 divisions take place within the spore before the exospore is 
 ruptured, so that the protonema is from the first a mass or a layer 
 of cells. 
 
 The Bryophyta (Muscineae) are divided into two classes, the 
 distinctive characters of which are as follows : 
 
 Class III. HEPATICJE (Liverworts). 
 
 Gametophytic Characters. Protonema, generally short-lived, 
 inconspicuous, a flattened expansion. 
 
 Adult shoot, generally dorsiventral ; thalloid in many forms ; 
 has unicellular root-hairs ; no trace of vascular tissue : leaves 
 (when present) destitute of a midrib. 
 
 Sporophytic Characters. The sporogonium remains within the
 
 318 PART IV. CLASSIFICATION. 
 
 calyptra until the spores are ripe ; the ruptured calyptra remains 
 as a vaginula, no portion of it being raised as a cap on the sporo- 
 gonium ; the elongation of the seta (when present) is sudden ; the 
 growth of the sporogonium is not effected by a two-sided apical 
 cell. 
 
 The archesporium (except in the Anthocerotacese) is a mass of 
 cells co-extensive with the endothecium ; in all cases (except 
 Ricciere) some of the archesporial cells are sterile, being frequently 
 developed into elaters ; a columella is present only in the Antho- 
 cerotacese. 
 
 There is no trace of vascular tissue in the sporophyte, nor are 
 there any stomata in its epidermis (except Anthocerotacese). 
 
 Class IV. Musci (Mosses). 
 
 Gamctophytic Characters. Protonema frequently persistent, 
 well-developed, generally filamentous. Adult shoot, radial or 
 isobilateral ; always differentiated into stem and leaf ; no root- 
 hairs, but branched multicellular rhizoids ; stem frequently with 
 a central strand of rudimentary vascular tissue ; leaves generally 
 with a midrib. 
 
 Sporophytie Characters. The sporogonium escapes from the 
 calyptra at an early stage ; a portion of the calyptra (with certain 
 exceptions) is carried up as a cap on the sporogonium ; the elonga- 
 tion of the seta is gradual ; the growth of the sporogonium is 
 (except Sphagnacese) effected by a two-sided apical cell. 
 
 The archesporium is not co-extensive with the endothecium, and 
 is generally a layer of cells ; the archesporial cells are all sporo- 
 genous, none being sterile or forming elaters ; there is usually 
 a well-developed columella in the capsule. 
 
 The seta frequently has a central strand of rudimentary vascular 
 tissue ; the epidermis of the capsule is generally provided with 
 stomata. 
 
 Class III. HEPATIOE (Liverworts). 
 
 A. The GAMETOPHYTE. The spore gives rise, on germination, 
 to a small protonema which is sometimes filamentous, but more 
 generally a flattened cellular expansion. 
 
 The Adult Shoot springs from the protonema. Its symmetry is 
 generally dorsiventral. It is commonly thalloid, but is differ- 
 entiated into stem and leaves in some forms (e.g. foliose Junger- 
 manniacese). Its growth is effected by an apical growing-point in
 
 GROUP II. BRYOPHTTA : HEPATIC^. 319 
 
 which there is either a group of initial cells (Marchantiacese, 
 Anthocerotacese), or a single apical cell (Jungermanniacese). The 
 branching is commonly dichotomous, taking -place in the plane of 
 expansion ; but the development of branches from the ventral 
 surface is constant in several genera. 
 
 The dorsiventral shoot bears numerous unicellular root-hairs 
 on its ventral (lower) surface ; when thalloid it also bears multi- 
 cellular scales (ventral scales') on the same surface ; when foliose, 
 it bears on this surface a row of small rudimentary leaves, termed 
 amphigastria, the fully developed foliage-leaves being borne in 
 two lateral rows, one on each flank of the shoot. 
 
 In the great majority of Hepaticae, the sexual organs are borne 
 on the dorsal (upper) surface, either scattered or in groups ; and 
 sometimes upon a specially modified portion of the shoot, termed 
 the receptacle, either sessile or stalked ; in the latter case the shoot 
 (e.g. higher Marchantiese) may be more or less clearly differentiated 
 into a vegetative and a reproductive part (gametophore). It is 
 only in some of the Jungermanniacese (Jungermanniacese acrogynse) 
 that the sexual organs are developed at the apex of the branches of 
 the shoot, a feature in which they approach the Musci. 
 
 The protonema bears but a single adult shoot ; and this, owing 
 to the transitory nature of the protonema, soon becomes an inde- 
 pendent plant. The plant is generally monoecious, but sometimes 
 dioecious. 
 
 B. The SPOROPHYTE is developed from the fertilized oosphere 
 (oospore) in the archegonium (see p. 312). It is a sporogonium, 
 which may consist merely of a capsule (Ricciese) ; or it may be 
 differentiated into a capsule and a foot (e.g. Anthoceros) ; or into a 
 capsule, a longer or shorter seta, and a foot (e.g. Marchantiese) ; 
 or into a capsule, a seta, and a rudimentary (hypobasal) foot (some 
 Jungermanniacese), a false foot (epibasal) being in some cases de- 
 veloped from the lower part of the seta. It never grows by means 
 of a two-sided apical cell as it does in the Mosses. 
 
 The internal differentiation of the capsule presents the following 
 varieties : It is in all cases differentiated into amphithecium and 
 endothecium ; in all, except most Anthocerotaceae, the archesporium 
 is co-extensive with the endothecium ; in the Anthocerotacese, the 
 whole or part of the endothecium constitutes a columella, a feature 
 in which the Anthocerotacese resemble the Musci. 
 
 In the Riccieae, as a rule, the whole archesporium is sporogenous ;. 
 whereas in all other forms some of the archesporial cells are
 
 320 PART IV. CLASSIFICATION. 
 
 sterile, and in many they are developed into elatcrs, elongated 
 cells with spirally thickened walls, generally becoming free from 
 each other. 
 
 The sporogonium remains enclosed in the calyptra until the 
 spores are mature when, if a seta be present, it suddenly elongates 
 and ruptures the calyptra, which persists as a vaginula at its base. 
 The capsule opens either by the decay of its wall, or more gener- 
 ally by the splitting of the wall from the apex downwards into 
 valves ; in some Marchantiese a lid, the operculum, is formed and 
 the capsule is opened by the throwing off of the lid. 
 
 The Hepaticse are classified as follows : 
 
 Order I. Marchantiacese. Order II. Jungermanniacese. Order III. 
 Anthocerotacese. 
 
 Order I. Marchantiaceae. 
 
 A. The GAMETOPHYTE. The spore gives rise on germination to a short 
 unbranched filamentous protonema which developes at its apex into a 
 flattened cellular expansion, from the margin of which the adult shoot 
 (commonly known as the plant) springs as a lateral branch. 
 
 The Morphology of the Adult Shoot. The adult shoot is undiiferentiated 
 into stem and leaf. Its symmetry is dorsiventral ; on the lower (ventral) 
 surface it bears numerous root-hairs, and also scales which are arranged 
 in one or two rows, or irregularly. 
 
 Growth is effected by an apical growing-point, situated in a depression, 
 possessing a transverse row of initial cells from which segments are cut 
 off dorsally and ventrally; the initial cells also undergo longitudinal 
 division, and thus increase in number. 
 
 The normal mode of branching is that which takes place in the plane 
 of expansion; it is dichotomous, and is effected in the manner described 
 on p. 132. 
 
 The sexual organs are in all cases developed on the dorsal surface, each 
 antheridium or archegonium arising from a single superficial cell. In 
 the simpler forms they are arranged in a continuous median row, 
 developed in acropetal succession ; in the higher forms they are borne on 
 a special structure termed a receptacle. 
 
 The receptac'e. In the higher Marchantiese the adult shoot is frequently 
 differentiated into a vegetative and a reproductive portion, the gameto- 
 phore; the gametophore is a branch (or a branch-system) bearing a 
 terminal receptacle, in which either the male (antheridiophore) or the 
 female (archegoniophore) organs are developed. 
 
 In the simpler forms the archegoniophore is simple, that is unbranched ; 
 the stalk presents a single furrow which represents the ventral surface of 
 the shoot. In Marchantia the stalk has two ventral furrows, showing 
 that it consists of the two coherent branches of the first dichotomy. The 
 receptacle itself is repeatedly branched: thus in Marchantia there are 
 eight groups of archegonia, corresponding to eight branches. The 
 receptacle is more or less distinctly lobed, thus showing its compound
 
 GROUP II. BRTOPHYTA : HEPATIC-E. 321 
 
 nature : each group of archegonia is situated between the bases of two 
 adjacent lobes. The complete elongation of the stalk does not take place 
 until the archegonia are fully developed, or even until one of them has 
 been fertilised. 
 
 It is only in a few of the higher Marchantieae that there is a highly de- 
 veloped antheridiophore. In Marchantia a definite terminal receptacle is 
 formed; it is discoid inform, and it is elevated on an erect stalk (see Fig. 
 198 A) : it is compound, having several growing-points, each of which 
 gives rise to antheridia in acropetal succession, and then ceases to grow ; 
 the stalk has two ventral furrows, showing that it consists of two 
 coherent branches. 
 
 In Marchantia the venter of each archegonium becomes surrounded by 
 a sac-like membrane, developed from the stalk-cell of the archegonium, 
 which is termed the perigynium (Fig. 194). The development of the 
 perigynium begins when the archegonium is nearly mature. 
 
 FIG. 1S>8. J 1'ortion of a plant of 3Iarchantia polymorp'ia (t), with atitheridiophores. 
 B Portion of a plant with a cupule containing gemmae; v v apices of the two branches. 
 (After Sachs.) C An archegoniophore with a doubly furrowed (r) stalk t, bearing a 
 terminal branched receptacle of which s is one of the rays ; h perichaetium ; fc sporogonia. 
 
 The distribution of the sexual organs is various : the plants may be 
 monoecious or dioecious (Marchantia). 
 
 The Structure of the Adult Shoot. The dorsal portion of the shoot consists 
 in all the Marchantiacese, of parenchymatous tissue, made up of cells con- 
 taining chloroplastids, which includes a number of air-chambers, giving 
 it an areolated appearance, whence it is termed the air-chamber-layer. 
 The chambers are formed by the unequal growth of the cells near the 
 growing-point, in consequence of which the surface presents alternating 
 elevations and depressions. In Marchantia the primary air-chambers be- 
 come completely closed in ; at the central meeting-point the growth of the 
 superficial cells take place vertically, leading to the formation of vertical 
 rows of cells which subsequently separate, leaving a canal between them. 
 This structure is distinguished as a compound pore. Compound pores of 
 M.B. Y
 
 322 
 
 PART IV. CLASSIFICATION. 
 
 this sort are found in the receptacles of other Marchantiese, the vegetative 
 parts of which have simple pores. 
 
 In many forms, the cells containing chloroplastids (assimilatory tissue) 
 are simply those which form the walls of the air-chambers ; in Marchantia 
 (Fig. 199) the cells forming the floor of the air-chamber, or the sides, or 
 even the roof, grow out into branched or unbranched filaments which fill 
 most of the air-cavity, thus largely increasing the assimilatory tissue. 
 
 Beneath the air-chamber-layer is a compact tissue, consisting of several 
 layers of cells elongated in the direction of the long axis of the branch, 
 which is without intercellular spaces, and contains but few chloroplastids. 
 In the Marchantieae the walls of these cells are generally thickened and 
 pitted ; some of the cells contain mucilage, and in Fegatella the mucilage- 
 cells form continuous rows ; other cells contain a dark-coloured oil-drop, 
 though such cells also occur in the air-chamber layer. 
 
 The ventral surface is formed by a layer of cells which, in the simpler 
 
 FIG. 199. Marchantia polymorplia. A A pore seen in surface view. B Section of a portion 
 of the dorsal region of the thallus, showing the air-chamber containing assimilatory tissue, 
 and the compound pore. ( x 210 : after Strasburger.) 
 
 forms, is not specially differentiated, but in some the cells of this layer 
 are remarkable for their small size; in Marchantia and Preissia there 
 are several layers of these small cells, forming a sort of ventral cortex. 
 
 The ventral scales consist of a single layer of cells, the walls of which 
 generally assume a violet colour ; each scale is developed from a single 
 superficial cell, or, as generally in the Bicciese, from a transverse row of 
 cells. In Marchantia polymorpha, in addition to the scales which arise 
 from the midrib, there are others which spring from the surface of the 
 lamina. 
 
 Unicellular root-hairs are produced in all Marchantiacese ; the com- 
 monest form has thin walls ; in the Marchantieae a second form occurs, in 
 which peg-like thickenings of the wall project into the cavity of the cell : 
 the simple root-hairs are developed mainly on the midrib, the thickened 
 hairs mainly on the lamina.
 
 GROUP II. BRYOPHYTA : HEPATKLE. 323 
 
 Ge.nmce are produced in Lunularia and Marchantia in special receptacles, 
 termed cupules, borne on the dorsal surf ac3 of the shoot ; in Lunularia the 
 cupule is crescsnt-shaped, in Marchantia it is circular (Fig. 198J5). The 
 cupule is formed by an outgrowth of the air-chamber layer, and in 
 Marchantia its margin is prolonged into laciniae. The gemmae spring 
 from single cells of the floor of the cupule, which elongate upwards and 
 divide transversely into a stalk call and a terminal cell, which, by 
 repeated growth and division, forms a flattened plate of tissue, several 
 layers of cells thick at the middle, thinning out to a single layer at the 
 margin, with a growing-point in a depression on each lateral margin. 
 The symmetry of the gemmae is isobilateral ; but when they fall on to the 
 soil and begin to grow, the undermost surface becomes the ventral, and 
 the uppermost the dorsal. Some of the superficial cells have no chloro- 
 plastids ; those of the surface next the soil grow out into root-hairs. 
 
 B. The SroROPHYTK. The degree of morphological and histological 
 differentiation of the sporophyte presents wide divergences in the different 
 groups. In the Ricciese, the whole embryo simply forms a spherical 
 capsule : in the Marchantiese, the capsule is developed entirely from the 
 epibasal cells, whilst the hypobasal cells give rise to a bulbous foot, which 
 attaches the embryo to the parent, and to a short stalk which bears the 
 capsule, and is formed at a relatively late stage by intercalary growth. 
 
 The differentiation of the tissue of the capsule into amphithecium and 
 endothecium is well-marked, except in the Riccieae. The archesporiuni is 
 coextensive with the endothecium. 
 
 In the Riccia the whole of the archesporial cells are sporogenous ; in 
 Corsinia, some of the archesporial cells are sterile, but these undergo no 
 special differentiation; in the Marchantiese the sterile cells assume an 
 elongated form, and their walls undergo spiral or annular thickening: 
 these specially modified sterile cells are the elaters, and, being very hj'gro- 
 scopic, they assist in the scattering of the spores. Each sporogenous cell 
 gives rise to four spores. 
 
 The wall of the capsule, which consists generally of a single layer of 
 cells, is but slightly developed in the Riccieae, and becomes entirely dis- 
 organised during the development of the spores. In the Marchantiese the 
 cells of the walls are generally thickened and the thickenings fibrous, in 
 which case the capsule opens by the splitting of the wall longitudinally 
 into a number of teeth. 
 
 The spores are generally tetrahedral, with two coats, the outer of which 
 (exospore) is tuberculate or reticulate on the surface. On germination 
 the exospore of the tetrahedral spore ruptures at the point of junction 
 of the three projecting angles. The spores of Lunularia and Marchantia 
 are small and spherical ; the exospore is feebly developed, and presents 
 a granular thickening. In consequence of the thinness of the exospore, 
 the whole spore is enabled to enlarge considerably on germination, and it 
 does not rupture at any special point. In Fegatella, cell-divisions take 
 place in the spores before they are scattered. 
 
 The venter of the archegonium keeps pace with the growth of the 
 developing embryo, forming the calyptra, and encloses it until the spores
 
 324 
 
 PART IV. CLASSIFICATION. 
 
 are ripe. In the Riccieae the spores are set free by the gradual disorgan- 
 isation of the calyptra and of the tissue of the thallus in which the 
 cah-ptra is embedded ; in the other Marchantiacese the capsule is forced 
 out of the catyptra by the elongation of the short stalk. 
 
 The order Marchantiacese includes the families Kicciese (Riccia, Oxy- 
 mitraX Corsinieae (Corsinia, Boschia), and Marchantiese (Marchantia, 
 Lunularia, Fegatella, etc.). 
 
 Order II. Jungermanniaceae. 
 
 A. The GAMETOFHTTE. On germination the spore gives rise to a proto- 
 nema which may be a solid ellipsoidal mass of cells (as in Pellia) with a 
 root-hair at one end ; or a flattened plate of cells (Eadula, Frullania) ; or 
 
 a filament, some- 
 
 f " times branched 
 
 (Lophocolea, 
 C h i 1 oscy phus) ; 
 however, the 
 differences in 
 form of the 
 protonema are 
 not of great 
 morphological 
 importance 
 since, in many 
 cases, flattened 
 and filamentous 
 forms have been 
 found to be pro- 
 duced from 
 spores of the 
 same plant. 
 
 The protone- 
 ma gives rise to 
 the adult shoot 
 by the forma- 
 tion, either from 
 a marginal cell, 
 if it is flat, or 
 
 from the terminal cell, if it is filamentous, of a growing-point with a 
 s ingle apical cell. 
 
 The Morphology of the Adult Shoot. The adult shoot may be differenti- 
 ated into stem and leaf, as in ihefoliose forms ; or undifferentiated, as in 
 the thalloid forms. Its symmetry is generally dorsiventral ; the only 
 radially symmetrical, erect-growing forms being Haplomitrium and some 
 species of Riella (e.g. R. hellcophijlla and Parian). 
 
 Most of the thalloid forms have a distinct midrib. The shoot bears 
 numerous unicellular root-hairs, as also club-shaped glandular hairs 
 which secrete mucilage, on its ventral (under) surface. In the dorsi- 
 ventral foliose forms, the stem bears a row of leaves on each flank, and 
 
 FIG. 200. Growing-point of thallus of Metzgeria furcata : t apical 
 cell ; sf etc., successive segments ; m' m" marginal cells ; p' super- 
 ficial cell ; i t cells of the midrib ; c clavate hairs. ( x 540 : after 
 Strasburger.)
 
 GROUP II. BRYOPHYTA : HEPATIC^. 325 
 
 generally a row of amphigastria on its ventral surface. In the radial 
 foliose forms, the leaves are borne in three rows in Haplomitrium, and in 
 two rows in the radial species of Riella; here there is no distinction of 
 amphigastria. 
 
 The growth of the shoot is effected by an apical growing-point which 
 possesses a single apical cell. The apical cell of the thalloid forms is most 
 commonly two-sided (Fig. 200) ; the base is directed outwards, the apex 
 inwards, and from the two sides segments are cut off alternately right 
 and left. But in Pellia the cell is bounded by four surfaces an external 
 free surface, an internal, and two lateral ; segments are successively cut 
 off along the internal and the two lateral surfaces. The apical cell of the 
 foliose forms, with the exception of Fossombronia and Riella which have 
 a two-sided apical cell, is a three-sided pyramid; its base is directed out- 
 wai-ds, its apex inwards, one side is ventral and the other two are dorso- 
 lateral ; this latter statement does not, of course, apply to Haplomitrium, 
 which is radial. 
 
 The normal mode of branching in the dorsiventral forms is that which 
 takes place at the growing-point in the plane of expansion. In the thal- 
 loid forms, as also in the foliose Fossombronia and Blasia, it may be 
 described as dichotomous (see p. 132) although the apical cell does not 
 undergo division so as to form the apical cells of two branches ; the apical 
 cell of the parent shoot persists, and that of the branch is developed from 
 an adjacent segment, either before or after further division. When the 
 two shoots develope with equal vigour, the resulting branch-system re- 
 sembles a dichotomy ; but when the parent shoot grows the more vigor- 
 ously throughout, the branches are lateral upon it and the branch-system 
 is a monopodium (see p. 19). In the foliose forms the mode of normal 
 branching is generally monopodial. The apical cell of a lateral branch is 
 developed from the lower (ventral) half of a dorso-lateral segment cut off 
 from the apical cell ; either from the whole of the segment, or from the 
 posterior (basiscopic) portion of it. 
 
 In some of these plants there is a formation of gemmx. In Aneura 
 certain cells of the margin and of the dorsal surface of the shoot each 
 become divided into two, anl the two cells thus formed are set free as a 
 bicsllular gemma, with probably a proper wall of its own, by the rupture 
 of the enclosing wall. In Blasia, the gemmae, which are solid multicellular 
 nearly spherical bodies, are developed in special receptacles (cupules) 
 situated on the dorsal surface of the apex ot the shoots ; their mode of 
 origin resembles that of the gemmae of Marchantia. In most foliose forms 
 the gemmae are developed from marginal cells of the leaves (e.g. Jumjer- 
 mannia ventricosa) or from cells near the growing-point of the stem (e.g. 
 .Junyermannia blcuspidala). In these forms the gemmae are usually uni- or 
 bi-cellular, but in Rtdula complanata (where they are formed on the leaf- 
 margin) they are flat multicellular plates of tissue. 
 
 The leaves are developed, generally speaking, one from each segment 
 formed from the apical call. In the typical Acrogynae each dorso-lateral 
 segment gives rise to a lateral leaf, and each ventral segment to a ventral 
 leaf (amphigastrium) ; though, as alread3 r mentioned, the amphigastria
 
 326 
 
 PART IV. CLASSIFICATION". 
 
 are wanting in many species. A characteristic feature of the leaves of 
 this group is that they are distinctly bilobed, at least when young ; this 
 is due to the fact that the mother-cell of the leaf is divided into two which 
 give rise to the two lobes. The leaves are sessile, and their insertion is at 
 first transverse to the long axis of the stem, so that one lobe is superior 
 or dorsal, the other inferior or ventral ; but by subsequent displacement 
 it becomes oblique. Since the leaves are situated close together, they thus 
 come to overlap each other, and this overlapping presents two forms: 
 either the posterior edges of the leaves overlap the anterior edges of those 
 next behind them (Fig. 201), when the leaves are said to be succubous ; or 
 the anterior edges of the leaves overlap the posterior edges of those next 
 in front of them (Fig. 202), when the leaves are said to be incubous. The 
 growth of the leaf is generally apical at first, and subsequently basal. 
 
 Fie. 201. Brooches of one of the aero- 
 rrrnous Junxermanniacese, P'a/iiochila as- 
 flenioides, seen from above: the leaves are 
 succubous ; at the apex, two of the shoots 
 benr sporopon'a, the one (b) having de- 
 l.isced, the oiher(n) being still closed; p 
 the involucre. 
 
 Fm. 202 Part of a shoot of Frul- 
 lania dilatata seen from below (x 20): 
 ul auricnlate lower leaf-lobes ; ol upper 
 leaf-lobe; the leaves are incubous; u 
 amphigastrium. 
 
 The sexual organs are generally borne on the main axis and its normal 
 branches, but in many cases they are confined to more or less specialised 
 ventral branches (gametophores). The place of development of the arche- 
 gonia affords the basis for the classification of the Jungermanniacese into 
 the two main groups, Acrogynee and Anacrogynse. In the former, which 
 includes nearly all the foliose forms, the archegonia are produced 
 from the apical cell and its youngest segments at the growing-point ; 
 hence when the formation of the archegonia takes place on a shoot its 
 further elongation is arrested. In the latter group, which includes all 
 the thalloid forms and some exceptional foliose forms, the archegonia are
 
 GROUP II. BHYOPHTTA : HEPATIC^E. 327 
 
 produced laterally, on the dorsal surface in the dorsiventral forms, on all 
 sides in the radial forms (species of Biella, Haplomitrium) ; hence the 
 growth in length of the shoot is not necessarily arrested. 
 
 The archegonia of the Acrogynae are borne eithe'r singly or in groups of 
 two or more. Each archegonium is developed from a single cell; when 
 the archegonium is single it is developed from the apical cell ; when there 
 are several archegonia, the development of them begins in the youngest 
 segment-cells of the growing-point. The archegonia are surrounded by 
 the leaves of the apex ; and in most cases the leaves of the last whorl are 
 coherent, forming an involucre, surrounding the single archegonium or 
 the group of archegonia. 
 
 The archegonia of the thai lo id Anacrogynae are borne in median dorsal 
 groups : in the radial Anacrogynae (Riella helicophyUa, Haplomitrium) 
 they are borne singly, scattered over the whole length of the stem as in 
 the former, or confined to the apical region as in the latter. They are in 
 all cases provided with some sort of protective organ. Among the thalloid 
 Anacrogynae the group of archegonia is surrounded, in Metzgeria, Aneura, 
 and Pseudoneura, by an involucre consisting of the short modified game- 
 tophore (ventral in Metzgeria) ; in Pellia, Symphyogyna, and Sphaero- 
 carpus a group (or each archegonium as generally in Sphaerocarpus) is 
 surrounded by an involucre developed as an outgrowth of the tissue of 
 the fertile branch. 
 
 The antheridia are borne, in all Jungermanniacese (except Haplomitrium) 
 on the dorsal surface of the shoot ; in Haplomitrium they are borne in 
 three rows on the sides of the apical region. 
 
 The antheridia are shortly stalked and are in all cases provided with 
 a protection. In Metzgeria the group of antheridia is invested by an 
 involucre which consists of the short modified ventral gametophore : in 
 the other thalloid Anacrogynae (e.g. Pellia) each antheridium is invested 
 by an involucre which grows up around it, so that it appears to be sunk 
 in the tissue of the shoot. In the Acrogynae the antheridia are borne, 
 singly or several together, in the axils of leaves; and in some forms 
 (e.g. Scapania, Lejeunia, Frullania) the upper lobe of the protecting leaf 
 is modified in form. 
 
 The distribution of the sexual organs varies even in the species of some 
 of the genera. Some of the Anacrogynse (e.g. Metzgeria, Pseudoneura, 
 Sphaerocarpus, Haplomitrium, etc.) are dioecious ; whereas others (e.g. 
 Pellia, some species of Aneura, Fossombronia, Symphyogyna) ar gener- 
 ally monoecious. In the monoecious forms the antheridia and archegonia 
 are generally borne on distinct branches (diclinous), but sometimes on the 
 same branch (monoclinous). When a dorsiventral shoot bears only 
 antheridia or archegonia, they are developed in the median line; but 
 when it bears both organs, the archegonia are median and the antheridia 
 lateral. 
 
 The Acrogynae are generally monoecious and diclinous. 
 
 The structure of the adult shoot of the Jungermanniaceae is very simple. 
 In thalloid forms which have no distinct midrib, the shoot consists of 
 parenchymatous cells forming a single layer at the margin and several
 
 328 PART IV. CLASSIFICATION. 
 
 layers (e.g. Pellia, Aneura) in the middle line of the shoot ; in those which 
 have a well-defined midrib (e.g. Metzgeria), the midrib consists of several 
 layers of cells, whereas the lamina consists of only a* single layer. In 
 Symphyogyna and Blyttia the midrib is traversed by a strand of elon- 
 gated prosenchymatous cells having thickened and more or less pitted 
 walls : a similar tissue occurs in the thick central portion of the shoot of 
 Pellia. 
 
 In the Acrogynse, the stem generally consists of an axial strand of 
 relatively thin-walled cells, surrounded by a cortex of narrow thick-walled 
 cells : the leaves are simply single layers of similar cells, and have no 
 midrib. 
 
 The root-hairs are, in all cases, destitute of the peculiar thickenings so 
 characteristic of the Marchantiacese. 
 
 B. The SPOKOPHYTE. The course of the development of the sporophyte 
 is, in its main features, essentially the same throughout the Jungerman- 
 niacese. 
 
 The oospore is divided by a transverse (basal) wall into two halves, 
 epibasal and hypobasal. The epibasal cell gives rise to the capsule and 
 its stalk (seta). It divides transversely, and the longitudinal divisions 
 follow in both cells so that the epibasal half of the embryo consists of two 
 tiers of each consisting of four cells. Further growth in length is effected 
 by the cutting off, by transverse walls, of segments from the cells forming 
 the apical tier ; but this apical growth is arrested, sooner or later, by the 
 formation of walls parallel to the free surface (periclinal) in the apical 
 cells, and also frequently in some of those below them, which indicate the 
 differentiation of the capsule-wall (amphithecium) from the internal mass 
 of cells (endothecium) which give rise to the spores and elaters. The 
 cells balow the capsule may, however, continue to grow and divide 
 transversely, and by means of this intercalary growth the full length of 
 the seta is attained; 
 
 In many of the Jungermanniacese (e.g. Pellia, Jungermannia, Frullania) 
 the lower end of the seta developes into a bulbous mass of cells forming a 
 false foot, the upper margin of which grows up so as to form a sheath round 
 the lower part of the seta in some cases. 
 
 The development of the hypobasal portion of the embryo is compara- 
 tively insignificant , in most cases it is merely a small appendage to the 
 lower end of the seta. The hypobasal cell enlarges somewhat, without 
 undergoing any division (e.g. Radula, often in Pellia); or it undergoes 
 transverse division to form a filament of two or three cells, the lowest of 
 which becomes elongated and grows down among the cells at the base of 
 the archegonium (e.g. Metzgeria, Aneura). In some forms, however (e.g. 
 Fossombronia), the hypobasal cell appears to give rise to a true foot, 
 bulbous in form, C9mparable to that of the Marchantieae (see p. 323). 
 
 In the further differentiation of the capsule, the cells of the amphithe- 
 cium undergo periclinal division so that the wall eventually consists of 
 two or more (up to six) layers of cells. In the wall-cells transverse 
 annular thickenings are usually developed. The planes of dehiscence of 
 the capsule, except in those forms which dehisce irregularly (Riella,
 
 GROUP II. BRYOPHYTA : HEPATIC JE. 329 
 
 Sphserocarpus), are marked out by four longitudinal rows of small-celled 
 tissue which correspond in position with the walls between the four apical 
 cells of the growing embryo. 
 
 The archesporium, which is co-extensive with the endothecium, presents 
 various degrees and forms of differentiation. In the Riellese it comes to 
 consist of a number of cubical cells, some of which become the mother- 
 cells of the spores, whereas the others persist as unaltered sterile cells. 
 In all the other Jungermanniacese &ome of the cells of the endothecium 
 are sterile, but they develope into elaters, becoming elongated in form 
 and spirally thickened, having sometimes two spirals, or only one. The 
 relative arrangement of the sterile and fertile cells, dependent upon the 
 growth of the capsule along different diameters, varies somewhat. In the 
 lower forms, the elongated archesphorial cells are arranged more or less 
 longitudinally, either quite straight (e.g. Frullania, Lejeunia), or radia- 
 ting from the apex of the capsule (Metzgeria, Aneura), or radiating from 
 the base of the capsule (Pellia, Badula): whereas in the higher forms 
 (Lepidozia, Calypogeia, Jungermannia), these cells are placed horizontally 
 round a central longitudinal axis, except at the apex where they radiate. 
 In most cases the sterile and fertile archesporial cells are mingled to- 
 gether, but in some cases certain parts of the archesporium give rise 
 especially to spores and others to elaters. Thus, in Pellia, the cells to- 
 wards the base and those in the longitudinal axis of the capsule form 
 only elaters, whereas in Jungermannia the formation of elaters is confined 
 to the cells near to the wall. 
 
 Whilst the development of the embryo is taking place, growth is also 
 proceeding in the archegonium and the adjacent tissue, giving rise even- 
 tually to the calyptra. Several of the archegonia of a group may be 
 fertilised, but generally only one gives rise to a fully developed sporo- 
 gonium, and itself takes part in the formation of the calyptra. The 
 calyptra is sometimes developed from the venter of the archegonium 
 alone (e.g. generally in the Acrogynae) ; in the Anacrogynae the adjacent 
 tissue of the shoot frequently takes part in its formation, as is shown by 
 the fact that the unfertilised archegonia of the original group are found 
 on the sides, or even on the top of the calyptra (e.g. Aneura, Pellia). The 
 wall of the calyptra consists of one or more layers of cells, and keeps pace 
 with the growth of the embryo which it encloses until the spores are mature. 
 The cells of the seta then rapidly elongate, causing the rupture of the 
 calyptra, and the capsule is exposed. The capsule then dehisces, 
 generally into four valves, sometimes irregularly, and the spore* are 
 set free. 
 
 The Jungermanniaceae may be classified as follows : 
 
 Series I. ANACROGYX.E : growth in length not necessarily arrested by 
 
 the development of archegonia. 
 Section A. Anelatereae : the sterile cells in the capsule do not 
 
 develope into elaters. 
 
 This section consists of the family Riellece: including the two 
 genera Kiella (foliose) and Sphaerocarpus (thalloid).
 
 odO PART IV. CLASSIFICATION. 
 
 Section B. Elatereae : the sterile cells in the capsule develope into 
 
 elaters. 
 
 o. Thalloid Forms : Metzgeria, Aneura, Pellia, etc. 
 ft. Foliose Forms : Fossombronia, Blasia, Haplomitrium (with radial 
 
 symmetry), etc. 
 Series II. ACBOGYN^: : growth in length arrested by the development of 
 
 archegonia ; all foliose. 
 
 This series includes a number of families of which the more 
 familiar genera are Plagiochila, Jungermannia, Scapania, 
 Lepidozia, Badula, Lejeunia, Frullania; etc. 
 Order III. Anthocerotaceae. 
 
 A. The GAMETOPHYTE. The protonema developed from the germinating 
 spore is a flattened plate of cells ; in Anthoceros the formation of the 
 flattened plate is sometimes preceded by the outgrowth of the contents 
 of the spore, covered by the endospore. into a filament at the apex of 
 which the plate of cells is developed. The adult shoot is developed as a 
 lateral out-growth from the flattened protonema. 
 
 The Morphology of the adult shoot. The adult shoot is thalloid, and its 
 symmetry is dorsiventral. It is semi-circular, or nearly circular, in out- 
 line in Anthoceros. There are no ventral scales 
 on the under surface, but numerous unicellular 
 root-hairs. 
 
 The growth of the shoot is effected, in Antho- 
 ceros, by a series of marginal growing-points. 
 In the growing-point there is a row of initial 
 cells, each of which acts as an apical cell ; their 
 form is wedge-shaped in Anthoceros, dorsal and 
 ventral segments being alternately cut off by 
 the formation of oblique walls. 
 
 (nat size) K the *ca "sules* Branching, or at least the formation of new 
 
 some as yet unopened. growing- points, takes place in the manner de- 
 
 scribed for the Marchantiacese (p. 132). 
 
 The sexual organs are developed from the dorsal segments formed in the 
 growing-point, and are situated in the middle line behind each growing- 
 point in Anthoceros. The antheridia are developed endogenously, and 
 remain enclosed in the tissue until maturity ; they are developed either 
 singly (some species of Anthoceros) or in groups. The archegonia are 
 sunk in the tissue, the apex of the neck reaching to the dorsal surface of 
 the shoot. The shoots are monoecious ; the sexual organs are sometimes 
 intermingled in the same group (frequently in Anthoceros). 
 
 The structure of the adult shoot. The adult shoot of Anthoceros consists 
 of several laj r ers of cells in the middle line, thinning out to a single layer 
 of cells at the margins. The tissue in the middle line consists of longi- 
 tudinally elongated cells, the walls of which, especially in the older parts 
 of the shoot, frequently present reticulate or even spiral thickening. 
 
 The chloroplastids of the Anthocerotaceae are peculiar, on account of 
 their relatively large size, and of the fact that they occur singly in the 
 cells and contain a pyrenoid (see p. 71).
 
 GROUP II. BRYOPHYTA : HEPATIC^. 331 
 
 B. The SPOROFHYTE. The early stages in the development of the 
 sporophj'te of the Anthocerotaceae appear to be much the same as in the 
 case of other Liverworts. The oospore divides transversely into an 
 epibasal and a hypobasal half : and each of these divides by two perpendi- 
 cular walls so that the embryo consists at this stage of eight cells. The 
 cells of the epibasal half divide transverse^ several times, and then 
 further apical growth in length is arrested by the formation of periclinal 
 walls, marking the differentiation of amphithecium and endothecium, first 
 in the four apical cells, and subsequently in those below them. By the 
 repeated formation of periclinal walls, the amphithecium comes to consist 
 of several layers of cells. The hypobasal cells undergo but few divisions, 
 giving rise to a bulbous foot, the superficial cells of which grow out into 
 papillae and penetrate between the cells of the adjacent tissue of the 
 gametophyte. 
 
 As regards the differentiation of the epibasal portion of the embryo, in 
 Anthoceros (Fig. 197) the archesporium is developed from the innermost 
 layer of cells of the amphithecium, a peculiarity, the only other instance 
 of which, in the Muscinese, is to be found in the Sphagnaceae: the 
 endothecium gives rise to an axial strand of sterile tissue, termed the 
 columtlla, which is completely invested (except at the base, where it is 
 continuous with the tissue of the foot) by the archesporium. 
 
 In all the genera some of the cells derived from the archesporium are 
 sterile. In some species of Anthoceros (e.g. vicentianus, giganteus, etc., 
 constituting the subgenus Anthocerites) these cells develope into elaters 
 with spiral thickening, each elater consisting of a row of cells with an 
 apparently continuous spiral band : in other species (e.g. tuberculatus, 
 glandulosus) the elaters have the same form, but they have no spiral band; 
 in others (Icevis, punctatus) the sterile cells do not form distinct elaters, but 
 a network of short cells, with spiral thickening, in the meshes of which 
 lie the mother-cells of the spores. 
 
 The sporogonium of Anthoceros has no seta ; when the apical growth 
 has ceased, the capsule continues to elongate by basal growth, and hence 
 does not ever become fully mature throughout. The pod-shaped capsule 
 splits from the apex into two valves (Fig. 203). Stomata occur in the 
 epidermis of the capsule in most species of Anthoceros, but they appear to 
 be wanting in the other genera. 
 
 Since the archegonia are sunk in the tissue of the shoot, the calyptra, 
 which invests the developing embryo, is developed mainly from the 
 surrounding tissue, and only to a small extent from the wall of the arche- 
 gonium.
 
 332 PART IV. CLASSIFICATION. 
 
 CLASS IV. MUSCI (Mosses). 
 
 A. The GAMETOPHYTE. The protoncma is more conspicuous in 
 the Musci than in the Hepaticse : it sometimes persists until the 
 sporogonia are developed and the spores are ripe (e.g. Ephemerum), 
 and in many cases the subterranean portion persists from year to 
 year. It is generally filamentous and much branched ; but in 
 some forms it is a flattened expansion (e.g. Sphagnum), or cylindri- 
 cal branched and shrubby, or it bears lateral flattened expansions 
 which are assimilatory organs (e.g. Tetraphis, etc.). The filamen- 
 tous protouema consists of a subaerial and of a subterranean 
 portion, which differ in that the cells of the former contain chloro- 
 plastids, their walls are colourless, and the septa are transverse ; 
 whereas those of the latter do not contain chloroplastids, and their 
 walls are brown and their septa oblique. The protonema presents, 
 in fact, a certain differentiation into shoot and root, the term 
 rhizoids being applied to the root-like filaments. This differ- 
 entiation is, however, of little morphological value, since the 
 differences between the shoot- and root-filaments depend entirely 
 on external conditions : thus, if the rhizoids be exposed to light 
 they assume the characters of the subaerial filaments. The flat- 
 tened protonema of Sphagnum bears rhizoids on its margins and 
 under surface. 
 
 The growth in length of the protonemal filaments is apical : the 
 terminal cell behaves as an apical cell from which segments are 
 successively cut off by transverse or oblique walls. 
 
 The Adult Shoot arises as a lateral bud on the subaerial portion 
 of the protonema. In some cases (Bryinese) the subterranean 
 portion gives rise to lateral buds : these are small, spherical or 
 lenticular, multicellular bodies of a brown colour, filled with re- 
 serve materials, and are termed bulbils ; when they are brought to 
 the surface they give rise to adult shoots, either directly or with 
 the intervention of protonema. 
 
 The adult shoot is in all cases differentiated into stem and 
 leaves, and may be branched or unbranched. Its symmetry is 
 commonly radial or isobilateral, less commonly dorsiventral. In 
 the former case it is attached to the soil by rhizoids springing 
 from its basal portion ; in the latter, by rhizoids developed on its 
 under surface. In Sphagnum, rhizoids occur only on young 
 shoots.
 
 GROUP II. BRTOPHYTA : MUSCI. 
 
 333 
 
 The growth of the adult shoot and its branches is effected by 
 means of an apical growing-point with a single apical cell which is 
 generally a three-sided pyramid. 
 
 Each segment cut off from the apical cell gives rise to a leaf : 
 hence the arrangement of the leaves, and the symmetry of the 
 shoot, is generally determined by the form of the apical cell. 
 Thus in Fissidens, the leaves are arranged in two rows and the 
 symmetry of the shoot is isobilateral : in other cases (e.g. Fontin- 
 alis) the leaves are in three rows, and the symmetry of the shoot 
 is radial. 
 
 Branching is confined to perennial shoots, and is lateral, never 
 dichotomous. When the growth of the main shoot is arrested by 
 the formation of 
 sexual organs at 
 the apex (acrocar- 
 pous), one (or 
 more) of the lateral 
 branches (termed 
 innovations) close 
 behind the apex 
 assumes the cha- 
 racters of the main 
 shoot and carries 
 on the growth : the 
 resulting branch- 
 sj'stem is cymose, 
 either sympodial or 
 dichasial according 
 to the number (one 
 or more) of the in- 
 novations at each 
 branching. When 
 the growth of the 
 main stem is not 
 thus arrested, the 
 sexual organs be- 
 ing borne on lateral branches (pleurocarpous), the branch-system 
 is monopodial and racemose. 
 
 The branches (except the innovations) frequently differ in 
 various ways from the primary shoot. Thus, in Sphagnum and 
 other pleurocarpous Mosses, the leaves of the branches differ in 
 
 FIG. 204. Longitudinal section through the apical region 
 of a stem of Fnntinalis antijtyretica, a Moss growing in water 
 (after Leitgeb) : v the apical cell of the shoot, producing three 
 rows of segments which are at first oblique and afterwards 
 placed transversely (distinguished by a stronger outline). 
 Each segment is first of all divided by the wall a into an 
 inner and an outer cell; the former produces a part of the 
 inner tissue of the stem, the latter the cortex of the stem and 
 a leaf. Leaf-forming shoots ari^e beneath certain leaves, a 
 triangular apical cell (z) being formed from an outer cell of 
 Hie segment, which then, like v, produces three rows of seg- 
 ments ; and each segment here also forms a leaf.
 
 334 PART IV. CLASSIFICATION. 
 
 size and shape from those of the primary shoot : in other forms 
 (e.g. Thuidium) the lateral branches have limited growth. 
 
 The development of the branches, though never axillary, is in- 
 timately connected with the arrangement of the leaves, since the 
 apical cell of a branch is developed from the same segment as the 
 corresponding leaf. Each branch is developed beneath the corres- 
 ponding leaf, either in the median line (e.g. Fontinalis), or on one 
 side of it (e.g. Sphagnum). However, a branch is not developed in 
 connexion with each leaf. 
 
 In most cases the adult shoot does not present any differentia- 
 tion into a vegetative and a reproductive portion (gametophorej, 
 but such a differentiation is to be found in certain forms. Thus, in 
 Splachnum, the male organs are borne upon a leafless prolongation 
 of the shoot. 
 
 In Sphagnum the apex of the female shoot grows out, after fer- 
 tilisation of the -archegonium, into a long leafless shoot termed a 
 pseudopodium, which bears the sporogonium (here destitute of a 
 seta) at its apex. In Aulacomnium and Tetraphis there is a some- 
 what similar terminal shoot, likewise termed a pseudopodium, 
 which bears at its apex a cluster of gemmae. 
 
 The Leaves present considerable variety in size and form : they 
 may be divided, in the first instance, into foliage-leaves and in- 
 volucral leaves. 
 
 The foliage-leaves are simple and sessile ; they are usually 
 inserted transversely on the stem, and are closely packed. They 
 are generally larger towards the upper than towards the lower 
 part of the shoot. In most pleurocarpous Mosses the leaves of the 
 lateral branches differ more or less from those of the main stem. 
 In some forms (e.g. Bryum roseum, Climacium, etc.), where the 
 branches take the form of creeping runners or stolons, the leaves 
 of these branches are reduced to scales (cataphyllary leaves). 
 
 The involucral leaves are arranged in one or more whorls, form- 
 ing an involucre round the sexual organs. Those surrounding a 
 group of male organs are commonly larger than the foliage-leaves, 
 and in some cases (e.g. Polytrichacese) are coloured red or yellow. 
 Those surrounding a group of female organs differ but little from 
 the foliage-leaves: the more internal leaves are smaller than the 
 external : the innermost leaves, distinguished as perichcetial leaves, 
 are quite rudimentary when the archegonia are mature, but after 
 fertilisation has taken place they grow up round the base of the 
 seta of the sporogonium.
 
 GROUP ii. BRYOPHYTA: MUSCI. 335 
 
 The Sexual Organs are borne in groups (rarely singly) at the 
 apex either of the main shoots (acrocarpous), or of lateral branches 
 (pleurocarpous), surrounded by involucral leaves, each group with 
 its involucre constituting a receptacle. Generally speaking the 
 growth of the shoot or branch ceases with the development of the 
 sexual organs, the apical cell itself giving rise to an antheridium 
 or an archegonium ; but in some male receptacles (e.g. Polytrichacese 
 and some other Bryinese, also Sphagnum) the apical cell persists as 
 such ; consequently the elongation of the shoot or branch is not 
 necessarily arrested by the development of the antheridia, and 
 appears to grow through the receptacle. 
 
 Among the sexual organs there are usually present multicellular 
 hairs, termed paraphyses: they are often filamentous, but in some 
 cases (e.g. male receptacle of Funaria) the terminal cells are large 
 and rounded ; they are hyaline, or coloured red or yellow, some- 
 times brownish, and the cells frequently contain chloroplastids. 
 They are more numerous and more highly developed in the male 
 than in the female receptacles ; they are rarely absent in plants 
 which grow in dry situations, but frequently in those forms which 
 grow in water or in damp places. Their function seems to be 
 that of sesreting water to prevent the drying-up of the sexual 
 organs. 
 
 The antheridia are generally club-shaped (spherical in Sphag- 
 num), and are shortly stalked (see Fig. 192). The antheridia 
 generally open at the apex to allow the spermatozoids to escape. 
 The archegonia are stalked ; the neck is long, and the venter is 
 but slightly dilated (Fig. 195). 
 
 The distribution of the sexual organs is various. The plant 
 may be monoecious (i.e. may bear both kinds of sexual organs), or 
 it may be dioecious : amongst the monoecious forms may be distin- 
 guished those which are monoclinous, that is, which have both 
 male and female organs in the same receptacle (e.g. Bryum la- 
 custre, cuspidatum, etc.), the archegonia being in the middle ; and 
 those which are diclinous, that is, which bear the male and female 
 organs in distinct receptacles : sometimes (e.g. Bryum pendulum, 
 arctic um, etc.) the plants are heteroclinous or polygamous, that is, 
 some receptacles are hermaphrodite, whilst others are unisexual. 
 In the dioecious species the male plant is usually the smaller, and 
 is short-lived. In some species the plants are sometimes monoecious 
 (either monoclinous or diclinous) and sometimes dioecious. 
 
 The Structure of the Adult Shoot. The stem presents more or
 
 336 PART IV. CLASSIFICATION. 
 
 less well-marked histological differentiation. The outer portion 
 consists of an epidermal layer, followed by one or more layers of 
 elongated prosenchymatous cells, with thickened walls which are 
 yellow or brown, forming the cortex which passes by gradual 
 transition into thin-walled parenchymatous ground-tissue ; in the 
 subterranean shoots of the Polytrichacese, however, the cortex is 
 parenchymatous and thin-walled, whilst the ground-tissiie is thick- 
 walled. 
 
 In species which live under such conditions that both transpira- 
 tion and the absorption of water may be actively carried on, a 
 central strand is differentiated in the longitudinal axis of the 
 stem, the structure of which presents two principal varieties ; it 
 may be simple, consisting of a group of thin-walled tracheides, 
 destitute of protoplasmic cell-contents (e.g. Funaria, etc.) ; or it 
 is compound, consisting of a group of thick-walled tracheides, or 
 of several groups of thin- walled tracheides with intervening paren- 
 chymatous or prosenchymatous cells, surrounded by several layers 
 of thin-walled elongated cells with oblique ends, containing abun- 
 dant protoplasm and starch-grains (e.g. Polytrichum). This cen- 
 tral strand is, in fact, a rudimentary vascular stele : the tracheides, 
 though unlignified, represent the wood or xylem : in the simple 
 form, the phloem is unrepresented; in the compound form it is 
 represented by the elongated cells which surround the xylem. 
 
 The structure of the leaves shows considerable variety. Most 
 commonly the leaf-blade consists of a single layer of cells, con- 
 taining chloroplastids, with or without a midrib. In the midrib of 
 those forms which have a central strand in their stems, there are 
 one or more rudimentary vascular bundles of a structure corres- 
 ponding to those in the stein. These bundles enter the stem as 
 leaf-traces, and either end blindly, or join the central strand of the 
 stem. The rest of the midrib is made up chiefly of thick-walled 
 prosenchymatous cells. It must not be overlooked that the absorp- 
 tion of water is effected, in the Mosses, mainly by the leaves. 
 
 The most remarkable deviations from the usual structure of the 
 lamina are those offered by the Sphagnacese and the Polytrich- 
 acese. In the Sphagnacese the constituent cells are of two kinds : 
 large empty cells with perforated walls (see p. 94, Fig. 73 A}, and 
 small cells containing chloroplastids. In the Polytrichacese, the 
 assimilatory tissue is borne on the surface of the broad midrib in 
 the form of numerous longitudinal plates, one cell thick. 
 
 The rhizoids which spring from the shoot are essentially similar
 
 GROUP ii. BRYOPHYTA: MUSCI, 337 
 
 to those of the protonema: in the Polytrichaceae they become 
 wound together into strands. 
 
 The gametophyte of the Musci possesses a remarkable capacity 
 for vegetative propagation. Thus the perennial protonema of many 
 species serves year by year to produce new adult shoots which, not 
 un frequently, become distinct plants. In the pleurocarpous forms 
 (e.g. Sphagnum, Hypnum) the main axes gradually die away from 
 behind, the lateral branches becoming isolated, and constituting 
 the main axes of new plants. In probably the majority of the 
 Musci almost any portion of the body, a piece of stem or a leaf, 
 will, under proper conditions, grow out into protonemal filaments, 
 which give rise to adult shoots in the usual manner. In certain 
 species, belonging to the Bryinese (Aulacomnium palustre, A. 
 androgynum, Tetraphis pellucida\ multicellular gemmae are pro- 
 duced at the apex of the stem, either free or enclosed in a cupule 
 (Tetraphis). In Aulacomnium palustre the gemmae appear to be 
 modified leaves ; in A. androgynum and in Tetraphis the gemmae 
 are smaller, and consist of but few cells ; in Tetraphis they are 
 borne on long stalks. On being placed under favourable conditions, 
 the cells of the gemma grow out into protonema. 
 
 B. The SPOROPHYTE. The oospore divides into two by a wall 
 (basal wall) transverse to the long axis of the archegonium : from 
 the epibasal half is developed the capsule (theca] and its long or 
 short stalk (seta\ whilst the hypobasal half gives rise to a more or 
 less well -developed foot : the whole being termed the sporogonium. 
 
 The segmentation of the oospore into octants (see p. 314) is 
 confined to the epibasal cell, and even this can only be traced in 
 Sphagnum, which in this respect resembles the Liverworts. In 
 the other Mosses, the epibasal cell undergoes one or more trans- 
 verse divisions, after which two oblique walls, cutting each other 
 at an acute angle, are formed in the terminal cell ; the cell marked 
 out by these two oblique walls is a two-sided apical cell by the 
 growth and segmentation of which the further development of the 
 embryo is effected. 
 
 At an early stage in the differentiation of the capsule (see Fig. 
 197) the amphithecium, consisting of one or more layers of cells, 
 can be distinguished from the endothecium. The amphithecium 
 constitutes eventually the wall of the capsule ; the internal tissues 
 being formed for the most part from the endothecium. 
 
 The archesporium becomes differentiated in various positions 
 within the' young capsule. It is differentiated, in the Sphagnaceae,
 
 od8 PART IV. CLASSIFICATION. 
 
 from the innermost layer of the amphithecium ; in the Bryinese, 
 from the external layer of the endothecium. The cells which 
 bound the archesporium on each side constitute the spore-sac. The 
 endothecial tissue which lies internally to the archesporium con- 
 stitutes the columella. In the Sphagnacese the archesporium is a 
 hollow hemisphere covering the top of the columella like a cap ; in 
 the Bryinese the archesporium is a hollow cylinder surrounding 
 the columella which extends to the apex of the capsule. In the 
 Bryinese a large intercellular space is developed in the amphi- 
 thecium, between its outer and its two inner layers ; in most 
 Polytrichacese a similar intercellular space is developed in the 
 endothecium internally to the spore-sac, between it and the central 
 portion of the columella. 
 
 At maturity the internal cells of the capsule become dry and 
 disorganised, so that it simply contains the spores which now lie 
 loose in its cavity. It dehisces by the throwing off of its apical 
 portion as a lid or operculum in Sphaguacese and the higher 
 Bryinese (Stegocarpse) ; or it ruptures irregularly or simply decays, 
 as in the lower Bryinese (Cleistocarpse). In the higher Bryinese 
 the mouth of the dehisced capsule bears a fringe, the peristome, 
 the development and structure of which will", be described sub- 
 sequently (p. 344). 
 
 The basal portion of the capsule, where it joins the seta, is 
 termed the neck. In the Polytrichacese the neck is considerably 
 dilated, as also in various species of Splachnum ; whilst in other 
 species of Splachnum it grows out into an umbrella-shaped struc- 
 ture. When the neck is thus markedly developed it is termed 
 the apophysis. 
 
 The histological differentiation of the sporogonium is well- 
 marked. There is a well-defined epidermis, in which, on the 
 capsule, stomata of various forms are generally present ; either 
 scattered all over, as in the Sphagnacese ; or confined to a par- 
 ticular region of the capsule, generally the neck or the apophysis, 
 in the Bryinese. The operculum and the peristome (Bryinese) 
 show considerable complexity of structure. The structure of the 
 seta in the higher Bryinese, where alone it is elongated, very 
 much resembles that of the stem : in many forms, even in such 
 in the stem of which no central strand is present, there is a 
 central strand in the seta, marked off from the ground-tissue by 
 one or two layers of sheath-cells. In the Bryinese also, the struc- 
 ture of the neck (or apophysis) is generally characterised by the
 
 GROUP II. BRYOPHYTA : MUSCI. 335) 
 
 presence of loose assimilatory tissue, rich in chloroplastids, the 
 intercellular spaces of which communicate with the outer air by 
 means of the stomata. 
 
 The hypobasal cell undergoes relatively few divisions. In the 
 Sphaguacese it gives rise to a bulbous foot. In the Bryinese (e.g. 
 Qrthotrichum, Barbula, Atrichum where the hypobasal cell under- 
 goes a single division by a transverse wall) the true foot is 
 rudimentary, but it is functionally replaced (e.g. Phascum, Ephe- 
 merum, Polytrichum) by the dilated lower end of the seta which 
 constitutes a false foot. 
 
 After fertilisation, the venter of the archegonium developes into 
 the calyptra which, for a time, keeps pace with the growth of 
 the contained embryo, but is eventually ruptured by the gradual 
 elongation of the seta. In Sphagnacese, and in some of the lower 
 Bryinese, the whole of the ruptured calyptra remains as a sheath, 
 the vaginula, round the base of the short seta ; in the higher 
 Bryinese the lower portion remains as the vaginula, whilst the 
 upper portion is raised up like a cap (still called calyptra) on the 
 top of the elongating sporogonium. The floor of the receptacle 
 (i.e. the apex of the sexual shoot) is also stimulated to growth, 
 forming in most cases a conical projection on which are borne the 
 paraphyses and the unfertilised archegonia, whilst in Sphagnacese 
 it elongates into the long pseudopodium (see p. 312). The perichse- 
 tial leaves also grow up round the lower part of the seta or of the 
 pseudopodium. 
 
 The sporogonium, possessing, as it usually does, assimilatory 
 tissue and stomata, can assimilate the carbon dioxide of the air, 
 and can transpire actively. The supply of water necessary to 
 meet the loss by transpiration is obtained, together with salts 
 in solution, from the gainetophyte, being absorbed from it by the 
 true (hypobasal) or the false (epibasal) foot, and travels to the 
 capsule through the rudimentary xylem-tissue of the central strand 
 present in the seta of the higher forms. It is a point of consider- 
 able physiological interest that the absorption of water in the 
 first instance by the gainetophyte is apparently effected for the 
 most part by the leaves rather than by the rhizoids. 
 
 The remarkable capacity for vegetative propagation manifested 
 by the gametophyte is shared by the sporophyte. It has been 
 ascertained that if portions of the capsule or of the seta, whilst 
 the cells are still living, be kept under favourable conditions, 
 the superficial cells will grow out into protonemal filaments. In
 
 340 PART IV. CLASSIFICATION. 
 
 this way the gametophyte may be derived from the sporophyte 
 'by budding, without the intervention of spores. 
 
 The principal orders of Mosses are the Sphagnacese and the 
 "Bryinese. 
 
 Onler I. Sphagnaceae (Bog-Mosses). 
 
 A. The GAMKTOPHYTE. The spore gives rise on germination to a fila- 
 mentous protonema ; when germination takes place in water, the proto- 
 nema remains filamentous and branches, but when it takes place on a 
 solid substratum the protonema assumes the form of a branched cellular 
 expansion attached to the substratum by root-like protonemal filaments. 
 In either case adult shoots are developed as branches upon the protonema. 
 
 The Morphology of the Adult Shoot. The shoot is radially symmetrical, 
 and is differentiated into stem and leaves. It consists of a main axis 
 bearing numerous lateral branches. 
 
 Growth is effected, in both the main axis and the lateral branches, by 
 means of a growing-point in which there is a three-sided apical cell. 
 
 The Sexual Organs are borne on specially modified lateral branches 
 (gametophores), the antheridia and archegonia being borne on distinct 
 branches, and in some species on distinct shoots. 
 
 The branch which bears antheridia (antheridiophore) is elongated and is 
 covered with small, closely packed, imbricate leaves, by the side of each 
 of which an antheridium is developed. The antheridium, which is raised 
 upon a long stalk, is spherical ; it opens by the splitting of the wall into 
 valves from the apex downwards. 
 
 The branch which bears archegonia (archegoniophore) is short ; it bears 
 at its apex a group of (1-5) archegonia, surrounded by rather large 
 involucral leaves with rudimentary perichsetial leaves. 
 
 The Structure of the Adult Shoot. The main axis has no central strand ; 
 it consists of a mass of elongated thin-walled parenchymatous cells, 
 which gradually passes over into an external zone of prosenchymatous 
 cells, the walls of which are thick and brown 5 externally to this is a 
 cortex, consisting of 1-5 layers of cells which are usually empty, and 
 have large holes in their walls (except the Sphagna cuspidata) ; in some 
 cases (Sphagna cymbifolia) the cortical cells have spiral thickenings. 
 
 The leaves vary in form according to their position ; thus stem-leaves, 
 branch-leaves, small scaly leaves, and involucral leaves may be dis- 
 tinguished. They are sessile, and have a broad insertion ; in most cases 
 the leaf is connected with the prosenchymatous tissue of the stem, the 
 leaf-tissue extending through the cortex. The stem-leaves have, at the 
 base, a pair of lateral appendages, the auriculae. 
 
 The leaf consists of a single layer of cells, and has no midrib. It is 
 made up of two kinds of cells : large empty cells of various forms with 
 perforated walls frequently with spiral or some similar form of thicken- 
 ing (Fig. 73, C}: small cells, arranged between the preceding, containing 
 protoplasm and chloroplastids. The relative arrangement of these two 
 kinds of cells affords a means of classification. Nostoc and other Algae 
 are frequently found in the large empty cells.
 
 GROUP ii. BRYOPHYTA: MUSCI. 341 
 
 The Sphagnacese have no special organs for vegetative propagation; 
 but they multiply vegetatively by the dying away of the main stems so 
 that the lateral branches become separate and constitute distinct plants ; 
 consequently these plants are found in considerable masses. They in- 
 habit damp, boggy spots, and retain a considerable quantity of water 
 in the open cells of the branches and leaves. Masses of Sphagnum thus 
 saturated with water form peat-mosses or peat-bogs, the water being 
 raised to the surface by means of the capillary system formed by the open 
 cells. 
 
 B. The SPOROPHYTE. The oospore, as in other Mosses, is divided by the 
 transverse basal wall into an epibasal and hypobasal half. The epibasal 
 half gives rise to the capsule : it grows at first apically, segments being 
 formed by transverse walls, each segment being divided into four cells 
 (quadrants) by walls at right angles to each other: after six or eight 
 
 FIG. 20(5. Longitudinal section (diagram- 
 matic : x 19) of the sporogonium of Spbag- 
 num : p* pseudopodium ; / foot ; c calyptra 
 
 FIG. 205. Part of shoot of Sphagnum with neck of archegonium h ; a* arche- 
 
 icutiwl iiun (nat. size). /: Capsules. Bporium. 
 
 segments have been formed, apical growth ceases, the further growth 
 being intercalary. The cells of each segment become differentiated each 
 into an external and an internal cell; the external cells constitute the 
 amphithecium, the internal cells the endothecium. The amphithecium 
 comes to consist of several layers by periclinal divisions, the first formed 
 and most internal layer constituting, in its upper half, the archesporium ; 
 the endothecium constitutes the columella. Thus the archesporium is a 
 hollow hemisphere which covers the columella as a cap. There is no 
 intercellular cavity formed in the capsule. 
 
 The hypobasal half of the oospore undergoes but few divisions, forming 
 a bulbous foot, the superficial cells of which grow out into short) 
 papillse. 
 
 The fully developed sporogonium consists of a capsule attached to the 
 foot by a very short seta ; the wall of the capsule consists of a single
 
 342 PART IV. CLASSIFICATION. 
 
 layer of cells, and has numerous stomata. The capsule opens by the 
 throwing off of the apical portion of the wall as an operculum. There is 
 no peristome. 
 
 When the cal3*ptra is ruptured, it remains as a vaginula round the 
 base of the capsule. No part of it is carried upon the top of the capsule. 
 
 The growth of the archegoniophore is stimulated by fertilisation. It 
 grows (Fig. 206 j?i) out at its apex into a long leafless stalk, the pseudo- 
 podium, expanded at the top into a cushion of cells in which the foot of 
 the sporogonium is embedded ; the perichsetial leaves grow and surround 
 the base of the stalk. 
 
 The order consists of the single genus Sphagnum, of which there are 
 very many species. 
 
 Order II. Bryineae. 
 
 A. The G ^METOPHYTE. The protonema is filamentous, though in some 
 cases (e.y. Tetraplris pellucida) it developes flattened cellular appendages 
 which are assimilatory organs. The subaerial portion of the protonema 
 is generally short lived, though in some cases it persists (e.g. Ephemerum) 
 at least until the sporogonium has been developed and the spores 
 are ripe : the subterranean portion frequently persists from year to year. 
 The subaerial portion gives rise to the gametophores as lateral buds ; in 
 some forms the subterranean portion produces lateral buds in the form of 
 bulbils (p. 332) which, when* they are brought to the surface, give rise to 
 gametophores either directly or indirectly with the intervention of 
 protonema. It is commonly the case that, when protonema is kept dry, 
 some of the cells grow larger and their walls thicker, whilst the other 
 cells perish ; the persistent cells, when moistened, develope into filaments. 
 
 The Adult Shoot does not present, with regard either to its morphologj- 
 or its histology, any especially characteristic features ; it varies in size 
 from a mere bud in such forms as Phascum and Ephemerum, where it is 
 annual, to a shoot several inches long in such forms as Fontinalis and 
 Polytrichum where it is perennial. In the latter case there is general 1}- 
 a central strand, and frequently leaf-traces, in the stem. It may be 
 either acrocarpous or pleurocarpous, a feature which is important in the 
 classification of the group. The leaves have commonly a midrib : the 
 lamina generally consists (e.g.. Funaria, etc.) of a single layer of cells. 
 The leaves of Leucobryum resemble those of Sphagnum in that they 
 consist of two kinds of cells, an internal layer of small living cells with 
 chloroplastids, and external layers of dead cells with perforated walls ; 
 the peculiar structure of the leaves of Polytrichum has been alread}- 
 described (p. 336). 
 
 B. The SPOROPHYTE presents features, both as to its morphology and 
 histology, which are characteristic of the group. It is differentiated into 
 a true hypobasal foot, a seta, and a capsule. The true foot is rudi- 
 mentary. The seta is relatively short in the lower forms; a false 
 (epibasal) foot is frequently developed from the lower portion of the seta. 
 The neck of the capsule has nearly always stomata in its epidermis, 
 and is developed into a distinct apophysis in some forms ( e.g. Splachnum, 
 Polytrichum). Part of the external layer of the endothecium becomes
 
 GROUP II. BRYOPHYTA : MUSCI. 343 
 
 the archesporium, which forms a hollow cylinder round the columella, 
 but does not extend over the top of it : an air-chamber is developed in the 
 amphithecium round the spore-sac, and is generally traversed by strands 
 of cells (containing chloroplastids) stretching from the wall of the capsule 
 to the spore-sac. In the lower forms the capsule is either indehiscent, its 
 wall becoming eventually disorganised, or it ruptures irregularly ; in the 
 higher forms, the apical portion of the wall is thrown off as an oper- 
 culum, and a peristome is generally developed round the aperture thus 
 formed. In all cases a portion of the calyptra is carried up as a cap on 
 the top of the developing sporogonium. 
 
 The Bryineae are classified as follows : 
 
 Tribe I. Cleistocarpee. Tribe II. Stegocarpae. 
 
 Tribe I. CLEISTOCARP^E. The adult shoots are generally minute, un- 
 branched, annual, and always acrocarpous; there is generally a central 
 strand in the stem, and a mid-rib in the leaf. 
 
 With regard to the sporogonium, the seta is generally short, sometimes 
 expanded at the base into a false (epibasal) foot (e.g. Phascum, Ephe- 
 merum), without any central strand in some forms. The capsule does 
 not open by means of an operculum, nor has it any peristome : it either 
 ruptures irregularly, or the wall simply 
 decays. 
 
 Tribe II. STEGOCARPAE. The character- 
 istics of this tribe are to be found in 
 the sporogonium, which is distinguished 
 by the formation of an operculum and, 
 
 generally, of a peristome. 
 
 FIG, 207. a Ephemerum, sernituui 
 The operculum is developed from the (x 3) . b 8hoot of AndreaM nira ii, f 
 
 apical portion of the capsule, either from with (K) capsule (nat. size). 
 the epidermis alone (e.g. Georgiaceae), or 
 
 from it and one or more of the subjacent amphithecial layers. The cell- 
 walls become cuticularised and assume a yellow or brown colour. The 
 outline of the operculum is circular; its form cap-like, more or less 
 flattened in some cases, more or less conical in others, sometimes apiculate. 
 
 The limit between the developing operculum and the rest of the capsule 
 (urn) is generally marked by a slightly prominent zone, consisting of one 
 or more rows of rather large epidermal cells, with cuticularised outer 
 walls, termed the ring or annulus : its position is just above the level of 
 the top of the spore-sac and of the air-chamber. 
 
 The peristome is developed within the operculum, from the innermost 
 layer or layers of the amphithecial cells; the entire walls, or only portions 
 of the longitudinal and transverse walls, of larger or smaller plates of 
 these cells, become thickened, cuticularised, and coloured yellow or brown. 
 The unthickened cell-walls, or the unthickened portions of them, break 
 a way as the capsule becomes ripe, leaving only the thickened portions 
 forming, as it were, a skeleton attached to the urn just below the level of 
 the annulus. The following are the principal varieties of peristome- 
 formation. In the Georgiaceae (e.g. Tetraphis) the peristome is developed 
 from the two layers of cells beneath the epidermis which forms the
 
 344 
 
 PART IV. CLASSIFICATION. 
 
 operculum : the walls of these cells all become thickened ; when the oper- 
 culum falls off this plate of tissue splits from the centre into four equal 
 segments which are the teeth of the 
 peristome. In most Mosses the peri- 
 stome is formed from a single layer of 
 cells, and consists of two rows of teeth, 
 an inner and an outer. This double 
 peristome is dependent upon the dis- 
 tribution of the cuticul arisation of the 
 walls : both the internal and the ex- 
 ternal walls of the peristomial cell- 
 layer become cuticularised, but the 
 lateral and part of the transverse 
 walls joining them remain unaltered 
 and eventually break away, leaving 
 the thickened internal and external 
 walls as separate strips, which may be 
 further divided longitudinally into 
 teeth. The teeth of the outer peri- 
 stome are generally larger than those 
 of the inner which are sometimes dis- 
 tinguished as cilia : their number is a 
 power of two (4-8-16-32-64.) There is 
 considerable variety in the structure 
 and form of the peristome ; this affords 
 a means of classification. The genus 
 Polytrichum, for instance, is charac- 
 terised by the fact that the teeth of 
 the peristome consist of strands of 
 thick-walled fibres, the tips of which are not free, as is usually the case, 
 but are connected by a membrane stretched over the aperture of the urn, 
 termed the epiphragm. 
 
 A peristome is not present in several genera (e.g. Gymnostomum , 
 H3 r menostomum, Schistostega, etc.); nor 
 in some species (e.g. species of Pottia and 
 Encalypta, etc.) belonging to genera in 
 which a peristome is usually present. 
 
 As the capsule matures, the cells(except 
 the spores) lose their cell-contents ; and 
 those whose walls have not become 
 thickened and cuticularised, dry up and 
 shrink, the shrinkage being necessarily 
 accompanied by the tearing of the thin 
 walls in various parts. The persistent 
 cuticularised walls are highly hygro- 
 
 FiG. 209. -Mouth of thethecaof { d k j j consequence of the 
 
 Fontmalis antipyretic.', ap Outer 
 
 peristome ; ip inner peristome ( x tensions set up by the unequal stretching 
 60.J and contraction of these walls, due to 
 
 FIG. 208. Funaria hygrometrica. A 
 An adult shoot (g), bearing a calyptra 
 (c). B A plant (g) bearing a nearly 
 ripe sporogonium ; s its seta ; / the 
 capsule ; c the calyptra. C Median 
 longitudinal section of the capsule : 
 d operculum ; a annulus ; p peristome; 
 cc'columella; h air-cavity ; s the arche- 
 sporium.
 
 GROUP II. BRYOPHYTA : MUSCI. 
 
 345 
 
 X J- 
 
 Fm. 210. Sporogoninm of Funaria hyyromelrica. A, s seta; b capsule; e calyptra (x6). 
 15 Section of a half-developed capsule (x 10): c columella ; archesporium ; I air-cavity; 
 d sub-opercular tissue ; p peristome. C Apical portion of the same capsule ( x 40) j d oper- 
 culum; id sub-opercular tissue; ap outer peristome; tp inner perisiome ; r ring; I air- 
 fpace; c coliimel'a ; s spore-sac. 
 
 variations in their moisture, that the splitting off of the operculum is 
 effected. 
 
 The Stegocarpse are classified as follows : 
 
 Sub-tribe AciWCARPM : archegonia terminal on 
 the main shoots ; but ths sporogonia are some- 
 times apparently lateral in consequence of the 
 growth of lateral branches (innovations) which 
 force the apex: of the main shoot to the side. 
 
 Sub-Tribe PLEUROCARP& .- archegonia (and 
 subsequently the sporogonia) borne terminally 
 on short lateral branches. 
 
 The following are among the more familiar 
 species of acrocarpous Mosses : 
 
 Dicranuni scoparium, with sickle-shaped leaves, 
 is common in woods. Leucobryum glaucum has 
 leaves consisting of several layers of cells, which. 
 resemble those of Sphagnum in their structure ; 
 it occurs in Pine-woods and on moors. Cerato- 
 don purpureus, with a red seta and a short stem, 
 is very common in various localities. Barbula 
 muralis grows in patches on walls and rocks; 
 the midrib of the leaves is prolonged into a 
 hair, so that the patches of Moss look greyish. 
 Tetraphis pellucida has bright green leaves ; it 
 u;rows on decayed tree-trunks, and bears gemmae 
 of peculiar form. Grimmia pulvinata occurs on 
 walls and stones in round greyish-green patches 5 
 the capsules have very short setae. Orthotrichum 
 affine and other species have also shortly-stalked 
 capsules, and are common on tree, Funaria ^< 
 hyyrometrica (Figs. 208, 210) has an oblique, jDear- c calyptra. 
 
 FIG. 211. Two plants of 
 P'tyMch /onnowtm bear-
 
 346 PART IV. CLASSIFICATION. 
 
 shaped capsule*, the long setae have the peculiarity of contracting into 
 a spiral on being wetted and dried ; it is common on walls and paths. 
 Pol ijtricJium formosum (Fig. 211) and other species are the largest of our 
 indigenous acrocarpous Mosses ; they have large dark green leaves and 
 long hairy calyptrse an'd are common in woods and on heaths. 
 
 The following are among the more familiar species of pleurocarpous 
 Mosses : 
 
 Fontinalis antipyretica floats in water. Neckera crispa, with flat out- 
 spreading leaves, grows on rocks. Tliuidium ahutimim and other species 
 grow on banks and in woods; they have regular, piniiately-branched stems, 
 and very small, closely-set leaves. Leucodon sciuroides is common on 
 tree-trunks. Bracliytliecium rutabulum is common in woods. Eurhyncliium 
 prcelonyum, with long creeping stems, occurs in woods and damp gardens. 
 Hypnum cupressiforme is very common on tree-trunks, and H. cuspidatum 
 and giganteum in bogs and ditches. Hylocomium triquetrum is very 
 commonly used for garlands; this and H. splendens, with remarkably 
 regular ramification, are both common in woods. 
 
 GROUP III. 
 
 PTEEIDOPHYTA (Vascular Cryptogams). 
 
 The distinguishing characteristics of the plants forming this 
 group are the following : The life-history presents a well-marked 
 alternation of generations, as in the Bryophyta ; but here it is the 
 sporophyte which is the more conspicuous form, constituting " the 
 plant." The sporophyte becomes quite distinct from the gameto- 
 phyte at an early period : it is differentiated (with but few* 
 exceptions) into root, stem, and leaf ; and in all cases it contains 
 well-developed vascular tissue. The gametophyte, generally 
 termed the protliallium, is a relatively small thalloid body, usually 
 short-lived, containing no trace of vascular tissue. 
 
 The group includes the three classes, Filicinse, Equisetinre, 
 Lycopodinse. 
 
 The SPOROPHYTE is developed from the oospore, which undergoes 
 division, in all cases, into an epibasal and a hypobasal half, by a 
 basal wall which is either more or less nearly parallel to the long 
 axis of the archegonium (Leptosporangiate Filiciuse) or more or less 
 nearly transverse to it : the epibasal half usually faces the neck of 
 the archegonium, but in the Lycopodinse the hypobasal half occupies 
 this position. In the Filicinae and Equisetinse, the formation of 
 the basal wall is followed by the formation of another wall at 
 right angles to it (qiiadrant-walT) so that the embryo now consists
 
 GROUP III. PTERIDOPHYTA. 347 
 
 of four cells which are quadrants of a sphere, and this is followed 
 by the formation of a third wall (octant-icall), at right angles to 
 both the preceding, so that the embryo now consists of eight 
 cells which are octants of a sphere. In the Lycopodinse the 
 segmentation leading to the formation of quadrants and octants is 
 confined to the epibasal half, the hypobasal half remaining un- 
 divided or undergoing a few irregular divisions. From the 
 epibasal half, the primary stem and one or two primary leaves 
 (cotyledons) are developed in all cases. The hypobasal half gives 
 rise, in the Filicinse and Equisetinse, to the primary root and to 
 the foot, with but few exceptions (e.g. Salvinia in which there is 
 no primary root) : in the Lycopodinse the hypobasal half gives rise 
 to a filament consisting of a few cells, termed the suspensor 
 (compare Phanerogams). 
 
 The foot (as also the suspensor) is an embryonic organ, no trace 
 of which persists in the adult. It is the organ of attachment of 
 the embryo-sporophyte to the gametophyte ; and it is also the 
 absorbent organ by which the embryo, until it is able to absorb and 
 assimilate food for itself, obtains its nourishment from the pro- 
 thallium (compare Bryophyta, p. 314). 
 
 The development of a suspensor in the Lycopodinse is an adap- 
 tation correlated with the fact that the nourishment of the 
 embryo in that group depends upon its coming into direct contact 
 with the tissue of the massive gametophyte, the cells of which 
 are filled with nutritive substances. 
 
 A primary root, that is, a root developed from the hypobasal 
 half of the oospore, and so situated at its origin that its growing- 
 point is in a straight line with that of the stem, only occurs 
 in the Filicinse and Equisetinse ; but even here it does not persist 
 as a tap-root in the adult : in these plants numerous adventitious 
 roots are developed. In the Lycopodinse, where there is no primary 
 root, all the roots are adventitious. 
 
 Some adult forms are altogether without roots : as Salvinia, 
 and some species of Trichomanes, among Filicinse; Psilotum and 
 Tmesipteris, among Lycopodinse. The functions of the root are 
 discharged, in Salvinia by modified leaves, in the others by 
 modified branches. 
 
 The branching of the root is generally lateral in the Filicinse 
 and Equisetinse; it is dichotomous in the Lycopodinse and in 
 Isoetes. In the former case, the lateral rootlets are developed, 
 in the Filicinse, from cells (rlnzogenic} of the endodermis which
 
 348 PART IV. CLASSIFICATION. 
 
 are opposite to the xylem-bundles of the stele ; in the Equi- 
 setinse, from the cells forming the inner layer of the two-layered 
 endodermis. 
 
 The stem is generally short and un branched in the Filicinse ; 
 generally elongated and much branched in the Equisetinse and 
 Lycopodinse. 
 
 The leaves are differentiated into foliage-leaves and sporophylls 
 in the Equisetinse and generally in the Lycopodinse, but not in the 
 Filicinse as a rule. The foliage-leaves are relatively large in pro- 
 portion to the stem in the Filicinse, relatively small in the Lyco- 
 podinse, reduced to cataphylls in the Equisetinse. 
 
 The growth in length of root, stem, and leaf, is effected by an 
 apical growing-point : the growing-point has generally a single 
 apical cell in the Filicinse (except root and stem of Marattiacese 
 and Isoetes) and Equisetinse ; in the Lycopodinse (as also in the 
 exceptional Filicinse) there is generally a group of initial cells. 
 
 The anatomy of the stem presents considerable variety. The 
 primary stem is in all cases monostelic (pp. 102, 116) : it may con- 
 tinue to be monostelic (e.g. Lycopodiacese, Isoetes, Osniundacese, etc.), 
 but more commonly it becomes polystelic (most Filicinse). The 
 vascular tissue of the wood consists of lignified spiral (protoxylem) 
 and scalariform tracheides, or- less commonly vessels ; the bast 
 contains no companion-cells. The bundles are generally closed 
 and cauline. The relative arrangement of wood and bast in the 
 stele is generally concentric (see p. 124) in the Filicinse and 
 Selaginellacese, and radial in the Lycopodiacese : or the bundles 
 may be conjoint and collateral as in the Equisetinse and some 
 Filicinse. 
 
 The reproductive organs are sporangia, generally borne on the 
 leaves (sporophytte) but sometimes directly on the stem (e.g. 
 Selaginella). Each sporophyll may bear many sporangia on its 
 inferior (dorsal) surface, as generally in the Filicinse and Equise- 
 tinse ; or a single sporangium on its upper surface (e.g. Lycopodium, 
 Isoetes), or in its axil (Selaginella). 
 
 When the sporophyll bears many sporangia, they are usually 
 arranged in groups ; each group is termed a sorus, and the more 
 or less well-developed cushion of tissue from which the sporangia 
 spring is termed the placenta. The sorus may be naked ; or it 
 may have a membranous covering, the indusium (e.g. many 
 Filicinse). 
 
 In the Filicinse the sporophylls are not confined to any special
 
 GROUP III. PTERIDOPHYTA. 349 
 
 portion of the shoot, so as to constitute a flower : but in some 
 cases (e.g. Osmunda, Ophioglossacese, Marsileaceae) they differ in 
 form and structure from the foliage-leaves. .In the Equisetinse 
 the sporophylls are highly specialised, and are grouped into cones 
 (flowers) at the ends of the fertile branches : similar cone-like 
 flowers, with less specialised sporophylls, occur in various 
 Lycopodinse. 
 
 The sporangia are unilocular, though in Isoetes they are incom- 
 pletely chambered by trabeculse : they are developed singly or in 
 groups (sori) ; in the latter case they are usually distinct, but in 
 some cases they are coherent (Marattiacese, except Angiopteris ; 
 Psilotacese) forming a synangium (see p. 52) : the synangium 
 should not, however, be regarded as the result of the cohesion of 
 originally distinct sporangia, but as a group of sporangia which 
 have not separated. The sporangium is developed either from a 
 single superficial cell (leptosporangiate) ; or from a group of super- 
 ficial cells (cusporangiate), and sometimes from deeper cells as 
 well : the mother-cells of the spores are derived from an arche- 
 sporium which is either a single hypodermal cell or a group of 
 hypodermal cells. 
 
 The spores produced in the sporangia, are single cells, with 
 generally two coats, endospore and exospore. Many of the Pterido- 
 phyta produce spores which are all quite alike, whence they are 
 said to be homosporous ; whereas others produce spores of two 
 kinds, small spores (micros pores) and large spores (macrospores or 
 mcgaspores), and are said to be heterosporous. 
 
 The sporangia of the heterosporous forms are distinguished as 
 microsporangia and macrosporangia, according to the kind of 
 spores which they develope : and when the sporophylls bear either 
 only microsporangia or only macrosporangia they are distinguished 
 as microsporophylls and macrosporophylls. The number of macro- 
 spores produced in the macrosporangium is generally small, though 
 they are numerous in Isoetes : thus there are four in Selaginella, 
 only one in the Hydropterideae. 
 
 The spores are generally set free by the dehiscence of the 
 sporangia : but in Salvinia the whole sporangium falls off and the 
 spores germinate within it. 
 
 B. THE G-AMETOPHYTE. The spore, on germination, gives rise 
 to a prothallium which is the gametophyte. It is very small 
 and inconspicuous, as compared with the sporophyte ; its body is, 
 generally speaking, thalloid ; there is no vascular tissue in its
 
 350 PART IV. CLASSIFICATION. 
 
 structure, and in many cases it does not become free from the 
 spore. It usually lives through but one short period of growth. 
 
 In any one of the homosporous forms, the prothallia developed 
 from the spores are all essentially alike ; generally speaking, any 
 one prothallium bears both male and female reproductive organs. 
 The morphology of the prothallium varies widely in these forms : 
 it may be a branched cellular filament (some Hymenophyllacese), 
 or a flattened expansion (Equisetinse, most Ferns), containing 
 chlorophyll abundantly ; or it is tuberous (Ophioglossacete, Lyco- 
 podiacese), either wholly or in part destitute of chlorophyll. It 
 becomes entirely free from the spore. 
 
 In the heterosporous forms the gametophyte is represented by 
 two individuals a male and a female prothallium ; the former is 
 the product of the germination of a microspore, the latter of the 
 germination of a macrospore. As compared with those of the 
 homosporous forms, the prothallia of the heterosporous forms are 
 relatively small ; moreover they do not become independent of the 
 spores from which they are developed. The male prothallium is 
 reduced to little more than a single male organ (antheridium) ; the 
 female prothallium is a small, usually green, cellular body pro- 
 jecting more (e.g. Salvinia) or less (e.g. Selaginella) through the 
 ruptured outer coat of the macrospore. 
 
 Generally speaking, the symmetry of the prothallium is dorsi- 
 ventral ; in the free-growing forms, the under surface generally 
 bears numerous unicellular root-hairs. The distribution of the 
 sexual organs on the prothallium varies ; they are frequently 
 confined to one surface, but are occasionally scattered over the 
 whole surface. The number of the sexual organs on a pro- 
 thallium is in some cases only one, in others it is consider- 
 able. 
 
 The sexual organs are antheridia (male) and archegoma (female). 
 The structure of the antheridium is simple ; it consists of a wall, 
 a single layer of cells, enclosing the mother-cells of the spermato- 
 zoids. The antheridia are developed from single superficial cells 
 of the prothallium ; when the prothallium is thin, the antheridia 
 project on the surface ; when the prothallium is tuberous, the 
 antheridia become sunk in the tissue. 
 
 The archegonium consists of a venter and a neck. As the 
 venter is, in all cases, sunk in the tissue of the prothallium, it 
 has no proper wall of its own, and is, in fact, simply a cavity 
 in the tissue ; the short neck consists of a single layer of cells
 
 GROUP III. PTERIDOPHYTA. 351 
 
 in four rows. The mature archegonium contains, in the venter, 
 the female cell (oosphere}. 
 
 The archegonium is developed from a single superficial cell of 
 the pro thallium. This cell divides transversely into two, an upper 
 and a lower ; the former, by growth and division, forms the neck 
 of the archegonium ; the lower cell projects into the developing 
 neck, and the projecting portion becomes cut off, constituting the 
 neck-canal-cdl which sometimes divides again into two (Maratti- 
 acese, Lycopodium) ; the remainder, now termed the central cell of 
 the archegonium, divides transversely into two unequal parts, the 
 upper and smaller being the ventral canal-cell, the lower and 
 larger being the oosphere. As the archegonium becomes mature, 
 the canal-cells become mucilaginous, the neck opens by the 
 separation of the cells at the apex, and the archegonium is ready 
 for fertilisation. 
 
 The male cell is a naked motile cell, a spermatozoid ; it is a 
 spirally coiled filament, pointed at the anterior end which bears 
 the cilia, becoming thicker towards the opposite end : the cilia 
 are numerous in Filicinse and Equisetinse ; two in Lycopodinse. 
 
 Each spermatozoid is developed singly in a mother-cell in the 
 antheridium. The whole of the contents of the mother-cell are not, 
 however, devoted to the spermatozoid : a portion remains unused, 
 and is discharged together with the spermatozoM, to which it 
 adheres for a time as a protoplasmic vesicle containing, amongst 
 other constituents, a portion of the nuclear substance of the 
 mother-cell (see Fig. 222). 
 
 The female cell, or oosphere, is a naked spherical cell lying in 
 the venter of the archegonium. Its development is described 
 above. 
 
 Fertilisation is effected by the entrance of spermatozoids into 
 the open neck of the mature archegonium, and the subsequent 
 fusion of one of them with the oosphere. When, as is usually the 
 case, numerous prothallia are developed near together on the 
 ground, and become wetted by rain or dew, the ripe antheridia 
 burst and set free the spermatozoids which, swimming actively in 
 the water, are attracted to the mature archegonia by means of an 
 acid excretion which is discharged from the neck of the arche- 
 gortium when it opens. The effect of fertilisation on the oosphere 
 is that it at once surrounds itself with a cell-wall becoming the 
 oospore, and then begins to develope into the young sporophyte. 
 
 In a few cases (e.g. species of Trichomanes and Lycopodium) the
 
 352 PART IV. CLASSIFICATION. 
 
 gametophyte (prothallium) multiplies vegetatively by means of 
 gemmae, which are short spindle-shaped rows of cells in the one 
 case, and globular multicellular bodies in the other. 
 
 The Life-History of the Pteridophyta presents in all cases, a 
 perfectly clear alternation of generations, the sporophyte and the 
 gametophyte being completely distinct. The oospore developes 
 into "the plant," be it Fern, Equisetum, or Lycopod, which bears 
 the sporangia and spores, and is the sporophyte. The spores, 
 when shed, germinate to form the gametophytes (prothallia) bear- 
 ing the sexual organs. 
 
 The Pteridophyta are classified as follows : 
 
 Class V. FILICINJ3. The sporophyte is characterised by 
 having relatively large and few leaves ; the sporophylls are gener- 
 ally similar to the foliage-leaves and are not aggregated into 
 flowers ; the sporangia are numerous on the sporophyll (except 
 Isoetes) and are arranged in sori ; the archesporium is a single 
 cell (except Isoetes); the embryo has a primary root (except 
 Isoetes, Salvinia, and possibly some species of Trichomanes) but 
 no suspensor. 
 
 The characters of the gametophyte vary widely. The sper- 
 matozoids are multiciliate. 
 
 Sub-Class Eusporangiatae. Each sporangium is developed 
 from a group of superficial cells. 
 
 HOMOSPORE.E. 
 Order 1. Opliioglossacece. Order 2. Marattiacea?. 
 
 HETEROSPORE.E : Order 1. Isoetacese. 
 
 Sub-Class Leptosporangiatae. Each sporangium is developed 
 from a single superficial cell. (Filices in limited sense.) 
 
 HOMOSPORE^. 
 
 Order 1. Osmundacece. Order 4. PolypodiacecK. 
 
 2. Schizceacece. ,, 5. Cyatheacece. 
 
 ,, 3. Glcicheniacece. ., 6. HymenophyllacecK. 
 
 HETEROSPORE^E. 
 Order 1. Snlviniacecr,. Order 2. Marsileaccai.
 
 GROUP III. PTERIDOPHYTA. 353 
 
 Class VI. EQUISETIN.E. The sporophyte is characterised 
 by the well-developed branched stem, with small whorled leaves 
 forming a sheath at each node ; the small peltate sporophylls are 
 aggregated into a cone-like flower at the apex of each fertile shoot, 
 and bear a few sporangia on the inner (inferior) surface ; the 
 archesporium is a single cell ; the embryo has a primary root 
 and no suspensor. All the existing forms are homosporous and 
 eusporangiate. 
 
 The gametophyte is a free, green, membranous prothallium, 
 generally dioeoious ; the spermatozoids are multiciliate. 
 
 Order 1. Equisetacece. 
 
 Class VII. LYCOPODIN^E. The sporophyte is characterised 
 by the well-developed branched stem with numerous small 
 scattered leaves ; the sporangia are borne singly either on the 
 upper surface of a sporophyll, or on the stem ; the sporophylls 
 resemble the foliage-leaves, but are sometimes aggregated into 
 cone-like flowers; the archesporium is multicellular ; the embryo 
 has a suspensor, but no primary root. All the existing forms are 
 eusporangiate. 
 
 The characters of the gametophyte vary widely. The sperma- 
 tozoids are biciliate. 
 
 Sub-Class HOMOSPOREJE : the sporophyte produces spores of one 
 kind only ; the prothallia are free, more or less tuberous, mon- 
 oecious. 
 
 Order 1. Lycopodiacece. Order 2. Psilotacea. 
 
 Sub-Class HETEROSPORE^: : the sporophyte produces microspores 
 and macrospores ; the former give rise to male, the latter to 
 female, prothallia ; the prothallium does not become free from the 
 spore. 
 
 Order 1. Selayinellacece. 
 
 The relations of these various groups may be simply expressed 
 as follows : 
 
 FILICIN^E. EQUISETIN.E. LYCOPODIN.S:. 
 
 Homosporous Filices \Lepto- 
 
 Heterosjiorous Hydropterideae - ' tporangiate. 
 
 Homotporous fOphioglossacese J_ E isetacese _ fLycopodiace* j } 
 
 iMarattiacese ) IPsilotacese ' K Eusporangiate 
 
 Heterosporous -Isoetacese (none existing) Selaginellacese ) 
 
 M.B. A A
 
 354 
 
 PART IV. CLASSIFICATION. 
 
 CLASS V. 
 
 A. HOMOSPOROUS EUSPORANGIATJE. 
 
 Order 1. Ophio'glossaceae. This order includes the three genera 
 Ophioglo'ssum, Botrychium, and Helminthostachys. 
 
 SPOROPHYTE. The stem is a subterranean rhizome (except in epiphytic 
 Ophioglossums), which does not branch at all in Ophioglossum, and but 
 little in Botrychium and Helminthostachys; it is usually short and 
 erect. The rather thick and fleshy roots are unbranched in Ophio- 
 glossum, but they give rise to adventi- 
 tious buds 5 they are branched in Bo- 
 trychium and Helminthostachys, and 
 produce no buds. The leaves are de- 
 veloped close together at the apex of the 
 rhizome, and are not circinate, or only 
 slightly so, in vernation ; their growth is 
 so slow that a leaf does not appear above 
 ground until the fifth year after its first 
 development ; generally, only a single 
 leaf appears a'bove ground each year, 
 when more are developed some of them 
 are sterile. The sporophylls are remark- 
 able for their peculiar branching (see p. 
 34) ; they are petiolate, and the petiole 
 branches into two, the one bearing a 
 sterile and the other a fertile lamina (Fig. 
 212), the fertile branch being situated on 
 the ventral surface of the sterile ; the 
 sterile lamina is leafy, whilst the fertile 
 lamina consists of little more than the 
 sporangia. In Ophioglossum the sterile 
 lamina is entire, and the fertile lamina is 
 spicate with two lateral rows of sporan- 
 gia ; in Botrychium the sterile lamina is 
 pinnate, and the fertile lamina is bi- 
 pinnate with marginal sporangia. The 
 sporangia are embedded in the tissue of 
 the sporophyll in Ophioglossum, but are 
 free in Botrychium and Helminthosta- 
 chys : they are not arranged in sori ; they 
 are globose, have no annulus, but dehisce 
 into two equal valves by a transverse 
 (Ophioglossum, Botrychium) or vertical 
 (Helminthostachys) slit; the wall of the 
 sporangium consists of several laj'ers of 
 cells ; the spores are numerous and tetra- 
 hedral. 
 
 FIG. 212. Botrychium Lv.na.ria 
 (nat. size) : w roots ; st stem ;bs 
 leaf-stalk ; x point where the leaf 
 branches ; the sterile lamina (6) 
 separating from the fertile branch
 
 GROUP III. PTERIDOPHYTA : FILICIN^E. 355 
 
 GAMETOPHYTE. The germination of the spores has not been observed, 
 but the mature prothallium has been described in the case of Ophioglosmm 
 pedunculosum and Botrychium Lunaria. In both cases it is tuberous, sub- 
 terranean, destitute of chlorophyll, monoecious ; the antheridia are sunk 
 in the tissue, and the short necks of the archegonia project but little. 
 It appears that the prothallium is saprophytic, though possibly it 
 may possess chlorophyll in the early stages of its development. In 
 Botrychium it is a somewhat ovoid body not more than half a line long, 
 with long scattered root-hairs, bearing the antheridia chiefly on its upper 
 surface, the archegonia chiefly on the lower. 
 
 Ophioglossum vulgatum (the Adder's tongue) is the British species of this 
 genus; O. lusitanicum has, however, been found in Guernsey. The 
 epiphytic species are O. pendulum and 0. palmatum, both tropical forms ; 
 the latter has palmately-lobed sterile fronds. Botrychium is represented 
 in the British Flora by B. Lunaria (the Moon-wort) which occurs in hilly 
 districts. Helminthostachys includes the single, species H. zeylanica 
 which occurs in the Eastern tropics.- 
 
 Order 2. Marattiaceae. This order includes the genera Marattia, 
 Angiopteris, Kaulfussia, and Danaea, none of which are European, but 
 are mainly tropical. 
 
 SPOROPHYTE. In its general morphology the sporophyte agrees with 
 that of the Ophioglossaceae ; but the leaves are more numerous, much 
 larger, compound, and circinate in vernation, and each bears a pair of 
 stipules. Branching of the stem occurs only in Danaea; in Kaulfussia 
 the stem is a subterranean, creeping, dorsiventral rhizome. The roots are 
 somewhat fleshy, and are much branched. The apical growing-point of 
 both root and stem consists of a group of a few (four or more) initial cells. 
 The sporophylls are not differentiated into a sterile and a fertile portion, 
 but have the appearance of foliage-leaves. The numerous sporangia are 
 borne in sori on the ribs of the under surface of the sporophyll ; in 
 Angiopteris the sporangia of a sorus are free, whilst in all the other 
 genera they are coherent, forming a synangium (see p. 349). The spores are 
 numerous, and are either tetrahedral or radial. 
 
 GAMETOPHYTE. On germination the spore gives rise to a dorsiveutral 
 green prothallium resembling that of the Leptosporangiate Ferns. 
 
 B. HETEEOSPOROUS EUSPORANGIATJE. 
 
 Order 3. Isoetaceae. This order includes the single genus Isoetes 
 which comprises about fifty species belonging to all parts of the globe. 
 Some of these are terrestrial (/. Duricei and Hystrix}, whilst others are 
 either altogether aquatic (e.g. I. lacustris, eckinospora, etc.), or amphibious 
 (e.g. I. velata, setacea, boryana). The British species are /. lacwtris, echino- 
 spora, and Hystrix. 
 
 Isoetes has, of recent years, been generally included among the 
 Lycopodinse ; but it betrays a relationship to the Filicinae in so many 
 features, such as its general habit, its embryogeny, the absence of any 
 cone-like fructification, the form of its spermatozoids, that it appears to 
 be more natural to place the plant in that group.
 
 356 PART IV. CLASSIFICATION. 
 
 SPOROPHYTE. The stem is small, unbranched, short and tuberous, with 
 either two or three longitudinal furrows which give it a lobed appearance. 
 It is closely covered with numerous, relatively long (1-12 in.), sessile 
 leaves. From the furrows of the stem there spring numerous, dicho- 
 itemously branched, somewhat fleshy roots. 
 
 The growth in length of the stem, which is very slow, is effected by an 
 apical growing-point consisting of several initial cells. The growing- 
 point of the root consists of small-celled meristem, and presents a similar 
 differentiation to that of the root of Dicotyledons (see p. 102). 
 
 The leaves are either fertile or sterile ; the fertile leaves each bear a 
 single sporangium, and are termed macrosporophylls or microsporophylls 
 in accordance with the nature of the sporangium which they severally 
 bear. The order of development of the leaves in each year is that first of 
 all macrosporophylls are produced, then microsporophylls, and finally a 
 few sterile leaves in some species. Hence, when the development is com- 
 pleted, the macrosporophylls are external in the rosette, the sterile leaves 
 (when present) internal, and the microsporophylls intermediate. The 
 sterile leaves persist during the winter, and form a protection in the next 
 spring to the young leaves developed internally to them at the growing- 
 point. 
 
 The fertile leaves, whether macro- or micro-sporophylls, consist of a 
 broad, sheathing base, with membranous margins, which bears a narrow 
 subulate lamina, flattened somewhat on the upper (ventral) surface. 
 Close above the insertion, on the upper or inner surface of the leaf-base, is 
 a pit, the fovea, in which the single sporangium is situated. In some 
 species the margin of the fovea is prolonged into a membrane, the velum. 
 which either partially (e.g. 1. lacustris}, or completely (terrestrial species), 
 covers the sporangium. Above the fovea, in the middle line, is another 
 smaller pit, the foveola, occupied by the somewhat swollen base of a pro- 
 jecting flattened membranous structure, the ligule, which is developed 
 from a single superficial cell of the young foveola, and is relatively much 
 larger in the quite young leaf than in the adult. 
 
 The sterile leaves are less highly developed than the fertile ; they are 
 smaller, especially as regards the leaf -base. In the terrestrial species they 
 are reduced to scaly cataphyllary leaves of a brown colour. 
 
 The sporangium is developed from a group of cells in the fovea. The 
 archesporium consists of a layer of hypodermal cells in the young 
 sporangium. In a microsporangium all the archesporial cells grow and 
 divide so as to form rows radiating from the free surface to the attach- 
 ment of the sporangium. Some of these rows of cells soon cease to grow, 
 and are not sporogenous, but remain as plates of tissue, termed trnbecufa; 
 which imperfectly chamber the cavity of the microsporangium. Of the 
 remaining cells, the majority constitute the mother-cells of the micro- 
 spores invested, towards the wall of the sporangium, by sterile cells 
 forming the tapetum. In a macrosporangium, the fertile archesporial 
 cells undergo but a single division, whilst the trabeculae are formed as in 
 the microsporangium. The large mother-cells of the macrospores are 
 isolated, and each is invested by a tapetal layer. Each spore-mother-cell 
 gives rise, finally, to four spores.
 
 GROUP III. PTERIDOPHYTA : FILICINVE. 
 
 357 
 
 GAMETOPHYTE. As Isoetes is heterosporous, the gametophyte is repre- 
 sented by distinct male and female individuals, which remain connected 
 with the spores producing them: they resemble those of Selaginel la ami 
 of some Gymnosperms (q. r.). 
 
 The male individual is developed from a microspore. The microspore 
 which has the form of the quadrant of a sphere and is consequently of 
 the bilateral or radial type undergoes,, on germination, division by a. 
 transverse wall, 
 formed near one 
 of its somewhat 
 pointed ends, into 
 two cells, a large 
 and a small : the 
 latter is the vegetav- 
 tive cell, and un- 
 dergoes no further 
 change ; the former 
 is the mother-cell 
 of the male organ or 
 antheridium. The 
 prothallium here is 
 thus very much re- 
 duced, consisting of 
 a single antheri- 
 dium and of a 
 single purely vege- 
 tative cell. The 
 antheridium, de- 
 veloped by the 
 growth and divi- 
 sion of the mother- 
 cell, consists of four 
 peripheral cells 
 forming the wall, 
 and of four central 
 cells, each of which 
 gives rise to a 
 single spirally 
 coiled multiciliate 
 spermatozoid. 
 
 The female indi- 
 vidual is developed 
 from a macrospore. 
 The macrospores 
 are much larger than the microspores, and are nearly globular in form ^ 
 though they belong to the tetrahedral type, as can be seen by the three 
 ridges on the spore where it was in contact with the other three developed 
 from the same mother-cell. On germination, the nucleus of the macro- 
 
 -J 
 
 Fie. 213. Itoetes lacustris (after Luerssen). A Plant, half 
 naLsize: r dichotomously branched roots. B Inner (ventral) 
 surface of base of a sporophyll : I ligule ; / fovea. C Longi- 
 tudinal section of base of a sporophyll : p the sporangium 
 in the fovea ; tr the trabeculae ; e the velum ; I the ligule. D 
 Transverse section of the base of a sporophyll : letters as in C.
 
 358 PART IV. CLASSIFICATION'. 
 
 spore undergoes repeated division ; this is followed by free cell-formation 
 in the apical region (the pointed end where the three ridges meet) of the 
 macrospore, the result being the formation of a small-celled tissue ; sub- 
 sequently cell-formation extends into the basal portion of the spore, a 
 tissue being formed there consisting of relatively large cells with coarsely 
 granular contents. Thus the macrospore becomes completely filled with 
 a mass of cellular tissue which constitutes the female prothallium : the 
 xipper small-celled tissue is the essentially reproductive portion, whilst 
 the lower large-celled tissue simply serves as a depository of nutritive 
 substances. 
 
 The female organ, the archegonium, is developed from one of the super- 
 ficial cells of the small-celled prothallial tissue, after the manner described 
 on page 351. It appears that two or three archegonia are usually formed : 
 but if none of these primary archegonia are fertilised, a small number of 
 additional archegonia may be subsequently developed. 
 
 The ai-chegonia are exposed, for the purpose of fertilisation, by the 
 splitting of the coats of the macrospore along the three ridges already 
 described : the prothallium does not, however, project from the spore, nor 
 does it become green. After fertilisation, the qospore developes into the 
 embryo: the foot of the embryo grows down into the large cells of the 
 basal portion of the prothallium, absorbs the nutritive substances which 
 were stored up in them, and thus supplies the embryo with food until 
 such time as its leaves and roots are sufficiently developed to enable it to 
 nourish itself in the usual way. 
 
 C. HQMQSPORQUS LEPTOSPORANGIATvE (Filices). 
 
 The orders constituting this group have so much in common 
 that they may be advantageously considered all together. 
 
 SPOROPHYTE. The body is differentiated into stem, leaf, and 
 root (generally) : the leaves are large in proportion to the stem, and 
 are relatively few in number. 
 
 The stem has either radial or dorsiventral symmetry. In the 
 former case it is commonly short and straight ; it grows into the 
 air erect, or at any degree between the vertical and the horizontal ; 
 its surface is generally completely covered by the insertions of the 
 spirally arranged leaves, and by adventitious root$ : it becomes, 
 however, elongated, to a considerable height sometimes, in the Tree- 
 Ferns. In the latter case, the stem grows as a rhizome either on or 
 in the soil, or on the surface of some tree upon which the plant lives 
 as an epiphyte : the leaves are borne on its dorsal surface, either 
 in two rows (e.g. species of Aneimia and Polypodium), or in a 
 single row (e.g. Lygodtum palmatum, Polypodium Heracleum and 
 P. quercifolium} : from the lower (ventral) surface, spring the 
 adventitious roots.
 
 GROUP III. PTERIDOPHYTA : FILICIN^E. 359 
 
 The growth in length of the stem, is effected by a growing-point 
 with a single apical cell (with the occasional exception of 
 Osmunda) : the apical cell is, as a rule, a" three-sided pyramid 
 with its spherical base at the surface : but in Pteris aquilina it 
 is usually a two-sided lenticular cell, with its longer axis in the 
 dorso- ventral plane. 
 
 The radial stems branch but little, least of all when the stem 
 is elongated, as in the Tree-Ferns ; and such branching as there 
 is appears to be mainly adventitious, the buds springing from the 
 bases of the leaves. In the dorsiventral stems there is normal 
 lateral branching, which takes place in the transverse plane : the 
 branches are borne on the flanks of the stem, and are frequently 
 (e.g. some Hymenophyllaceae) axillary in their origin. 
 
 The leaves are for the most part fojiage-leaves, though scaly 
 leaves are found on the subterranean rhizomes of Onoclca Stru- 
 thioptcris and Osmunda regalis, and in some cases the sporophylls 
 are more or less differentiated from the sterile leaves. 
 
 The foliage-leaves are relatively large, sometimes entire (e.g. 
 Scolopendrium), but generally more or less deeply and repeatedly 
 pinnately lobed or branched; sometimes dichotomously branched 
 (e.g. Platycerium, species of Schizaea). 
 
 The leaves in all cases have apical growth ; the growing-point 
 has, in most of the orders, a two-sided apical cell, whilst in the 
 Osmundaceae the apical cell is tetrahedral. In Lygodium ; where 
 the leaf is a climbing organ, the apical growth is long continued. 
 
 The leaf arises from a single superficial cell of the growing- 
 point of the stem. When young it is strongly hyponastic (see 
 p. 211), so that, as it elongates and branches, both the main axis 
 of the leaf (phyllopodium) and the lateral branches become inrolled 
 upon themselves like a crosier ; in other words, the vernation is 
 circinate: as it grows older the growth becomes epinastjc, and 
 thus the leaf becomes expanded. 
 
 In the great majority of these Ferns the sporophylls are simply 
 foliage-leaves bearing sporangia on the dorsal surface, b,ut in 
 certain cases they are more or less specialised. Thus, in Onocleq 
 Struthioptcris, the sporophylls are smaller than the foliage-leaves, 
 and have narrower pinnae : in the Hard Fern, Blechnum borealc, 
 the sporophylls are longer and have narrower pinnae than the 
 foliage-leaves : in Osmunda regalis the pinna? of the upper branches 
 of the sporophyll are reduced to little more than the midrib, the 
 pinnules' being represented by clusters of sporangia: in Aneimia
 
 360 
 
 PART IV. CLASSIFICATION. 
 
 (e.g. A. Phyllitidis) generally the lowest pair of pinnae of the 
 sporophyll alone bear sporangia ; these pinnse consist merely of the 
 nervature bearing numerous sporangia, and are erect on much 
 elongated secondary petioles : in Platy cerium alcicorne there is 
 a curious instance of specialisation ; the foliage-leaves are broad, 
 and closely appressed to the substratum, whereas the sporophylls 
 are erect, narrow, and branched. 
 
 The sporangia are but rarely borne on the superior (ventral) 
 surface of the sporophyll (e.g. Olfersia cervina) ; more commonly 
 
 FIG. 2U. Sori (s) of the most important groups of Leptosporangiate Ferns, all seen from 
 balow. A Pinna of Trichomanes sinuosum, one of the HymenophyllacesB : r projecting 
 placenta; s sporangia; i indu&ium ; at a half of the indusium is removed. B Pinna of 
 Davallia (Leucostegia) at s the one-valved indusium (i) is turned back. C Part of a leaf of 
 Pteris eerrulata -. 8 the sporangia; m the inverted margin. D Pinnule of Nephrodium at 
 s the indusium is removed, and at r the sporangia also. E Pinnule of an Asplenium at 
 a the indusium is turned back. F Pinna of Polypodium vulgare with naked sori at r the 
 sporangia are removed. (All a-e x 3 to 6.) 
 
 on the margin (e.g. Hymenophyllacese, Dicksonia, Davallia) ; but 
 as a rule, on the dorsal surface, either near to the margin (e.g. 
 Pteris, Adiantum), or distant from it (e.g. Asplenium, Aspidium, 
 etc). They are usually developed in connexion with the nervature 
 of the sporophyll, but sometimes also from the intervening tissue
 
 GROUP III. PTERIDOPHYTA : F1LICINJE. 
 
 361 
 
 of the lamina (Acrostichese, such as Polybotrya, Chry sodium) : in 
 the former case they occur in groups, termed son, which are 
 commonly isolated, but occasionally (e.g. Pteris) a continuous 
 marginal sorus is formed. 
 
 The sorus generally consists of a large number of sporangia : in 
 the Gleicheniacese, however, the number is small (2-8); and in 
 some cases (e.g. Lygodium) there is only a single sporangium. 
 The sporangia of the sorus are borne on a projection of tissue, the 
 placenta or receptacle, which presents various forms : it may be a 
 slight rounded elevation (e.g. Aspidium) ; or more elongated and 
 conical (e.g. Cyathea, Hymenophyllum) : or very long and filiform, 
 bearing sporangia only at its base (e.g. species of Trichomanes, 
 Tig. 214 ^4) ; or a ridge (e.g. Pteris, Blechnum). 
 
 FIG. 215. A dehisced spor- 
 angium of Asiridium Fillx-mas 
 (xOO): a the stalk, with a 
 glandular hair p ; r tho annu- 
 lus ; the stomium. 
 
 FIG. 216. Sections of young sporangia; A of a 
 Fern (Mohria), B of Equisetum (x 150): w wall; t tape- 
 turn; a s archesporium. 
 
 The sorus is quite bare in many forms (Gleicheniacese ; 
 Osmundacese ; Alsophila among Cyatheacese ; Schizseaceae, except 
 Lygodium ; Polypodiese) ; in others it is more or less covered by a 
 protective membrane, the indusium, which is an outgrowth of the 
 tissue of the leaf, generally of the epidermis alone. When it 
 springs from the placenta below the sorus, it is somewhat cup- 
 shaped : thus it is urceolate and entire in Trichomanes (Fig. 214 
 A), Lygodium, Cyathea, Davallia. When it springs from the apex 
 of the placenta, above the sorus, the indusium has the general 
 appearance of a peltate scale, either orbicular in outline (Aspidium) 
 or reniform (Nephrodium, Fig. 214 D). When it is developed on 
 one side of the sorus, the indusium is a long narrow scale, attached
 
 362 
 
 PART IV. CLASSIFICATION. 
 
 along its length, and overlying the sorus (e.g. Asplenium [Fig. 214 
 .E], Blechnum. Scolopendrium [Fig. 217];. In some cases, where 
 the sori are near the margin, they are protected by a false 
 indusium, which is merely the incurved margin of the leaf (e.g. 
 Cheilanthes, Adiantum, some species of Pteris [Fig. 214 C]}. In 
 Pteris aquilina, and some other species, in addition to the false 
 indusium, there is also a membrane along the inner side of the 
 
 FIG 217. Scolopendrium vulgare (Hart's-tongue Fern). A Transverse section of a sorus ; 
 indusinm; * g sporangia. B-E Sporangia ; B and E seen sideways ; C in front ; D from 
 the back ; F a spore. (A x 50 ; B-E x 145 ; F x 510 : after Strasburger.) 
 
 sorus, which is a kind of lateral indusium, adapted to protect a 
 continuous marginal sorus. 
 
 In some forms (e.g. Aspidium Filix-mas, Fig. 215) the stalks of 
 the sporangia bear glandular hairs ; sometimes even the sporangia 
 themselves.
 
 GROUP III. PTERIDOPHYTA : FILICIDE. 3G3 
 
 With the possible exception of the Osinundaceae, each sporangium 
 is developed from a single superficial cell. The cell grows so as to 
 project more or less : it is then divkied-krte-fcwo eells an outer, 
 the mother-cell of the sporangium ;_aa inner, the stalk-cell by a 
 horizontal waH. As the mother-cell of the sporangium grows, it 
 undergoes division by the successive formation of three oblique 
 walls, intersecting one another below at an angle of about 60, and 
 reaching above to the wall of the motherrcell ; at this stage the 
 sporangium consists of three latero-basal external cells surrounding 
 the pointed lower end of a tetrahedral cell, the spherical base of 
 which occupies the summit of the sporangium. A wall is now 
 formed in the tetrahedral cell, parallel to its spherical free surface, 
 and intersecting the three oblique walls ; so that the sporangium 
 now consists of four peripheral cells, forming the wall, and a central 
 cell. From the central cell are cut off, by successive walls parallel 
 to its sides, four cells which give rise to the tapctum by subsequent 
 growth and radial, and sometimes tangential, division ; the remain- 
 ing internal tetrahedral cell constitutes the unicellular arche- 
 sporium from which the spores are derived. 
 
 As the young sporangium grows, it gradually assumes its 
 definitive form, which is mo^t commonly ovaL-lenticular. The four 
 primary peripheral cells undergo repeated radial division, and form 
 the wall of the sporangium, which ultimately consists of a single 
 layer of cells with cuticularised walls : a portion of the wall is in 
 all cases developed to form the ring or annulus, by means of which 
 the dehiscence of the sporangium is effected, the walls of which 
 are specially thickened and cuticularised, coloured yellow or brown, 
 and are elastic. The form and position of the annulus varies in 
 the different groups : thus in the Polypodiaceae (Fig. 217), where 
 the sporangium is attached to the stalk by the margin, the incom- 
 plete annulus is a projecting row of cells with their longer axes 
 transverse, extending round the margin in the plane of the stalk, 
 with which it is connected on one side, but not quite reaching it 
 on the other. 
 
 As the development proceeds, the formation of the spores takes 
 place in the interior of the sporangium. The archesporial cell under- 
 goes repeated division, with the result that usually sixteen cells are 
 formed, which are the mother-pells of the spores (Fig. 216). At this 
 stage the tapetal cells undergo disintegration, so that the mass of 
 spore-mother-cells floats freely in the liquid thus produced. Each 
 mother-cell then undergoes division to form four spores.
 
 364 PART IV. CLASSIFICATION. 
 
 The sporangium may be sessile (Gleicheniaceae, most Schizseacese. 
 Hymenophyllacese) ; or shortly stalked (Lygodium, Cyatheacete, 
 Osmundacese * ; or it may have a usually rather long slender stalk 
 consisting of two or three longitudinal rows of cells (Polypodiacese) ; 
 this is dependent upon whether the originally-formed stalk-cell 
 developes further or not. 
 
 The spores are set free by the dehiscence of the sporangium ; 
 this takes place at a certain part which, though different in the 
 various forms of sporangia, is always closely connected with the 
 annulus and is termed the stomium (see Fig. 215) ; dehiscence 
 begins by a split between (not through) the cells of the stomium. 
 In the Polypodiaceae the plane of dehiscence is at right angles to 
 the long axis of the sporangium, and the stomium is situated on 
 the margin between the end of the annulus and the stalk. 
 
 A striking feature in the general morphology of these plants is 
 the presence on the stem and the bases of the leaf-stalks, especially 
 when young, of numerous scaly hairs (ramenta or palece), which 
 consist usually of a single layer of cells, with more or less thickened 
 brown walls ; they are of various shape, and frequently have 
 marginal glandular hairs secreting tannin or mucilage, the latter 
 generally in the neighbourhood of a growing-point or stem or leaf. 
 Less commonly, glandular hairs are developed on the leaves, as in 
 species of Gymnogramme (Gold and Silver Ferns), in which the 
 under surface of the leaves is covered with a yellowish dust, 
 consisting of minute needles of resinous and waxy substances, 
 secreted by the hairs. Root-hairs occur on subterranean stems 
 and leaf-stalks. 
 
 A primary root is developed, probably in all forms, but in no 
 case does it persist in the adult. In the full-grown plant all the 
 roots are adventitious; they spring in great numbers from the 
 stem or the leaf-stalks. The roots are small and branched ; the 
 branching is lateral, and the growing-points of the young roots 
 are developed each from a single cell of the endodermis, termed 
 a rhizogenic cell, situated opposite to a xylem-bundle of the 
 central cylinder. In most cases the growing-point of the root 
 has a single pyramidal apical cell (see Fig. 86) with three flat 
 sides and a spherical base directed outwards. 
 
 Adventitious buds, subserving vegetative propagation, are com- 
 monly produced ; they arise most frequently on the subterranean 
 portions of leaf-stalks (as inPteris aquilina, Aspidium Fili.i--mas\ 
 and sometimes, as in Onoclea Struthiopteris, the bud grows into
 
 GROUP III. PTERIDOPHYTA : FITJCINJE. 365 
 
 a subterranean stolon which eventually throws up at its apex a 
 whorl of green leaves, thus constituting a new plant ; but also 
 frequently from the lamina, as in Asplenium (Diplazium} celtidi- 
 folium. A. bulbiferum, and other species. The bud originates from 
 a single epidermal cell. 
 
 General Histology. The structure of stem, petiole, and root, is 
 characterised throughout by the presence of hypodermal layers, 
 and, generally, of scattered strands of sclerenchymatous tissue, 
 consisting of more or less elongated ground-tissue cells with more 
 or less thickened brown-coloured walls ; and by the predominance 
 of scalariform vascular tissue in the xylem which consists, with 
 but few exceptions, of tracheides. 
 
 The stem is, at its first development, monostelic, with a single 
 axile stele : in some forms this structure obtains (with or without 
 pith) throughout the whole stem (e.g. Hymenophyllaceae, Lygodium, 
 Schizaea) : in the Osmundaceae also the stem is monostelic through- 
 out, the stele eventually consisting of a ring of bundles enclosing 
 a pith : in the other families the stem becomes polystelic. 
 
 In the monostelic stem the bundles are sometimes conjoint and 
 collateral (e.g. Trichomanes among Hymenophyllaceae, Osmun- 
 daceae) : in all other cases the arrangement of the bundles in the 
 stele is concentric, or, more strictly speaking, bicollateral (p. 123), 
 since the phloem does not quite completely surround the xylem- 
 bundles. The concentric steles are cauline and usually consist 
 of two wood- and two bast-bundles, with usually an endodermis 
 and a pericycle: in some cases, however, where the stele is 
 small (e.g. some species of Polypodium) there is no pericycle, 
 its place being taken by a layer of cells formed by the division 
 of the primitive endodermis (p. 115) into two layers. 
 
 In the polystelic stem the course of the steles is such that they 
 form a meshwork, each mesh corresponding to the insertion of a 
 leaf : the bundles of the leaf join those forming the corresponding 
 mesh in the stem. The form of the mesh is determined by the 
 number and insertion of the leaves : when the leaves are numerous 
 and closely arranged, the meshes are relatively short and broad ; 
 when the leaves are few and scattered, the meshes are long and 
 narrow. 
 
 In a monostelic stem, such as that of Osmunda, though the 
 bundles are numerous, no such meshwork is formed. The bundles 
 are here common. A single bundle enters the stem from each leaf, 
 runs straigh-t through several internodes, and then curves to join
 
 366 
 
 PART IV. CLASSIFICATION. 
 
 Fm. 218. Embryogeny of the sporophyte of Pteris serrulata ( x 235 : after Kienitz-Gerloff). 
 A In longitudinal section: B transverse section, at right angles to the preceding : C older 
 embryo in longitudinaj Section. The vertical arrows indicate the long axis of the arche- 
 goniurn, pointing to the neck : the horizontal arrows indicate the longitudinal axis of 
 the prothallium, pointing to its organic apex. I-l Bsisal wall; 11-11 transverse wall; 
 Ill-Ill median wall : r apical cell of root ; I apical cell of cotyledon ; s apical cell of stem ; 
 /foot. 
 
 with the bundle of a'n older leaf, seven leaves intervening between 
 the two. 
 
 Embryogeny of the Sporophi/te. The sporophyte is developed 
 from the fertilised female cell, the oospore : the development has 
 only been studied in species of Polypodiacese, and has been found 
 to be as follows. The oospore is first of all divided into two cells 
 by the formation of a wall, the basal 
 icall, which nearly coincides with the 
 long axis of the archegonium : a second 
 wall is then formed, the transverse wall, 
 at right angles to the preceding, with 
 the result that the spherical embryo now 
 consists of four cells or quadrants : then 
 a third wall, the median wall, is formed 
 in a plane at right angles to both the 
 preceding walls, the embryo now consist- 
 ing of eight equal cells or octants. Of 
 these octants, four belong to one half of 
 the embryo, which is termed the cpibasal 
 half; and four to the other half, the 
 hypobasal half: from these octants the 
 primary organs of the sporophyte are 
 developed. Beginning with the four 
 epibasal octants, the two apical octants 
 (i.e. nearest to the neck of the arche- 
 
 FIG. 219,-^Adiantum CapiHus- 
 Venerit. The prothallium (pj>) 
 seen from below with young 
 Fern attached to it by its foot ; i 
 its first leaf or cotyledon ; w' its 
 primary, to" secondary, roots; 
 h root-hairs of the prothallium 
 (x about 3). (After Sachs).
 
 GROUP III. PTERIDOPHYTA : FILICIX.E. 
 
 367 
 
 gonium) give rise to the growing-point of the first leaf or cotyledon : 
 of the two deeper (towards the venter of archegonium) octants, 
 the one constitutes the growing-point of the stem, whilst the 
 other gives rise to nothing beyond possibly some hairs. Of the 
 four hypobasal octants, one of the two apical octants gives rise to 
 the growing-point of the primary root, which is diametrically 
 opposite to the growing- point of the stem; whilst the other gives 
 rise to no special member : the two deeper hypobasal octants give 
 rise to the embryonic absorptive organ, the foot. The gradual 
 development of these members is dependent upon growth and 
 corresponding cell-division, and at an early stage histological 
 differentiation 
 into cortical and 
 stelar tissues is 
 apparent in 
 them. For a 
 time the tissue 
 of the venter of 
 the archegon- 
 ium keeps pace 
 by growth with 
 the increasing 
 size of the em- 
 b r y o : but 
 eventually the 
 primary root 
 and the cotyle- 
 don become free, 
 and ultimately 
 also the stem 
 (Fig. 220). In 
 the meantime 
 the embryo is 
 
 nourished by means of the foot which has become a mass of tissue 
 filling the venter of the archegonium : it absorbs from the adjacent 
 cells the organic substances formed in the prothallium by means of 
 the chloroplajStids which most of the cells contain. The primary 
 root and the cotyledon are both small and short-lived : the former 
 is succeeded by the numerous adventitious roots, the latter by the 
 true foliage -leaves. The foot is a merely embryonic organ : it 
 disappears when the young sporophyte has become firmly attached 
 
 FIG. 220. Section of young plant of Pteris aquilina still 
 attached to the prothallium by its foot : p prothallium ; / foot ; 
 r primary root ; s growing-point o f primary stem ; I primary 
 leaf or cotyledon. (Magnified: after Hofmeister.)
 
 368 
 
 PART IV. CLASSIFICATION". 
 
 to the substratum, and is capable of independently absorbing and 
 assimilating food. 
 
 GAMETOFHYTE. The gametophyte is a prothallium, always con- 
 taining chloroplastids, generally a dorsiventral, flattened, cellular 
 expansion, or sometimes filamentous, which is developed from a 
 spore, but which becomes completely free from the spore. In 
 the dorsiventral prothallium the reproductive organs, as also the 
 root-hairs, are confined to the inferior (ventral) surface. 
 
 The prothallium is typically rnonoscious : the male organs, or 
 antheridia, are developed first, and are consequently situated 
 towards the posterior or basal end of the prothallium; the later- 
 formed archegonia lie towards the anterior or apical end. It 
 sometimes happens, however, that, owing to imperfect nutrition, 
 the growth of the prothallium does not proceed beyond the stage 
 
 Fia. 221. Diagram of the prothal- 
 lium of a Leptosporangiate Fern : under 
 side (x 10). ar Archegonia; an anthe- 
 ridia ; fc root-hairs. 
 
 FIG. 222. Antheridium of Adiantum 
 Capillus-Teneris (x550). p Prothallium ; 
 a antheridium ; s spermatozoid ; b the 
 vesicle containing starch-grains. 
 
 necessary for the formation of the antheridia, so that exclusively 
 male prothallia may be sometimes found ; less commonly, well- 
 nourished prothallia fail to produce antheridia, and consequently 
 exclusively female prothallia are found. The practical result of 
 this successive formation of the antheridia and archegonia is that 
 but few of them can possibly mature at the same time on one and 
 the same prothallium ; and, consequently, cross-fertilisation is 
 almost certainly ensured.
 
 GROUP III. PTERIDOPHYTA : FILICIJUE. 869 
 
 The development of the prothallium commences with the rupture 
 of the outer coat (exospore) of the germinating spore, which takes 
 place either along three lines meeting at an angle, when the spore 
 is tetrahedral, or by a longitudinal slit when the spore is bilateral, 
 the contents covered by the inner coat (endospore) being exposed. 
 Most commonly this cell grows out into a filament, cell-divisions 
 taking place in the transverse plane only, so that the prothallium 
 consists of a longitudinal row of cells. At length a longitudinal 
 wall is formed in the terminal cell of the filament ; cell-division 
 then proceeds in two planes, giving rise to a flattened plate of cells, 
 further growth being effected by means of a two-sided apical cell. 
 After a time the activity of the apical cell ceases, a periclinal wall 
 being formed in it ; whatever further growth takes place is effected 
 by the marginal cells. At this stage the prothallium becomes 
 somewhat heart-shaped, the anterior depression indicating the posi- 
 
 L" 
 
 FJG. 223. Polypodium. vulgare. A Youug arcbegonium, not yet open: K' neck-canal- 
 11 ; K" ventral canal-cell : o young oosphere. B Mature archegonium open. ( x 210 
 
 after Strasburger.) 
 
 tion of the organic apex (Fig. 221). The cells lying anteriorly in the 
 middle line now begin to divide in a plane parallel to the surface, 
 with the result that the prothallium becomes thickened in this 
 region, and eventually a " cushion :> of tissue, several layers of 
 cells in thickness, is produced, which projects on the lower 
 (ventral) surface, and bears the archegonia. 
 
 The sexual organs. The antheridium is developed from a 
 single superficial cell. The free surface of this cell grows out into 
 a blunt protuberance, which is cut off by a transverse wall. The 
 projecting cell thus formed generally undergoes division by the 
 formation "of a transverse wall near its base, so that it comes to 
 
 M.B. B B
 
 370 PART IV. CLASSIFICATION. 
 
 consist of two cells, the lower of which is the stalk-cell, the upper, 
 the anther-id ial cell. The latter grows, becoming more or less 
 spherical, and undergoes repeated cell-divisions which result in 
 the formation of a wall, consisting of a single layer of cells, sur- 
 rounding a large central cell from which, by further division, the 
 mother-cells of the spermatozoids are formed. When mature, 
 absorption of water causes the rupture of the antheridium ; the 
 mother-cells of the spermatozoids are now set free, and the 
 spermatozoids soon escape from the mother-cells as coiled ciliated 
 filaments, each having usually attached to it posteriorly a vesicle 
 of granular protoplasm, the remains of the contents of the mother- 
 cell (see Fig. 222). 
 
 The archegonium. The general description given above (p. 351) 
 of the development and structure of the archegonium, and of the 
 process of fertilisation, will suffice for tnis group of the Pterido- 
 phyta. It should, however, be mentioned that only a single neck- 
 canal-cell is developed. 
 
 The root-hairs retain in all cases their typical unicellular 
 structure. They arise as tubular outgrowths from single cells, 
 having, at first, colourless walls, which eventually become 
 thickened, and assume a brown colour ; the cavity of the hair is 
 cut off by a septum from that of the cell from w_hich it springs ; 
 their form is most commonly elongated and cylindrical, but some- 
 times (e.g. Hymenophyllacese) they are short and slightly branched. 
 The development of the root-hairs begins at the earliest stage in 
 the formation of the prothallium. Generally speaking, the root- 
 hairs are developed laterally, and as the prothallium assumes the 
 flattened expanded form, the development extends inwards from 
 the margin, over the inferior surface, and forwards as far as the 
 posterior part of the cushion. 
 
 The life of the gametophyte is, as a rule, short, being limited 
 by the fertilisation of an archegonium. If, however, fertilisation 
 does not take place, the prothallium continues to grow for several 
 months, or even years in the case of Osmunda. 
 
 Propagation of the gametophyte by means of a gemmae is common 
 in the Hymenophyllacese, but it has also been observed in certain 
 Polypodiacese (Vittaria, Monogramme). In Hymenophyllum, the 
 gemmae are small flat plates of cells ; in species of Trichomanes, 
 Vittaria, and Monogramme, they are short spindle-shaped filaments, 
 consisting of a single row of (6-9) cells, borne on a unicellular 
 stalk or sterigma ; in Trichomanes, the gemma is attached at its
 
 GROUP III. PTERIDOPHYTA : FILICIN.E. 371 
 
 centre to the stalk, so that its long axis is at right angles to the 
 stalk ; in Vittaria and Monogramme, the gemma is attached to the 
 stalk by one end. The sterigmata are developed either singly or 
 several together, from a single cell of the prothallium ; and the 
 gemmae may be borne singly or several together on one sterigma. 
 
 It will have been observed that the gametophyte of the homo- 
 sporous leptosporangiate Ferns presents, in its development, its 
 root-hairs, its propagation by gemmae, remarkable and suggestive 
 resemblances to the gametophyte of the Hepaticse. In the general 
 morphology, too, of the gametophyte, there are striking corres- 
 pondences between the two groups : thus, in both groups (with 
 certain exceptions in both) the first stage in the life of the game- 
 tophyte is a filamentous protonema, which is, however, relatively 
 small and short-lived, except in the Fern Trichomanes where the 
 gametophyte does not develope beyond the protonematous stage. 
 The protonema in both groups gives rise to a single flattened, ex- 
 panded shoot, the adult sexual shoot of the Hepaticae, the prothallium 
 of the Ferns, bearing the sexual organs. 
 
 Order 1. Hymenophyllaceae ; this order contains the simplest forms 
 The leaf-blade almost always consists of a single layer of cells ; the sorus 
 is always marginal (Fig. 214 A) and indusiate, the sporangium sessile or 
 shortly-stalked, and the annulus entire and horizontal. 
 
 Almost all the species are tropical. Trichomanes radicans and Hymeno- 
 phyllum Tanbridgense and unilaterale (or Wilsoni) alone occur in Britain. 
 Some species of Trichomanes have no true roots. 
 
 Order 2. Polypodiaceae. The annulus of the stalked sporangium is 
 incomplete and vertical (Fig. 215 r), that is to say, it is not continuous at 
 the base : indusium present or absent. Almost all our native Ferns belong 
 to this order, which is exceptionally rich in genera. 
 
 The following are the chief families : 
 
 (a) Pteridece. Sori coalescent along the margin of the leaf (Fig. 214 6')," 
 with a spurious indusium. Pteris (Pteridium) nquilina, the Bracken, has 
 a stem which grows at some depth below the surface of the soil, and throws 
 up every year a single large, much-segmented leaf (frond) : it has also a 
 true lateral indusium. Adiantum, the Maiden-hair Fern, belongs to this 
 group, as also Cheilanthes. 
 
 (6) Aspleniece. The sorus, which is situated on the under surfaca of the 
 leaf, is elongated or linear, and the lateral indusium springs from the vein 
 to which it is attached (Fig. 214 E). Aaplenium Ruta muraria, the Wall- 
 B,ue, is nob uncommon on walls and rocks ; A. Trichomanes is also abund- 
 ant, with simple pinnate leaves and a shining black rachis. Athurt:im 
 F'dix foemina, the Lady Fern, is common in damp woods. Scolopendritim 
 vulgare, the Hart's-tongue, with entire leaves, is common in damp hedge- 
 raws and woods (Fig. 217). Blechnum (Lornaria), the Hard Fern, as also
 
 372 PART IV. CLASSIFICATION. 
 
 Ceterach, may be included here, though the indusium may be rudimen- 
 tary or absent. 
 
 (c) Aspidiect'. Sorus on the lower surface of the leaf, orbicular in form 
 and covered \>y a peltate or reniform superior (Fig. 214 _D) or inferior 
 indusium. Nephr odium (Lastrcea) Filix mas, the male Fern, and other 
 species resembling it, with a thick tufted crown of leaves, are not rare in 
 woods. Aspidium is the Shield-Fern : A. (Polystichum) Lonchitis is the 
 Holly-Fern : "Woodsia, Onoslea, and Cystopteris (Bladder-Fern), with an 
 inferior indusium, also belong to this group. 
 
 (d) Polypodies. The sorus, which is on the under surface of the leaf, is 
 naked (Fig. 214 F). In the section Polypodium the leaves are articulated 
 to the stem, so that when they die and fall off they leave a roundish scar ; 
 the leaves are usually borne in two rows on the dorsal surface of the 
 rhizome. Polypodium vulgare, with simple pinnate leaves, is common on 
 tree-trunks, rocks, etc. In the section Phegopteris the leaves are not 
 articulated to the stem, so that when they die, fragments of the leaf -stalks 
 remain attached to it : Cryplogramme crispa is the Parsley-Fern : Pliegop- 
 tsris Dryopteris and polypodioides are the Oak- and Beech-Ferns. 
 
 Order 3. Cyatheaceae. Distinguished from the Polypodiaceae only by 
 the presence of a complete annulus. 
 
 The Tree-Ferns belong to this family. Cibotium and Dicksonia have 
 marginal sori with two-valved inferior indusia : Cyathea, Hemitelia, and 
 Alsophila have their sori on the under surface of the leaf : Alsophila alone 
 has no indusium; in Cyathea it is cup-shaped, and in Hemitelia one- 
 valved. 
 
 Order 4. Gleicheniaceae, including the genus Gleichenia with a hori- 
 zontal annulus ; no indusium : all tropical. 
 
 Order 5. Schizaeaceae, including the genera Schizaea Aneimia, Mohria 
 and Lygodium, with a projecting apical annulus to the almost sessile 
 sporangium, occur only in the tropics. Lygodium is the most remarkable 
 genus ; its pinnate leaves grow to a great length, and twine round supports 
 by means of their midribs : it alone has an indusium, and the sorus is 
 usually unisporangiate. 
 
 Order 6. Osmundaceae. The shortly-stalked sporangia have a rudi- 
 mentary annulus consisting of a group of cells just below the apex; they 
 burst open by a longitudinal slit on the side opposite to this. 
 
 Osmunda re/jails, the Fern-Royal, is a not very common but well-known 
 Forn. Only the upper pinnae of the leaves are fertile, and develope little or 
 110 mesophyll ; the sori are marginal, and consist of a great number of 
 sporangia; they have no indusium. The only other genus is Todea, 
 belonging mainly to Australasia.
 
 GROUP III. PTERIDOPHYTA : FILICIN^. 373 
 
 D. HETEROSPOROUS LEPTOSPORANGIAT.E. 
 
 (Hydropteridese or Rhizocarpae.) 
 
 This group includes the four genera, Salvinia, Azolla, Marsilea, 
 Pilularia ; of these the two former constitute the order Salviniacese, 
 the two latter the order Marsileacese. They are all more or less 
 aquatic in habit, Salviuia and Azolla being free-floating fugacious- 
 plants, whilst Marsilea aud Pilularia are perennials growing in 
 bogs and marshes. 
 
 SPOROPHYTE. The stem is a horizontal dorsiventral rhizome. 
 It generally bears foliage-leaves in alternating longitudinal rows 
 (four rows in Salvinia ; two rows in the other genera) on the dorsal 
 (superior) surface ; and roots in one (Marsileaceae) or two (Azolla) 
 longitudinal rows on the ventral (inferior) surface. In Salvinia, 
 however, there are no roots, but the stem bears in place of 
 them two rows of submerged leaves on its ventral surface. The 
 lateral branches, sometimes very numerous, are borne on the 
 flanks. 
 
 The foliage-leaf presents a considerable variety of form. In 
 Salvinia it is broad and flat, sessile and entire, with a well- 
 marked midrib ; in Azolla the leaf is small and two-lobed, the 
 lower lobe being submerged, whilst the upper floats on the surface 
 of the water : in Marsilea the leaf has a long erect petiole bearing 
 a paripinnate bijugate compound lamina of four leaflets: in 
 Pilularia the leaf is cylindrical and erect. 
 
 Circinate vernation obtains in the Marsileacese, but not in the 
 Salviniaceae : in Salvinia the vernation is conduplicate, and in 
 Azolla the lamina is expanded from the first. 
 
 In Salvinia the leaves are borne in a whorl of three at a node, 
 two being a pair of opposite foliage-leaves, and the third a sub- 
 merged leaf (p. 17) ; in the other genera the phyllotaxis is alternate. 
 
 The suljmcrged leaf of Salvinia consists of a number of long 
 filamentous branches, springing from a short petiole, and densely 
 covered with multicellular hairs. 
 
 The sporangia are of two kinds, microsporangia and macro- 
 sporangia : they are bsrne in sori enclosed in structures termed 
 sporocarps. The morphology of the sporocarp is, however, 
 altogether different in the two orders, and the same term ought 
 not to be applied to both : it would be well to restrict the term 
 " sporocarp " to the more complex fructifications of the 
 Marsileacese.
 
 374 
 
 PART IV. CLASSIFICATION. 
 
 In the Salviniacese the so-called sporocarp is simply a sorus of 
 sporangia, either micros porangia or macrosporangia, but not both, 
 surrounded by an inferior indusium (Fig. 224). In Salvinia the 
 sori are borne at the apices of the basal branches of a submerged 
 leaf, and may be comparatively numerous (4-20) on one leaf : in 
 Azolla the sori are borne at the apices of the segments of the lower 
 (ventral) submerged lobe of a leaf, and that leaf is always the first 
 (basal;i leaf of a fertile branch which is sometimes less vigorously 
 
 developed than the purely vegeta- 
 tive branches ; each leaf usually 
 bears only two sori, but in A. nilo- 
 tica there are four. In Salvinia 
 the sori are all of the same size, 
 whereas in Azolla the sori contain- 
 ing microsporangia are consider- 
 ably larger than those containing 
 macrosporangia. In both genera 
 the tip of the fertile leaf -segment 
 expands into a cellular cushion, the 
 placenta, from the superficial cells 
 of which the sporangia are de- 
 veloped : the indusium is developed 
 as an annular outgrowth from the 
 base of the placenta, becoming cup- 
 shaped, and eventually closing over 
 the sorus : it consists of two laj-ers 
 of cells which, in Salvinia, are 
 separated by large air-chambers 
 and are connected by longitudinal 
 cellular trabeculse. In both genera 
 the microsporangia of a sorus are 
 numerous (about 40 in Azolla, more 
 in Salvinia) : the macro-sporangial 
 sorus consists, in Salvinia, of many 
 (up to 25) macro-sporangia, whereas 
 in Azolla there is but one. Both 
 kinds of sporangia are borne by the 
 same plant. 
 
 In the Marsileacese the sporocarp consists of a leaf-branch 
 enclosing a number of sori, and each sorus includes both micro- and 
 macrosporangia. In Marsilea the fertile leaf -branches spring from 
 
 FIG. 224. A Apical portion of the stem 
 of Salvinia natans, seen obliquely from 
 below (nat. size) : 1 1 aerial leaves ; ic >c 
 aquatic leaves, with sori, *s; fc ter- 
 minal bud of the stem. B Longitudinal 
 section through three fertile teeth of an 
 aquatic leaf ( x 10), forming two sori 
 with microsporangia, (a) one with 
 macrosporangia; t indusium. (After 
 Sachs.)
 
 GROUP III. PTERIDOPHYTA : FILICIXJE. 
 
 375 
 
 the ventral surface of the petioles of the foliage-leaves (compare 
 Ophioglossacese), and each bears a sporocarp at the end of a longer 
 or shorter stalk : the petiole bears a single fertile leaf-branch near 
 its base in some species, or two or more adnate branches springing 
 from the same point ; or it bears (e.g. M. polycarpd) a series of 10- 
 20 branches, one above the other, each bearing a single sporocarp. 
 In Pilularia the fertile leaf-branches ap- 
 pear to be also developed from the ventral 
 surface of the foliage-leaves : each leaf has 
 at its base a single almost sessile sporo- 
 carp. 
 
 The sporocarp of Marsilea (Fig. 225) is 
 dorsiventral, somewhat pod-shaped, with 
 its dorsal margin directed upwards ; the 
 stalk is continued along the dorsal margin 
 as a midrib : the sporocarp may, in fact, 
 be regarded as being developed from the 
 laminar portion of the leaf-branch. The 
 sporocarp of Pilularia is globular, though 
 it is slightly pointed at the apex : it may 
 be likewise regarded as being a leaf- 
 branch, four (usually) leaflets or segments 
 being concerned in its construction. In 
 both genera, especially in Marsilea, the 
 wall of the sporocarp is composed of several 
 layers of cells with thick hard walls : 
 vascular bundles, springing from the stalk, 
 are distributed in the wall. 
 
 The number of sori in the sporocarp of 
 Marsilea varies from five to twenty-three 
 in the different species : they are developed 
 in tubular cavities, extending from the 
 ventral margin of the sporocarp for some 
 distance towards the dorsal margin, which 
 are disposed in two longitudinal rows, one 
 row on each side of the middle line ; when 
 young, these cavities are open at the ventral 
 margin, but the apertures become closed as the sporocarp matures ; 
 the external wall of each cavity developes into a projecting ridge of 
 tissue, the placenta, which bears the sorus, consisting of a single 
 median row of macrosporangia and a double row of microsporangia 
 
 FIG. 225. Stem of Xarsilea 
 Salvatrix with leaves (reduced 
 one-half). K Terminal bud ; 
 b b leaves ; / / sporocarps 
 borne on petioles.
 
 376 PART IV. CLASSIFICATION. 
 
 on each flank. The cavities are surrounded by parenchymatous 
 tissue. 
 
 The globular sporocarp of Pilularia contains four (sometimes two 
 or three) cavities, extending longitudinally from the base to the 
 apex, enclosed by parenchymatous tissue. The placenta is a ridge 
 of tissue on the external wall of the cavity, bearing the sorus which 
 consists, in its upper part, of microsporangia, and in its lower of 
 one or more macrosporangia. The cavities at first communicate 
 with the outer air at the apex of the sporccarp, but eventually be- 
 come completely closed. 
 
 In their development, the sporangia of the Heterosporous Lepto- 
 sporangiatse resemble those of the Homosporous Leptosporangiatse 
 (see p. 363) in all essential points : but no annulus is developed. In 
 each sporangium sixteen spore-mother-cells are developed from the 
 single tetrahedral archesporial cell, and each of these mother-cells 
 undergoes division to form four spores : but whereas in the micro- 
 sporangia all these sixty-four spore-rudiments develope into micro- 
 spores, in the rnacrosporangium only one developes into a 
 macrospore, the others being abortive. 
 
 The development of the spores in this group, is remarkable on 
 account of the important part played by the multinucleate proto- 
 plasmic mass (epiplasm), derived from the disorganisation of the 
 tapetal cells, in which the free spore-mother-cells are embedded at 
 the time when the development of the spores is commencing. 
 Taking first the Salviniacese : the microsporangium of Salvinia 
 contains, when mature, a number of microspores embedded in a 
 spongy mass of a substance, which gives some of the reactions of 
 corky cell-walls and is derived from the protoplasm of the tapetal 
 cells : in Azolla the microspores are likewise embedded in this 
 substance, but in more than one group or massula (2-8) according 
 to the species ; each massula is surrounded by a membrane, bearing 
 in some species a number of anchor-like hairs, the glochidia. In 
 Salvinia the macrospore also is invested by a layer of this spongy 
 substance, constituting the episporc or perinium. This is also the 
 case in Azolla, but here the perinium is remarkably developed : over 
 the rounded dorsal surface of the radial macrospore, the perinium 
 is a thick membrane, firm at the surface, spongy within, with 
 warty projections bearing filaments of the same substance : on the 
 three flattened surfaces of the ventral aspect of the macrospore the 
 perinium forms three or more large spongy masses which constitute 
 the so-called floats of the spore ; at the pointed apex of the spore,
 
 GROUP III. PTERIDOPHYTA : FILICIX.E. 377 
 
 between these masses, the perinium usually terminates in a tuft of 
 delicate filaments. 
 
 In the Marsileaceae the spores become invested by a perinium, 
 secreted by the epiplasm, consisting of an inner layer made up of 
 prisms placed with their long axes perpendicular to the surface of 
 the spore, and of an outer layer which is homogeneous in the case 
 of the microspore ; but in the case of the macrospore it is stratified, 
 swells up enormously on being wetted, and gives the cellulose- 
 reaction. 
 
 In all cases the spore has its own proper coats, the exospore and 
 the endospore, of the usual constitution. It contains a mass of 
 granular protoplasm, with a nucleus, and encloses numerous starch- 
 grains, oil-drops, and proteid granules. 
 
 The root is altogether absent in Salvinia ; in the other genera 
 the primary root is of but short duration, and the root-system con- 
 sists of numerous adventitious fibrous rootlets which have an apical 
 growing-point with a tetrahedral apical cell. In Azolla the root- 
 cap is but imperfectly developed, and in A. caroliniana it is 
 completely thrown off after a time. 
 
 General Histology. In the Salviniacese the stem is monostelic ; 
 in the Marsileacese it is polystelic. 
 
 On the whole the histology of these plants generally resembles 
 that of the allied homosporous Ferns, though in consequence of 
 their more or less aquatic habit the intercellular spaces of these 
 plants are more conspicuous, especially in Salvinia and in the root 
 of Pilularia where they form large air-chambers. 
 
 The Einbryogeny of the Sporophyte. The early divisions of the 
 oospore are essentially the same as in the allied homosporous Ferns. 
 The individual peculiarities of subsequent development are briefly 
 as follows. In Salvinia the whole of the hypobasal half goes to 
 form the foot, no primary root being developed ; of the four 
 epibasal octants, one gives rise to the growing-point of the stem, 
 and two to that of the first leaf or cotyledon, and from the basal 
 region of these octants a transverse layer of cells is cut off which 
 eventually elongates forming a cylindrical hypocotyl, sometimes 
 termed the caulicle ; the cotyledon is termed the scutiform leaf on 
 account of its form and mode of attachment ; the young stem first 
 produces one or two isolated foliage- leaves, and then the regular 
 development of the whorls of two foliage-leaves and one water-leaf 
 (see p. 373) begins. In the other three genera, two of the epibasal 
 octants give rise to the first cotyledon, one to the growing-point of
 
 378 PART IV. CLASSIFICATION. 
 
 the stem, and the fourth to a second cotyledon, so that here there 
 are two cotyledons : the hypobasal octants give rise to foot and root 
 in the usual manner. 
 
 THE GAMETOPHYTE. As these plants are heterosporous, the 
 gametophyte is represented by distinct male and female indivi- 
 duals : these remain connected with the spores producing them. 
 
 The male individual is developed from a microspore : it consists 
 of a rudimentary prothallium, represented by a single cell, bearing 
 a single male organ (antheridium). 
 
 In Salvinia the germination of the microspores takes place with- 
 in the microsporangium ; the inner coat (endospore) of the spore 
 grows out as a longer or shorter tube through the ruptured outer 
 coat (exospore), and eventually makes its way through the wall of 
 the sporangium so that its free end is in the water outside : a trans- 
 verse wall is formed within it which cuts off the apical portion of 
 the tube as the fertile portion of the prothallium. 
 
 In Azolla the microspores germinate within the massula. The 
 exospore of the tetrahedral spore ruptures along the three edges, 
 and the endospore protrudes as a papilla at the apex. A transverse 
 wall is formed across the base of the papilla, which now becomes 
 the mother -cell of the single antheridium. The spermatozoids 
 probably escape from the massula on the deliquescence of its 
 substance. 
 
 In the Marsileaceae the -male prothallium is formed altogether 
 within the microspore ; the spore divides into two cells : a small 
 basal vegetative cell and a larger one which is the mother-cell of 
 the antheridium. In all cases the prothallium has no chlorophyll. 
 
 The male organ, or antheridium, is developed from the antheri- 
 dial mother-cell mentioned above. It generally undergoes divisions 
 so as to form a central cell surrounded by a single layer of cells 
 forming the wall of the antheridium. But Salvinia is peculiar in 
 that the central cell of each antheridium is not completely sur- 
 rounded by a parietal layer of cells, but comes to the surface of the 
 antheridium. The central cell then undergoes further divisions to 
 form the mother-cells of the spermatozoids, of which there are eight 
 in the Salviniaceae and thirty-two in the Marsileacese. 
 
 The male cells are spermatozoids, which resemble those of the 
 homosporous leptosporangiate Ferns in all essential features of 
 their form and development, as also in their extrusion from the au- 
 theridium. In the Marsileacese, the male prothallium is enclosed 
 within the microspore until the antheridium is mature, when the
 
 GROUP III. PTERIDOPHYTA : FHJCINJE. 
 
 379 
 
 spore-walls are ruptured by the swelling of the cells of the con- 
 tained prothalliura, and the spermatozoids are set free. 
 
 The female individual is a small multicellular prothallium of a 
 green colour, and is developed from a macrospore to which it re- 
 mains attached. The development of the prothallium begins 
 inside the macrospore at its pointed apical end, where there is 
 an aggregation of protoplasm in which the nucleus lies. The 
 nucleus divides, and this is followed by the formation of a cell- 
 wall between the two nuclei, cutting off the apical portion of the 
 spore, as a small cell, from the basal larger portion ; this first 
 wall is termed the diapltragru, and it marks off that portion of the 
 macrospore which gives rise to the prothallium from that portion 
 which takes no part in the process. The small cell then un< 
 repeated division to form the pro- 
 thallium which consists, in the Salvi- 
 niacese, of several layers of cells (at 
 least in the middle region), and in the 
 Marsileaceae of two layers only. As 
 the prothallium developes, the coats of 
 the macrospore split into three valves 
 at the apex, so that now the prothal- 
 lium is in direct relation with the 
 exterior. Whilst in the Marsileacese 
 the prothallium projects but little from 
 the spore, in the Salviniaceae (especially 
 Salvinia), where it is larger, the 
 greater part of it is outside. 
 
 R 
 
 FIG. 226. Gametophyte of Sal- 
 vinia (x 60). A Macrosporangium 
 m with a germinated macrospore sp 
 
 No cell-formation takes place in the (dotted outline) ; pt female pro- 
 
 larger basal portion of the macrospore SEyJSfiLT 71 
 
 below the diaphragm, though nuclear microspore isolated from a micro- 
 division has been observed in Azolla. sporangium ; 8 p spore -,pt male pro- 
 rn,. -n T_ . , thallium ; a antheridia. 
 
 Ihis eventually becomes filled with 
 
 starch and other nutritive substances for the nutrition of the 
 
 embryo. 
 
 The female organ, or archegonium, differs in no essential feature 
 of structure or development from that of the homosporous lepto- 
 sporangiate Ferns. In the Marsileacese, only a single archegonium 
 is developed ; it arises from a cell in the middle of the upper sur- 
 face of the prothallium : in Azolla, if the archegonium does not 
 become fertilised, a few more archegonia may be subsequently de- 
 veloped : in Salvinia, at least three archegonia are always formed,
 
 380 PART IV. CLASSIFICATION. 
 
 the first anteriorly in the middle line, the second and third one on 
 each side of the first. If none of these become fertilised, the pro- 
 thallium resumes its growth both in breadth and length, and a 
 second row of archegonia is formed in front of the first. Similarly 
 a third and a fourth row, with an increased number of archegonia 
 in each (seven or more), may be successively produced. In Pilu- 
 laria also the prothallium grows to a considerable size if the arche- 
 gonium is not fertilised, though no more archegonia are formed. 
 
 The female cell, or oosphere, developed in each archegonium, does 
 not require any special description. 
 
 Order 7. Salviniaceae : microsporangia and macrosporaiigia in distinct 
 sori, each sorus being covered by an indusium ; the spores are surrounded 
 by spongy mucilage, forming an episporium or perinium round the in- 
 dividual macrospores, and holding all the microspores together within the 
 sporangium (Salvinia) or in several groups or massulse (Azolla) ; the female 
 prothallium is relatively large and bears several archegonia. 
 
 No species of Azolla is European: Salvinia natans occurs in Southern 
 Europe. 
 
 OrderS. Marsileaceae : microsporangia and macrosporangia in the same 
 sorus, a number of sori being enclosed in the specially modified sporo- 
 phyll-segment, the whole forming a sporocarp ; each spore is invested by 
 a mucilaginous prismatic perinium : the female prothallium is relatively 
 small, and bears but a single archegonium. 
 
 Pilularia globulifera is the one British species belonging to this order. 
 The European species of Marsilea are M. pubescens, which occurs in the 
 Mediterranean region, and M. quadrifoliata, in Central Europe. 
 
 CLASS VI. EQUISETIN^. 
 
 This class includes, among existing plants, only the homosporous 
 order, Equisetacese ; but there are many extinct fossil forms, some 
 of which are undoubtedly heterosporous. 
 
 Order 1. Equisetaceae. This order includes the single genus Equisetum 
 (Horsetail). Of the twenty species of this genus, about half are British (E. 
 arvense, maximum, silvaticum, paluntre, limosum, hyemale,trackyodon,varieya- 
 tum, pratense, iitorale). 
 
 THE SPOUOPHYTE. The utern consists of a horizontal, subterranean, much- 
 branched rhizome ; some of the branches come to the surface, and are the 
 sub-aerial shoots. The rhizome and its branches are very distinctly seg-
 
 GROUP III. PTERIDOPHYTA : EQUISETIN.E. 
 
 381 
 
 mented into nodes and internodes. At each node is borne a whorl of scale- 
 leaves forming a continuous sheath. The branches, as also the adventi- 
 tious roots, spring from the nodes, a bud being developed in the axil of each 
 leaf, and an adventitious root from the base of each bud ; but in the 
 sub-aerial shoots the rudimentary roots do not grow out, whilst in the 
 subterranean shoots relatively few of the buds grow into branches. In 
 certain species (E. arvenie, silvaticum, maximum, palmfre, etc.) some of the 
 subterranean branches 
 become tuberous. 
 
 The sub-aerial shoots 
 generally live for one 
 season only, and are her- 
 baceous in texture, but 
 in some species they 
 persist (e.g. E. hiemale, 
 trachyodon, variegatum). 
 They are generally green 
 in colour, and their sur- 
 face is more or less 
 strongly ribbed. Some 
 of these shoots are sterile, 
 whilst others are fertile, 
 bearing the sporangia. 
 In most species the 
 sterile and fertile shoots 
 are alike (Equiseta ho- 
 mophyadica), but in the 
 four species E. arvense, 
 maximum, silvaticum, 
 pratense (Equiseta hete- 
 rophyadica) they are 
 more or less widely dif- 
 ferent. Thus in E. 
 arvense and maximum, 
 the fertile shoots are 
 developed early in the 
 spring, and are un- 
 branched, whereas the 
 copiously branched 
 sterile shoots are not 
 developed till the sum- 
 mer ; moreover the fer- 
 tile shoots are not green. 
 In E. pratense the dif- 
 ference between the 
 
 PIG. 227. Median longitudinal section of the apical por- 
 tion of a vegetative shoot of Equisetum arvense ; p apical 
 growing-point ; g bud-rudiment ; g'-g'" stages in the de- 
 velopment of lateral buds; v r> developing adventitious 
 roots on the buds ; TH central ground tissue ; vs develop- 
 ing (common) vascular bundle; n nodal diaphragms, 
 (x 26: after Strasburger ) 
 
 fertile and sterile shoots is le.^s marked, the former bearing a few whorls 
 of simple branches. In E. silvaticum the fertile shoot has no branches at 
 first, but alter the [shedding of the spores the terminal cone dies off, the
 
 382 
 
 PART IV. CLASSIFICATION. 
 
 shoot throws out branches, and thus comes to be a sterile shoot. In some 
 species the sub-aerial shoots are generally unbranched (e.g. E. hiemale 
 trachyodon, variegatuni). 
 
 The leaves are either cataphylls or sporophylls. The cataphylls, repre- 
 senting the foliage-leaves, are borne in whorls at the nodes, having a 
 common attachment, so that they form a leaf-sheaf at each node. They 
 are small and brown in colour. 
 
 The sporophylls, like the 
 cataphylls, are developed 
 in whorls, but owing to 
 the fact that the inter- 
 nodes between the whorls 
 do not elongate, the sporo- 
 phylls are aggregated into 
 a cone-like flower situated 
 terminally on the shoot 
 (Fig. 228), or less common- 
 ly (e.g. E. palustre) on some 
 of the lateral branches. 
 The leaf-sheath below the 
 cone, marking off the re- 
 productive from the vege- 
 tative region of the shoot, 
 is peculiar, being gener- 
 ally very much reduced, 
 and is termed the ring 
 (see p. 57). 
 
 Each sporophyll has a 
 small hexagonal lamina 
 which is inserted on the 
 axis of the cone by a short 
 stalk attached to the 
 centre of the inner surface 
 of the lamina. Thus the 
 sporophyll is peltate. It 
 bears on its inner (dorsal) 
 surface a small number 
 (5-10) of sporangia ar- 
 ranged round the leaf- 
 stalk. 
 
 The sporangia are some- 
 what elongated in form, 
 
 and are sessile. The wall of the sporangium consists of a single layer 
 of cells with spiral thickening. Dehiscence takes place longitudinally 
 on the side facing the leaf-stalk. The archesporium is usually a single 
 cell from which are derived the mother-cells of the spores, each of which 
 give rise to four spores. 
 
 The spores, which are all of one kind, are developed tetrahedrally, but 
 
 lv 
 
 FIG. 228. A Upper portion of a fertile branch of 
 Equisetum palustre. v Leaf-sheaths, below which the 
 branches (r) spring; w the uppermost sterile sheath 
 (ring); a the flower; s the peltate sporophylls. B 
 Transverse section of the stem ( x6) : c central cavity ; 
 s the vascular bundles arranged in a circle, each having 
 a carinal cavity, fc ; / the vallecular cavities ; r the 
 ridges. C Sporophyll with sporangia ( x 10) : t the 
 stalk ; sp the sporangia. I) Diagram of the course 
 taken by the vascular bundles where two internodes 
 meet ; i i the internodes ; fc the node.
 
 GROUP III. PTERIDOPHYTA : E^UISETIfOE. 
 
 383 
 
 are nearly spherical when ripe. Each spore has two coats, exospore and 
 endospore, and originally a perinium is present. The perinium, as it 
 developes, becomes irregularly thickened in such a way that, when the 
 thin portions are destroyed, the thickened portions remain as four fila- 
 ments, the elaters, all attached at one point only to the spore. These 
 elaters are very hygroscopic. When the air is dry they expand, and 
 stand out stiffly from the spore ; when moistened, they suddenly roll up 
 spirally round the spore. The spores become entangled by their elaters, 
 so that when set free from the sporangium a number of the spores fall to 
 the ground and germinate near together. 
 
 The roots are all adventitious, though a short-lived primary root is 
 developed. They 
 are developed at 
 the nodes of the 
 rhizome. 
 
 General Histo- 
 logy. A striking 
 feature in the 
 anatomy of the 
 stem is the pre- 
 sence of large, 
 mainly lysigen- 
 ous, air-cavities : 
 thus, in some 
 species, the rhi- 
 zome has a large 
 centra] cavity 
 in each inter- 
 node (Fig. 230 C, 
 a) ; a similar 
 cavity is present 
 in the internodes 
 of the aerial 
 shoots of nearly 
 all the species 
 (Fig. 230 A, ); 
 the central cavi- 
 ties of successive 
 internodes are 
 
 shut off from each other by diaphragms at the nodes (Fig. 227 n) : a 
 series of similar cavities occurs always in the cortex, alternating with the 
 vascular bundles internally and with the surface-ribs externally, hence 
 termed vail ecu 1 nr cavities (Fig. 230 1>) ; finally, in connexion with each vas- 
 cular bundle, there is a large cavity, the carinal cavity (Fig. 230 c), extend- 
 ing, like the others, from one node to another. 
 
 The growing-point of the stem, and of its branches, is apical, and has a 
 tetrahedral apical cell (Fig. 229). 
 
 In the aerial shoots (except specialised fertile shoots of E. arvenie, etc.) 
 
 FIG. 229. Growing-point of the stem of ISquisetum. arvensc, in 
 longitudinal section; t apical cell; '" successive segments; 
 p anticlinal segment-wall ; m wall dividing the segment into an 
 upper and a lower cell ; pr penclinal wall dividing the segment 
 into an inner and an outer cell ; fff" successive whorls of leaves ; 
 9 initial cell of a lateral bud. (After Strasburger: x 240.)
 
 384 
 
 PART IV. CLASSIFICATION. 
 
 there is a considerable development of assimilatory tissue in the cortex, 
 strands of this tissue corresponding in position with the furrows on the 
 surface in which the stomata are developed ; whilst opposite the ridges on 
 the surface there are cortical strands of sclerenchyma. The development 
 of assimilatory tissue in the shoots and branches is correlated with the 
 absence of foliage-leaves, the functions of foliage-leaves having therefore 
 to be discharged by the shoots and branches. The epidermal cell-walls 
 are impregnated with silica. 
 
 Within the cortex, and almost abutting upon the large central cavity, 
 is a ring of distinct vascular bundles which run down the internode from 
 
 -End. 
 
 FIG. 230. Portions of transverse sections of stems of species of Equisetum (after 
 Pfltzer: x 36). S rhizome of E. litorale ; C rhizome of E. sihaticum ; A aerial stem of E. 
 palustre, in which the structure is the same as in C, but the markings of the internal en- 
 dodermal layer are not developed; a central cavity ; 6 vallecular cavities in the cortex ; c 
 carinal cavities in the vascular bundles ; JGnd. endodermis. 
 
 the leaves at the node. Each bundle is collateral, closed and common, 
 with very rudimentary xylem consisting of the few annular vessels of the 
 protoxylem and of two small groups of scalariform tracheids. 
 
 The root grows in length by means of a tetrahedral apical cell ; in its 
 mode of growth, development of root-cap, etc., it essentially resembles 
 that of the Ferns. Its structure is rather peculiar : the vascular 
 cylinder consists (usually) of three wood-bundles and three bast-bundles, 
 and is invested by two layers of sheathing-cells, the outer of which has 
 the characteristic marks of an endodermis, whilst the inner appears to be 
 a pericycle and gives rise to the growing-points of the lateral roots ; how- 
 ever, the inner layer is, as a matter of fact, not a pericycle, but the inner-
 
 GROUP III. PTERIDOPHYTA : EQUISETIN^E. 385 
 
 most layer of the cortex, the endodermis being the last layer but one of the 
 cortex (p. 115). Hence it appears that here, as in the Ferns, the lateral roots 
 spring from the innermost layer of the cortex. There is no pericycle in 
 the root of Equisetum. 
 
 Embryogeny of the Sporophyte. The oospore is divided by a transverse 
 basal wall, and then becomes segmented into octants, as in the Filicinae. 
 Of the four epibasal octants, one gives rise to the growing-point of the 
 primary stem ; two to the first cotyledon ; and the fourth to the second 
 cotyledon : the two cotyledons cohere to form a leaf-sheath round the 
 young primary stem. Of the four hypobasal octants, one gives rise to 
 the growing-point of the primary root, and two to the foot. 
 
 The primary stem grows erect, and its leaf-sheaths are three-toothed, 
 the three leaves corresponding to the three segments cut off from the 
 apical cell of the stem ; it branches at its base ; stouter shoots with an 
 increasing number of teeth in the leaf-sheaths are successively produced, 
 and eventually a branch is produced which becomes the perennial sub- 
 terranean rhizome. 
 
 The GAMETOPHYTK is a green, dorsiventral, lobed prothallium which be- 
 comes quite free from the spore. The prothallia are generally dioecious, 
 the female prothallia being larger than the male ; but the distinction of 
 sex is not absolute, for the female prothallia may eventually bear male 
 organs, and the male prothallia female organs ; it appears to depend 
 largely on conditions of nutrition. 
 
 The germinating spore divides into two cells : one of these contains no 
 chloroplastids, and grows out into a root-hair, the other contains chloro- 
 plastids, and grows and divides to form the first lobe of the prothallium, 
 which branches as its development proceeds, some of the branches of 
 the female prothallia growing erect. On its under surface the prothal- 
 lium bears numerous root-hairs. 
 
 At first the prothallium consists throughout of a single layer of cells ; 
 in the female prothallium, however, one of the lobes becomes thick and 
 fleshy, consisting of several layers of cells formed by repeated horizontal 
 cell-division, and this constitutes the archegoniophore. 
 
 The male organ, or antheridium, is developed from a single cell of the 
 margin of the male prothallium : this cell undergoes repeated division, 
 with the result that a wall, consisting of a single layer of cells, is formed 
 surrounding a central cell from which, by subsequent divisions, the 
 numerous mother-cells of the male cells are developed : the antheridium 
 eventually dehisces by the separation of the cells forming the roof, in 
 consequence of the swelling-up of the contents of the antheridium. The 
 male prothallium bears several antheridia, one being developed terminally 
 on each lobe, and others in succession on the lateral margins. 
 
 The male cell is a spermatozoid, which is larger than that of any other 
 Pteridophyta ; it has only two or three coils, and bears a tuft of short 
 cilia at its anterior pointed end. 
 
 The/ei?e organ, or archegonium, resembles, in all essential features of 
 its structure and development, that of the typical Filicinse : a distinctive 
 peculiarity -is afforded by the long recurved terminal cells of the neck, 
 M.B. C C
 
 PART IV. CLASSIFICATION. 
 
 and by the relatively small neck-canal-cell. Each prothallium bears a 
 number of these organs : they are developed each from an anterior 
 marginal cell, and, as the prothallium continues to grow, the organs 
 come to lie on its upper surface. 
 
 The female cell is an oosphere, and calls for no special remark. 
 
 CLASS VII. LYCOPODIN.E. 
 
 SUB-CLASS HOMOSPORE^E. 
 
 Order 1. Lycopodiaceae. This order contains the two genera Lyco- 
 podium and Phylloglossum : the former is a large genus, six species being 
 
 British (L. Selago, 
 inundatum, annot- 
 inum, davatum, 
 alpinum, complan- 
 atum} and com- 
 monly termed 
 Club-mosses : the 
 genus Phylloglos- 
 sum has a single 
 species (P. Drum- 
 mondii) found in 
 Australia and 
 New Zealand. 
 
 THESPOKOPHYTE. 
 The stem. In Ly- 
 copodium the.stem 
 is slender and 
 much branched, 
 erect (e.g. L. Sela- 
 go), or growing 
 
 FIG. 231.-Portion of Zycopodium vlavatum, somewhat smaller horizontally on 
 than nat. size : s, the cone-like flower. B a single sporophyll (b) the surface of tJ 
 from the cone, bearing a sporangium sp, which has dehisced ( x 10). ground (e.g. L. 
 
 davatum [Fig.28i] 
 
 annotinum), or beneath the surface as a rhizome (e.g. L. alpinum, com- 
 planatum) : the branching is in some cases dichotomous, in others mon- 
 opodial ; it may take place in all directions, or in one plane only (L, 
 complanatum). 
 
 The leaves. In some species of Lycopodium all the leaves are alike (e.g. 
 L. Selago) ; but in most species the foliage-leaves and the sporophylls are 
 more or less widely different. 
 
 The foliage-leaves are small and very numerous in Lycopodium ; their 
 arrangement is various, whorled, or spiral, or in decussate opposite pairs 
 (L. complanatum, etc.) : in the last case there is heterophylly (p. 41), as the de- 
 cussate leaves on the flattened sterile shoots vary in size, those on the lateral
 
 GROUP III. PTERIDOPHYTA : LYCOPODIX.E. 387 
 
 margins of the shoots being larger than those on the flattened surfaces. 
 The leaves are sessile, simple, and have a rudimentary midrib. 
 
 The sporophylls present considerable variety. _ In L. Selago and its 
 allies they are quite like the foliage-leaves ; in most species of Lycopodium 
 (e.g. L.inundatum, clacatum, Phlegmaria, etc.) the clearly differentiated 
 sporophylls are aggregated into terminal cone-like flowers, and in some 
 cases the branch bearing the cone grows out into a long peduncle (L. 
 dauatum, cotnplanatum, etc.). 
 
 The sporangia are borne singly on the upper surface of the sporophylls 
 near their base. The archesporium consists of a single row or of a few 
 rows of cells which, by their division, give rise to the mother-cells of the 
 spores. The sporangia are unilocular, somewhat reniform in shape, and 
 (in Lycopodium) seated on a short broad stalk ; they dehisce by a longi- 
 tudinal slit. 
 
 The spores are all of one kind, and are tetranedral in form ; they have 
 the ordinary structure. 
 
 The roots are all adventitious. In the erect species of Lycopodium they 
 spring as a tuft from the basal end of the stem : in the procumbent species 
 they are born singly on the under surface of the stem. The roots branch 
 dichotomously in alternate planes. 
 
 General Histology. The growing-point of stem and root alike consists, 
 in Lycopodium, of small-celled meristem, no apical cell being present. 
 Both stem and root have an axial vascular cylinder consisting of alter- 
 nating bundles of wood and of bast arranged radially (p. 125) : thus the stem 
 is monostelic, and its structure only differs from that of the stouter roots 
 in respect of the larger number of bundles present: in smaller roots there 
 is only one wood- and one bast-bundle. In the stem the bundles fre- 
 quently anastomose, more especially in the erect-growing species, so that 
 transverse sections taken at different levels present diverse pictures. The 
 wood-bundles consist of scalariform tracheids, with the exception of the 
 protoxylem. Neither stem nor root grows in thickness. In both stem 
 and root there is an endodermis, the cells of which have the characteristic 
 marking when young, but eventually become thick-walled and corky. 
 
 The leaves of Lycopodium are of verj- simple structure ; they usually 
 have stomata on both surfaces. 
 
 Embryogeny of the Sporophyte. The early stages have only been observed 
 in L. Phlegmaria, where the oospore is divided by a transverse basal wall, 
 the cell next to the neck of the archegonium being the hypobasal cell, 
 and the lower cell the epibasal. The hypobasal cell developes into a short, 
 cylindrical, usually unicellular, suspensor (p. 347). The somewhat hemi- 
 spherical epibasal cell becomes segmented into four octants "by two walls 
 at right angles to each other and to the basal wall ; and then the octants 
 are divided transversely, by a wall at right angles to the two preceding, 
 into two tiers or stages of four cells each. Of these two tiers the lower 
 forms a short hypocotyl (as in Salviuia, see p. 377) which is commonly (but 
 erroneously) called the foot, though it is morphologically quite different 
 from the foot of the Filicinse and Equisetinse. The upper tier of cells 
 gives rise to the first leaf or cotyledon, and to the primary stem. The
 
 388 PART IV. CLASSIFICATION. 
 
 first root eventually springs adventitiously from cells belonging to the 
 upper tier, below the cotyledon : its origin is exogenous. (Compare em- 
 bryogeny of Selaginella, p. 393). 
 
 Vegetative Propagation. In the creeping forms, as the main stems die off, 
 the younger branches become independent and constitute new individuals. 
 In some species there are gemmae, as in L. Selago, where they are borne on 
 the stem, and are modified leafy branches ; and as in L. cernuum, where 
 they are small tubercles borne on the roots. 
 
 THE GAMETOPHYTK. In so far as the gametophyte has been investigated, 
 it is a monoecious prothallium, either containing chlorophyll (L. inun- 
 datum and cernuum), or destitute of chlorophyll (L. annotinum and Phleg- 
 maria) and saprophytic. 
 
 The morphology of the prothallium offers considerable variety. In 
 some species (e.g. L. inundatum) the prothallium is tuberous ; its base is 
 embedded in the soil, and bears root-hairs ; its apex projects above the 
 surface and bears a tuft of green leafy lobes : the sexual organs are de- 
 veloped in a zone from a layer of tissue which long remains merismatic 
 and which is situated just below the apical tuft of lobes ; occasionally 
 some antheridia are developed on the lobes. Whilst in these species the 
 prothallium is very small and simple, in L. PJilegmaria and some other 
 species it is considerably larger and more complex. It consists here of 
 a cylindrical, monopodially-branched body, with apical growing-points 
 similar in structure to those of the sporophyte. The superficial layer of 
 cells, representing an epidermis, gives rise to a number of root-hairs. 
 The sexual organs are developed on special branches, yametophores, though 
 antheridia sometimes occur on the vegetative branches ; the gametophores 
 are shorter and thicker than the vegetative branches, sometimes even 
 tuberous, and on the upper surface bear the sexual organs surrounded by 
 stout multicellular hairs, paraphyses. 
 
 The male organs (antheridia) are sunk in the tissue of the prothallium : 
 they resemble those of the Eusporangiate Filicirise. Their development 
 precedes that of the female organs. 
 
 The male cells are spermatozoids, oval in shape, and have two cilia. 
 
 The female organs (archegoma) have short necks which project but 
 little above the surface of the prothallium ; they have the structure 
 usual among Pteridophyta. 
 
 The female cell (oosphere) requires no special description. 
 
 In consequence of its position and of its mode of development, the 
 embryo is forced downwards into the tissue of the fleshy prothallium, being 
 anchored, as it were, at one end by the suspensor (see p. 347). As it grows 
 it destroys the cells of the prothallium with which it comes into contact, 
 and absorbs the nutritive substances stored in these cells by means of the 
 so-called foot, the superficial cells of which grow out into short papillae. 
 In its further growth the embryo becomes more and more curved until it 
 regains the surface of the prothallium and projects. In L. Phleymaria 
 the embryo remains for some time enclosed in a sac, the calyptra, formed 
 by active growth of the prothallial tissue. 
 
 The life of the prothallium is short and closes, in most cases, with the
 
 GROUP III. PTERIDOPHYTA : LYCOPODIN.E. 389 
 
 development of an embryo from the oospore, but in L. Phleymaria it 
 seems to persist from one season to another. In the latter species the 
 prothallia are multiplied vegetatively by the isolation of branches, as 
 also by small multicellular bulbils. 
 
 Order 2. Psilotaceae. This order consists of the two genera Psilotum 
 and Tmesipteris ; of these the former is widely distributed in the tropics ; 
 the latter is confined to Australia, New Zealand, and Polynesia, and 
 lives epiphytically, and perhaps parasitically, on the trunks of Tree- 
 Ferns. 
 
 THE SPOROPHYTE. The most striking feature in the morphology of 
 these plants is the total absence of roots, the functions of these organs 
 being performed by specially adapted stem-branches bearing minute scale- 
 leaves, and covered with root-hairs. 
 
 The stem. In Psilotum the subterranean shoots have unlimited apical 
 growth : they are much branched, apparently dichotomously, but it 
 seems probable that the branching is really lateral. The subaerial 
 shoots generally arise as lateral branches on the subterranean shoots : 
 they have limited apical growth; they are branched, the mode of branch- 
 ing being probably the same as that of the subterranean shoots ; and they 
 bear small scattered leaves. 
 
 The stem of Tmesipteris appears to agree in all essential morphological 
 points with that of Psilotum ; but with this conspicuous difference, that 
 it is much less branched. 
 
 The leaves. In both genera the leaves of the subaerial shoots are of two 
 kinds. In Psilotum the vegetative leaves are minute scales, whereas in 
 Tmesipteris they are relatively well-developed as foliage-leaves: they 
 are simple and sessile. The sporophylls, on the contrary, are petiolate and 
 bilobed in both genera, a single sporangium being borne on the upper 
 surface of each sporophyll just at the junction of the basis of the two 
 lobes : they are not borne in cones. 
 
 The i>poran<jia are synangia (p. 52) ; that is, they are not unilocular. but 
 multilocular capsules : in Psilotum the synangium is generally trilocular 
 (sometimes 2-4 locular), in Tmesipteris bilocular. Each loculus opens by 
 a longitudinal -slit. The origin of the archesporium has not been fully 
 traced : but it appears probable that it consists primarily of a layer of 
 cells, some of which become the mother-cells of the spores, whilst the lest 
 are sterile and form the tissue of the walls separating the loculi. 
 
 The spores are developed in tetrads from the mother-cells ; bilaterally, 
 as in Tmesipteris 5 or either bilaterally or tetrahedrally, as in Psilotum- 
 They have the typical structure. 
 
 THE GAMETOPHYTE. No observations have as yet been made on the 
 gametophyte of either genus, and consequently the embryogeny of the 
 sporophyte is also unknown. 
 
 SUB-CLASS HETEROSPOREjE. 
 
 Order 3. Selaginellaceae. This order consists of the single genus 
 Selaginella, of which the numerous species are very widely distributed: 
 but only one, S. spinosa (selayinoides), is British.
 
 390 
 
 PART IV. CLASSIFICATION. 
 
 THE SPOROPHYTE. The primary stem is slender and elongated, erect, or 
 more commonly procumbent ; its symmetry is bilateral, isobilateral when 
 erect, dorsiventral when procumbent ; the branches spring from the flanks 
 of the primary stem, and, as this is subsequently repeated, the resulting 
 branch-system lies in one plane ; the mode of branching is lateral, though 
 it appears to be dichotomous. In some few species, however, the branches 
 have radial symmetry (e.g. 8. spinosa). 
 
 At the points at which the normal branching takes place, leafless 
 branches, termed rhizopkores, are in some species developed in a plane at 
 right angles to that of the normal branching ; thus in S. Kraussiana 
 they arise singly on the upper surface of the stem at the points of normal 
 branching, whilst in S. Martensii two are developed at each such point, 
 one on the upper and one on the lower surface. The direction of growth 
 of the rhizophore is such that the apex eventually penetrates into the 
 soil, when roots arise from it and it ceases to grow. 
 
 These organs have been regarded as roots, and are sometimes so desig- 
 nated still. But in view of the important morphological facts that the 
 rhizophore is of exogenous origin like 
 the leafy branches; that it has no 
 root-cap, whilst the true roots of Sel- 
 aginella have one ; and finally, that 
 sometimes a rhizophore will develope 
 leaves and even cones, the probability 
 is that they are modified branches com- 
 parable with the root-like branches of 
 the Psilotacese. 
 
 The leaves can be readily distin- 
 guished as either foliage-leaves or 
 sporophylls. A characteristic feature 
 in their morphology is the development 
 of a small lirjuh on the upper surface 
 of each leaf near its base. 
 
 The foliage-leaves are simple, small, 
 sessile, and rather numerous. Those 
 borne on the radial branches are all 
 alike, and are arranged spirally; the 
 
 bilateral branches show remarkable heterophylly, there being leaves 
 of two sizes in decussate pairs, each pair consisting of one lai-ge and one 
 small leaf ; when the branch bearing these two kinds of leaves is dorsiven- 
 tral, the four rows of leaves show displacement, with the result that the 
 two rows of small leaves are borne on the upper surface of the branch, and 
 the two rows of larger leaves are borne infero-laterally (Fig. 232). 
 
 The sporophylls are generally collected into more or less distinct cone- 
 like flowers ; they do not differ materially from the foliage-leaves, and, 
 like them, may be all of one size or of two sizes. 
 
 The sporangia are shortly stalked and unilocular ; they arise singly 
 from a group of superficial cells of the stem just above the insertion of 
 fach sporophyll ; the wall, when mature, consists of two layers of cells; 
 
 FIG. 2S2.-Sel<iginella helvetica (nat. 
 size) : s the upright fertile shoot, with 
 sporangia in the axils of the leaves. 
 On the procumbent sterile shoot, the 
 leaves on the under side i) are larger 
 than those on the upper side (o).
 
 GROUP III. PTERIDOPHYTA : LYCOPODIN.E. 
 
 391 
 
 the archesporium probably consists of a single row of cells, and is entirely 
 sporogenous. 
 
 There are two kinds of sporangia, macrosporangia and microsporangia, 
 distinguished by the kind of spores which they produce, and by their size. 
 The macrosporangia each give rise to generally four (sometimes 2 or 8), 
 relatively large macrospores ; the microsporangia each give rise to a con- 
 siderable number of microspores. 
 
 The relative distribution of the two kinds of sporangia presents some 
 variation. As a rule both kinds of sporangia are present in the same cone, 
 so that, like the flower of most Angiosperms, it contains both microsporo- 
 phylls and macrosporophylls ; in this case there may be several macro- 
 sporophylls at the 
 lower part of the 
 cone, or only a 
 single one. 
 
 The spores are de- 
 veloped in fours 
 from the mother- 
 cells resulting from 
 the growth and 
 multiplication of 
 the archesporial 
 cells. They are 
 developed tetra- 
 hedrally: but in the 
 macrospora n g i u m 
 usually only one 
 of the mother-cells 
 undergoes division 
 to form spores. 
 The structure of 
 the spores is normal. 
 The roots are all 
 adventitious- and 
 endogenous. In 
 some species (e.g. S. 
 cuspidata and Wil- 
 de nodi) they spring 
 directly from the 
 lower surface of the 
 stem at the points where branching takes place. In other (e.y. S. 
 Marleiisii and Kraussiana) cases they spring from near the apex of the 
 rhizophores after the rhizophores have reached and entered the soil. The 
 roots branch monopodially. 
 
 FIG. 233. Prothallium and embryo of Selaginella Martensii 
 (x 65: after Pfeffer) s coat of macrospore ; p prothallium ; 
 o archegouiam ; d-d diaphragm ; end so-called endosperm : B 
 an embryo (there is a smaller one to the right) : * snspensor ; 
 c c developing cotyledons ; ( stem ; r origin of the root ; / o- 
 ca'.led foot. 
 
 General Histology. The stem is, in some species (S. spinulosa and denticu- 
 lata), monostelic, but in most species it is polystelic (two or three). The 
 epidermal and the ground-tissues of the stem are prosenchymatous, with-
 
 392 
 
 PART IV. CLASSIFICATION. 
 
 out intercellular spaces. In correlation with this each stele is suspended, 
 by delicate trabecular cells developed from the endodermis, in an air- 
 chamber': each vascular bundle going to a leaf is in a similar chamber 
 which communicates in the lamina with the external air through the 
 stomata. Each stele is surrounded, towards the air-chamber by a peri- 
 cycle consisting of one or sometimes two layers of cells. The stele is 
 circular or oval in transverse section, it usually consists of two or more 
 bundles arranged concentrically, the bast forming a peripheral layer 
 and the wood-bundles joining in the centre. 
 
 Rhizophore and root are both monostelic, and without air-shambers : 
 the stele contains but one bast- and one wood-bundle. 
 
 B 
 
 FIG. 234. Etnbryogeny of Sela.ginella Martensii (after Pfeffer). Two isolated embryos at 
 different stages, A Younger embryo ( x 610) B older ( x 165) : s suspensor ; c 1 c 2 cotyledons ; 
 ststem; I young foliage-leaves ; hyp hypocotyl ; r root; /so-called foot. 
 
 The bundles are all closed ; there is no secondary growth in thickness. 
 
 The leaves are very simple in structure ; they have a midrib with a 
 single vascular bundle : the epidermal cells contain chloroplastids which, 
 like those in the other cells, are large and are present in small numbers 
 (sometimes only one) in the cells. The stomata are usually confined to 
 the under surface, on the sides of the midrib. 
 
 The growth in length of the stem is effected by an apical growing-point 
 which has, in some species (e.g. S. Martensii), a two-sided or three-sided 
 apical cell ; whilst in others (e.y. S. Lyalli, Pervillei, etc.) it consists of
 
 GROUP III. PTERIDOPHYTA : LYCOPODIN^E. 393 
 
 small-celled stratified meristem. The structure of the growing-point of 
 the rhizophore agrees with that of the stem in the various species : but 
 the apical cell, when present, is a four-sided pyramid at first, becoming 
 eventually two-sided. The growing-point of the root has a tetrahedral 
 apical cell. 
 
 Embryogeny of the Sporophyte (p. 347). The embryogeny of Selaginella 
 closely resembles that of Lycopodium. The oospore undergoes division, a 
 transverse basal wall being formed : the upper or hypobasal cell developes 
 into a unicellular or few-celled suspensor : the lower or epibasal cell appears 
 to undergo division into four octants, which eventually form two tiers of 
 cells : from the basal tier of cells the hypocotyl is developed ; from the 
 apical tier the growing-point of the stem and those of the two cotyledons. 
 The hypocotyl elongates, and curves so as to escape from the prothallium 
 and the spore ; the convexity of the curve becomes somewhat protuberant 
 and is usually (but erroneously) termed the " foot," though it doubtless 
 acts as an organ of absorption ; morphologically it cannot be a foot since 
 it is epibasal in origin ; it would more appropriately be termed a feeder. 
 The first root eventually springs, endogenously and adventitiously, from 
 the posterior portion of the convex surface of the hypocotyl ; it is not a 
 true primary root because it is epibasal in origin (Figs. 233, 234). 
 
 THE GAMETOPHYTE. 
 
 Selaginella being heterosporous, the gametophyte-generation is repre- 
 sented by distinct male and female individuals, which are rudimentary 
 prothallia bearing the male and female organs respectively : the sexual 
 organisms resemble those of Isoetes (p. 357) and of Gymnosperms. 
 
 The male prothallium is developed inside the microspore : the germina- 
 tion of the spore begins with the formation of a wall across the pointed 
 apical end of the spore, cutting off a small cell, the vegetative cell : the rest 
 of the spore goes to form the single antheridium which consists of a layer 
 of parietal cells enclosing the mother-cells of the spermatozoids. When 
 the development of the spermatozoids is completed, the coats of the micro- 
 spore burst, as also the wall of the antheridium. and the spermatozoids are 
 set free. 
 
 The male cell is a spermatozoid ; it is a somewhat club-shaped slightly 
 twisted body, bearing two cilia at its pointed anterior end. 
 
 The female prothallium is developed inside the macrospore (Fig. 233) : 
 germination begins with the formation of a wall, termed the diaphragm, 
 across the apical end of the macrospore : in the smaller upper cell thus 
 cut off cell-division proceeds, resulting in the formation of the meniscus- 
 shaped prothallium consisting of compact small-celled tissue : the larger 
 portion of the spore, below the diaphragm, is rich in reserve materials: 
 here cell-formation goes on but slowly, a large-celled loose tissue (some- 
 times called endosperm) being produced which serves to nourish the em- 
 bryo which is forced down into it by the elongation of the suspensor. 
 
 The walls of the spore eventually split along the angles, thus forming 
 an apical aperture by means of which the upper surface of the prothallium 
 which now oecomes green, is exposed.
 
 394 PART IV. CLASSIFICATION. 
 
 The female organ or archegonium is developed from a single superficial 
 cell at the centre of the upper surface of the prothallium (here several 
 cells thick) ; it does not call for any special description if the first arche- 
 gonium fails to become fertilised, others may be subsequently formed. 
 
 The female cell or oosphere is contained in the venter of the archegonium. 
 
 SUB-KINGDOM. 
 PHAXEBOGAMIA (OR SPEEMAPHYTA). 
 
 The Gymnosperms and Angiosperms are all heterosporous plants, 
 having a definite alternation of generations, which is, however, 
 not readily perceived on account of the great reduction of the 
 sexual generation, and of the fact that the female gametophyte 
 remains enclosed in the macrospore, that the macrospore remains 
 enclosed in the macrosporangium, and that the macrosporangium 
 remains for a long time attached to the sporophyte, the result being 
 the development of a seed. The reduction of the gametophyte and 
 the formation of the seed are the features which essentially distin- 
 guish the Phanerogams from the higher heterosporous Pteridophyta 
 such as Selaginella and Isoetes. 
 
 A. THE SPOROPHYTE. As in the Pteridophyta, so here, the plant 
 itself is the sporophyte or asexual generation. 
 
 It is unnecessary to go into detail at present with regard to the 
 morphology of the vegetative organs, an account of which is given 
 in the section on General Morphology, and subsequently in the 
 description of the classes and orders. 
 
 The Reproductive Organs of the sporophyte are sporangia of 
 two kinds, microsporangia and macrosporangia, which are usually 
 borne on sporophylls, but sometimes directly on the axis : the 
 modified shoots bearing the sporangia constitute flowers ; and 
 often bear, in addition to the sporophylls, other floral leaves (hyp- 
 sophylls, see p. 57), protective or attractive in function, some of 
 which usually constitute a perianth. 
 
 The flowering shoot constitutes an inflorescence, which may 
 consist of one or many flowers, according to the extent to which 
 the shoot branches. 
 
 The Flowsr see p. 55) is a sporangium-bearing shoot or sporo- 
 phore, of limited growth, with usually undeveloped or feebly de- 
 veloped internodes, so that the sporophylls and hypsophylls which 
 it bears are closely aggregated together. Most commonly the 
 flower includes both kinds of sporangia, that is, it is monoclinous
 
 PHAN'EROGAMIA. >, ' 
 
 or hermaphrodite ; but it frequently contains but one kind of 
 sporangium 'unisexual) : in the latter case there are two kinds 
 of flowers, microsporangiate and macrosporangiate, which may be 
 borne by the same individual, when thev are said to be diclinous 
 and monoecious; or by two distinct individuals, when they are 
 dioecious (see p. 61). Occasionally the same plant produces both 
 monoclinous and unisexual flowers, when it is said to be polygam- 
 ous. The microsporangiate flowers are frequently termed stamin- 
 ate, and the macrosporangiate flowers carpellary < p. 56 > : the 
 former are indicated by the sign $ , the latter by the the sign , 
 and monoclinous flowers by the sign . In the Gymnosperms 
 the flower always has bnt one kind of sporangium : in the Angio- 
 sperms it generally, though by no means always, has both kinds. 
 The flower of the Gymnosperms is nearly always destitute of a 
 perianth. 
 
 The special morphology of the Perianth is dealt with under 
 the Angiospermae, in which class it attains its highest develop- 
 ment. 
 
 The Sporophyfo are of two kinds : microsporophylls. otherwise 
 known as stamens ; and macrosporophylte, otherwise known as 
 ctirpete : the former bear exclusively microsporangia, the latter 
 exclusively macrosporangia. The sporophylls present considerable 
 varietv of form, and are on the whole more highly specialised than 
 in any of the Pteridophyta. 
 
 The microsporophyll, or stamen (see p. 56 1, in its most highly 
 specialised form, consists of a stalk of varying length, theJUament 
 bearing a terminal structure, the an*h( r, which is a sorus of one 
 or more microsporangia embedded in more or less placental tissue. 
 lu the less highly organized Phanerogams \e.g. most Gymno- 
 s perms;, the microsporophylls are morphologically simpler, having 
 the general character of sessile or shortly-stalked scaly leaves. 
 
 The macrosporophyU, or carpel, bears usually macrosporangia 
 see p. 53 . In the Angiosperms the carpel, either by itself or by 
 cohesion with others, forms a closed cavity, the onary, which is 
 frequently prolonged at its apex into a longer or shorter process, 
 the ftyh\ bearing at its summit a glandular surface, the stigtaa : 
 sometimes the style is absent, so that the stigma is sessile on the 
 ovary : within the ovary the macrosporangia are developed. In 
 the Gymnosperms, the macrosporophylls <when present do not 
 cohere, either individually or several together : so that in this 
 group there is no ovary, style, or stigma ; they are thus distin-
 
 396 PART IV. CLASSIFICATION. 
 
 guished from the Angiosperms, in which there is always an ovary 
 and a stigma. 
 
 The Sporangia are of two kinds, micro sporangia or pollen-sacs, 
 and macrosporangia or ovules. The development of the sporan- 
 gium is, in both, eusporangiate (see p. 53). The sporangia are, as 
 a rule, borne on the sporophylls ; bat in some few cases (microspor- 
 angia rarely, e.g. Naias ; macrosporangia of Taxus, Polygonum, 
 Primulacese, etc.) they are borne on the axis. 
 
 The micro sporangia, or pollen-sacs, may be developed either 
 singly or in a sorus of two or more ; they may be very numerous 
 on the sporophyll, as in the Cycadacese. When borne on the 
 sporophylls, they are developed on the lower (dorsal) surface of 
 the microsporophyll in the Gymnosperms ; whereas in the Angio- 
 sperms they are usually developed both on the upper (ventral) and 
 the lower surfaces. 
 
 The microsporangia either project freely or are embedded in the 
 placental tissue of the member bearing them. The multicellular 
 hypodermal archesporium is either a row or a layer of cells. The 
 archesporial cells undergo, as a rule, division, giving rise to the 
 sporogenous cells together with a more or less extensive transitory 
 layer of investing cells, the tapettim, which is eventually dis- 
 organised. The microsporangium is, with few exceptions, unilo- 
 cular. 
 
 The microsporangium eventually dehisces, generally by a longi- 
 tudinal slit, less commonly by a transverse slit or by a pore. 
 The dehiscence is mainly effected by a layer of tracheidal cells, 
 differentiated as part of the wall, which are highly hygroscopic. 
 
 The microspores, or pollen-grains, are developed from the sporo- 
 genous mother-cells of the sporangium. As a rule each mother- 
 cell divides so as to give rise to four microspores, all of which 
 develope. As a rule, also, the microspores eventually become quite 
 free from each other, but to this there are exceptions, thus, in the 
 Mimosese, while the pollen-grains are isolated in some species, 
 in other species they cohere in groups of 4, 8, 12, 16, or 32, de- 
 rived from one, two, three, or more mother cells ; again, in the 
 Orchidacese, whilst Cypripedium has isolated pollen-grains, in 
 most genera the pollen-grains are in groups of four (tetrads), and 
 cohere into a mass (or 2-8 masses), the pollinium, of varying 
 consistence. 
 
 The microspore has, as a rule, the ordinary structure of a spore 
 (see p. 50) ; it is a nucleated cell, with a certain amount of granu-
 
 PHANEROGAMIA. 
 
 397 
 
 lar nutritive material in its cytoplasm, and has two coats, an 
 intine and an exine, the structure of the latter being elaborate in 
 many cases. The spore has 
 not, however, always two 
 coats. In some cases there 
 is no exine, and only a 
 single thin coat, as in the 
 cells of the pollinia of Or- 
 chids and Asclepiads, and 
 in certain plants whose 
 flowers develope under wa- 
 ter, such as certain Naiad- 
 aceae. In others, again, 
 there is but one coat, but 
 it is thick and is cuticular- 
 ised externally (e.g. Senecio), 
 or the two coats are only distinguishable at those points at which 
 the pollen-tubes will be eventually protruded (e.g. Onagracese). 
 
 FIG. 235. A Pollen-grain of Cucwbita Pepo, 
 showing the lid-like areas through which the 
 pollen tubes will protrude ( x240). B Section of 
 one of these areas ( x 540) (after Strasburger). 
 
 Fm. 236. Pollen-grains of Malva crispa. A Grain seen from surface ; B section of wall, 
 showing the exine with its alternate spines and pores, the latter closed internally by the 
 delicate innermost layer of the exirie ; C germinating pollen-grain with pollen-tubes; D the 
 same in section, showing the protrusion of the pollen, tubes through the pores. (A, B,D 
 XalO; Cx 240-: after Strasburger.)
 
 PART IV. CLASSIFICATION. 
 
 The exine is frequently highly differentiated with special refer- 
 ence to the protrusion of the pollen-tubes : it may be porous (e.g. 
 Malvacete, Fig. 236) ; or there may be thin areas at certain points; 
 or (Onagracepe") much-thickened areas where the pollen-tubes are 
 eventually developed ; or, again, areas are marked off here and 
 there which come off like lids under the pressure of the developing 
 pollen-tube (Fig. 235). 
 
 The development of the microspores has already been dealt with 
 in general (see p. 85), so that it will be only necessary here to 
 mention certain special points. The mother-cells of the micro- 
 spores either remain coherent during the development of the 
 microspores, or (as in many Monocotyledons) they become free and 
 float in the granular fluid, derived from the disorganisation of the 
 tapetum, which fills the pollen-sac. The walls of the mother-cells 
 usually become very much thickened, especially in the planes of the 
 future divisions. The division of the mother-cell is either 
 successive (Monocotyledons, Cycads), or simultaneous (most 
 Dicotyledons and Conifers) ; in the former case the microspores are 
 usually bilateral, in the latter tetrahedral. The form of the 
 mature microspore varies widely ; it may be spherical, etc. ; in 
 plants in which pollination takes place under water, the microspore 
 becomes elongated and filiform (e.g. Zostera). 
 
 In some cases the germination of the pollen-grain begins before 
 it is set free from the dehisced pollen-sac, so that it consists of two 
 (sometimes more in Grymnosperms) cells at the time of pollination. 
 
 The macrosporangia, or ovules, are developed singly, or in pairs, 
 or more commonly several together, from a more or less well- 
 developed cushion of tissue, the placenta. When the ovules are 
 borne on sporophylls, the placenta is either marginal, or less 
 commonly, it is ventral, including the whole of the upper or inner 
 surface of the carpel with, sometimes, the exception of the midrib 
 (e.g. Butomxis, Nymphsea). When the ovules are borne on the 
 axis, they are either terminal (e.g. Taxus, Polygonum) or lateral 
 (e.g. Primulacese, Compositse). 
 
 The macrosporangium, like the microsporangium, makes its 
 appearance as a small cellular prominence on the surface of the 
 organ which bears it, formed by the division of a group of hypo- 
 dermal cells. The macrosporangium proper (sometimes distin- 
 guished as the nucellus) is invested by one or two coats, which 
 grow up from the base, but do not completely close over the apex, 
 leaving there a narrow channel termed the micropyle ; the base of
 
 PHAXEROGAMIA. 
 
 399 
 
 the macrosporangiuin, where the coats and the tissue of the 
 sporangium proper become indistinguishable, is termed the 
 chalaza. The macrosporangium is not, as a ride, embedded in the 
 placental tissue, and is sometimes borne on a longer or shorter 
 stalk, the funicle. The point of attachment of the macro- 
 sporangium, whether it be sessile or stalked, to the placenta, is 
 termed the Jiilum. 
 
 The form of the macrosporangium presents many varieties, of which 
 the following are the more common (Fig. 237). When the micro- 
 pyle, the chalaza, and the funicle (or the hilum) all lie in one and 
 the same straight line, the ovule is said to be orthotropous : when 
 the micropyle and the chalaza lie in the same straight line, but not 
 the funicle, the ovule being bent back against the funicle (termed 
 the raphe along the line of contact), the ovule is anatropous ; when 
 
 FIG. 237. Diagrams of the Ovule : A orthotropous (Polygonum) ; B anatropous (Lily) ; 
 C campylotropons (Bean): /funicle; of the outer integument; ti the inner integument; 
 m micropyle ; fc nucellus ; em embryo-sac : r the raphe ; c chalaza. 
 
 the ovule itself is curved, so that the micropyle and the chalaza do 
 not lie in the same straight line, the ovule is campy lot ropous. 
 Various intermediate forms occur which may be easily imagined. 
 
 The archesporium (see p. 53), which here, as elsewhere, is hypo- 
 dermal, consists generally of one cell. In some cases the arche- 
 sporial cell undergoes no division (e.g. Tulipa Gcsni-riana, Lilium 
 bulbiferurn) but directly developes into the mother-cell of a 
 macrospore ; but, as a rule, the archesporial cell (or cells) under- 
 goes more or less frequent division. Thus, in most Phanerogams, 
 the division of the archesporial cell begins with the cutting off, 
 by a periclinal wall, of a sterile cell towards the organic apex 
 (micropylar end) of the macrosporangium or sometimes two such 
 sterile cells which, with or without further division, represent a 
 tapetal layer. The large remaining cell now undergoes division
 
 400 PART IV. CLASSIFICATION. 
 
 into two by a transverse wall, and one or both of these cells may 
 divide in a similar manner. Thus a longitudinal row of large 
 cells, two to four in number, is formed, all of which are potentially 
 mother-cells of macrospores. In a few plants (Cycads and some 
 Couiferae among Gymuosperms ; some Amentales, among Angio- 
 sperms) the growth of the archesporial cells is more extensive, 
 leading to the production of a considerable mass of sporogenous 
 tissue, as in the macrosporangia of the Pteridophyta. 
 
 Generall} r speaking, only one of the cells of the sporogenous 
 tissue shows any sign of developing into a macrospore ; and in the 
 normal Angiosperms, this cell is generally the lowest (nearest the 
 chalaza) of the longitudinal row described above. The growth of 
 the fertile mother-cell of the macrospore is vigorous. It causes the 
 displacement and absorption of the sterile cells of the sporogenous 
 tissue. 
 
 The macrosporangium is indehiscent, and only becomes detached 
 from the plant after it has developed into a seed. 
 
 The macrospore (megaspore) or embryo-sac is, as a rule, deve- 
 loped singly in the macrosporangium ; and, further, it is always de- 
 veloped singly from its mother-cell without any indication of that 
 division into four, which is characteristic of the development of 
 spores in general. It is in fact impossible, as a rule, to fix upon 
 any stage at which the transition from macrospore-mother-cell to 
 macrospore may be considered to take place ; for the mother-cell 
 simply grows and becomes the macrospore without any special 
 differentiation. However, in the Cycadaceae, the wall of the 
 mother-cell undergoes that differentiation which is characteristic 
 of spores, so that the wall of the macrospore consists of two layers 
 the outer of which is cuticularised. The macrospore is simply a 
 large cell, containing vacuolated protoplasm in which lies a 
 nucleus, and having, as a rule, a wall of cellulose. 
 
 In the course of its growth, the macrospore frequently causes the 
 absorption of more or less of the tissue of the nucellus, more 
 especially towards the micropylar end. It commonly attains 
 such a size that little or none of the nucellar tissue remains : 
 in some cases, however (e.g. Gymnosperms, Scitaminese, most 
 Xymphseacese), the macrospore does not grow to such an extent, so 
 that a considerable mass of nucellar tissue is left, which persists to 
 some extent in the seed as perisperm, its cells being then filled 
 with nutritive substances. 
 
 General Histology. The following are the principal characteris-
 
 PHANEROGAM I A. 401 
 
 tic features : The apical growth of shoot and root is only excep- 
 tionally effected by means of a single apical cell ; the small-celled 
 meristem of the growing-point of the stem is'more or less distinctly 
 differentiated into dermatogen, periblem, and plerome ; stem and 
 root are monostelic, with but few exceptions (p. 102) ; the vascular 
 bundles of the stem are generally collateral ; both root and stem 
 generally present secondary growth in thickness (except Monoco- 
 tyledons and a few other cases) by means of a normal cambium- 
 ring ; the growing-points of the lateral roots are developed from 
 the pericycle of the parent root (see p. 134). 
 
 The Embryoyeny of the Sporophytc. The sporophyte is 
 developed from the fertilised oosphere in the ovule. The develop- 
 ment of the embryo is not continuous, but is in two 'stages, which 
 may be conveniently distinguished as the intra-scminal and the 
 extra-seminal. The intra-seminal stage includes the whole of the 
 development which the embryo undergoes during the conversion of 
 the ovule into the ripe seed that is, during what is known as the 
 " ripening of the seed." The extra-seminal stage includes the 
 development of the embryo which follows the sowing of the seed ; 
 that is, the escape of the embryo from the seed, and the gradual 
 development of the characters of the adult plant. The interval 
 betw r een these two stages may be brief, or it may extend over many 
 years if the seed be kept dry. The " germination " of the seed 
 when sown is simply the resumption of development by the embryo 
 in consequence of* exposure to the necessary conditions of moisture, 
 warmth, etc. 
 
 In most Phanerogams, each oospore gives rise to a single em- 
 bryo ; but in most Grymnosperms each oospore gives rise to more 
 than one embryo (four or many), thus exhibiting polycmbryony. 
 
 Generally speaking, the oospore divides into two by a transverse 
 wall: the upper of the two cells remains coherent to the micropylar 
 end of the embryo-sac and developes into a suspensor, which bears 
 at its lower end the other cell, termed the embi-yo-cell, from which 
 the whole or a considerable part of the body of the embryo is de- 
 veloped (cf. Lycop.odinse, pp. 387, 393). 
 
 The suspensor is for the most part a temporary organ of the 
 embryo, but it frequently contributes the primary root to the 
 embryo. It commonly becomes a filament of a single row of cells. 
 Its function is, chiefly, to place the embryo in such a position 
 within the developing seed that it can easily avail itself of the 
 nutritive materials stored in the adjacent cells.
 
 402 
 
 PART IV. CLASSIFICATION. 
 
 The embryo-cell divides, as a rule, into two by a longitudinal wall, 
 then transversely, and then in a plane perpendicular to both the 
 preceding, into octants ; but while the four anterior octants are 
 octants of a sphere, this is not the case with the four truncated pos- 
 
 FIG. 239. Embryogeny of Dicotyledons as represented by Capsella Bursa~Pastori$ (dia- 
 grammatic, after Goebel and Hanscein). A-D Successive stages: susp. suspensor; einb. 
 embryo; 1-1, 2-2, octant-walls ; a lowest cell of suspenscr, dividing in B to form the hypo- 
 pbysial cell h ; in C the hypopbysial cell has divided into two, h, and h,, the former con- 
 Btituting the periblem, the latter the dermatogen, of the growing-point of the primary 
 root ; in D, h, has undergone a periclinal division to form the primitive root-cap : d derina- 
 togen ; c periblem ; pi. plerome ; cot. cotyledons, between which lies the growing-point of 
 the primary stem.
 
 PHANEROGAMIA. 403 
 
 terior octants abutting on the suspensor. In some cases, the trans- 
 verse division precedes the longitudinal. From the anterior octants 
 are developed, in Dicotyledons generally (Fig. 238), the two coty- 
 ledons and the growing-point of the primary stem, but the growing- 
 point of the primary root is supplied from the last cell of the 
 suspensor (Fig. 238 A, a) which divides transversely into two (Fig. 
 238 B) and contributes the cell h, the hypophysis, to complete the 
 
 Fro. 239. TSmbryogeny of Monocotyledons, as represented by Alisma Plantago (diagram- 
 matic, after Goebel, Hanstein, and Famintzin). A-C Successive stages: a embryo-cell; 
 b lowest cell of suspensor, susp. : the products of the repeated transverse division of b are 
 indicated (c, d, e, f) in B and C. In C, a has given rise to the single terminal cotyledon : 
 cto the growing-point of the primary stem; d and e form the bypocotyl; the growing- 
 uoint of the root is developed from/; ep dermatogen. D is a mature embryo, less highly 
 magnified : cot. cotyledon ; st. growing-point of stem ; Jii,p. bypocotyl. The nuclei of 
 the cells are indicated in A and B. 
 
 root-end of the embryo. In Monocotyledons, on the other- hand, 
 the embryo cell gives rise, as a rule (Fig. 239 A and (7, a), only 
 to the single terminal cotyledon; whilst the last cell of the
 
 404 PART IV. CLASSIFICATION. 
 
 suspensor (Fig. 239 A, 6) gives rise to the growing-point of the 
 stem, which is here lateral (Fig. 239 (7, c ; D, sf), and to that of 
 the root by a hypophysial cell (/). 
 
 With regard to the histological differentiation of the embryo, 
 the first step, after the division into octants, is the formation of 
 periclinal walls marking off a superficial layer, which is the 
 dermatogen (Figs. 238, 239) ; this differentiation proceeds from the 
 anterior end, or apex, backwards towards the posterior end of the 
 embryo. In those plants in which the root-end of the embryo is 
 formed by a hypophysial cell contributed by the suspensor (Fig. 
 238 7?, 7?), the dermatogen-layer is completed by the periclinal 
 division of the hypophysial cell, the inner cell forming the 
 periblem of the growing-point, the outer forming the dermatogen 
 which undergoes further periclinal division to form the primitive 
 root- cap. In the meantime, anticlinal and longitudinal walls 
 have also been formed, so that the embryo, as it increases in size, 
 consists of an increasing number of cells. The degree of histo- 
 logical differentiation attained varies widely : in the highest forms 
 (Fig. 238 D~) a cylinder of plerome is differentiated in the axis 
 of the embryo, so that the three primary tissue-systems, der- 
 matogen, periblem, and plerome, are clearly defined. 
 
 The degree of morphological differentiation attained by the 
 embryo in its in tra -seminal development also varies widely, as 
 does also the size of the embryo. In the ripe seed of most Orchids 
 and parasitic plants (e.g. Orobanche, Monotropa, etc.), the body of 
 the embryo presents no differentiation into members. In most 
 plants, the embryo, in the ripe seed, consists of the following 
 members : (a) one, two, or several cotyledons ; (6) a primary stem 
 bearing the cotyledon or cotyledons, but not projecting beyond 
 them, termed the hypocotyl, passing posteriorly into (c) the primary 
 root or radicle. In some plants (e.g. Triticum and other Grasses, 
 Phaseolus, Vicia, Amygdalus, etc.) the primary stem has elongated 
 beyond the insertion of the cotyledon or cotyledons, and bears the 
 rudiments of future foliage-leaves ; this portion of the primary 
 shoot is termed the plumule or epicotyl. 
 
 The size and texture of the cotyledons vary with the functions 
 which they have to perform. When, as in exalbuminous seeds, 
 such as peas and beans, the cotyledons are themselves the store- 
 houses in which food is deposited for the nutrition of the embryo 
 during its extra-seminal development, they are relative!} 7 large. 
 thick, and fleshy : but when, as in albuminous seeds (e.g. Ricinus,
 
 PHANEROGAMIA. 405 
 
 Grasses, etc.), the food is stored in the endosperm, the cotyledons 
 are absorbent organs and, though still relatively large, are not 
 thick and fleshy. 
 
 In a few Phanerograms (e.g. Utricularia, which never developes 
 any root, Ruppia rostellata, Wolffia arrldza) no primary root is 
 developed or even indicated. 
 
 The extra- seminal development of the embryo may be briefly 
 described as follows : The first event is the elongation of the 
 hypocotyl, with the result that the radicle passes, through the 
 micro pyle, out of the seed into the soil, where it becomes firmly 
 attached. The other members then escape from the seed, the coat 
 of which becomes more or less split. In those cases in which the 
 growth of the hypocotyl is active, the cotyledons appear above the 
 surface of the soil, that is, they are e.pigean (e.g. Cucurbita, Ricinus, 
 Radish, Sunflower, Scarlet Runner, etc., most G-ymuosperms), either 
 leaving the seed-coat in the soil, or carrying it up to the surface. 
 In those cases in which the growth of the hypocotyl is compara- 
 tively slight, the cotyledons do not reach the surface of the sail, 
 that is, they are hypogcan (e.g. Vicia Faba, Pea, Grasses, etc.) : 
 here it is the epicotyl (plumule) which grows rapidly, and is the 
 first member to appear above ground. The part which first appears 
 above ground, whether it be hypocotyl, epicotyl, or cotyledon, 
 usually does so in the form of an arch, so that the apex is not 
 exposed to injury whilst the member is forcing its way up through 
 the soil. 
 
 Epigean cotyledons become green in colour, and in many cases 
 (e.g. Sunflower, Radish) assume the appearance, and discharge the 
 functions, of foliage-leaves ; but they do not ever precisely resemble, 
 either in size or form, the true foliage-leaves of the plant to which 
 they belong. 
 
 Vegetative Propagation is common among Phanerogams, by 
 means of bulbs (e.g. Lily, Onion, and many other Monocotyledons), 
 tubers (Potato), tuberous roots (Dahlia), etc. 
 
 B. THE GAMETOPHYTE. As all Phanerogams are heterosporous, 
 the sexual generation is represented by two individuals, a male 
 and a female, developed respectively from the microspore and the 
 macrospore. 
 
 The Male Prothallium is, in all cases, filamentous and relatively 
 small, consisting of but few cells. The first indication of its 
 development is the division of the nucleus of the microspore, which 
 may take place even before the microspore escapes from the micro-
 
 406 
 
 PART IV. CLASSIFICATION. 
 
 sporangium, and this is followed by cell-formation. In the Angio- 
 sperms the cell-formation is simple, consisting in the aggregation 
 of protoplasm round one of the two nuclei, without any formation 
 of cell-wall, so that a small primordial cell, the generative cell, is 
 formed, floating freely in the protoplasm of the microspore which, 
 with the other nucleus, constitutes the vegetative cell. In the 
 Gymnosperms the process is rather more complicated. In the 
 simplest case (e.g. the Yew), the microspore divides into two cells, 
 separated by a cell- wall ; of these the one, the antheridial cell, 
 undergoes division into two, a stalk-cell, and a generative cell ; 
 
 whilst the other remains as an undivided vegetative cell. In some 
 cases, however (e.g. Larch, Ginkgo, Fir), generally three cells are 
 successively cut off by parallel septa (Fig. 240) : of these the two 
 first formed are merely vegetative cells, and undergo disorgani- 
 sation, whilst the last is the antheridial cell, and undergoes 
 division into a generative cell and a stalk-cell.
 
 PHAXEROGAMIA. 
 
 407 
 
 In both Angiosperms and Gymnosperms, the pollen-tube is 
 formed by the outgrowth of the large vegetative cell : in both 
 cases the generative cell (after being set" free when necessary) 
 enters the pollen-tube together with the vegetative nucleus ; the 
 vegetative nucleus becomes disorganised, whilst the generative cell 
 undergoes division into two; either into two equal generative cells, 
 as is generally the case, or in two unequal cells only one of which 
 is generative (e.g. Taxus). More than one pollen-tube may be 
 developed from the microspore (Fig. 236). 
 
 Thus the male individual in the Phanerogams is a prothallium 
 consisting of but few cells, and the antheridium is at most two- 
 celled. 
 
 The male cell is usually a small 
 nucleated primordial cell in the pol- 
 len-tube, and is either the original 
 generative cell itself, or a product 
 of its division ; but in some Gymno- 
 sperms (Cycas, Zamia, Ginkgo) it is 
 a large spirally-coiled inulticiliate 
 spermatozoid. It is eventually ex- 
 truded through the apex of the 
 pollen-tube. 
 
 The Female Prothallium is de- 
 veloped in the interior of the macro- 
 spore (embryo- sac) in a similar 
 manner to that of the heterosporous 
 Pteridophyta : but, in the Phanero- 
 gams it does not at any period pro- 
 ject from the macrospore as it does 
 in the Pteridophyta, though this 
 occurs exceptionally in the Cyca- 
 daceae. 
 
 The development of the prothal- 
 lium (or endosperm) is simple in the 
 Gymnosperms. The nucleus of the 
 macrospore divides ; repeated nuclear 
 division takes place, until a large 
 number of nuclei are formed which lie in the protoplasm round 
 the wall of the macrospore ; between these nuclei cell- walls are 
 developed, so that a cellular tissue is produced, the cells of which 
 grow and multiply by division until the cavity of the niacro- 
 
 Fio. 241. The female prothallinm 
 of Gymnosperms (t.g. Finns), shown 
 in a longitudinal section of the ovule 
 ( x about 15; diagrammatic) : 1 1 in- 
 tegument ; m micropyle ; K nacellus 
 (macrosporangium) ; E embr.vo-sac 
 (macrospore) ; t female prothallium 
 (endosperm), in which are situated, to- 
 wards the micropyle, two archegonia, 
 c, with neck h ; ps pollen-tube enter- 
 ing the neck of the left archegoniani ; 
 p pollen-grain seated on the apex of 
 the nucellns.
 
 408 
 
 PART IV. CLASSIFICATION. 
 
 spore is entirely filled with this tissue which constitutes the 
 prothallium. 
 
 In the Angiosperms the development of the prothallium is more 
 complicated in that it generally takes place in two stages, the one 
 preceding, the other following, fertilisation. The nucleus of the 
 macrospore divides into two : of these the one travels to the micro- 
 pylar pole, the other to the chalazal pole of the macrospore ; each 
 nucleus then divides, and each of the four so formed divides again, 
 so that eight nuclei are formed, four at the micropylar, and four at 
 the chalazal pole of the macrospore ; one nucleus is then conveyed 
 
 from each pole toward the 
 centre of the macrospore, where 
 the two nuclei meet and fuse 
 into one which is termed the 
 definitive nucleus of the ma- 
 crospore or embrj-o-sac. Three 
 nuclei now lie at each pole, 
 and around these aggregation 
 of protoplasm takes place, so 
 that cells are formed : those at 
 the chalazal pole soon acquire 
 a cell-wall, and are termed 
 antipodal cells : those at the 
 micropylar end do not form 
 any cell-wall ; one of them is 
 the female reproductive cell or 
 oosphere, the other two are 
 sterile (though in rare cases 
 they are fertile), and are 
 termed the syncrgidcp, the 
 three together constituting the 
 egg-apparatus. This is the 
 extent to which the develop- 
 ment of the female prothallium 
 takes place previously to fer- 
 tilisation (Fig. 242.) In most 
 Angiosperms the structure of the prothallium is completed by the 
 formation, after fertilisation has taken place, of additional cellular 
 tissue : this process is initiated by the division of the definitive 
 nucleus of the macrospore, nuclear division is repeated, cell-forma- 
 tion takes place in the manner described above for the G-ymno- 
 
 FIG. 242. The female prothallium of An- 
 giosperms, shown in a longitudinal section of 
 the ovule, before fertilisation ( x 70) : ai outer, 
 ii inner, integument ; m micropyle ; / funicle. 
 K Maero*porangium (nucellus). E Macro- 
 spore (embryo-sac), fc Definitive nucleus of 
 the embryo-sac. The female prothallium 
 consists of the egg-apparatus at the micro- 
 pylar end of the macrospore, and of the group 
 of antipodal cells at at the chalazal end. The 
 egg-apparatus consists of two synergidse s, 
 and an oosphere e.
 
 PHANEROGAMIA. 409 
 
 sperms, and the macrospore becomes more or less completely filled 
 with cellular tissue, commonly termed endosperm. 
 
 The degree of development attained by the endosperm in Angiosperms 
 is various. Whilst, as a rule, it completely fills the embryo-sac, leaving 
 room, however, for the embryo, in some cases it occupies but a portion of 
 the embryo-sac, as in the Coco-nut, where it forms a thick parietal layer; 
 or, as in Nymphaea, Viscum, Lathrsea, Thesium, Rhinanthus, etc., where 
 the development of endosperm is confined to the upper half of the embryo- 
 sac. In some cases the endosperm is rudimentary, being represented 
 merely by a number of nuclei, as in Tropseolum, Alismaceae, Orchidaceae ; 
 and in Canna even this rudimentary development is wanting. 
 
 The antipodal cells do not, as a rule, undergo any further development, 
 but in some cases (e.g. some Graminacese) they have been observed to 
 divide and give rise to a considerable mass of cells. 
 
 The female organ is essentially an archegonium. In most 
 Grymnosperms it is actually an archegonium, like that of the 
 Pteridophyta ; it is developed from a single superficial cell of the 
 prothallium at the micropylar end, and has a neck containing a 
 canal-cell, leading to the ventral cavity in which lies the female 
 cell or oosphere. In the Angiosperms the female organ is reduced 
 to a single naked cell : the three cells constituting the egg- 
 apparatus represent each an archegonium reduced to a single cell ; 
 but one cell only is a true fertile oosphere, the other two (the 
 synergidse) being sterile as a rule. 
 
 Pollination. In view of the fact that the female cell (oosphere), 
 and the prothallium bearing it, remain (as a rule) permanently 
 enclosed in the macrospore, and that the macrospore remains en- 
 closed in the indehiscent macrosporangium, it is clear that the 
 process of fertilisation can only be effected when the microspore 
 germinates in immediate proximity to the macrosporangium. The 
 bringing of the microspore into such close relation with the macro- 
 sporangium is what is termed pollination (see p. 232). "W hen the 
 pollen of any one flower is brought into relation with the macro- 
 sporangium of the same flower, the case is one of self-pollination : 
 when the pollen of an}' one flower is brought into relation with the 
 macrosporangium of another flower (whether on the same plant, or 
 on another plant of the same species), the case is one of cross- 
 pollination. 
 
 The microspores when so brought are placed under conditions of 
 moisture and nutrition favourable to their germination. In Gymno- 
 sperms, where there is no ovary and no stigma, the microspore is
 
 410 PART IV. CLASSIFICATION. 
 
 brought into Direct contact with the macrosporangium (Fig. 241). In 
 the Angiosperms, where there is an ovary and a stigma, the micro- 
 spores cannot come into direct contact with the macrosporangium ; 
 they fall upon the stigma and germinate on its moist surface : the 
 pollen-tubes then grow into the ovary, down the style if there is 
 one, and finally enter the ovules. 
 
 In certain cases flowers are so modified as to ensure self-pollina- 
 tion : instances of this are afforded by species of Viola, Lamium 
 amplexicaule, Oxalis Acetosella, and others, where the plant (in 
 addition to the ordinary flowers) bears inconspicuous flowers which 
 do not open, and in which self-fertilisation is perfectly effected by 
 the pollen ; these peculiar flowers are said to be cleistogamous. 
 
 In the great majority of Phanerogams, however, cross-pollina- 
 tion is the rule. In the case of diclinous or dioacious plants (e.g. 
 Gymuosperms) it is clear that pollen must be conveyed from a 
 staminate to a carpellary flower. It is also known that in a great 
 number of monoclinous flowers, pollination is effected by the trans- 
 fer of pollen from one flower to another : in some of these cases it 
 has been demonstrated that it is only the pollen of another flower 
 which can effect fertilisation ; in other cases, that the pollen of the 
 same flower, though not absolutely useless, has less fertilising 
 power than that of another flower; and in yet other cases, that 
 though the pollen of the flower itself has sufficient fertilising 
 effect, yet the progeny is less vigorous than when pollen is 
 supplied from another flower. 
 
 The conveyance of pollen from one flower to another is effected, 
 in the case of a number of plants with inconspicuous flowers (e.g. 
 Gymnosperms, Grasses, many Dicotyledonous Forest-trees), by the 
 agency of the wind, when they are said to be anemopliilous ; but 
 in the case of flowers which are conspicuous by their size, colour, 
 perfume, or by their secretion of honey, the conveyance is effected 
 by the insects which are attracted to visit the flowers; such 
 flowers are said to be entomophilous. 
 
 Among the contrivances for the prevention of self-pollination 
 in monoclinous flowers, one of the simplest is the arrangement of 
 the anthers and stigma in such positions that the pollen cannot 
 possibly reach the stigma of the same flower, e.g. Aristolochia 
 (Fig. 243). Or secondly, the abortion of all the microsporangia in 
 some flowers and of all the macrosporangia in others ; in such 
 flowers the organs in question are present, but they are not 
 functional : this is an approach to the diclinous condition ; it
 
 PHANEROGAMIA. 411 
 
 occurs in the Tiger-Lily, in which the anthers are commonly 
 abortive in some flowers and the ovaries in others. Thirdly, 
 dichogamy frequently occurs, that is, that the stigmas and sta- 
 mens attain their functional activity at different times : flowers in 
 which this occurs are either protandrous, that is, the anthers are 
 first developed and have already shed their pollen when the stigma 
 of the same flower is capable of receiving it ; or they are proto- 
 gynous, that is, the stigma is fully developed before the anthers of 
 the same flower are ready to shed their pollen : in the latter case 
 self-pollination is obviously only excluded if the stigma is withered 
 before the pollen is shed ; there are, however, protogynous flowers 
 in which the stigma remains fresh for a long time and which may 
 be pollinated by their own pollen. As examples of protandrous 
 flowers, those of the Umbelliferse, and most of the Composite, 
 Lobeliacese, and Campanulacese may be mentioned ; and of proto- 
 gynous flowers, Aristolochia, Arum, Scrophularia nodosa, and 
 some species of Plantago, but this condition is less common than 
 the preceding. 
 
 Among the contrivances which lead to the cross-pollination of 
 flowers by the agency of insects, the means of tempting insects to 
 visit the flowers, such as bright colours, odours, and the secretion 
 of honey, must first be mentioned. The peculiar marking of the 
 flower serves in many cases the purpose of guiding insects to the 
 nectary. The form of the flower, the situation of the honey, the 
 position of the stamens, and their relation to the other parts of the 
 flower, particularly to the stigma, the relative development in 
 point of time of the different parts, all these circumstances com- 
 bine and co-operate to secure cross-pollination, and sometimes to 
 aljow of the visits of particular insects only, as, for instance, of 
 butterflies with long probosces : though there are also cases in 
 which the insects must occasionally convey the pollen to the 
 stigma of the same flower. A simple arrangement of this kind 
 known as heterostylism or dimorphism, and which occurs in species 
 of Primula, Pulmonaria, Linum, Polygonum, etc., may be men- 
 tioned here. These plants have two forms of flowers ; in one 
 form the stamens are short and the style much longer, so that the 
 stigma projects above the anthers ; in the other form, on the 
 contrary, the anthers are on long filaments above the stigma ; 
 they are both so constructed that the anthers of one form stand on 
 the same level as the stigma of the other. From the position of 
 the nectary, and the form of the rest of the flower, an insect
 
 412 
 
 PART IV. CLASSIFICATION. 
 
 visiting it is obliged to take up the same position at each visit ; 
 consequent^ after it has visited a flower of the one form, when 
 it visits a flower of the other form, it touches the stigma of the 
 latter with the same part of its body with which in the first 
 flower it brushed the anthers, and thus the pollen which it 
 carried away with it from the anthers of the one flower is trans- 
 ferred to the stigma of the 
 other. Observations made by 
 artificially transporting the 
 pollen have shown that fer- 
 tilisation is most complete 
 when the pollen of stamens 
 of a certain length is con- 
 veyed to the stigma of a 
 style of the same length. 
 The same is the case with 
 trimorphic plants, e.g. Oxalis, 
 Lythrum Salicaria: in these, 
 three forms of flowers occur 
 with three different lengths 
 of styles and stamens. 
 
 The flower of Aristolocliia 
 Clematitis (Fig. 243) is pro- 
 togynous ; insects can pene- 
 trate without difficulty down 
 the tube of the perianth, 
 which is furnished on its 
 internal surface with hairs 
 which point downwards, and 
 they thus convey to the 
 stigma the pollen they have 
 brought with them from 
 other flowers ; the hairs, how- 
 ever, prevent their return. 
 When the pollen has reached 
 the stigma, its lobes (Fig. 
 243 A and B ri) spring up- 
 wards, and thus the anthers, which now begin to open, are made 
 accessible to the insects ; these, in their efforts to escape (Fig. 
 243 i), creep round the anthers and some of the pollen adheres to 
 them ; by this time the hairs in the tube have withered, and the 
 
 FIG. 213. Flower of Aristolochia : A before, 
 and B after fertilisation; r the tube of the 
 perianth ; kf the cavity below ; n stigma ; a 
 anthers ; t an insect ; fc/ovarr. (After Sachs.)
 
 PHANEROGAMIA. 
 
 413 
 
 insect escapes, dusted over with pollen which, in spite of ex- 
 perience, it proceeds to convey in like manner to another flower. 
 Those flowers which are ready for pollination have an erect posi- 
 tion, and the tube of the perianth is open above so that the insect 
 can readily enter; after pollination the peduncle bends downwards 
 and the tube is closed by the broad lobe of the perianth, so that 
 it is impossible for insects to enter flowers which have been fer- 
 tilised. 
 
 In the flower of Epipactis (one of the Orchidacese), the anther is 
 situated above the stigma and does not shed its pollen in isolated 
 grains ; but when a certain 
 portion of the stigma (the abor- 
 tive anterior lobe), known as 
 the rostellum (Fig. 244 ft), is 
 touched, the two pollinia (p. 396), 
 together with a mass of sticky 
 substance (retinaculum) derived 
 from the rostellum, are removed 
 from the pollen-sacs, adhering 
 to the foreign body (Fig. 244 
 F, Ji). The insect creeps into 
 the flower to obtain the honey 
 which is secreted in the cavity 
 of one of the leaves of the peri- 
 anth, the labellum (Fig. 244 Z) ; 
 as it withdraws from the flower, 
 it carries away the pollinia on 
 its head, and on entering the 
 next flower, deposits them upon 
 the stigma. 
 
 Fertilisation. As in other 
 plants, so here, the process of 
 fertilisation consists in the fu- 
 sion of the male and female 
 reproductive cells. The male 
 cell (see p. 407), whether it be 
 a sperrnatozoid or not, escapes 
 from the pollen-tube and enters 
 the oosphere ; the nucleus of 
 the male cell (male pronu- 
 cleus) and " that of the female 
 
 FIG. 241. Epipaclis l+tifolia : A longi. 
 tudinal section through a flower-bud; B 
 open flower after removal of the perianth. 
 with the exception of the labellum, I ; C 
 the reproductive organs, after the removal 
 of the perianth, seen from below and in 
 front ; D as B, the point of a lead-pencil ' 
 tb) is inserted after the manner of the pro- 
 boscis of an insect ; E and F the lead- 
 pencil with the pollinia at ached ; fK ovary ; 
 t labellum, its sac-like depression serving 
 as a nectary ; n the broad stigma ; en the 
 connective of the single fertile anther ; p 
 pollinia ; Ji the rostellum ; x the two lat- 
 eral staminodes ; i place where the labellum 
 has been cut off ; * the gynostemium. (After 
 Sachs.)
 
 414 PART IV. CLASSIFICATION. 
 
 cell (female pronudeus] approach each other and fuse into one 
 the two protoplasms likewise fusing. Fertilisation is now com- 
 plete ; in consequence, the oosphere surrounds itself with a cell- 
 wall, becoming the oospore. and begins to develope into the embryo- 
 sporophyte. Further details are given in the sections on Gymno- 
 sperms and Augiosperms respectively. 
 
 The Results of Fertilisation. The most direct result of fertilisa- 
 tion is the development of the embryo (see p. 401) from the oospore, 
 a process which involves the conversion of the ovule into the seed. 
 But the effect of fertilisation is not limited to this : a process of 
 growth is initiated in various other parts of the flower so that 
 they undergo marked changes in structure, accompanied by con- 
 siderable increase in size, the product being the structure known 
 as the fruit (p. 61). In some cases the carpels only are affected, 
 besoming either fleshy and succulent (e.g. Plum), or dry and hard 
 
 (e.g. Poppy) ; in others, 
 the floral axis becomes 
 fleshy (e.g. Strawberry) ; 
 in others again the peri- 
 anth-leaves also (e.g. 
 Mulberry). It is con- 
 venient to regard as 
 
 F. 245,-Sections of ripe seed. A * ~, * A* Only those 
 
 showing E endosperm. B Piper, showing both endo- which are developed from 
 
 sperm E, and perisperm P. C Almond, devoid of the gynseceum a l one ; 
 endosperm; s the testa; e embryo; oe its radicle; 
 
 c cits cotyledons. an d as false fruits, or 
 
 pseudocarps, those in 
 
 the formation of which other parts of the flower or of the inflor- 
 escence take part. 
 
 The seed (p. 62) is produced from the ovule, as a consequence of 
 the fertilisation of the female cell contained within the ovule : its 
 characteristic feature is that it contains an embryo. The seed 
 (Fig. 245) may contain little or nothing but the embryo, in which 
 case it is said to be cxalbuminous (e.g. Pea, Bean, Sunflower, 
 Almond, Oak) : or it may contain, in addition to a small embr} r o, 
 a considerable portion of the female prothalliam (endosperm), when 
 it is termed albuminous (e.g. Grasses and other Monocotyledons, 
 Ranunculacese) : in a few rare cases the albuminous seed contains, 
 in addition to the embryo and endosperm, some of the nucellar 
 tissue of the macrosporaugium which is termed perisperm (e.g. 
 Nymphseacese, Zingiberaceae) : in Canna, Chenopodiacese, etc., 4
 
 PHAXEROGAMIA. 415 
 
 there is perisperm but no endosperm in the ripe seed, though it has 
 been ascertained in some cases that endosperm is originally 
 formed. 
 
 A formation of endosperm takes place in nearly all seeds, even 
 exalbuminous seeds : but in these latter it is more or less dis- 
 organised and absorbed by the growing embryo, so that little or 
 none remains in the ripe seed. 
 
 Whether the seed be albuminous or exalbuminous, it contains 
 (except in some parasitic or saprophytic plants, such as Orchids, 
 etc.) a supply of organic substances for the nutrition of the 
 embryo during its exti'a-seminal period of development. These 
 substances may be mainly stored in the cells of the cotyledons, as 
 in exalbuminous seeds ; or in the cells of the endosperm, or in 
 the cells of the perisperm, when present, as in albuminous seeds. 
 The substances are nitrogenous and non-nitrogenous. The nitro- 
 genous substances are proteids, deposited in the solid form as 
 aleuron (see p. 80), and are present in all seeds. The non-nitro- 
 genous substances are starch, in the form of starch-grains (see 
 p. 78), in starchy seeds (e.g. Peas, Beans, Cereals, etc.) ; or fat, 
 (in the form of oil-drops (see p. 80), in oily seeds (e.g. Linseed, 
 Rape, Castor-Oil seed, etc.). 
 
 The seed is generally enclosed in a single integument, the testa, 
 derived from the outer integument of the ovule, the inner integu- 
 ment of the ovule having been absorbed ; sometimes, however, the 
 seed has two integuments derived from those of the ovule, an 
 outer testa, and an inner endopleura (e.g. Euphorbiacese, Rosacese) : 
 in others again neither of the ovular integu- 
 ments persists into the seed, in which case the 
 wall of the embryo-sac is in direct contact 
 with the wall of the ovary. 
 
 In a few cases additional integuments or 
 appendages are developed in connexion with 
 the seed, such new growths being designated 
 by the general term aril. The aril may be 
 developed from either the f unicle or the hilum : 
 or from the micropyle, when it is distinguished 
 as an arillode. Good examples of a funicular 
 aril, which gjows up round the seed like an 
 additional integument, are afforded by the 
 Nutmeg, where it forms the Mace ; (Fig- 246), 
 the Yew, Water-Lily (Nymphsea), Passion-
 
 416 PART IV. CLASSIFICATION. 
 
 Flower. The Willow has a funicular aril in the form of a tuft 
 of woolly hairs. The most striking example of a membranous 
 micropylar aril is the Spindle-tree (Euouymus) : in Euphorbia and 
 Polygala the micropylar aril is a small mass of tissue, and in 
 Asclepias it is a tuft of hairs. Other excrescences, not especially 
 connected with either the hilum or the micropyle (sometimes dis- 
 tinguished as caruncles or strophioles), occur in certain plants ; 
 thus in the Violet and the Celandine (Chelidonium) an elevated 
 ridge marks the course of the raphe, and in the Willow-herb 
 (Epilobium) a tuft of hairs springs from the chalaza. 
 
 The most important point to be considered is, however, that of 
 the structural conditions which determine the production of a seed 
 in the Phanerogams, the feature which sharply defines this group 
 of plants from all others. The structural conditions are briefly as 
 follows : -the macrospore (embryo-sac) is not set free from the 
 macrosporangium (ovule), as is the case in the heterosporous 
 Pteridophyta ; nor does the macrosporangium itself separate from 
 the plant producing it until it has ripened into the seed : this 
 being so, the macrospore germinates inside the macrosporangium, 
 producing there the female prothallium with its reproductive 
 organs : fertilisation of the oosphere, as also the development of 
 the embryo from the oospore, takes place inside the macrospore; 
 and thus the seed is formed. If the macrospore were set free 
 from the macrosporangium, no seed would be formed ; but in 
 that case the condition of things would be that which actually 
 exists in the higher heterosporous Pteridophyta, such as Sela- 
 ginella and Isoetes. 
 
 Some seeds can germinate as soon as they are shed : but, for 
 the most part, they only do so after a period of quiescence, though 
 they may lose their germinating power if this period be too pro- 
 longed. 
 
 The Dissemination of the Seed. Fruits are either dehiscent, so 
 that the seeds escape, or they are indcliiscent : in the former case the 
 seeds, and in the latter case the fruits, present various adaptations 
 for ensuring their dispersal. The most conspicuous are those 
 which ensure dispersal by the wind : of this nature are the wing- 
 like appendages of the fruit in the Maple, Ash, Elm, etc. ; and 
 of the seed of Pinus, Catalpa, etc. : also the hairy appendages of 
 fruits (e.g. the pappus of Composite, the feathery style of Clema- 
 tis, etc.), and of seeds (e.g. on those of Grossypium the Cotton-plant, 
 Willow, Poplar, etc.). Other adaptations ensure dispersal by
 
 GROUP III. PHANEROGAMIA. 417 
 
 animals ; such are the hooks on fruits (forming burrs), as in var- 
 ious Boraginacese, Compositse, Galium, etc. : the succulence and 
 agreeable taste of many indehiscent fruits also promotes the dis- 
 persal of the seeds, the fruits being eaten by animals and the seed 
 being protected from digestion by hard protective tissue either in 
 the fruit (endocarp) or in the seed-coat (testa). In some cases (e.g. 
 Ecballium Elaterium, the Squirting Cucumber ; Impatiens noli- 
 me-tangere ; Oxalis Acetosella ; Hura crepitans) the fruit de- 
 hisces suddenly, ejecting and scattering the seeds with consider- 
 able force. Some fruits, provided with a long appendage (awn), 
 bore their way into the soil (e.g. Stipa pennata, Erodium). 
 
 The Life-history of the Phanerogams is essentially similar to 
 that of the heterosporous Pteridophyta, though, on account of the 
 structural peculiarities which bring about the formation of a seed, 
 it is not quite so easy to trace. The sporophyte, or asexual genera- 
 tion, is represented by the plant itself, bearing macro- and micro- 
 sporangia and macro- and micro-spores. The gametophyte, or 
 sexual generation, is represented by the male and female pro- 
 thallia developed respectively from the microspore and the 
 macros pore ; though it is here very much reduced, even more so 
 than in the highest heterosporous Pteridophyta. Thus there is a 
 definite and regular alternation of generations, since the male 
 and female prothallia can only be developed from the spores of 
 the sporophyte; and, on the other hand, the sporophyte can 
 only be developed from the immediate product of fertilisation, the 
 oospore. 
 
 The life-history of these plants is made clear by a morphological 
 consideration, as indicated in the following table, of the structure 
 of the seed : 
 
 Seed-coats . . . \ = macrosporangium of parent- 
 Perisperm (if present) / sporophyte. 
 
 Endosperm = gametophyte : female pro- 
 
 thallium. 
 Embryo . . . = young sporophyte. 
 
 When a plant perishes after once producing flowers and seeds, 
 it is said to be monocarpous. In rare cases (e.g. Agave ameri- 
 cana) several or even many years elapse before the plant blooms : 
 more common are annual plants (indicated by the sign 0), i.e. 
 such as complete the whole course of their development in a single 
 
 M.B. E E
 
 418 
 
 PAET IV. CLASSIFICATION. 
 
 year, as the Wheat ; and biennials, which do not blossom until the 
 second year of their life, when they perish, as the Turnip, Carrot, 
 Beetroot, etc. By polycarpous plants are meant such as produce 
 flowers and fruit year after year ; such are trees and shrubs, as 
 also many herbaceous plants which have underground rhizomes, 
 tubers, etc. 
 
 The sub-kingdom Phanerogamia falls into two natural divisions ; 
 the one containing but a single class : the other, two classes. 
 
 GROUP IV. GYMNOSPERM.E. 
 
 Sporophytic Characters. The ovule is not enclosed in an ovary, 
 nor is there any style or stigma : in pollination, the pollen-grain 
 enters the micropyle and comes into direct contact with the 
 nacellus: the flowers are never monoclinous, and are generally 
 without a perianth : there are no companion-cells in the phloem, 
 and the secondary wood does not (except Gnetacese) contain true 
 vessels. 
 
 Gametophytic Characters. The female prothallium is com- 
 pletely formed before fertilisation : the female organ is generally a 
 well-developed archegonium : the male cell is sometimes a sper- 
 matozoid. 
 
 CLASS 8. G-YMNOSPERALE 
 GROUP V. ANGIOSPERM.E. 
 
 Sporophytic Characters. The ovule is enclosed in an ovary, and 
 there is always a stigma : the pollen-grain does not come into 
 direct relation with the ovule, but falls upon the stigma and 
 germinates there : the flowers are commonly monoclinous and 
 possess a perianth : there are companion-cells in the phloem, 
 and the secondary wood generally includes true vessels. 
 
 Gamctophytic Characters. The female prothallium is only 
 partly formed before fertilisation : the female organ is a reduced 
 unicellular archegonium : the male cell is never a spermatozoid. 
 
 CLASS 9. MONOCOTYLEDONES. CLASS 10. DICOTYLEDOXES.
 
 GROUP IV. GYMNOSPERM.E. 419 
 
 GROUP IV. GYMNOSPERM^. 
 
 The plants of this class are all perennial trees and shrubs, for 
 the most part evergreen : they are classified into the three natural 
 orders, Cycadaceae, Coniferse, and Gnetaceae. 
 
 THE SPOROPHYTE. 
 
 General Morphology of the Vegetative Organs. The 
 
 body is distinctly differentiated into stem, leaf, and root. 
 
 The Stem grows above ground, usually erect, but climbs in 
 several species of Gnetum : it is woody, and is generally branched 
 monopodially : the symmetry of the main stem is radial, whilst 
 that of the branches is frequently bilateral, either isobilateral (e.g. 
 Thuja, phylloclades of Phyllocladus) or dorsiventral (e.g. species of 
 Abies, Taxus, and many other Coniferse in which the branches are 
 horizontal). The branches in many Coniferse (e.g. Pinus, Larix, 
 Cedrus, Ginkgo) are dimorphous, being either long shoots or dwarf- 
 shoots (see p. 23) : in the other forms the dwarf-shoots bear foliage- 
 leaves and fall off, sooner or later, with the leaves which they 
 bear : in Pinus the dwarf-shoots alone bear foliage-leaves, whilst 
 in the other genera the long shoots bear foliage-leaves as well. 
 
 The Leaves are either foliage- leaves or scale-leaves. The foliage- 
 leaves are either small and numerous, as in the Coniferse ; or large 
 and few, as in the Cycadacese, and as in Welwitschia where there 
 are only two foliage -leaves : they are branched only in the 
 Cycadacese : they are sessile in the Coniferse and in Welwitschia : 
 their growth is basal : their form varies considerably, one of the 
 most peculiar forms being that characteristic of certain Conifers 
 i Abietinese) where the leaf is needle-like (acicular) and either 
 flattened or prismatic and angular. The leaves fall annually 
 in only a few forms (e.g. Larix, Ginkgo) ; in the others the leaves 
 persist for two to ten years, or, as in Welwitschia, throughout the 
 life of the plant. 
 
 Scale-leaves, destitute of chlorophyll, occur in nearly all the 
 Cycadacete, in most Conifers (absent in most Cupressinese) and in 
 Ephedra (Gnetacese). 
 
 The Primary Root always persists as a tap-root. 
 
 General Histology. The Stem. The growing-point of the 
 stern, whilst generally conforming to the structure characteristic of 
 Phanerogams (see p. 102), does not present a clearly-marked differ-
 
 420 PART IV. CLASSIFICATION. 
 
 entiation into dermatogen, periblem and plerome. The stem is 
 monostelic : the primary vascular bundles are collateral, are open, 
 and have the usual general struct are ; they are generally arranged 
 in a single circle round the pith. Secondary growth in thick- 
 ness takes place as a rule by means of a normal cambium-ring. 
 In the Cycadacese and Couiferse, the secondary wood consists 
 exclusively of tracheides with rounded or elongated bordered pits 
 and of parenchymatous medullary rays, but true vessels are formed 
 in the Grnetacese ; the secondary bast has generally the normal 
 structure, but in some cases (Abietinese) it has no bast-fibres. 
 
 The Foliage-leaf is characterised by its well-developed epidermis 
 the cells of which are fibrous (Pinus, Torreya) : the stomata 
 are always depressed below the surface, and are borne usually on 
 the under surface only, when the leaf is flat (e.g. Abies, Taxus, 
 Cfiiikgo, etc.), or on the upper side only (Juniperus), but on all 
 sides when the leaf is acicular (e.g. Piuus, Picea, etc.) : the 
 epidermis is supported by a hypodermal layer of fibrous scleren- 
 chymatous cells : when the leaf is flat, the mesophyll is more or 
 less clearly differentiated into palisade and spongy tissue, but when 
 it is acicular, the mesophyll is uniform throughout, consisting of 
 parenchymatous cells with curiously infolded walls (Fig. 93, p. 114) : 
 the acicular leaves (Abietinese) have a single central vascular 
 strand enclosing two bundles which give off no branches : in the 
 flattened leaves there may be several ribs which either do (e.g. 
 Grinkgo) or do not branch in the lamina, and in all these cases the 
 bundles end blindly. A remarkable feature in the structure of 
 the leaf is the presence, in all the genera, of a tissue, termed 
 transfusion-tissue (p. 118), which consists of parenchymatous 
 cells, some of which contain no protoplasm and have pitted walls, 
 being in fact tracheides, whilst others contain protoplasm and have 
 unpitted walls. The use of the transfusion- tissue is to compensate 
 for the absence of a much-branched vascular system in the leaf, 
 the tracheidal cells serving to distribute water from the xylem of 
 the bundles to the mesophyll, the other cells serving to convey 
 organic substances formed in the mesophyll to the phloem of the 
 bundles. 
 
 The Root grows in length by means of a growing-point differen- 
 tiated into dermatogen, plerome and periblem, and root-cap as in 
 Dicotyledons (see p. 103) ; there are commonly two xylem-bundles 
 in the stele : the cambium-ring is formed in the usual way : the 
 phellogen is derived from the pericycle.
 
 GROUP IV. GYMNOSPERM.S. 421 
 
 General histological peculiarities. In all the Coniferae, except 
 Taxus, resin-ducts (see p. 98) are present : they are always to be 
 found in the leaves and in the cortex of the stem, sometimes also 
 in the pith of the stem (Ginkgo), in the primary wood (Finns, 
 Larix), or in the primary bast (Araucaria) : they are absent from 
 the root in many genera, and when present they never occur in the 
 cortex, but are situated in the primary wood (Pinus, Larix), in the 
 primary bast (Araucaria), or as a single canal in the centre of the 
 conjunctive tissue (Cedrus, Abies) : they are formed also in the 
 secondary wood (Pinus, Picea, Larix) or in the secondary bast 
 (Cupressus, Thuja), of both stem, and root. Mucilage-ducts re- 
 sembling the resin-ducts of the Coniferae, occur in the cortex of the 
 stem in the Cycadacese. 
 
 The bast of the Gymnosperms resembles that of the Pterido- 
 phyta, and differs from that of the Angiosperms, in that it contains 
 no companion-cells (see p. 96), the function of these cells being 
 performed by certain cells belonging either to the medullary rays 
 (Abietineae, some Cupressineae) or to the bast-parenchyma. 
 
 The General Morphology of the Reproductive Organs. 
 The reproductive organs are microsporangia (pollen-sacs) and macro- 
 sporangia (ovules) : the microsporangia are borne- on sporophylls, but 
 (except Gnetum) the macrosporangia are sometimes borne directly on 
 the axis (e.g. macrosporangia of Taxeae and of the Gnetaceae) : they 
 are developed on distinct shoots, and frequently on distinct plants 
 (e.g. Cycadaceae : some Coniferae, such as the Taxeae ; Gnetaceae 
 generally). 
 
 Certain shoots, are more or less clearly differentiated as floiccrs ; 
 the only exception being Cycas in which there is- no proper macro- 
 sporangiate flower. The flower is always unisexual : its structure 
 varies widely ; it may consist merely of a terminal sporangium 
 invested by a few small bracts (e.g. macrosporangiate flower of 
 Taxeae) ; of a terminal sporangium with a rudimentary perianth 
 (macrosporangiate flower of Gnetaceae) ; of one or more sporophylls 
 borne on a short axis and surrounded by a perianth (micro- 
 sporangiate flower of Gnetaceae) ; or of a larger or smaller number 
 of sporophylls arranged on an elongated axis, the- whole forming a 
 cone. 
 
 The SporophylU are of two kinds, distinguished by the nature 
 of the sporangia which they respectively bear, as microsporophylls 
 and macrosporophylls. When the flower is a cone, the sporophylls. 
 have a general resemblance to scaly leaves: in other flowers-
 
 422 
 
 PART IV. CLASSIFICATION. 
 
 (Taxeae, Cycas, Gnetaceae) they have various and specialised 
 forms. 
 
 The microsporopliyll (stamen) occurs in its simplest form in the 
 Cycadaceae, where it is a large stout scale bearing usually an in- 
 definite number of microsporangia on its under surface. In some 
 of the Coniferae (e.g. Pinus), the microsporophyll essentially re- 
 sembles that of the Cycadaceae, though it is much smaller (in 
 proportion with the smaller flowers) and bears only two micro- 
 sporangia. In the other Coniferse the microsporophylls, bearing 
 2-15 sporangia, show more or less distinct differentiation into 
 a stalk bearing a terminal leafy expansion, until, in Taxus, a 
 stage is reached where the microsporophyll consists of a stalk 
 
 FIG. 217 . A Microsporophyllary (or staminal) 
 flower of Alie pectinata; b scaly bracts; o mi- 
 crosporophyll with two microsporangia (pollen- 
 sacs). B Microspore (pollen-grain) (highly 
 inag.) ; e exine expanded into two hollow vesicles 
 II) ; y male prothallinm. (After Sachs.) 
 
 TIG. 248.-Pinus sylvesl ris ( x 7 : after 
 Strasburger) : Macrosporophyll b, bear- 
 ing on its upper surface the placental 
 scale /r, which bears two ovules at its 
 base; c apophysial projection of the 
 placental scale; m micropyle of the 
 ovule within which pollen-grains have 
 lodged. 
 
 bearing a peltate lamina, on the tinder surface of which the spor- 
 angia are developed. In other words, the microsporophyll con- 
 sists of a filament bearing a sorus of sporangia which constitutes 
 an anthei- (see p. 395). In all cases the microsporangia are 
 developed on the morphologically under (dorsal) surface of the 
 sporophyll. 
 
 The gradual differentiation of the microsporophyll, which can be 
 traced in the Coniferae, leads on to the more complete differen- 
 tiation and specialisation which obtains in the Gnetaceae and in
 
 GROUP IV. GYAINOSPERM-E. 423 
 
 the Angiosperms. In Grnetum, however, there are no microsporo- 
 phylls. 
 
 The macrosporophyll (carpel) appears in" a simple, yet typical, 
 form in Cycas (see Fig. 253), the one Gymnosperm which has no 
 distinct macrosporangiate flower. Here the carpels are essentially 
 similar to the foliage-leaves, though they are smaller, of a yellow 
 colour, and of a somewhat different form : they are, in fact, de- 
 veloped at the growing-point of the stem in the place of a whorl 
 of foliage-leaves. The few sessile macrosporangia are borne 
 laterally on the lower part of the sporophyll. 
 
 In the other Cycadaceae, the macrosporophyll is a stout seal}- 
 leaf, thickened at its outer end, bearing usually two lateral ovules, 
 one on each side. 
 
 In the Coniferse, the simplest form of macrosporophyll is a scalj* 
 leaf bearing a single macrosporangium on its upper surface : in 
 other forms the superior surface of the macrosporophyll is clearl}- 
 marked out, by outgrowths of various kinds, into an apical and a 
 basal half, the latter alone bearing the (1-7) macrosporangia (e.g. 
 Cupressinese) : in the Abietinese (Pinus, Larix, etc.) the sporangi- 
 ferous structure of the preceding families is developed from the 
 base of the carpel as a placenta! scaZe, which is much larger than 
 the carpel itself, and bears the two macrosporangia on its upper 
 surface. In the Taxese the macrosporophylls are rudimentary 
 (e.g. Phyllocladus, Cephalotaxus) or absent (e.g. Torreya, Taxus) ; 
 even when present they do not bear the macrosporangia. 
 In the Gnetacese there are no macrosporophylls. 
 The microsporangia (pollen-sacs) are borne, in nearly all cases, 
 on the lower (dorsal) surface of a sporophyll ; they may be numer- 
 ous (about 1,000) as in some Cycadaceae ; or few (2-15) in the 
 Coniferse and Gnetaceaef scattered (some Cycads), or more 
 commonly grouped into one or more sori, with more or less well- 
 developed placental tissue ; either imbedded in the tissue of the 
 sporophyll (e.g. Abietinese), or freely suspended (eg. Grinkgo) : in the 
 Cupressinese, the sporangia, when young, are covered by an out- 
 growth of the under surface of the sporophyll which is comparable 
 to the indusium of Ferns. In Grnetum, as there is no micro- 
 sporophyll, the two microsporangia are borne on the apex of the 
 floral axis. 
 
 The structure of the microsporangium is simple : it is unilocu- 
 lar; it contains, at an early stage, a mass of spore-mother-cells 
 derived from the archesporium, surrounded by a layer of ta petal
 
 424 PART IV. CLASSIFICATION. 
 
 cells also derived from the archesporium, and by a wall consisting 
 of one, two, or more, layers of cells : each, spore-mother-cell gives 
 rise to four microspores, which are usually tetrahedral, but 
 bilateral in the Cycads. The dehiscence is generally longitudinal. 
 
 The microspores (pollen-grains) present no special features be- 
 yond the fact that in some genera of Coniferae (e.g. most Abietineae) 
 the exine is dilated into two hollow expansions which lighten the 
 pollen-grains and facilitate their dispersal by the wind. 
 
 The macrosporangia (ovules) are borne either terminally on a 
 floral axis (e.g. Taxese, Gnetaceae), or on the upper surface of a 
 macrosporophyll ; on the floral axis they are borne singly, on the 
 sporophylls their number varies (1-7) : they are orthotropous and 
 sessile, the micropyle being directed either towards the axis of the 
 cone (in Abietineae), or away from it (Cupressineae) : they have a 
 single integument, though in some genera (most Taxoideae) au 
 arillus is eventually developed. 
 
 The macrospore (embryo-sac) is developed singly in the macro- 
 sporangium, by the growth and maturation of the mother-cell 
 which does not undergo division into four as in the Pteridophyta. 
 In the Cycadacese the wall of the macrospore, like that of spores 
 generally, is differentiated into two layers, the outer of which is 
 cuticularised. 
 
 Pollination. The microspores are conveyed by the wind from 
 the microsporangiate to the macrosporangiate flowers, the Gymno- 
 sperms being anemophilous, and they come into direct relation with 
 the ovule. In the case of cone- flowers, the scales separate at the 
 time of pollination, to permit of the pollen-grains being blown in 
 between them. The micropyle of the ovule secretes a mucilaginous 
 liquid which catches one or more of the pollen-grains : by the 
 gradual evaporation of this liquid, the pollen-grain is drawn 
 down the micropyle and is lodged on the apex of the nucellus, 
 where it germinates. 
 
 Embryogeny of the Sporophyte. The Gymnosperms are 
 remarkable in that they are frequently polyembryonic (most Cu- 
 pressineae, Abietineae, and Gnetacese), though the ripe seed eventually 
 contains only a single embryo (see p. 401). 
 
 In the Coniferae (except Ginkgo) the type of development is 
 essentially the same throughout, though with slight variations. 
 In the Abietinese the nucleus of the oospore descends towards the 
 lower end of the cell, and divides into two, and each of these again 
 into two; cell-formation takes place, walls being formed in two
 
 GROUP IV. GYMNOSPERMJE. 
 
 425 
 
 planes at right angles to each other, so that the lower end of the 
 oospore is occupied by a group of four cells lying in one plane ; 
 these cells then divide by transverse walls, "so that three tiers of 
 four cells each are formed ; of these, each cell of the middle tier 
 grows out into a long unicellular suspensor ; those of the upper tier 
 
 FIG. 249. Fertilisation, and early stages in the embryogeny, of Picta excelsa (x90; 
 after Strasburger). A Oosphere, with nucleus on, and canal-cell cl. B Fertilisation in pro- 
 gress : p pollen-tube ; sn nucleus (male pronncleus) of the male cell novr in the oosphere 
 on female pronucleus. C Fusion of male and female pronnclei. D Commencing cell-forma- 
 tion at the chalazal end of the oospore ; E a further stage : F three tiers of four cells each 
 have been formed : G the cells of the middle tier have elongated into snspensors, bearing 
 the single embryo at their lower end. 
 
 simply maintain the connexion of the suspensors with the rest of 
 the oospore; those of the lowest tier, whilst also contributing to the 
 suspensors, -each give rise to an embryo : from the cells at the base
 
 426 
 
 PART IV. CLASSIFICATION. 
 
 FIG. 250. Later stages in the embryogeny of the sporopbyte of Picea excclsa (after 
 Btrasburger). A Optical section of young embryo borne on the end of the suspensors ( x 240) : 
 B older embryo, with suspensor and embryonal tubes ; nt this stage the growing- points of 
 primary root and stem are already differentiated : C half-grown embryo in surface-view: 
 D longitudinal section of a half-grown embryo : E surface-view of the apex of the ehoot of 
 this embryo (x27): F longitudinal section of a fully developed embryo in a ripe seed; e 
 cotyledons; h hypoctyl; pi apex of the plerome in the root; cp root-cap; m pith; op pro- 
 cambial ring.
 
 GROUP IV. GYMXOSPERMJE. 
 
 427 
 
 of the embryo, one or more embryonal tubes are developed which 
 
 grow backward along the suspensor. Picea cxcelsa departs from 
 
 this type in that the suspensors remain coherent, bearing at their 
 
 end the cells of the lowest tier which develope into but a single 
 
 embryo, whereas in 
 
 the typical Abie- 
 
 tineae four embryos 
 
 originate from each 
 
 oospore (polyembry- 
 
 ouy). Only a single 
 
 embryo is developed 
 
 from the oospore in 
 
 Thuja (Cupressineae) 
 
 and in the Taxeae. 
 
 The cotyledons 
 vary in number : 
 one, in Ceratozamia, 
 and sometimes in 
 other Cycadaceae ; 
 two, in the Cycada- 
 ceae generally, in 
 the Cupressinese 
 generally, in the 
 Taxoidese, and in the 
 Gnetaceae ; in the 
 Cupressineae some- 
 times 3-5 ; in the 
 Abietineae 5-15. 
 The cotyledons are 
 generally epigean, 
 but they are hypo- 
 gean in the Cyca- 
 daceae. 
 
 The growing-point 
 of the root is in all 
 cases differentiated 
 endogenously, at 
 some distance from 
 the posterior end of 
 
 the embryo. 
 
 FIG. 251. Germinating seeds of Pinu* Pinea : I first 
 stage, ia longitudinal section : II second stage, with pro- 
 truding radicle ; A external view ; B view after removal of 
 half the seed-coat ; C longitudinal section, without seed- 
 coat; J) transverse section, without seed-coat; I/I ger- 
 mination is here completed, the cotyledons havingexpanded, 
 and the hypocotyl elongated : seed-coat ; e endosperm ; TC 
 radicle ; c cotyledons ; y micropyle ; r red membrane (re- 
 mains of nucellus) ; * the embryo-sac.
 
 428 
 
 PART IV. CLASSIFICATION. 
 
 THE GAMETOPHTTE. As the G-ymnosperms are heterosporous, the 
 sexual generation is represented by a male and a female individual. 
 
 The Male Individual is a prothallium developed from the micro- 
 spore as described on p. 405. It consists of two or more cells, one 
 of which grows out into a pollen-tube (see Fig. 240). 
 
 Fro. 252. 4 Longitudinal section of the micropylar portion of the female prothailium of 
 Picea excelsa snowing two archegonia ( x 100) : c neck of archet*onium ; cl canal-cell. 
 If Surface-view of unopened neck of an archegonium ( x 250). C Pollen-tube penetrating 
 to the oosphere through the neck of the archegonium ( x 250). (After Sirasburger.)
 
 GROUP IV. GYMNOSPERALE. 429 
 
 The male organ is a rudimentary antheridium consisting of two 
 cells, the stalk-cell and the generative cell. 
 
 The male cell is derived from the generative cell of the anther- 
 idium which travels into the pollen-tube; this cell undergoes 
 division into two similar cells, near the apex of the pollen-tube, 
 both of which are, as a rule, functional male cells. In Cycas, 
 Zamia, and Ginkgo, each of these two cells actually developes into 
 a large multiciliate spermatozoid ; whilst in those forms in which 
 the male cell is not a spermatozoid, it is of somewhat spherical 
 or oval form. When, as in Juniperus, and other Cupressinese, 
 several archegonia are' fertilised by means of a single pollen-tube, 
 repeated cell-division takes place in the pollen-tube. 
 
 The Female Individual is a prothallium (sometimes called 
 endosperm) developed within the macrospore. The germination 
 of the macrospore begins with the division of its nucleus ; nuclear 
 division is repeated until a large number of nuclei are formed, 
 lying in the parietal protoplasm of the spore ; free cell-formation 
 then takes place, walls being formed between the cells so that the 
 interior of the macrospore is lined by a layer of cells which grow 
 and divide until the cavity of the macrospore is entirely filled. 
 It is characteristic of Gymnosperms that the development of the 
 prothallium is uninterrupted, and that it is completed before the 
 female organs are developed and, consequently, before fertilisation 
 can have taken place. 
 
 The female prothallium is a mass of parenchymatous tissue, 
 which does not, as a rule, protrude to any extent from the spore, 
 and which, in consequence of the exclusion of light, is destitute 
 of chlorophyll ; the only exception to this rule is offered by the 
 Cycadacese where, if the female organ is not fertilised, the pro- 
 thallium, resuming its growth, protrudes through the micropyle 
 and turns green in the light. 
 
 The female organ is an archegonium, and is developed from a 
 single superficial cell of the female prothallium at its micropylar 
 end. The mother-cell generally divides transversely into two ; 
 an upper, the neck-cell ; a lower, the central cell : the neck-cell 
 usually divides, by two vertical walls, into four cells, which form 
 the neck ; the central cell grows, and divides transversely at its 
 upper end so as to cut off a small cell, the canal-cell, which lies 
 in the canal formed by the separation of the neck cells, and a 
 large cell which is the female cell or oosphere (Fig. 252). 
 
 The number of archegonia developed on the female prothallium
 
 430 PART IV. CLASSIFICATION. 
 
 varies from a small number (3-5) iii the Abietinea^ to a large 
 number (20-60) in Welwitschia and Gnetum. The archegonia 
 are either scattered (Abietinese), or in a group (Cupressinese) : 
 when scattered, the central cells are surrounded by a layer of 
 small cells belonging to the prothallium ; when in a group, the 
 central cells are in actual contact and have a common investment 
 of small cells. 
 
 The female cell or oosphere is a relatively large nucleated cell, 
 the protoplasm of which is so highly vacuolated that it presents a 
 frothy appearance. 
 
 Fertilisation. When the microspore has reached the apex of the 
 nucellus, it developes a pollen-tube which penetrates the tissue of 
 the nucellus, making its way to the archegonia which have been, 
 or are being, developed on the prothallium inside the macrospore. 
 Generally speaking, the pollen-tube, on reaching the macrospore, 
 pierces its wall, and enters the neck of an archegonium (when 
 scattered), or spreads out over the necks of a group of adjacent 
 archegonia ; a male cell is forced out through the mucilaginous tip 
 of the pollen-tube into the oosphere, or into each of the oospheres 
 of a group of archegonia so that one male organ fertilises several 
 archegonia ; the act of fertilisation is completed by the fusion of 
 the male pronucleus with the female pronucleus, to constitute the 
 nucleus of the oospore (Fig. 249). 
 
 With regard to those forms in which the male cell is a sperma- 
 tozoid, in Cycas and Ginkgo the pollen-tube does not approach the 
 archegonia, but by its growth causes the absorption of much of the 
 micropylar portion of the nucellus, so that a cavity containing 
 liquid is formed, into which the spermatozoids are discharged. In 
 Zamia the pollen-tube comes into contact with the neck of the 
 archegonium, into which it discharges the two spermatozoids 
 together with a drop of liquid. In all cases the spermatozoids 
 swim down the neck of the archegonium to the oosphere, and one 
 of them enters it and fertilises it. 
 
 The Results of Fertilisation. 
 
 1. The fruit. In all the Gymnosperms which have a cone-like 
 macrosporangiate flower (Cycadacese, except Cycas ; Coniferse, 
 except Taxe3e), one effect of fertilisation is to cause more or less 
 considerable growth in the macrosporophylls, or in the placental 
 scales, as also tissue-change resulting in their becoming woody 
 (e.g. Pinus, Abies, etc.) or fleshy (e.g. Juniperus), the product being 
 the fruit.
 
 GROUP IV. GYMNOSPEBM.E. 431 
 
 The fruit-cone, in most cases, sets free the seed by the separa- 
 tion of the macrosporophylls, or of the placeutal scales, which fall 
 off from the axis of the cone, leaving it bare (most Cycadaceae, also 
 Abies, Cedrus) ; or they merely separate enough to let the seeds 
 fall out, and then the cones either remain on the tree (e.g. Larix), 
 or, as is more commonly the case, drop off entire. However, where 
 the fruit is a berry-like cone (e.g. Juniperus), the macrosporophylls 
 do not separate, and the dispersal of the seed depends on the fruit 
 being eaten by animals. 
 
 2. The seed is albuminous in all Gymnosperms, the single 
 straight embryo being imbedded in the endosperm (see Fig. 251 /) 
 in all cases, also, some portion of the nucellar tissue persists as 
 perisperm, amounting, in the Cycadaceae and Coniferae, to little 
 more than a membranous layer. 
 
 The development of the seed-coats varies widely. In the 
 Cycadacese the testa consists of two layers, an outer fleshy and 
 succulent, and an inner hard and woody, so that the seed bears a 
 superficial resemblance to a fruit such as a plum. In those Coni- 
 ferae in which the seeds are produced in a cone-fruit, the testa is 
 hard and tough ; but in those in which the seed is exposed from 
 the first, the testa is either fleshy (e.g. Ginkgo, Cephalotaxus), 
 being developed after the manner of that in the Cycadaceae, or it 
 is hard, and is invested by a succulent aril (e.g. Taxus). In those 
 Coniferae with woody cones (e.g. Abietineae, most Cupressineae) 
 the seed is usually winged, either by means of a membranous 
 outgrowth of the testa, or (Abietineae) by the adhesion to the seed 
 of a thin strip of tissue, split off from the surface of the placental 
 scale. 
 
 Classification of the Gymnospermce. 
 
 The group contains the following three orders : 
 
 1. CYCADACE.E: the trunk is generally un branched : the leaves 
 are large and branched : no vessels in the secondary wood. 
 
 2. CONIFERAE : trunk much branched : leaves many, small, and 
 unbranched : no vessels in the secondary wood. 
 
 3. GrXETACE^E : habit various : flowers have a rudimentary 
 perianth : there are vessels in the secondary wood. 
 
 Order 1. Cycadaceae. The CycadacesB are plants which, in many re- 
 spects, show affinity with the Ferns, while, on the other hand, they re- 
 semble the Palms in external appearance. The stem is tubercular or 
 cylindrical. The vegetative leaves are of two kinds ; scaly leaves, brown 
 and dry, closely covering the surface of the stem ; foliage- leaves, pinnate,
 
 432 
 
 PART IV, CLASSIFICATION. 
 
 of a leathery consistency, produced annually or at a longer interval, 
 forming a crown at the top of the stem ; the foliage-leaves are generally 
 developed expanded, but in Cycas the pinnae are circinate in vernation, as 
 is also the phyllopodium in Stangeria and Zamia. 
 
 The dioecious flowers are produced, either singly or several together, at 
 the apex of the stem ; they are cones (except Cycas). The development 
 of the cones does not arrest the growth in length of the stem : hence the 
 stem may be regarded as a sympodium, its growing-point being maintained 
 by either dichotomous or lateral branching (p. 18). The macrosporo- 
 phylls of Cycas do not constitute a true flower, since they are not borne, 
 as in the other genera, on a special axis, but simply take the place of a 
 whorl of foliage-leaves. The cones consist of an elongated axis, bearing 
 
 numerous spirally- arranged 
 scaly sporophylls, which vary 
 in number from 30 to 600. The 
 microsporophylls bear on the 
 under surface usually numerous 
 (2 to 1000) microsporangia, either 
 scattered or in sori (Cycas, 
 Stangeria, Zamia). The macro- 
 sporophylls bear two orthotro- 
 pous macrosporangia, one on 
 each flank, developed upon the 
 peltate terminal lamina; but the 
 exceptional macrosporophylls of 
 Cycas (see Fig. 253) may bear as 
 many as 5-6 macrosporangia. 
 
 The macrosporangia are all 
 sessile, and have a single in- 
 tegument, and are of consider- 
 able size ; those of Cycas are as 
 large as a plum before fertilisa- 
 tion. 
 
 In the coniferous genera, the 
 macrosporangiate flower be- 
 comes the fruit; that is, a dry 
 cone, the sporophylls of which 
 fall away, and so set free the 
 
 In Cycas, the sporophylls bend outwards and drop off, bearing the 
 seeds. The seed is covered by a testa, developed from the integument of 
 the ovule, which is succulent externally and stony internally. It con- 
 tains a single straight embryo, on a coiled suspensor, lying in the endo- 
 sperm. The embryo has generally two cotyledons (one in Ceratozamia, and 
 occasionally in other genera also), which are hypogean. 
 
 The Cycadaceae, of which there are nine genera, and about seventy-five 
 species, are all tropical or subtropical. 
 
 Order 2. Coniferae. This order includes the Pines, Firs, Cypresses, 
 Yews, etc., which, for the most part, are extra-tropical, inhabiting more 
 especially the northern hemisphere. 
 
 Fi&. 253. Sporophylls of Cycads. A macro- 
 sporophyll of Cycas revoluta (J nat. size) : / 
 pinnae; s ovules. B Macrosporophyll of 
 Zamia muricata, with two ovules (s); C 
 microsporophyll of this species with numerous 
 inicrosporangia (p).
 
 GROUP IV. GYMN'OSPERM^. 
 
 433 
 
 The conspicuous features of their morphology are the regular mono- 
 podial branching of the stem, the small (often acicular) simple leaves, and 
 the tap-root. In their histology, these plants resemble the Dicotyledons 
 in that the stem grows in thickness by a normal cambium-ring ; but the 
 vascular tissue of the wood consists entirely of tracheides with bordered 
 pits. The presence of resin-ducts is another characteristic feature. 
 
 The flowers are never monoclinous; some genera are dioecious. The 
 microsporangiate flower is a cone, consisting of an elongated axis bearing 
 microsporophylls (Fig. 254), which are generally somewhat peltate in form. 
 Each microsporophyll bears two or more microsporangia on its under (dor- 
 sal) surface. The macrosporangiate flower is also a cone in certain cases 
 (Pinoideae, Fig. 255), in which case the macrosporophylls bear the macro- 
 
 FIG. 254. Pinus montana (Pumilio). A Longitudinal section of a microsporangiate flower 
 ( x 10). B Longitudinal section of a microsporophyll, showing the cavity of one pollen-sac 
 (x 20). C Transverse section of a microsporophyll, showing the cavities of both pollen- 
 sacs. D Germinating two-celled microspore of Ptnus sylvestris, showing the expansions of 
 theexine(x 400). (After Strasburger.) 
 
 sporangia; in other cases there is a less perfect cone, or none at all 
 (Taxoidese, see Fig. 258), the macrosporophylls are either rudimentary or 
 absent, and the macrosporangia are generally borne on the axis. 
 
 In some genera (e.g. Pinus, Juniperus) the seed takes two years to ripen ; 
 in the first year, pollination takes place, and the pollen-tube begins to 
 grow through the tissue of the nucellus ; in the second year, after a period 
 of rest, the pollen-tube completes its growth, reaches the archegonium, and 
 fertilises the oosphere ; as a consequence, the embryo is developed, and the 
 ovule is changed into a seed. 
 
 M.B. V F
 
 434 
 
 PART IV. CLASSIFICATION. 
 
 A 
 
 In spite of the fact that so many of the Coniferse are polyembryonic (see 
 p. 424), and that each ovule contains several archegonia, the ripe seed con- 
 tains only a single embryo, though occasionally two are found (e.g. 
 Ginkgo). The embryo has two, or more, cotyledons, which are usually 
 epigean. 
 
 The order, which includes 34 genera and about 350 species, may be 
 naturally divided into the two sub-orders, Pinoideae and Taxoidese, based 
 upon the structure of the macrosporangiate flower ; each of these sub- 
 orders includes several families, the 
 chief of which are described below. 
 
 Sub-order I. PINOIDEAE. The ma- 
 crosporangiate flowers are cones ; the 
 seed has a woody or leathery testa, 
 is enclosed between the macrosporo- 
 phylls or the placental scales, and 
 has no aril. 
 
 Fam. 1. Abietlnece : monoecious ; 
 on its upper surface at the base, the 
 macrosporoph3'll bears a large pla- 
 cental scale on the upper surface of 
 which two inverted macrosporangia 
 are borne. The ripe seed has two 
 wings derived from tissue of the 
 placental scale ; the microsporophyll 
 bears two microsporangia ; micro- 
 spores usually have expansions of 
 the exine; all leaves arranged spir- 
 ally ; cotyledons, more than 2, com- 
 monly 5, sometimes as many as 15. 
 
 The more important genera may 
 be distinguished as follows : 
 
 A. No dwarf-shoots; placental 
 scales flat ; seed ripens in one year ; 
 stem bears whorled branches. 
 
 1. Fruit-cones erect, fall- 
 ing to pieces when ripe ; 
 foliage-leaves flat, cylin- 
 drical at the base, and not 
 decurrent; placental scales 
 about the same length as 
 
 the macrosporophylls . Abies. 
 
 2. Fruit-cones pendent, 
 falling off entire ; foliage- 
 leaves with decurrent pro- 
 jecting base. 
 
 Leaves 4-angular ; placental scales much longer than the 
 
 macrosporophylls Plcea. 
 
 B. Long and d \varf -shoots. 
 
 FIG. 255. Abies pectinaia. A Carpel c, 
 seen from above (ventral surface), show- 
 ing s the placental scale, and sfc the two 
 ovules (mag.) B Mature cone (nat. size) ; 
 p axis ; c carpel ; s enlarged placental 
 scale. C Ripe placental scale (s) isolated, 
 seen from above; so, the two seeds, each 
 with a wing (/). (After Sachs.)
 
 GROUP IV. GYMNOSPERM.E. 435 
 
 1. Placental scales flat; foliage-leaves borne on both long 
 and dwarf-shoots ; branching of the stem irregular. 
 
 (a) Leaves annually deciduous ; seed ripens In one year . Larix. 
 
 (b) Leaves persistent ; seed ripens in two years . . . Cedrus. 
 
 2. Placental scales thickened externally into an apophysis : 
 foliage-leaves confined to the dwarf-shoots : branches whorled. Finns. 
 
 1. Abies, the Silver Firs. The foliage-leaves are flat, marked on the 
 under surface with two longitudinal white streaks, and show in section 
 two lateral resin-ducts: the macrosporangiate cone is developed in the 
 axil of a leaf borne on a shoot of the previous year, at some distance from 
 its apex, and when ripe falls to pieces so that the naked axis remains. To 
 this genus belongs A. pectinata (A. alba], the Silver Fir, the emarginate 
 leaves of which stand out in a comb-like manner from the branches. 
 
 2. Picea. the Spruce Firs. The foliage-leaves are quadrangular, and 
 have two lateral resin-ducts : the macrosporangiate cone is borne 
 terminally on a shoot of the previous year, becomes pendent after 
 fertilisation, thus enabling the seeds to drop out, and then falls off entire. 
 To this genus belong P. excdsa, the Norway Spruce, the leaves of which 
 are compressed laterally. 
 
 3. Larix, the Larches. The deciduous leaves are arranged spirally on 
 long shoots, and also in clusters on dwarf -shoots developed in the axils of 
 the leaves of the long shoots of the previous year : the microsporangiate 
 cones are borne terminally on leafless dwarf-shoots, the macrosporangiate 
 cones terminally on leafy dwarf-shoots. L. europ&a is the common 
 Larch, a native of the Alps and Carpathians. 
 
 4. Cedrus, the Cedars. This genus differs from Larix in that the 
 leaves, which are arranged in the same way, persist for more than one 
 year, and in that the seed takes two years to ripen. The genus includes 
 three species: C. Libani, in Asia Minor; C. atlantica, in the Atlas moun- 
 tains of North Africa: C. Deodara, in the Himalayas. 
 
 5. Pinus, the Pines. The thick placental scales are expanded at their 
 free end into a flattened rhombic surface, the apophysis : the seed takes two 
 years to ripen : the foliage- leaves persist for several years and are confined 
 to dwarf-shoots which bear cataphyllary leaves at their bases, and are 
 borne in the axils of the catapl^llary leaves of the long shoots of the same 
 year : the primary branches are arranged in false whorls near the apex of 
 the shoot of any one year, and the branches of a higher order are de- 
 veloped in the same manner : the microsporangiate cones take the place of 
 dwarf-shoots at the base of a long shoot of the same year, and are closely 
 packed : the macrosporangiate cones also occupy the place of dwarf-shoots 
 near the apex of long shoots of the same year. 
 
 In the section Pinaster, the apophysis has a rhombic free surface with a 
 central projection (umbo) : it includes the sub-genus Pinea, characterised 
 by the fact that each dwarf-shoot bears two leaves, with about twenty 
 species, including Pinus si/lvestrli, the Scots Pine ; P. Laricio, the Black 
 Pines ; P. Pinaster, the Cluster Pine of South Europe ; P. montana, the 
 Mountain Pines of Europe; P. Pinea, the Stone Pine of the South of 
 Europe, the "seeds of which are large and edible.
 
 436 
 
 PART IV. CLASSIFICATION. 
 
 Fam. 2. Cupress inece : monoecious, sometimes dioecious : macrosporo- 
 phylls with a projecting placental outgrowth. : seeds axillary, erect, often 
 winged : microspores without expansions of the exine : leaves always 
 arranged in whorls. 
 
 In the sub-family Cupressince, including the genera Cupressus and 
 Chamsecyparis, the ripe cone is woody and consists of 2-6 pairs of peltate 
 macrosporophylls coherent by their margins in a valvate manner. The 
 genus Cupressus, the Cypress, has several seeds on each macrosporophyll : 
 in Chamaecyparis each macrosporophyll bears only two seeds. 
 
 The sub-family Juniperince, including the single genus Juniperus, is 
 distinguished from the other sub-families in that the flowers are, as a 
 rule, dioacious ; the ripe cone is somewhat fleshy, resembling a berry or a 
 drupe ; it usually consists of one whorl of macrosporophylls each bearing 
 one or two wi 
 
 FIG. 256. A Branch of Thuja occi- 
 dentdlis ( x 6) showing heteropbylly : fc 
 flank-leaves ; / surface-leaves ; h resin- 
 receptacle. B Fruit of Biota orientals 
 (nat. size) : /macrosporophylls with ven- 
 tral outgrowths d ; d (in the middle line) 
 sterile sporophyHs. 
 
 FIG. 257. A Macrosporangiate 
 flower of Juniperus Sabina, seen from 
 above : //fertile macrosporophylls, 
 bearing macrosporangia s; ff 
 upper part of sterile sporophylls 
 (mag.). JB and C JunipertM com- 
 7u inn's. S young fruit: /// macro- 
 pporophyllB, of which the anterior 
 is turned down : e the ovules. C ripo 
 fruit; the limits of the three ciirpels 
 are only distinguishable at the 
 pox. 
 
 In the section Oxycedrus (including Juniperus communis, the Juniper : 
 J. Oxycedrus, J. macrocarpa, and other species), the cone consists of 1-2 
 whorls; and in the section Sabina (including J. Sabina, J. ciryiniana, 
 etc.), it consists of 2-3 whorls ; the innermost or uppermost whorl alone is 
 fertile as a rule in Oxycedrus, but is sterile in Sabina : the (2-3) seeds are 
 free in most forms : in Sabina the flowers are generalh- monoecious, and 
 the leaves (including sporophylls) are usually in whorls of 2, whilst in 
 the other sections they are in whorls of 3. 
 
 Sub-order II. TAXOIDE.E : the macrosporangiate flowers are. as a rule,
 
 GROUP IV. GYMNOSPERM^E. 
 
 437 
 
 not cones ; the seed usually projects beyond the macrosporophylls (when 
 present) and has a succulent testa or an arillus: flowers generally 
 dioecious. 
 
 Fam. 1. Taxece : the macrosporophylls are usually rudimentary or 
 absent, and the macrosporangia are borne on the axis : the seed has an 
 arillus in some forms, while in others it has a succulent testa : micro- 
 sporophylls with 2-9 microsporangia : microspores without expansions of 
 the exine. 
 
 PhyllocJadus, remarkable for its rudimentary leaves and for the de- 
 velopment of its dwarf-shoots into phylloclades, has thick persistent 
 macrosporophylls ; in the axil of each there is a single erect macrosporan- 
 gium with an arillus : flowers sometimes monoecious. Ginkgo Uloba (Salis- 
 buria adiantifolia), the Maiden-hair Tree, is characterised by its fan- 
 shaped deciduous leaves with furcate venation : the macrosporophylls are 
 rudimentary: the macrosporangia are borne in an opposite pair at the end 
 of a short stalk : no arillus, bat the testa of the seed becomes succulent. 
 Taxus(the Yew) has only long shoots: nor has this genus any macro- 
 sporophylls, the macrosporangia 
 being borne singly at the end 
 of short lateral shoots, and the 
 seed has a fleshy arillus : there 
 are no resin-ducts in the tissues : 
 the microsporophyll is peltate, 
 bearing 5-9 microsporangia on 
 its under surface. 
 
 Order 3. Gnetaceae. This 
 order includes but three genera, 
 Ephedra, Gnetum, and Wel- 
 witschia. Though they differ 
 widely from each other in many 
 respects, they agree in that they 
 have opposite leaves ; flowers 
 which are not cones and which 
 have a rudimentary perianth, 
 but have no macrosporophylls 
 as the macrosporangia are borne on the axis : an albuminous erect seed ; 
 a dicotyledonous embryo ; and secondary wood which contains true 
 vessels. They are generally dioecious. 
 
 Ephedra is a genus of shrubby plants, with rudimentary leaves, some- 
 what resembling an Equisetum. It is especially remarkable on account 
 of its peculiar embryogeny. Habitat, warmer temperate zone. 
 
 Gnetum is a genus of shrubs or trees, for the most part climbers, but 
 some erect-growing (Gnetum Gnemori) : with its broad well-developed foli- 
 age-leaves, with pinnate venation, it resembles the Dicotyledons in habit. 
 Habitat, the tropics. 
 
 Welwitschia includes the single species W. mirabilis .- it is remarkable 
 for its short thick stem, prolonged below into a tap-root, with a broad flat 
 somewhat circular bilobed upper surface, a single long persistent foliage- 
 
 FIG. 258. A Branch of Taxus baccaia bearing 
 a fruit/, which consist* of a fleshy arillns en- 
 closing a seed. B Longitudinal section of the 
 end of a branch terminating in a macrospo- 
 rangiate flower: b scaly bracts; fc terminal 
 macrosporansrium(nucellu8); v the integument; 
 m the micropyle : a the rudiment of the arillns 
 (X20).
 
 438 PART IV. CLASSIFICATION. 
 
 leaf being borne at the margin of each lobe: the inflorescences are borne in 
 dichotomous cymes, usually in the axil of each of the two leaves. Habitat, 
 Damaraland, Western South Africa. 
 
 GROUP V. ANGIOSPERALE. 
 
 The plants of this group are to a large extent herbaceous annuals, 
 triennials, or perennials ; but it also includes a great number of 
 shrubs and trees. 
 
 THE SPOROPHYTE. 
 
 The General Morphology of the Vegetative Organs is so 
 varied that it cannot be dealt with in a general way. The reader 
 is referred to the treatment of the subject in Book I., and to the 
 descriptions given in the systematic account of the group. 
 
 The General Morphology of the Reproductive Organs. 
 The reproductive organs are pollen-sacs (microsporangia) and ovules 
 (macrosporangia), borne generally on sporophylls, but sometimes 
 directly on the floral axis (e.g. microsporangia of Naias, etc. ; 
 macrosporangia of Polygonum, Primulacese, etc.) : they are de- 
 veloped on special shoots differentiated as flowers, and the flowers 
 are arranged in a more or less complex branch-system, the in- 
 florescence. 
 
 The Inflorescence (see p. 54). It is only in comparatively few 
 cases that the primary axis of the plant terminates in a flower ; 
 such plants are said to uniaxiol : it is usually not until the secon- 
 dary or tertiary branches, or even those of a higher order, are 
 developed, that a flower is formed. Such plants are said to be 
 bi-j tri- 1 or poly-axial. 
 
 The floral axis of the Angiosperms frequently forms an elaborate 
 branch-system which is usually sharply defined, as a sporophore, 
 from the vegetative shoots, and which bears leaves which are 
 either sporophylls or hypsophylls (p. 55). 
 
 In the inflorescence, as usually in all parts of the shoot of 
 Augiosperms, the branching is almost always monopodial and 
 axillary. Some apparent exceptions may be easily reduced to this 
 type : thus, in the racemes of most of the Craciferse the bracts at 
 the bases of the individual lateral branches are abortive, and the 
 same occurs in many of the Compositae. In the Solanaceae and 
 Boraginaceae the bract often undergoes displacement, so that it
 
 GROUP V. ANGIOSPERM.E. 439 
 
 appears to be inserted laterally upon the axillary branch ; on the 
 other hand, it sometimes happens that the axillary branch is 
 adherent to the main shoot for some distance. 
 
 The flowers of an inflorescence are either sessile or stalked, the 
 stalk being termed a pedicel. 
 
 In accordance with the principles of branching laid down on 
 p. 18, the different forms of inflorescences may be classified as 
 follows : 
 
 A. Racemose Inflorescences consist of a main axis (rhachis, peduncle), 
 bearing a number of lateral branches developed in acropetal (or centri- 
 petal) succession, constituting a monopodial branch-system. The lateral 
 branches do not usually grow longer than that portion of the main axis 
 which lies above their points of origin. If the lateral shoots of the first 
 order terminate in a flower without again branching, the inflorescence is 
 said to be simple ; but if they branch, it is compound. 
 
 These inflorescences are also termed indefinite, not because the apical 
 growth of the main axis of its branches is unlimited, but because, owing 
 to the acropetal succession in the development of the flowers, the growth 
 of branches of a high order is arrested, by the development of a terminal 
 flower, earlier than that of branches of a lower order : for instance, the 
 growth of the secondary branches is arrested before that of the main axis, 
 that of the tertiary branches before that of the secondary branches, and 
 so on ; hence these inflorescences are sometimes termed centripetal. 
 
 I. Simple racemose inflorescences : 
 
 (a) With an elongated main axis: the lateral shoots spring from the axis 
 at some distance from each other. The three following forms may be 
 distinguished : 
 
 (1) The spike, in which the lateral branches are flowers which are sessile 
 on the main axis, or have very short pedicels (Fig. 259 A) ; e.g. the inflor- 
 escence of the Plantain (Plantago). The small spikes of the Glumales are 
 termed spikelets. 
 
 (2) The spadix, which differs from the spike only in having a thick and 
 fleshy axis ; a large bract forming a sheath, called a spathe, commonly 
 grows at the base of the inflorescence and envelopes it more or less ; e.g. 
 Arum and Bichardia. 
 
 (3) The raceme, in which the lateral branches are flowers with pedicels 
 of nearly equal length, e.g. the Cruciferse, as the Eadish, Cabbage, etc. ; in 
 these the bracts of the individual flowers are not developed ; also Berberis 
 and others. 
 
 (/3) With a short main axis ; the lateral branches are set closely together 
 on the short or flattened main axis. 
 
 (4) The capitulum (head) in which the short main axis is conical or disc- 
 shape/I or even hollowed out, and is closely covered with lateral branches 
 int&e form of sessile flowers (Fig. 259 D), e.g. the Composite, as Dande- 
 lion, Sunflower : also the Scabious. The bracts (paleae) of the individual
 
 440 
 
 PART IV. CLASSIFICATION. 
 
 flowers (Fig. 259 D p) are sometimes wanting ; but the whole head is sur- 
 rounded at the base by a number of bracts forming an involucre (Fig. 
 259 D i) which gives the inflorescence the appearance of being one single 
 flower. 
 
 (5) The umbel, composed of a number of lateral branches, in the form of 
 pedicillate flowers, springing together from a very short axis which com- 
 monly terminates in a flower (Fig. 259 Cd) ; e.g. the Umbelliferae and the 
 Ivy. The bracts of the separate pedicels forming the rays are usually 
 present in diminished number ; they form an involucre. 
 
 II. Compound racemose inflorescences are formed when the lateral shoots 
 which bear flowers, as described above, are again branched ; or, in other 
 words, when inflorescences of the types above enumerated are united to 
 form a larger inflorescence ; for instance, when several capitula are 
 arranged on the main axis in the same way as the flowers of a raceme. 
 The same terms are applied to the first ramification of the compound in- 
 florescence as to the simple ones described above ; the above-mentioned 
 
 example, for 
 instance, is a 
 raceme of capi- 
 t u 1 a, and is 
 termed a capi- 
 tulate raceme. 
 Compound in- 
 florescences may 
 be classified as 
 follows : 
 
 (a) Homogene- 
 ously compound : 
 in these the 
 branches of the 
 first and second 
 (or higher) or- 
 ders are of the 
 same character. 
 
 (6) The compound spike 5 in this form many simple spikes are arranged 
 on the main axis of the inflorescence in the same way as the flowers in a 
 simple spike, or, in other words, the main axis of the spike bears secondary 
 spikes instead of single flowers, e.g. the inflorescence of "Wheat, Rye, 
 etc. 
 
 (7) The compound raceme] in this case smaller racemes grow on the 
 main axis of the raceme; the ramification is in many cases still further 
 repeated in such a way that it is more complex at the base of the primary 
 raceme than towards the apex, e.g. the Grape-vine (Fig. 259 B). 
 
 (8) The compound umbel (Fig 259 C). This is far more common than a 
 simple umbel, and is in fact usuallj' called an umbel ; the separate simple 
 umbels (Fig. 259 C d) are then called umbellitles, and their respective invol- 
 ucres are incolucels. 
 
 (/3) Heteroyeneotmly compound iu.iorescznces ; in these the branches of the 
 
 FIG. 269. Diagrams of the varieties of racemose inflorescences. 
 A Spike. B Compound raceme. C C impound umbel ; ti rays 
 of the umbel ; i involucre ; d secondary rays of the umbsllnles ; 
 i, involucel. D A capitulum ; i involucre ; b flower; p bracteoles.
 
 GROUP V. ANGIOSPERMJt;. 441 
 
 different orders are dissimilar. In consequence of this so many com- 
 plicated forms arise that it is impossible to enumerate and name all the 
 combinations. As examples, the following will o'nly be mentioned : the 
 capitulate raceme, which consists of a number of capitula arranged in a 
 raceme ; it occurs in many of the Composite, e.g. Petasites : the spicale 
 capitulum, which consists of several spikes forming a capitulum, as in 
 the Scirpoidese : the spicate raceme, whi^h occurs in many Grasses, in 
 which the last branches of a compound raceme are spikes. 
 
 B. C'ymose Inflorescences; the main axis produces one, two, or more 
 lateral branches rarely several at the same level below its apex, which 
 grow more vigorously than the main axis, and repeat the same type of 
 branching. 
 
 These inflorescences are also termed definite because the growth of each 
 axis is arrested, by the development of a terminal flower, before that of 
 the lateral branch or branches which it bears. The simplest kind of 
 definite inflorescence is that in which the axis (peduncle) does not branch 
 but bears a single terminal flower. 
 
 Cymose infloresences are also termed centrifugal, because the development 
 and expansion of the flowers begins with the primary axis, and occurs 
 successively in the axes of the second, third, and higher orders. 
 
 I. In the simple cyme the ramification in the secondary and higher 
 orders follows the same type. 
 
 (a) Without a pseud-axis. 
 
 The cyme : beneath the terminal flower spring several three or more 
 lateral shoots of equal vigour, e.g. many Euphorbias. This inflorescence 
 greatly resembles the true umbel, and in fact cannot be distinguished 
 from a true umbel which has a terminal flower. The identification of an 
 inflorescence as belonging to the cymose type depends in many cases on 
 the fact that in the higher orders of branching the cymes are reduced to 
 dichasia. 
 
 The dichasium (Figs. 10 and 11(7) consists of only two equal lateral 
 shoots arising at the same level below the terminal flower, and branching 
 in a similar manner. The successive false dichotomies commonly de- 
 cussate, e.g. Valerianella and the weaker inflorescences of many Euphor- 
 bias. 
 
 (j3) With a pseud-axis. 
 
 The scorpioid cyme (cincinnus and rhipidium): in this the lateral 
 branches occur alternately on opposite sides (Fig.ll A and B) : Boraginacese, 
 Crassulaceae, Iridaceae, Commelynaceae, etc. 
 
 The helicoid cyme (bostryx and drepanium) : the lateral branches of the 
 successive ramifications always occur on the same side (Fig. 11 Z>) : this is 
 frequently found in Monocotyledons, such as Hemerocallis, Ornithogalum, 
 Alstroemeria, Juncacese. 
 
 It has been ascertained, however, that in many cases (various Solanaceae 
 and Boragiiiacese) the so-called scorpioid cymes are monopodial : the axis 
 is therefore not a pseud-axis but a true one, and the inflorescence must be 
 regarded as a unilateral raceme. 
 
 II. Compound cymose inflorescences arise on the one hand from the reduc-
 
 442 PART IV. CLASSIFICATION. 
 
 tion of the ramification in the higher orders, as, for instance, when the 
 secondary members of a cyme are not cymes, but dichasia ; these are 
 dichasial cymes ; they occur in many Euphorbias : again, when dichasia 
 terminate in scorpioid or helicoid cymes. On the other hand it sometimes 
 occurs that helicoid cymes are combined to form scorpioid cymes, as in 
 Geranium. 
 
 C. Compound racemose and cymose inflorescences. It may occur that a 
 compound inflorescence changes in type in the different ordei-s of 
 ramification. Thus the branches of the first order may exhibit a race- 
 mose arrangement, and those of the second a cymose arrangement, as 
 in the dichasial racemes of many Euphorbias (e.g. E.Esula, amygdaloides], 
 in the scorpioid racemes of the Horse-Chestnut, and in the helicoid 
 capitula of many species of Allium. On the other hand the branches 
 of the first order may have a cymose, and those of the second a race- 
 mose arrangement ; for instance, the helicoid cymes of capitula in 
 Cichorium. 
 
 Finally, there are certain terms used in describing inflorescences which 
 refer only to the general external appearance rather than to the mode of 
 formation of the inflorescence : thus, the panicle is a pyramidal inflorescence 
 generally of the racemose type, at least in its first ramification : the 
 corymb is a racemose inflorescence of which all the ultimate ramifications 
 lie in one plane and bear flowers, e.g. the Elder, many Cruciferse : the 
 amentum (catkin) is a simple or compound spicate inflorescence, usually 
 pendulous and elongated, bearing inconspicuous unisexual flowers, 
 which falls off entire from the plant when the flowering is over. Of 
 cymose inflorescences there is the fascicle, consisting of a number of 
 flowers on pedicels of equal length (Sweet William); the glomerule 
 (Nettle and Box) or verticillaster (many Labiatse), consisting of a few 
 sessile or shortly pedicillate flowers ; and the anthela, which is a compound 
 inflorescence, in which the branches of the first order are gradually 
 shorter from below upwards (or rather from without inwards), as in 
 Juncaceae. 
 
 To a floral axis arising from the ground, with no leaves, or with only a 
 few bracts, bearing a single flower or a more or less complex inflorescence, 
 the term scape is applied. 
 
 The Bracts (p. 43) are leaves borne on the inflorescence, in the 
 axils of which the flowers are developed : there may be a single 
 large bract, termed a spathc, enclosing the whole inflorescence, as 
 in Palms and in the Arum Lily (Richardia cKtliiopica) where 
 the bract is white ; or the bracts may be brightly coloured (petaloid), 
 as in Poinsettia and other Euphorbiacese where they are red, and 
 in Leycesteria formosa, Melampyrum, etc. ; or the bracts may be 
 scaly, forming an involucre round the inflorescence as in the Com- 
 positae : the glumes of the Grasses are scaly bracts. The bracts are 
 frequently not very unlike the foliage-leaves, differing from them 
 mainly in form and size.
 
 GROUP V. ANGIOSPERM.E. 
 
 443 
 
 The portion of the floral axis below the flower (i.e. the peduncle 
 or the pedicel) commonly bears one or more bracteoles or prophylla . 
 In most Monocotyledons there is a single posterior prophyllum, 
 whilst in most Dicotyledons there are two lateral prophylla. 
 
 In some cases several bracteoles are arranged in a whorl, forming 
 an epicalyx, either close beneath the flower (as in Malva, Anemone 
 Hcpatica, Dipsacus, or at some distance below it (other species 
 of Anemone). In some plants (Nyctaginaceae) the epicalyx may 
 become an involucre enclosing several flowers ; this is due to the 
 fact that flowers are developed in the axils of some of the bracte- 
 oles of the terminal flower. Though they are generally green, the 
 bracteoles are sometimes brightly coloured, as in some Amarantacese 
 and Nyctaginacese ; or scaly, 
 as the lodicules of Grasses. 
 
 The Flower (p. 55) is a shoot 
 of limited growth, with un- 
 developed or but slightly de- 
 veloped internodes, bearing, as 
 a rule, both perianth-leaves 
 and sporophylls on the some- 
 what shortened and expanded 
 terminal portion of the axis 
 which is the receptacle or 
 torus. 
 
 The perianth -leaves are 
 generally differentiated into 
 two series : an outer, of usually 
 rather small green leaves, the 
 sepals, constituting the calyx : 
 an inner, of usually conspicuous 
 brightly coloured leaves, the 
 petals, constituting the corolla. 
 
 The flower is usually mono- 
 clinpus (hermaphrodite) ; but is 
 not infrequently unisexual, when it is diclinous, or even dioecious. 
 The sporangia, with but few exceptions, are borne upon sporo- 
 phylls (see p. 56) : the microsporophylls (stamens) constitute 
 the andrcecium, the macrosporophylls the yyna:ceum, of the 
 flower. 
 
 It occasionally happens, that one or more of the internodes 
 within the flower may be developed to some extent : for instance, 
 
 PIG. 260. Diagram of an angiospermous 
 flower: Ke calyx; K corolla ; / filament of 
 stamen; a anther with two pollen-sacs in each 
 half which are opened, showing the pollen- 
 grains (p). On the stigma (n) are pollen- 
 grains (p) which have germinated; the 
 pollen-tube (p) penetrates the style (g) as 
 far as the cavity of the ovary (F), reaching 
 the ovule (S) ; t the integument of the ovule ; 
 em the embryo-sac ; E the oosphere.
 
 444 
 
 PART IV. CLASSIFICATION. 
 
 the internode (termed anthophore) between the calyx and the corolla, 
 as in Lychnis and some other Caryophyllacese ; that (termed gono- 
 phorc) between the corolla and the androecium, as in the Passion- 
 Flower, and in Orchids where the styles adhere to it forming 
 the gynostemium or column ; that (termed gynophore) between 
 the andrcesium and the gynseceum, as in some Gentians and some 
 Cruciferse. 
 
 When the axis grows, as is usually the case, equally in all parts, 
 the gynseceum, being nearest to its apex, is the uppermost part of 
 the flower. When this is the case its insertion is above that of 
 the androecium and perianth (Fig. 261 fl), and the ovary is said to 
 be superior and the flower hypogynous, as in Ranunculus, Papaver, 
 Lilium, and Primula. But in a great number of plants the 
 perianth and androecium are raised by the intercalary growth of a 
 
 FIG. 261. Diagram of H hypogynous; P perigynous; E epigynous flowers; a axis 
 fc calyx ; c corolla ; sstamsns; /carpels; n stigma; sfc ovule. 
 
 lower portion of the axis (as represented by the outer portion of the 
 torus) and stand on a circular rim surrounding the apex of the 
 axis which lies at a lower level. Of this condition two different 
 forms occur : in the one, the carpels are inserted in the depression 
 at the apex of the axis (Fig. 261 P), and there form one or more 
 ovaries free from it, primarily at least, though they may sub- 
 sequently become adherent to it ; in such cases, as in the Rose and 
 Apple, the flower is said to be perigynous : in the other, the car- 
 pels spring from the upper rim of the cavity which is formed by 
 the axis itself and simply cover it in at the top ; such flowers are 
 said to be epigynous, and the ovary to be inferior, e.g. Gfourds and 
 Umbelliferae (Fig. 261 E). Many transitional forms between these 
 two extremes are found. 
 
 Stipules are sometimes developed in connexion with the floral
 
 GROUP V. ANGIOSPERMJE. 445 
 
 leaves ; thus in sDme Rosaceae (Poteatilla, Comarum, Geum, Al- 
 chemilla) the stipules of the sepals form a calyculus or epicalyx : 
 stipules are developed in connexion with the petals of some 
 Sapotacese (Dipholis, Mimusops) : and in connexion with the 
 stamens of Allium, Ornithogalum, some Zygophyllaceae, etc. 
 
 The Phyllotaxy of the Floicer. The floral leaves, like the 
 foliage-leaves on the stem (see p. 10), are frequently arranged 
 spirally, (e.g. Calycanthus, Anemone, Trollius) when the flower is 
 acyclic. The most common divergence is f, but higher divergences 
 also occur, especially in the androecium, when numerous small 
 organs are inserted upon an expanded axis (e.g. Ranunculus). In 
 the spiral or acyclic flower there is either no well-marked dis- 
 tinction of the various series, that is, the members of the calyx, 
 corolla, and androecium, are connected by intermediate forms (e.g. 
 Nymphsea) ; or the various series are sharply defined, each series 
 taking up one or more turns of the spiral. 
 
 In most cases the floral leaves are arranged in whorls, that is, 
 the flowers are cyclic. Cyclic flowers are connected by inter- 
 mediate forms with the acyclic, especially through pentamerous 
 forms. Thus some pentamerous flowers are hemicyclic, that is, 
 some of their floral leaves are arranged spirally, and the others in 
 whorls. Instances of a spiral perianth combined with cyclic 
 sporophylls are afforded by those flowers in which the members of 
 the perianth, calyx, or corolla are developed in f succession, and 
 the prefloration is quincuncial (see p. 43) ; the perianth is spiral 
 in the flowers of the Cannabinacese and Chenopodiacese ; the calyx 
 is spiral in the flowers of the Bindweed (Calystegia Septum), the 
 Rose, some Boraginacese (Cerinthe, Echium, etc.), Geraniacese, 
 Oxalidaceae, Linaceae, Caryophyllacese, and many other dicotyle- 
 donous orders ; both calyx and corolla are spiral in Camellia, 
 though the phyllotaxy is not -. In other cases, the sporophylls 
 are spirally arranged, whilst the perianth-leaves are cyclic. For 
 instance, in Magnolia, Ranunculus, and Helleborus, both stamens 
 and carpels are spirally arranged ; and in Delphinium and Acoui- 
 tum, the stamens only. 
 
 Closely related to the foregoing cases of phyllotaxy occurring 
 in fact not only in flowers of closely allied species, but also in 
 flowers of the same species are certain of the typical forms of 
 cyclic arrangement in which each series (whether perianth, calyx, 
 corolla, or androecium), instead of consisting of five floral leaves, 
 taking up two turns of a spiral with a divergence of -* , consists of
 
 446 PART IV. CLASSIFICATION. 
 
 four or six leaves arranged in two whorls, consisting respectively 
 of two or three leaves. 
 
 For purposes of comparative description, it is convenient to re- 
 gard each turn of the spiral in an acyclic or a hemic} 7 clic flower as 
 equivalent to a whorl : thus a well-defined series with f arrange- 
 ment would represent two whorls. 
 
 As in the case of the foliage-leaves (see p. 9), so in that of the 
 floral leaves, the order of development is as a rule acropetal : hence 
 each whorl of the flower is developed later than the one external 
 to it, and earlier than the one internal to it. When, however, a 
 series of floral organs is becoming degenerate, its development is 
 retarded ; for instance, in the Compositse, Valerianaceae, and Um- 
 belliferse, the degenerate calyx is developed after the corolla, or 
 even after the androecium. The members of each whorl may be 
 developed either simultaneously or successively. 
 
 In their arrangement, also, the floral leaves resemble the foliage- 
 leaves. When, in an acyclic or hemicyclic flower, the spiral is 
 continuous with the same divergence from one series of floral 
 organs to another, the members of the successive series lie on the 
 same radii drawn from the centre of the flower, that is, they are 
 directly superposed. A good example of this is afforded by the ter- 
 minal flower of the inflorescence of Berberis (Fig. 262 ; occasionally 
 in Epimedium, and also in Gagea among Monocotyledons), where the 
 stamens, petals, and sepals are all directly superposed. When, on 
 on the other hand, the divergence varies from one series to another, 
 direct superposition does not occur, but some form of alternation, 
 as is generally the case in acyclic flowers : for instance, the calyx 
 of certain (pentamerous) forms of Anemone and other Ramin- 
 culacese is arranged with a % divergence, whereas the divergence 
 of the stamens is y\ or T 8 T . In hemicyclic flowers with a simple 
 spiral perianth and cyclic stamens (e.g. Cannabinacese, Cheno- 
 podiacese), the stamens are superposed on the perianth-leaves. 
 
 When the floral leaves are in whorls consisting of equal numbers 
 of members, the general rule is that the members of the successive 
 whorls alternate with each other : thus, in a flower with calyx, 
 corolla, androecium, and gynaeceum, each consisting of a single 
 whorl of five members, the petals alternate with the sepals, the 
 stamens with the petals, and the carpels with the stamens ; and 
 if radii be drawn from the centre of the flower, it will be seen that 
 the stamens are opposite to the sepals and the carpels to the petals, 
 or more briefly, that the stamens are antiscpalous and the carpels
 
 GROUP V. ANGIOSPERM.E. 
 
 447 
 
 are antipetalous. This is not, however, a case of direct super- 
 position, since the corolla intervenes between the androecium and 
 the calyx, and the androecium intervenes between the gynseceum 
 and the corolla. 
 
 There are, however, certain cases in which this law of alter- 
 nation does not prevail, in which, that is, the members of 
 successive whorls are directly superposed. Tor instance, the (4-5) 
 stamens are directly antipetalous in several natural orders 
 (Primulacese, Plumbaginaceae, Ampelidaceae, Rhamnaceae) ; again, 
 in some Campanulacese (e.g. Campanula Medium, Fig. 263) the (5) 
 carpels are directly superposed on the stamens. 
 
 The Floral Diagram. These various arrangements of the floral 
 leaves, like those of the foliage-leaves, are most clearly represented 
 
 FIG. 262. Floral diagram (ground-plan) 
 of an acyclic flower, with \ divergence in 
 the calyx, corolla, and androeciam (ter- 
 minal flower of Berberis : after Eichler). 
 
 Fio. 263. Floral diagram of Cam- 
 panula Medium : the five carpels are 
 directly superposed on the stamens. 
 (After Eichler). 
 
 by means of diagrams (see p. 13). In & floral diagram, the calyx 
 lies externally, and the gynseceum, as being the uppermost series 
 of organs (even in epigyhous flowers) lies most internally. In order 
 to be able readily to distinguish the various series, symbols are 
 used which recall some peculiarity of their form : thus the mid-rib 
 of the sepals is indicated, and, in the case of the stamens, the 
 anthers. 
 
 If only such relations of position as can be actually observed in 
 a flower are indicated in the diagram, a simple empirical diagram 
 is the result. If, however, the results of the investigation of the 
 development of the flower and of the comparison of it with others 
 be borne in mind, a general plan of arrangement will be detected, 
 and the individual peculiarities of arrangement, quite apart from 
 any variation in the form of the organs, will be seen to be due 
 either to the suppression of one or more whorls or of one or more
 
 448 PART IV. CLASSIFICATION. 
 
 members of a whorl, or, more rarely, to a multiplication of the 
 whorls or of their members. If, however, the organs which are 
 absent, but which should typically be present, be indicated in the 
 empirical diagram by dots, it becomes a theoretical diagram. In 
 this way it is possible to arrive at general types on which large 
 numbers of flowers are constructed. Fig. 264, for instance, is the 
 empirical diagram of the flower of the Lily, and it is at the same 
 time the type on which the flower of Grasses (Fig. 265) is con- 
 structed in which certain members are suppressed. 
 
 lu constructing a floral diagram the position of the main axis 
 should be indicated by a dot placed above the diagram : the bract, 
 which would of course be exactly opposite to it, may or may not 
 be indicated : the side of the flower toward the main axis is said 
 to be posterior, and that toward the subtending bract, anterior. 
 A plane which passes through the flower and also through the 
 main stem and the median line of the bract is termed the 'median 
 
 FIG. 264. Floral Diagram Fra. 265. Floral Diagram FIG. 266. Floral Dia- 
 
 of a Lily. of a Grass. gram of a Crucifer ; the 
 
 median stamens are 
 duplicated. 
 
 plane or section of the flower : the plane which cuts the median 
 plane at right angles is the lateral plane or section : and the 
 plane which bisects the angles made by the intersection of the 
 median and lateral planes is the diagonal plane or section : any 
 plane other than these is said to be oblique. By means of these 
 conceptions the position of the parts of a flower may be accurately 
 indicated : thus, in describing the flower of the Cruciferse (Fig. 
 266), the two external sepals lie in the median plane ; the two 
 inner sepals, the two outer stamens, and the two carpels, in the 
 lateral plane ; whilst the petals and the four inner stamens lie in 
 the diagonal planes. 
 
 The number and the relations of the different parts of the flower 
 may be indicated not by diagrams only, but also by formulae in 
 which, as in the diagrams, for the sake of clearness, all the
 
 GROUP V. AXGIOSPERM.E. 449 
 
 peculiarities of form are overlooked. Thus the diagram Fig. 264 
 may be expressed by the formula KB, C\ A3 + 3, (?, which 
 means that the calyx jfiT, and the corolla C, each consist of a single 
 whorl of three members, the androecium of two whorls each of 
 three members, and the gynaeceum of one whorl of three members, 
 all in regular alternation. When one whorl is superposed on 
 another, the superposition is indicated in the formula by a line | 
 between the whorls. If the number of members in any whorl is 
 variable, the letter n is used instead of a number. Thus, for 
 instance, Kn, C*n, An + n, Go. is the theoretical formula' of most 
 Monocotyledons. The absence of a whorl is expressed by a cypher 
 0, and of individual members by the number of those actually 
 present. Thus the formula for the flower of a Grass (Fig. 2G5) is 
 AT), (70, A3 + 0, G l . Superior and inferior ovaries are indicated 
 by a stroke below or above the corresponding figure, and duplica- 
 tion by the exponent 2 ; thus the diagram Fig. 266 is represented 
 by the formula K2 + 2, C x 4, A2 + 2 2 , G, the x after C in- 
 dicating that the position of the petals is diagonal, i.e. that the 
 four petals alternate with the four sepals, as if the latter all 
 belonged to the same whorl. The bracket in which the number of 
 the carpels of the gynseceum G is enclosed, indicates that the 
 members thus bracketed are coherent. Staminodia may be dis- 
 tinguished by a -j- before the figure. When the perianth is not 
 differentiated into calyx and corolla, it is expressed by the letter 
 P: thus the formula for the flower of Chenopodium is P5 | A5 
 
 <T. 
 
 The Number of Members in a Whorl shows considerable varia- 
 tion : thus, in Monocotyledons it is generally three (rarely two or 
 five), whereas in Dicotyledons it is frequently five, less frequently 
 two or four, rarely three (e.g. Berberis, Rheum, Polygonum). The 
 number of members in a whorl is indicated by the terms di- tri- 
 tctra- penta-merous, etc. Whorls containing the same number 
 of members are said to be isomerous ; or, when the number of 
 members is not uniform, heteronierous. Flowers having isomerous 
 whorls are said to be encyclic or isocyclic, whereas when the 
 whorls are heteronierous the flowers are said to be heterocyclic. 
 Of these two conditions the latter is the more common, though the 
 former is frequently realized (e.g. many Monocotyledons). The 
 heterocyclic condition is due either to the number of members in 
 one or more of the whorls being smaller (oligomery) or greater 
 (pleiomery} than that which is the typical number. The com-
 
 450 PART IV. CLASSIFICATION. 
 
 moner cases of oligomery are to be found in the whorls of 
 sporophylls, especially in the gynseceum : for instance, the 
 typically pentamerous flower of the Saxifragaceas is heterocyclic 
 because of the oligomerous (dimerous) gynseceuin ; similarly, in the 
 Scrophulariacese, the androecium is generally, and the gynseceum is 
 always, oligomerous, the former consisting of but two or four 
 stamens, the latter of but two carpels. Pleiomery is of less 
 frequent occurrence : however in the Cruciferse (Fig. 266) the 
 whorls of the calyx, the outer whorl of stamens, and the 
 gynseceum, are dimerous, but the corolla and the inner whorl of 
 stamens are tetramerous and hence pleiomerous : similarly, one or 
 more whorls of the androBcium in the Papaveracese and Poly- 
 gonacese are pleiomerous : and probably in other cases where the 
 number of the stamens is twice that of the petals or sepals, that 
 is, where the flower is diplostemonous, the condition is due rather 
 to pleiomery (duplication) of a single whorl than to the develop- 
 ment of two whorls as is usually assumed (see below, under 
 pleiotaxy). Pleiomery of the corolla is common in double flowers. 
 
 Heterornery necessarily affects the alternation of the floral 
 leaves of the successive whorls. Thus, in the Cruciferse, where 
 the calyx consists of two alternating dimerous whorls, and the 
 corolla of a single tetramerous whorl, the four petals alternate 
 with the four sepals just as if the sepals all belonged to a single 
 whorl. When, as is very frequently the case, the gynseceum is 
 oligomerous, the carpels (or carpel) present do not appear to occupy 
 any definite position with regard to the preceding organs. 
 
 The Number of Whorls in the Flower. The simplest case is 
 that in which each series of floral organs calyx, corolla, androe- 
 cium, gynseceum occupies a single whorl, or is monocyclic : this 
 is realized in a few natural orders, either accompanied with 
 regular alternation (e.g. Caprifoliacese generally, Iridacese, Orchi- 
 dacese), or with antipetalous stamens (e.g. Rhamnacese, Ampeli- 
 dacese). In this case the flower is tctracyclic. 
 
 More commonly one or more of the series may occupy two 
 whorls, or be dicyclic. This is generally the case when the whorls 
 are dimerous (e.g. both corolla and androacium of Oleacese and 
 Fumariaceae ; corolla of Papaver ; calyx and androecium of Cruci- 
 ferse; perianth of Urtica and Morus). Where the whorls are 
 trimerous the dicyclic condition is frequent : thus in the majority 
 of Monocotyledons there are two whorls of stamens whilst all the 
 other series of the flower are monocyclic, so that the flower is
 
 GROUP V. ANGIOSPERMJE. 
 
 451 
 
 diplostemonous with regular alternation : in the comparatively 
 few trimerous flowers of Dicotyledons the dicyclic condition may 
 be observed in the androecium (Rheum, Polygonum, Berberis), or 
 in calyx, corolla, and androecium. The f- calyx, which is to be 
 found in very many Dicotyledons, may be regarded as equivalent 
 to a dicyclic calyx (see p. 446). A dicyclic gynseceum. is to be 
 found in a few Monocotyledons (e.g. Alisma, Butomus) and 
 Dicotyledons (e.g. Malvaceae such as Malva, Althaea, Lavatera). 
 
 The conclusion to be drawn from these facts is that in the com- 
 plete dichlamydeous monoclinous flowers of Angiosperms there 
 are, as a general rule, five whorls of floral leaves ; the flowers are 
 pcntacyclic. In most Monocotyledons the five whorls belong, one 
 to the calyx, one to the corolla, two to the androecium, and one to 
 the gynseceum : in most Dicotyledons they belong, two to the 
 calyx, one to the corolla, one to the androecium, and one to the 
 gynseceum. 
 
 If, now, such a pentacyclic flower with regularly alternating 
 whorls be taken as a type or standard of comparison, it will be 
 observed that many flowers deviate from it by having either a 
 larger or a smaller number of whorls, the deviation being combined 
 in some cases with direct superposition. 
 
 Pleiotaxy, or an increase in the number of the whorls in a 
 flower, is characteristic of 
 a number of genera be- 
 longing to various natural 
 orders. Instances have 
 been mentioned above of 
 Monocotyledons and of 
 Dicotyledons having flow- 
 ers with a dicyclic gynse- 
 ceum, and of Dicotyledons 
 with a dicyclic corolla or 
 androecium : but the num- 
 ber of whorls is some- 
 times much greater (15 
 in Aquilegia), when the 
 flowers, as also the special 
 series, are said to be poly- 
 cyclic. Thus, the calyx 
 is polycyclic in Nandina 
 (Berberidaceee) ; the androecium, in Aquilegia, Rosa, and Papaver- 
 
 Fie. 267. Floral diagram of Rota toriuntosa, 
 showing the polycyclic androecium and gynseceum. 
 (After Kichler.)
 
 452 PART IV. CLASSIFICATION*. 
 
 acese ; the gyna?ceum, in some Alismacese and Butomacese. In 
 some cases, one series becomes polycyclic at the expense of 
 another : thus in the acyclic flowers of Clematis, Anemone, and 
 Caltha, the petals are replaced by stamens so that the number of 
 turns of the spiral ^ = whorls) in the androecium is increased whilst 
 the corolla disappears. The " doubling" of flowers is commonly 
 due to the polycyclic development of the corolla, the additional 
 whorls being either new formations, or the result of the more or 
 less complete replacement of the sporophylls by petals. . 
 
 An important case is that to be found in several Dicotyledonous 
 orders ^Ericaceae, Crassulaceae, Saxifragaceae, some Caryophyllaceae, 
 Onagraceae Fig. 270, Geraniacese/ Oxalidaceae, Rutaceae Fig. 
 268) where the flower is diplostemonous, and the androecium is 
 apparently dicyclic : but the flower is not simply diplostemonous 
 v as in the Monocotyledons^, because the whorls do not alternate 
 regularly ; the stamens of the apparently 
 outer whorl are directly antipetalous, conse- 
 
 quently the stamens of the inner whorl are 
 antisepalous, and the carpels (in eucyclic 
 flowers^ are antipetalous. Such flowers are 
 said to be ot>diplostemonous. 
 
 Oligotaxy, or a decrease in the typical 
 number of whorls in a flower, is frequently 
 FIG. 268. Diagram of due to suppression. For instance, owing to 
 the suppression of one whorl of stamens in 
 some Monocotyledons, either the outer (some 
 Hfemadoraceae, also Cypripedium), or the inner (Iridaceae, most 
 Orchidacea?\ the androecium is monocyclic. In some cases a whole 
 series is suppressed : for instance the corolla may be absent 
 (e.g. Glaux, among the Primulacese ; Alchemilla, Sanguisorba, 
 among the Rosaceae : some Caryophyllaceae, such as Sagina 
 apetala, Scleranthus, etc.) : or the androscium or gyna?ceum 
 (diclinous or dioecious flowers, such as those of Sedum Rhodiola, 
 Rhamnus cathartica, Hydrocharidaceae, ray-florets of Compositse, 
 etc.) : or the whole perianth (Frajcinus excelsior}. 
 
 Although it is true that both oligotaxy and oligomery are 
 frequently due to sujjpression, in the one case of one or more 
 whorls, in the other of one or more members of a whorl, it must 
 not be assumed that this is the only possible explanation. On 
 the contrary, it is very probable that the simple structure of 
 the flower in some plants ( c.g. Urticales and Amentales among
 
 GROUP V. ANGIOSPERM.E. 
 
 453 
 
 Dicotyledons) is not the result of suppression, but is itself typical : 
 in other words, these flowers are probably to be regarded, not as 
 reduced, but as primitive, belonging to plailts which are, it may 
 be, of a relatively low type among Phanerogams, but which are on 
 the up-grade^ and not on the down-grade of organisation. 
 
 The Symmetry of the Flower. The flower presents all the 
 varieties of symmetry which are discussed in Part I. (p. 4) ; these 
 are mainly determined by the number and the relative develop- 
 ment of the floral leaves, and in a few cases by the development 
 of the floral axis or receptacle. 
 
 The symmetry may be radial or actinomorphic. When an 
 eucyclic flower is also regular, that is, when the members of each 
 whorl are similar to each other in size and form, it can be divided 
 into symmetrical halves 
 by sections made in two 
 or more planes, the halves 
 produced by section in one 
 plane being similar to 
 those produced by section 
 in one or more other 
 planes. Such a flower is 
 poly symmetrical (see p. 
 6). The number of these 
 planes of symmetry de- 
 pends upon the numerical 
 constitution of the flower. 
 Thus a regular eucyclic 
 trimerous flower (e.g. 
 many Monocotyledons) can 
 be so divided in three planes, the median and the two diagonals, 
 that all the three pairs of resulting halves are exactly alike (Fig. 
 269 B). Similarly, the pentamerous flower of Primula, Geranium, 
 species of Campanula, is divisible in five planes (Fig. 269 A}- 
 But where the flower is tetramerous (e.g. Fuchsia, Euonynni* 
 europceus), there are but two planes of section, the median and the 
 lateral, which will give exactly similar halves, though the flower 
 is also symmetrically but diversely divisible in the diagonal planes 
 (Fig. 270 A); or, again, where the flower is hexamerous (e.g. 
 species of SeduuVt it is symmetrically divisible in twelve planes, 
 but the halves produced by the section in six of the planes are 
 unlike those produced by section in the other six planes. 
 
 A B 
 
 FIG. 239. A Diagram of the pcntameroua flower 
 of Primula, showing the five planes of symmetry; 
 the stamens are antipetalons ; there are no pro- 
 phylla. B Diagram of the trimerons flower of 
 Lilium, showing the three planes of symmetry. 
 (After Eichler.)
 
 454 
 
 PART IV. CLASSIFICATION. 
 
 The symmetry may be isobilateral ; in this case the flower is 
 divisible into symmetrical halves in two planes, but the halves 
 produced by section in one plane are unlike those produced by 
 section in the other plane. Thus, a regular eucyclic dimerous 
 flower (e.g. Circcea lutetiana, Fig. 270 B ; Fraxinus dipctala\ 
 is symmetrically divisible in the median and lateral planes, but the 
 halves produced by the median section differ from those produced 
 ~by the lateral section. This is true also of some regular hetero- 
 cyclic flowers, such as those of the Cruciferas, Jasminum, Olea euro- 
 pcea, Cornus, Hamamelis, the whorls of which are 2- or 4-merous, 
 and of the somewhat peculiar flower of Dicentra. 
 
 The symmetry may be zygomorpMc, that is, the flower may be 
 monosymmetrical, there being only one plane in which it is sym- 
 metrically divisible. Monosymmetry is characteristic of irregular 
 
 flowers, whether eucyclic 
 or heterocyclic ; of flow- 
 ers, that is, in which the 
 members of one or more 
 whorls differ in various 
 respects among themselves, 
 accompanied frequently by 
 a reduction in the typical 
 number of members in one 
 or other of the whorls, fre- 
 quently of the androacium : 
 it is, in fact, to irregular 
 flowers that the term 
 zygomorphic is specially 
 
 applied in Descriptive Botany. Such a flower usually presents a 
 clear distinction into two diverse portions, an anterior and a 
 posterior, separated by the lateral plane, whilst the two lateral 
 halves about the median plane are symmetrical ; hence it is clearly 
 dorsiventral (Fig. 271). 
 
 Dorsiventrality is presented by some flowers which, so far as 
 their early development is concerned, or even so far as is shown by 
 their floral diagram, are actinomorphic, isobilateral, or simply zy- 
 gomorphic, the dorsiventrality being due to the subsequent irregu- 
 lar development of some of the floral leaves ; as in some eucyclic 
 flowers (e.g. among Monocotyledons, Amaryllis, Gladiolus ; among 
 Dicotyledons, Dictamnus, and other Rutese, species of Impatiens, 
 Pelargonium), and in some heterocyclic flowers (e.g. some Scrophu- 
 
 FIG. 270 X Diagram of the tetramerons flower 
 of Fuchsia, showing the four planes of symmetry. 
 B Diagram of the dimerous flower of Circsea, show- 
 ing isobilateral symmetry.
 
 GROUP V. AXGIOSPERM.E. 
 
 455 
 
 lariacese, Labiatse, some Caprifoliacese, Violacese, Echium, Lobelia, 
 Orchidaceae, the marginal flowers of the inflorescences in some 
 Umbelliferae and the ray-florets of some Compositae). The degree 
 of irregularity in these flowers varies widely; the irregularity 
 may be very slight, due to the more active growth of the 
 leaves (perianth-leaves only, or stamens also) of one half of the 
 flower, either the posterior (e.g. Gladiolus), or the anterior (e.g. 
 Amaryllis), which causes an upward or a downward curva- 
 ture; this is more marked in Dictamnus where the calyx and 
 corolla tend to form two lips, an upper and a lower ; this bilabiate 
 form of flower is more fully developed in the calyx and corolla 
 of the Labiatse, the corolla 
 (personate, the lips being 
 closed) of the Scrophulari- 
 acese, and of the Orchidacese 
 and Lobelia. In not a few 
 cases the irregularity of the 
 flower is increased by the 
 development of spurs from 
 some portion of the perianth 
 (e.g. among Monocotyledons, 
 Orchis, Rhinopetalum, from 
 the corolla ; among Dicotyle- 
 dons, Linaria, Viola, from the 
 corolla ; Pelargonium, from 
 the calyx). A remarkable 
 morphological feature is 
 offered by the flowers of 
 Orchis and of Lobelia which 
 are resupinate ; that is, in consequence of torsion of the pedicel, 
 the posterior side of the flower becomes anterior. The plane of 
 symmetry is generally median in these flowers. 
 
 In some few cases the irregularity, leading to dorsiventrality, 
 is due, not to the unequal development of the floral leaves, but 
 to the configuration of the floral receptacle, so that the floral 
 leaves are not developed in a radially symmetrical manner (e.y. 
 Reseda, Papilioneae, Fig. 272). 
 
 When in irregular flowers the single- plane of symmetry is the 
 median plane, the flower is dorsiventral : but there are other cases 
 (e.g. flowers of some Fumariaceae, Fumaria, Corydalis) in which 
 the single plane of symmetry is the lateral ; these flowers are 
 
 FIG. 271. Dorsiventral flower of a Heracleu 
 (mag.)
 
 45G 
 
 PART IV. CLASSIFICATION. 
 
 therefore not dorsiventral, that is, they have not an tero- posterior, 
 but lateral, asymmetry. The zygomorphic symmetry of a flower 
 is indicated in its floral formula by symbols ; when the plane of 
 symmetry coincides with the median plane the symbol ^ is used, 
 and when it coincides with the lateral plane the symbol ->. 
 
 Sometimes regular flowers are developed by plants which 
 usually produce irregular flowers : these exceptional flowers are 
 termed pcloria. This is due in some cases to the fact that the 
 primitive number and arrangement of the floral organs is not 
 disturbed by the irregular development of the parts which 
 usually takes place : such cases are distinguished as regular 
 peloria (e.g. Viola, Gloxinia, Labiatse, etc.). In other cases the 
 peloric flower is to some extent the result of the symmetrical 
 
 development of the irregularity 
 
 O o (e.g. the development of five 
 
 spurred petals and five sta- 
 mens in Linaria). Dorsiven- 
 tral flowers are, generally 
 speaking, such as are borne 
 laterally on the inflorescence ; 
 whilst the terminal flowers 
 (which may be regarded as 
 peloric) are frequently regular. 
 Peloric lateral flowers are, 
 however, known to occur. 
 
 There remain to be con- 
 sidered those flowers which 
 cannot be symmetrically di- 
 vided in any plane : such flowers are asymmetric. Amongst these 
 are to be included most of the acyclic or hemicyclic flowers in 
 which the number of members is high and the divergence vari- 
 able (e.g. Calycanthus, some Ranunculacese, etc.) : the asymmetry 
 of most of these is approximately, though not quite accurately, 
 actinomorphic, but in some it is dorsiventral (e.g. Delphinium, 
 (Fig. 273 A,) Aconitum). Asymmetry is rare in cyclic flowers, 
 but is to be found in some heterocyclic flowers : for instance, in 
 Tropseolum, (Fig. 273 5,) Canna and other Marantacese, Valeriana 
 and other Valerianacese, where the asymmetry is dorsiventral and 
 is due to oligomery and irregularity combined, whilst in other 
 cases (e.g. some Paronychiese), it is due merely to oligomery. 
 
 FIG. 272. Diagram illustrating dorsiventral 
 symmetry in leguminous flowers: A Vicia 
 Faba, (Papilionese) : B Cercis SiUquastrum 
 (Casalpinieae) : in both cases the odd sepal 
 is anterior : the plane of symmetry is median.
 
 GROUP V. AXGIOSPERM.E. 
 
 457 
 
 Tlie Floral Organs. 
 
 The Perianth is completely absent, that is, the flower is achlamy- 
 dcous, in a few families (e.g. Piperacese, Aracese, Graminaceae, many 
 Cyperacese, Salicacese). When present, it is usually differentiated 
 into calyx and corolla, the flower being termed dicldamydcous or 
 biscriate : when the calyx and corolla clearly differ from each 
 other in colour, texture, etc., the flower is said to be heterochlamy- 
 dcous for instance, when the calyx is green and the corolla highly 
 coloured (as in most* Dicotyledons, and in some Monocotyledons 
 such as Tradescantia and Commelyna) ; or when the calyx is col- 
 oured (petaloid) and the petals reduced to nectaries (as in Helleborus 
 and other Ranunculacese). When the perianth-leaves are all alike, 
 the flower is said to be homochlamydeous. This condition may be 
 due to different causes in different cases : the flower is sometimes 
 homochlamydeous, even though calyx and corolla are differentiated, 
 because the sepals and petals are very similar, as in most Monoco- 
 tyledons where the sepals are often petaloid : in other cases the 
 flower is homochlamydeous, because only one series of perianth- 
 leaves is developed ; that is, because the flower is monoclilamy- 
 dcous. The flower may be monochlamydeous, because, though 
 typically dichlamy- 
 deous, either the 
 calyx or the corolla 
 is suppressed (e.g. 
 calyx suppressed in 
 some Umbelliferse 
 and Composite ; co- 
 rolla suppressed in 
 most Thymelseacese, 
 Paronychiese, Glaux, 
 some Rosacese such 
 as Alchemilla and 
 Sanguisorba); where 
 the corolla is sup- 
 pressed or rudiment- 
 ary the calyx is 
 
 frequently petaloid (e.g. Clematis, Anemone, Caltha, and other 
 Ranunculacese) : or the flower may be monochlamydeous merely 
 because the perianth is undifferentiated (simple), and is then 
 generally sepaloid (e.g. Urticacese, Betulacese, Chenopodiacese, etc.), 
 or petaloid '(e.g. some Amarantaceae). 
 
 I. Floral diagrams illustrating asymmetry. 
 A Dorsiveutrally asymmetrical hemicyclic flower of Del- 
 phinium Ajaels : B Dorsiventrally asymmetrical heterocy- 
 clic flower of Tropoeolum majug : br subtending bract ; 
 p- t >, prophylla. (After Eichler.)
 
 458 
 
 PART IV. CLASSIFICATION. 
 
 The individual leaves of the perianth may be either perfectly 
 separate (eleutlieropeialous or polypetalous corolla, eleutherosepal- 
 ous or polysepalous calyx), e.g. Ranunculus ; or they may cohere 
 from the base upwards, so as to form a longer or shorter tube, 
 which divides at its upper end into as many teeth or lobes as there 
 were originally leaves (gamosepalous calyx, gamopetalous corolla) 
 (Fig. 274 A B C c and B k) ; e.g. the Primrose and the Tobacco 
 plant. In Dianthus (the Pink) the sepals alone are coherent, as 
 also in Daphne (Fig. 274 Z>) where the corolla is absent. More 
 rarely all the leaves of the perianth cohere to form one tube, e.g. 
 the Hyacinth and allied genera ; the six lobes of the tube corre- 
 spond to the three 
 sepals and the three 
 petals. The simple 
 perianth also may con- 
 sist of separate leaves 
 (eteutlieropliyllous or 
 polypliyllous peri- 
 anth^, e.g. Amarantus, 
 or the leaves may be 
 
 k 
 
 
 coherent (gamophyl- 
 lous\ e.g. Aristolo- 
 chia. 
 
 D 
 
 FIG. 274. Cohesion of sepals and petals. A Flower of 
 Convolvulus arvensis, with a funnel-shaped corolla (c) ; and 
 a 5-partite calyx (k). B Nicotian* Tabacum, with a 5-cleft 
 calyx (it) ; tubular corolla (r), with a distinct 5-toothed 
 limb (). C The rotate corolla of Sambucns. D Gamose- 
 palous calyx of Daphne Mezereum ; r the tube ; s the limb. 
 
 The degree of division 
 presented by gamophyl- 
 lous perianths into 
 teeth or lobes is indi- 
 cated by the same terms 
 which are used in de- 
 scribing the incision of 
 the leaf-blade (page 37). 
 The form of the gamo- 
 petalous corolla may be 
 
 campanulale, as in the Campanula ; funnel-shaped (or infundibuliform), as 
 in the Bindweed (Fig. 274 A) ; rotate, as in the Elder (Fig. 274 C). The 
 upper and lower portions may frequently be distinguished, the lower as 
 the tube (Fig. 274 B r), the upper expanded part as tlie limb (Fig. 274 B s). 
 Other peculiarities of form are connected with the symmetry of the flower 
 (page 453). 
 
 The petal frequently consists of two parts, the daw and the 
 limb, as in the Pink (Fig. 275 A B). The Corona (paracorolla) 
 in the Narcissus and Lychnis is formed by ligular outgrowths
 
 GROUP V. ANGIOSPERM^:. 459 
 
 from the claws (Fig. 275 B l\ Any segmentation of the petal, as 
 in the Pink (Fig. 275 A) is unusual ; emarginate or obcordate 
 petals are more common. In many cases the petals have spur- 
 shaped appendages (Violet, p. 455), or they are prolonged at the 
 base into tubes, as in Helleborus and Aconitum. This peculiarity 
 is connected with the secretion of the nectar 
 
 The Reproductive Organs of the Flower are sporangia of two 
 kinds, microsporangia and macrosporangia, borne usually on 
 sporophylls, though sometimes directly on the floral axis. The 
 flower is usually monoclinous ( $ , hermaphrodite, see p. 395) ; but 
 it is not infrequently unisexual, in which case the flowers are 
 either microsporangia te ( , staminalj or macrosporangiate ( ? , car- 
 pellary). The plants which have unisexual flowers may be either 
 
 P , 
 
 FIG. 275. A Petal of Dianthus superbus, with (n) the claw and (p) the limb, much divided. 
 B Petal of Lychnis : n claw ; p limb ; I ligula. C Flower of Potentilla, seen from below : 
 c corolla; fc calyx ; a epicalyx. 
 
 moncecious (e.g. Zostera, Arum, Carex, Typhaceae, Zea, Betnlaceae, 
 Euphorbia, Buxus, Juglans, Quercus, etc.) : or dioecious (e.g. some 
 Palms, Vallisneria, Cannabinacese, Salicacese, Mercurialis, Yiscum, 
 etc.) : or polygamous. Of polygamy there are several varieties : 
 thus, the plant may bear monoclinous flowers and staminate 
 flowers (e.g. Veratrum, ^Esculus Hippocastanum, Celtis) ; or mo- 
 noclinous flowers and carpellary flowers (e.g. Thymus vulgar is and 
 T. Serpyllum, Parietaria dijfusa and P. officinalis) : or it bears 
 monoclinous flowers and both staminate and carpellary flowers (e.g. 
 Fraxinus excelsior, Saponaria ocymoidcs}. 
 
 Some flowers are probably primarily unisexual ; that is, there 
 is no reason to believe that the unisexual condition is due to 
 the suppression of either micro- or macrosporangia (e.g. Hemp, 
 Oak, Walnut, Poplar, Willow). Others are secondarily unisexual : 
 that is, there is reason to believe, either from their development
 
 460 PART IV. CLASSIFICATION. 
 
 and structure, or from their relation to allied hermaphrodite forms, 
 that they are typically monoclinous, but have become unisex- 
 ual by suppression : thus, in the Cucurbitacese some genera (e g. 
 Cucurbita, Cucumis, Bryonia, etc.) have unisexual flowers, whilst 
 in others the flowers are always hermaphrodite ; similarly, in the 
 Caryophyllacese, the flowers are generally hermaphrodite, but in 
 the species Lychnis vespcrtina and L. diurna they are unisexual. 
 In some unisexual flowers traces of the missing organs are to be 
 found, such as staminodes in carpellary flowers (e.g. Feuillea 
 among the Cucurbitacese ; Laurus nobilis), or rudimentary pistils 
 in staminate flowers (e.g. Rhamnus cathartica, Lychnis vespcrtina 
 and diurna). 
 
 It sometimes happens that typically dioecious plants become 
 exceptionally monoecious (e.g. development of ? flowers on ^ 
 plants of Cannabis sativa ; or of ^ flowers on ? plants of 
 Cannabis sativa and Mercurialis annua) : or that a typically 
 monoecious diclinous plant bears some monoclinous flowers (e.g. 
 Ricinus). 
 
 The Andrcecium comprises the microsporophylls (one or more) 
 of the flower, the stamens. Each stamen usually consists of two 
 parts ; a slender stalk called the filament (Fig. 276 s), and a 
 placental portion which bears the pollen-sacs (Fig. 276 D p,) known 
 as the anther (Fig. 276 a). The anther consists of two longi- 
 tudinal halves, termed thecce, each of which usually contains two 
 pollen-sacs ; these two halves are united by the placental portion 
 of the filament which is known as the connective (Fig. 276 c). 
 This is occasionally very narrow, so that the two halves of the 
 anther lie close together (Fig. 276 A l a): in this case it may be 
 that the anther is not sharply marked off from the filament, and 
 is attached throughout its whole length to the filament (aclnatc, 
 Fig. 277 C) : when the anther is sharply marked off from the 
 filament, it may be attached to the filament by its base, when it is 
 said to be innate or basifixcd (e.g. Tulip) ; or the filament is in- 
 serted in the middle of its dorsal surface, when it is dors (fixed 
 (Fig. 277 A) ; in the last case it may be articulated as by a joint, 
 so that the anther with the connective can oscillate on the apex 
 of the filament (versatile anther, Fig. 276 C), as in Grasses aucl 
 some other plants. But the connective is often broader, so that 
 the two halves of the anther are widely separated (Fig. 276 B) : 
 it may be much elongated (distractile) and very delicate, so that 
 with the filament it forms a T-shaped body (Fig. 276 C) ; in this
 
 GROUP V. AXGIOSPERM.E. 
 
 461 
 
 plant, the Sage, the further peculiarity is exhibited that one- 
 half of the anther is abortive and is modified for another purpose. 
 It is only rarely, as in Herb Paris (Fig. 277 (7), that the con- 
 nective is prolonged beyond the anther into a point, or into a 
 bristle as in the Oleander. 
 
 FIG. 276. Stamen : .4, Of Lilium : s fila- 
 ment ; a the dorsiflxed anther. A., Side 
 view. B Of Tilia : c connective. C Of 
 Salvia, with dorsifixed versatile anther: 
 b is the half of the anther that has been 
 modified. J) Transverse section of the 
 anther of Hypericnm (mag.) : p the 4 
 pollen-sacs ; c connective. 
 
 FIG. 277. A Stamen of Allium. H 
 Of Faccinium Xyrtillus. C Of Part* 
 quadrifolia (mag.) : / filament; c 
 connective ; o anther; b appen- 
 dages ; p the pores by which the 
 anther opens. 
 
 The filament is usually round and stalk-like, of a delicate 
 coloured or colourless tissue, with a central vascular bundle ; it is 
 occasionally flattened ; when it is very short or absent the anthers 
 are sessile. 
 
 In some plants, e.g. Allium (Fig. 277 .4), the filament has 
 what appear to be stipular appendages ; in others, e.g. Erica (Fig. 
 277 B\ the anther is furnished with appendages, such as spurs 
 and so forth : in Viola, the spurs borne by the two anterior sta- 
 mens are glandular. In certain plants the stamens, that is to 
 say the filaments, branch ; either, like most leaves in a plane 
 perpendicular to the median plane, as in Myrtaceae and Fu- 
 mariaceae, or in various planes, as in Ricinus (Fig. 278) and 
 Hypericacese ; an anther is borne on each of the branches of the 
 filament. 
 
 Somewhat similar in appearance, but essentially different in 
 structure are the coherent stamens of the Papilionese and other
 
 PAET IV. CLASSIFICATION. 
 
 plants. The stamens of each flower may be coherent into one or 
 more bundles. The arrangement becomes complicated when the 
 filaments are at the same time coherent and branched as in the 
 Malvaceae. When the filaments are all coherent into a single 
 bundle (e.g. Malvacese), they are said to be monaddphous ; when 
 in two bundles (e.g. some Papilionese, Fumariacese), they are 
 diadelphous ; when in several bundles (e.g. Hypericacese), they are 
 polyadelphous. In the Compositse (e.g. Sunflower and Thistle), 
 though the filaments are free, the anthers become coherent or 
 syngenesious. When the stamens are quite free from each other 
 they are said to be polyandrous. 
 
 Besides these varieties of cohe- 
 sion, adhesion frequently occurs ; 
 that is the filaments adhere to 
 other portions of the flower, par- 
 ticularly of the perianth, so that 
 they or when they are very 
 short, the anthers appear to be 
 inserted not upon the axis of the 
 flower, but upon the leaves of the 
 perianth (epipetolout or epiphyl- 
 lous) : this condition is most fre- 
 quently present when the petals 
 themselves are connate and form 
 a tubular corolla, e.g. Primula. 
 The adhesion of the stamens to 
 the carpels is of rarer occurrence 
 (e.g. Orchidacese, Aristolochia) ; 
 the flower is then termed gynan- 
 drous. 
 
 In many flowers it happens that certain filaments, occupying a 
 definite position with regard to the other parts of the flower, are 
 longer than ths others ; thus, of the six stamens of the Cruciferse 
 (e.g. Wallflower), four are much longer than the other two ; of the 
 four stamens of the Labiatae, (e.g. Lamium), two are longer than 
 the other two. In the former case the stamens are said to be te- 
 tntdynamous, in the latter didynamous. 
 
 Stamens which bear no anthers are termed stanii nodes : they 
 are frequently petaloid (e.g. Canna). In many acyclic flowers 
 (e.g. Nymphsea), the stamens and the petals are connected by 
 intermediate structures, of which it is difficult to say whether 
 
 FIG. 278. Part of a staminal flower of 
 Ricinus communis cut through length- 
 ways : / / the basal portions of the 
 compoundly-branched stamens ; o the 
 anthers. (After Sachs.)
 
 GROUP V. ANGIOSPERM^E. 
 
 463 
 
 they are to be regarded as petaloid stamens or as staminoid 
 petals. 
 
 The Microsporangia or Pollen-Sacs are borne on the anther. 
 There are commonly four of them (quadrilocular anther), two 
 forming a sorus in each longitudinal half (or theca) of the anther, 
 situated usually side by side, but sometimes (Lauracese) one above 
 the other ; in the former case the typical arrangement seems to be 
 that of each pair of pollen-sacs one belongs to the anterior or inner 
 surface of the anther, the other to the posterior or outer surface. 
 
 In some cases, however, there are but two pollen-sacs (bilocular 
 anther) ; this may be due to the non-development of one longi- 
 tudinal half of the anther (e.g. Cucurbitacese, Salvia, Canna) ; or 
 to branching (e.g. Adoxa, Malvaceae) ; or to the abortion of one 
 pollen-sac, generally 
 
 the posterior one, of ff 
 
 each pair (e.g. As- 
 clepiadaceae) ; or 
 (some Lauracese) of 
 the upper or lower 
 one of each pair ; or, 
 finally, to the early 
 fusion of the arche- 
 sporia of two adja- 
 cent pollen-sacs 
 (some Orchidacese). 
 In the Aracese the 
 process of fusion is 
 carried to such an 
 extent that all four archesporia fuss, so that the anther is uni- 
 locular. 
 
 Each pollen-sac encloses an archesporium from which the 
 mother-cells of the microspores (pollen-grains) are developed by 
 division ; each group of spore-mother-cells is invested by a layer of 
 granular cells, the tapetum (Fig. 279 f), which eventually becomes 
 disorganised : externally to this is the wall of the pollen-sac con- 
 sisting of one or more layers of cells with usually reticulately 
 thickened walls, followed by the epidermis at the surface. 
 
 The pollen-sacs dehisce usually by a longitudinal slit which, 
 when the anther is quadrilocular, is generally so situated that it 
 at once opens into both the pollen-sacs of each half of the anther, 
 and frequently the tissue separating each pair of pollen-sacs be- 
 
 FIG. 279. Transverse section of a yonng anther of Sam- 
 lucus racemosa ( x 80) : c the connective with the vascular 
 bundle ; ps the four pollen-sacs (microsporangiaj ; p the 
 mother-cells of the pollen; t tapetal layer; tc the wall of 
 the pollen-sac.
 
 464 PART IV. CLASSIFICATION. 
 
 comes dried up and ruptured whilst the anther is ripening : some- 
 times the dehiscence of the pollen-sac is transverse (Alchemilla) ; 
 sometimes it is valvular (Berberidacese) ; or by apical pores 
 (Ericaceae, Polygalacese). Though in a quadrilocular anther the 
 pollen-sacs typically belong, two to the inner (ventral), two to the 
 outer (dorsal), surface of the anther, it frequently happens that in 
 the course of their development they become somewhat displaced, 
 so as to appear all to belong to either the inner or the outer sur- 
 face ; hence, when dehiscence takes place, the pollen is shed, in the 
 former case, towards the centre of the flower, when the anthers are 
 said to be introrse ; and, in the latter case, towards the periphery 
 of the flower, when the anthers are said to be extrorse. These 
 terms are similarly applicable in the case of bilocular anthers. 
 Introrse anthers are the more common ; extrorse anthers occur in 
 the Aristolochiacese, Iridacese, Juncaginese, Aracese, and in various 
 genera of other orders. In rare cases some of the anthers of the 
 flower are introrse, and others extrorse, as in some species of 
 Polygonum (P. Bistorta, tataricum, aviculare, etc.), where the 
 anthers of the outer whorl are introrse, and those of the inner 
 whorl extrorse ; and as in most Lauracese, where the anthers of the 
 innermost staminal whorl are extrorse, whilst those of the outer 
 whorls are introrse. 
 
 The Microspores or Pollen- grains. The essential features in the 
 structure and development of the microspores have been already 
 fully described (see pp. 85 and 396). 
 
 The shapes of the pollen-grain are very various : it may be 
 spherical, oval, triangular, etc., or 
 long and cylindrical (confervoid) 
 as in the Naiadacese. 
 
 On germination the pollen- 
 grain gives rise to one or more 
 pollen-tubes, which consist of 
 outgrowths of the intine : these 
 penetrate the exine (when pre- 
 FIG. 2so. Germinating pollen-grain of sent), either rupturing it irregu- 
 
 Epilobium (highly mag.) bearing a , , j , . . , 
 
 pollen-tubes;* exine ;,' intine ; a b c the larl J> Or at determinate points 
 
 three spots where the exine is thicker in where the exine is thinner and 
 
 Malvaceae), or where there are 
 lid-like areas which are easily removed (e.g. Cucurbitacese, 
 Fig. 235). These points are definite in number (1, 2, 3, 4, or 
 more), sometimes very numerous (Malvaceae).
 
 GROUP V. ANGIOSPERM^E. 
 
 405 
 
 The Gyna>ceum or Pistil is always the terminal structure of 
 the flower, occupying the apex of the floral axis. It consists of the 
 macrosporophylls or carpels, which, in the Angiosperms fprm the 
 whole or part of the ovaries, that is, closed cavities containing the 
 ovules. If in a flower where there are several carpels, each of 
 them closes by the cohesion of its margins, they form so many 
 ovaries ; the gynseceum is then said to be apocarpous (Fig. 281 .4), 
 e.g. Ranunculus, Pseonia, and Butomus : if there is only one carpel 
 (Fig. 281 J3), the pistil is said to be apocarpous and simple : if 
 several carpels in one flower cohere and form a single ovary (Fig. 281 
 (7), the gynseceum is said to be syncarpous, e.g. Poppy and Lily. 
 Intermediate forms occur in that the carpels may cohere by their 
 lower ends whilst their upper ends remain free (Fig. 281 D). 
 
 The ovary is said to be monomerous when it is formed of only 
 
 FIG. 281. 4 Apocarpous gynseceum of Aconite. B Simple apocarpous gynseceum of 
 Melilotus. C Tetramerous syncarpons gynsecenm of B/iamnm cathartica. D Ovary of 
 Saxifraga, formed of two carpels which diverge towards the top: t tonu ; /ovaries; 
 g style ; n stigma ; b ventral suture. 
 
 one carpel (Figs. 281 B and 282 A), the margins of which cohere 
 on the side opposite to the midrib. The outer side along which the 
 midrib runs is the dorsal surface (Fig. 282 A r), and the midrib itself 
 is the dorsal suture; opposite to it is the line of cohesion, the 
 ventral suture, which runs therefore along the ventral surface. The 
 cavity thus enclosed (loculus) is not usually divided by dissepi- 
 ments, but it is a simple cavity, as in the Vetch ; such an ovary is 
 said to be unilocular. False or spurious dissepiments, formed by 
 growths on the inner surface, occur in some few instances, as in 
 Astragalus. 
 
 When, on the other hand, several carpels cohere to form a syn- 
 carpous ovary, it is polymerous (di- tri- or tetra-merous, etc). The 
 .syncarpous ovary is unilocular (Fig. 282 B) when the individual 
 
 M.B. H H
 
 466 PART IV. CLASSIFICATION. 
 
 carpels cohere simply by their edges without any portion of them 
 projecting inwards ; but if the margins project into the cavity 
 so as to form incomplete longitudinal dissepiments, the ovary is 
 chambered (Fig. 282 C), e.g. Poppy ; but since the chambers are 
 open towards the centre, the ovary is still unilocular. When the 
 margins form dissepiments which meet in the middle, the ovary is 
 multilocular (Pig. 282 D) ; sometimes the margins turn outwards 
 again towards the circumference. In the last case the individual 
 loculi are completely separated ; but there are others in which the 
 margins of the carpels do not extend so far towards the centre at 
 the upper part as at the lower, but the two margins of each carpel 
 simply cohere together above ; consequently the lower part of the 
 ovary is polymerous and multilocular, while the upper part is 
 composed of a number of monomerous ovaries, e.g. Saxifraga (Fig. 
 281 D). In all these cases the floral axis may grow up into the 
 
 FIG. 282. Transverse section of ovaries ; p placenta. A Monomerous and unilocular ; 
 ) dorsal suture : b ventral suture ; placentation marginal. B Polymerous and unilocu- 
 lar ; placentation parietal. C Pol.vmerous and many-chambered, but unilocular ; pla- 
 centation parietal. D Polymerous and multilocular ; placentation axile. 
 
 interior of the cavity of the ovary, and when the ovary is multi- 
 locular the axis may coalesce with the dissepiments. 
 
 False dissepiments may be formed in polymerous ovaries by in- 
 growths from the internal surface of the carpels ; thus the ,ovar} r 
 of the Boraginaceae and Labiatae is originally bilocular, but each 
 loculus becomes divided into two by a false dissepiment, and when 
 the fruit is ripe the four loculi separate completely ; similarly, the 
 unilocular ovary of the Cruci ferae becomes spuriously bilocular. 
 
 The inferior oYary of epigynous flowers (see p. 444) is com- 
 monly polymerous, but it may be either unilocular or multilocular. 
 
 In some bases the axis is prolonged between the carpels, con- 
 stituting a carpophore, as in the Geraniacese and Umbelliferse 
 (Fig. 287). 
 
 The Style (Figs. 281 and 283) is the prolongation of the upper 
 part of the carpel : it is commonly a slender cylinder, but some-
 
 GROUP V. ANGIOSPERMJE. 
 
 467 
 
 times it is leafy and petaloid (e.g. Iris). Monomerous ovaries have 
 but one style ; polymsrous ovaries have as many styles as there are 
 carpels, which may cohere throughout their whole length, or at 
 their lower parts only, the uppsr parts remaining distinct ; or they 
 may remain quite free, and they may even branch. The style 
 originally arises from the apex of the ovary, but it is frequently 
 displaced forwards, by the vigorous development of the dorsal 
 portion of the carpel, on to the inner side, so as to appear to be a 
 prolongation of the floral axis (gynobasic style) : this is conspicuous 
 in the Boraginacese and Labiatse, where it is surrounded by the 
 four rounded loculi of the ovary which have been already men- 
 tioned (p. 466). The style is sometimes very short, 
 and appears only as a constriction between the 
 ovary and the stigma, as in the Poppy. In some 
 rare cases it is hollow, but it is usually filled 
 with a loose tissue, called conducting tissue, 
 through which the pollen-tube can easily pene- 
 trate. 
 
 The Stigma (Figs. 281 and 283 n) is usually 
 terminal, but it may be lateral (e.g. Iris) ; it is 
 distinguished by being covered with papillae, or 
 frequently with hairs, and by the secretion of a 
 sugary fluid which retains the pollen-grains which 
 fall upon it, and which promotes the development 
 of the pollen-tubes. The stigma is often evidently 
 distinct from the style, appearing as a lobed ex- 
 pansion ; in other cases it seems to be merely a 
 portion of the style at its end or sometimes on 
 its side. In the Poppy it is a sessile disk-shaped 
 expansion on the upper surface of the ovary ; more rarely it is 
 represented by bands of papillae on the ovary itself, when it is said 
 to be pleurogynous. 
 
 The number of the stigmata often affords a means of ascertaining 
 whether the ovary is monomerous or polymerous ; for instance, the 
 ovary of the Compositse seems, at first sight, to be monomerous ; 
 but the two short branches of the style, each bearing a stigma, 
 show that it is dimerous. On the other hand, this character may 
 be misleading : for instance, in various Grasses the ovary bears 
 two or three stigmata, either directly, or springing from the style ; 
 hence it might be inferred that the ovary is di- or tri-merous, whilst 
 as a matter of fact it is monomerous. In this respect some few 
 
 Fio. 283. Gj" 
 naeceum of the 
 Lily : / ovary ; g 
 
 style; * stigma 
 (nat. size).
 
 468 PART IV. CLASSIFICATION. 
 
 other plants, belonging to the Naiadacese and other families, re- 
 semble the Grasses. 
 
 The Macrosporangia or Ovules are always enclosed in the cavity 
 of the ovary, either singly or in larger or smaller number. Usually 
 they may be readily seen to be developed on the carpels (Fig. 284 
 A, B, C), but in many cases they appear to be developed from the 
 floral axis (Fig. 284 Z), F, G). However, from careful comparative 
 examination, it seems that the apparently axial ovules may be re- 
 garded in some cases as having been developed on the carpels, their 
 position on the axis being merely the result of a more or less con- 
 siderable subsequent displacement due to the coalescence of the 
 carpels with the axis. That portion of the ovary which bears the 
 ovules is called the placenta. 
 
 The ovules, when borne by^ the carpels, are but rarely developed 
 over the whole surface of the carpel, but are confined to the margin : 
 in other words the placentation is rarely superficial but generally 
 marginal. Superficial . placentation (Fig. 284 (7) is to be found in 
 Butomus, Nymphsea, and Nuphar, the dorsal sutiTre (midrib) of the 
 carpel being the only sterile portion of its internal surface. Of mar- 
 ginal placentation there are two varieties : in the one the ovary is 
 syncarpous but unilocular, and the contiguous placental margins of 
 the carpels constitute so many placentas on the wall of the ovary, 
 that is, the placentation is parietal (Fig. 282 S, (7), as in the 
 Violacese, Cruciferse, Papaveracese, Ribesiese, Orchidacese, etc. ; in 
 the other the ovary is syncarpous and multilocular, the margins of 
 the carpels meeting in the centre and there bearing the ovules, so 
 that each placenta is at the inner angle of each loculus, that is, the 
 placentation is axile or axillary (Fig. 282 Z>, and Fig. 284 B) : in 
 a monomerous ovary (Fig. 282 A, and Fig. 284 A) the placentation 
 is essentially parietal, but it is simply termed marginal. 
 
 The position of attachment is a point of descriptive importance, 
 more especially where the number of ovules is small, or where there 
 is but one, in the loculus. When the ovule is attached to the roof 
 so that it down hangs into the loculus, it is said to be pendulous ; 
 when it is attached high up, but at the side, it is suspended 
 (Fig. 284 E) ; when it is attached to the side and projects straight, 
 it is horizontal ; when it is attached at the side, but towards the 
 base and stands up into the loculus, it is ascending. 
 
 When the ovules are borne, either actually or apparently, by the 
 axis, the placentation is said to be axial. When many ovules are 
 borne on the axial placenta (as in the Primulacese, Santalacese, etc.,
 
 GROUP V. ANGIOSPERM.E. 
 
 469 
 
 Fig. 284 <?), the placentation is termed free central. When there 
 is but a single ovule in the loculus, the placentation is basilar or 
 basal, and the ovule is erect : in this case the ovule is borne either 
 terminally at the apex of the floral axis (e.g. Polygonum, Piper, 
 Xaias, Tig. 284 F) ; or laterally, below or behind the actual apex 
 (e.g. Composites, Fig. 284 D). 
 
 FIG. 231. Diagram* of the different mode* of Placentation. A Monomeroug ovary of 
 Helieborns, opened along the ventral suture ; t the ovules on (q) the marginal placenta. 
 B Transverse section of the ovary of Nicotiana : / wall of the ovary ; q placenta, largely 
 developed by the union of the margins of the carpels (axile placentation). C Transverse 
 section of the ovary of Bntomus. The ovules are scattered over the whole of the inner 
 surface, except the midrib, m (superficial placentation). D Longitudinal section of an 
 ovary of one of the Compositae : / the wall ; the erect, anatropous ovule () grows from the 
 base by the side of the apex of the axis, a. Longitudinal section of the ovary of one of 
 the Umbelliferae ; in each chamber an anatropous ovule is suspended. F Longitudinal 
 section of Bheutn ; a single erect orthotropous ovule grows at the apex of the floral axis. 
 G Longitudinal section of the ovary of one of the PrimulacesB; the ovules grow on a 
 prolongation of the axis (free central placentation). Fig. 282 B represents parietal 
 placentation. 
 
 For other descriptive terms relating to the ovule, refer back to 
 p. 398. 
 
 The macrosporangium, or ovule, consists primitively of a mass of 
 cellular tissue, the nucellus, invested by one or two integuments, 
 with a micropyle at the apex (see p. 398) : generally speaking, two 
 integuments are present in the Monocotyledons, in most polypetal- 
 ous Dicotyledons (with exceptions such as some Umbelliferse and 
 Ranunculacese), and in the Cucurbitacese among Gamopetalse ;
 
 470 PART IV. CLASSIFICATION. 
 
 whereas there is only one integument in the Gamopetalse (except 
 Cucurbitacese) and in the polypetalous orders, Umbelliferae and 
 Ranunculacese. In some few cases (e.g. Santalaceae, Loranthacese), 
 where the development of the ovule is degraded in correlation with 
 the parasitic habit of the plants, the ovule has no integument. 
 
 The Macrospore or Embryo-sac. The structure and development 
 of the macrospore are described on p. 400. 
 
 Accessory Organs of the Flower. The most common of these is 
 the Nectary^ a glandular organ secreting odorous or sweet liquid, 
 and thus attracting insects. The nectary is sometimes borne on 
 some other organ which is not thereby materially modified (e.g. 
 petals of Ranunculus, stamen of Viola) ; or on a specially modified 
 perianth-leaf (e.g. petals of some Ranunculaceae, as Helleborus, 
 Eranthis, Delphinium), or on staminodes (e.g. a whorl in Parnassia) : 
 in some cases it is borne on the carpels, in the septa of a multi- 
 locular ovary (septal glands of many Monocotyledons, Liliacese, 
 Amaryllidaceae, and Iridacese). Generally the nectary is borne on 
 the floral axis, when it is described by the general term disc : in 
 the Cruciferse there is generally a whorl of four nectaries at the 
 insertion of the stamens ; or the disc may be developed as a ring 
 of tissue round the base of the ovary (e.g. Rutacese, Rhamnacese, 
 Celastracese) ; or on the upper surface of the inferior ovary (e.g. 
 Umbelliferse). 
 
 The position of the axial nectaries or discs is various : in some 
 flowers it is extra-staminal, and then it is situated either between 
 the androecium and the corolla (e.g. Capparidacese, Sapindace?e, 
 Resedacese), or less commonly, between the corolla and the calyx 
 (e.g. some Apocynacese, such as Nerium) : in others it is intta- 
 staminal, that is, between the androecium and the gynseceum (as 
 in Rutacese, Rhamnacese, Celastracese, etc.). Again, the disc is 
 generally hypogynous, but sometimes epigynous (Umbelliferse). 
 
 Generally speaking, when the nectaries, of whatever kind, are 
 towards the outside of the flower, the anthers are extrorse (e.g. 
 Ranunculaceae) ; and when towards the centre of the flower, the 
 anthers are introrse. 
 
 The General Histology of the sporophyte is sufficiently treated 
 of in Part II., and in the general account of the Phanerogams 
 (p. 400). 
 
 The Embryogeny of the sporophyte is considered on p. 401. 
 
 The Gametophyte is considered on p. 405. 
 
 Fertilisation. After reaching the stigma (see p. 409) the pollen-
 
 GROUP V. AXGIOSPERMJ5. 
 
 471 
 
 grains protrude the pollen-tubes which penetrate through the tissue 
 of the style into the cavity of the ovary, and through the micropyle 
 of each ovule to its nucellus (Fig. 285 P ri). The time required by 
 the pollen-tube for this process depends partly on the distance 
 of the pollen-grain from the ovule and partly on the specific 
 peculiarities of the plant ; thus the pollen-tube of the Crocus takes 
 only from one to three days to traverse the style, which is from 
 five to ten centimetres in length ; but in the Orchids, where the 
 length of the style varies from two to three millimetres, several 
 days, weeks, or even months are needed, and it is during this 
 process that the ovules are formed in the ovary. 
 
 The Results of Fertili- 
 sation. The Seed is de- 
 scribed on p. 414. 
 
 The Fruit. In view of 
 the variety in the struc- 
 ture and morphology of 
 the fruit of Angiosperms, 
 a somewhat detailed ac- 
 count of it is necessary. 
 
 The word fruit, in its 
 strictest sense, means the 
 whole product of the de- 
 velopment of the gynae- 
 ceum as a result of fertili- 
 sation (p. 61). If other 
 parts of the flower take part 
 in the formation of the 
 organ which is formed in 
 
 consequence of fertilisation, and which contains the seed (of what, in 
 short, is commonly called the fruit), it is termed a spurious fruit 
 or pseudocarp. The apple, for instance, is such a spurious fruit, 
 for the outer fleshy part belongs to that part of the axis of the 
 perigynous flower which surrounds the ovaries and which still 
 bears the sepals (Fig. '2 A}. What are called the pips of the 
 apple are the seeds. This kind of spurious fruit is termed a 
 pome. The strawberry also is a spurious fruit : in it the recep- 
 tacle, which belongs of course to the axis, developes largely and 
 becomes fleshy and bears the true fruits (achenes) in the form 
 of small hard grains. The fig is another example of a spurious 
 fruit ; it "is, in fact, a fleshy receptacle (i.e. an axis) which bears 
 
 FIG. 235. Diagram of an ovule shortly after 
 fertilisation ; a outer, and t inner integuments ; j 
 f unicle : k nucellns. S Embryo-sac in which is 
 the embryo developed from the fertilised oosphere. 
 The sac also contains the endosperm-cells which ura 
 ?>eing formed by free cell-formation. P The pollen- 
 tut*, passing through the micropyle, n.
 
 472 PART IV. CLASSIFICATION. 
 
 a multitude of distinct flowers situated inside the cavity of 
 the receptacle, and the individual fruits appear as hard grains ; 
 such a fruit is termed a syconus. Again when the ovaries and 
 floral envelopes of closely crowded flowers, as in the Mulberry 
 and the Pine-Apple, become succulent, a kind of spurious fruit is 
 formed which is termed a sorosis. 
 
 Iii other cases, a husk, called the cupule, is formed, which con- 
 tributes to the formation of a spurious fruit : this is formed by the 
 bracteoles and is not developed until after fertilisation ; it may 
 surround either a solitary distinct fruit, like the acorn-cup, or 
 several distinct fruits, like the four-valved spiky husk of the 
 Beech-tree or the prickly husk of the edible Chestnut. 
 
 W hen the fruit consists of one or more monomerous ovaries, it 
 is said to be apocarpous : examples of this occur in Kanunculus, in 
 the Raspberry, where the individual ovaries 
 are succulent, and in the Star-Anise (Fig. 
 286). The individual fruits may be de- 
 veloped in very different ways ; they may 
 be dehiscent or indehiscent, dry or succu- 
 
 r H f lent - 
 
 & When the fruit consists of a single polv- 
 
 FiG.286. FrnitoflZKcium ... .1,1 
 
 onisatum -. st peduncle ; // merous ovary, it is said to be syncarpouft. 
 the separate fruits, each When the carpels of such a fruit separate 
 septicidally during the process of ripening, 
 so that it ultimately appears as if a number 
 of distinct fruits were present, it is termed a scMzocarp : it may 
 thus split into only two distinct fruits, as in the Umbelliferae (Fig. 
 287) ; or, as in the Geraniacese and many Malvacese, into several 
 distinct fruits : each of them is termed a coccus or mericarp ; the 
 individual coccus is generally indehiscent (dehiscent in most Eu- 
 phorbiacese). 
 
 In various multilocular ovaries only one loculus becomes fully 
 developed and bears seeds, as in Valerian, the Coco-Nut, and the 
 Oak ; the others are abortive. It sometimes happens in cultivated 
 plants that the fruit becomes perfectly formed without any develop- 
 ment of seed, as in a particular seedless variety of Grape, the 
 Banana, the Pine-Apple, etc. 
 
 In all true fruits the wall of the ovary forms the pericarp or 
 rind. In some more or less succulent fruits, the pericarp consists 
 of three distinct layers ; the external layer is the epicarp, the 
 -middle the mesocarp, and the innermost the endocarp.
 
 GROUP V. ANGIOSPERM/E. 
 
 473 
 
 The following varieties of true fruits have been distinguished by the 
 character of the pericarp, whether it is dry or succulent, hard or soft. 
 and by the dehiscence or indehiscence of the pericarp. 
 
 A. DRY FRUITS. The pericarp is woody or coriaceous ; when ripe, the 
 sap has usually disappeared from all the cells. 
 
 I. Dry Jndehiscent Fruits. The pericarp does not rupture, but encloses 
 the seed until germination; the testa is usually thin, and frequently coa- 
 lescent with the pericarp. 
 
 (1) One-seeded fruits : 
 
 (a) The nut (glans), e.g. Acorn, Hazel-Nut (but not the Walnut) ; the 
 dry pericarp is hard and sclerenchymatous : it is inferior and 
 syncarpous. 
 
 (b) The aakene is superior and monome- 
 rous : the pericarp is thin and cori- 
 aceous ; e.g. the Rose and the But- 
 tercup. The similar fruit of the 
 Compos itse is a cypsela 5 it is in- 
 ferior and dimerous. 
 
 The fruit of Grasses, termed a 
 caryopsis, is very similar to the 
 achene; it differs from it in that 
 the testa and the pericarp closely 
 adhere, whereas in the achene they 
 are not adherent. 
 
 (2) Many-sseled fruits: these (schizocarpn) 
 commonly split into one-seeded fruits, which 
 usually enclose the solitary seeds until germin- 
 ation: e.g. the Umbelliferse (Fig. 287) and Maple, 
 with two, the Euphorbiacese with three, meri- 
 carps ; the Geraniacese, with five mericarps ; 
 and most Malvaceae, where the fruit is termed 
 a carcerule, and splits into many mericarps. 
 
 The pericarp of dry indehiscent fruits is 
 sometimes developed into a membranous wing 
 (e.g. Ash, Elm, Birch) ; to such a fruit the term 
 samara is applied : the fruit of the Maple is a 
 double samara. 
 
 II. Dry Dehiscent Fruit*. The pericarp rup- 
 tures and allows the seeds, which usually have a firm and thick testa, to 
 escape: they are commonly many-seeded. 
 
 (1) Dehiscence longitudinal. 
 
 (a) The follicle, consisting of a single carpel which dehisces along 
 
 the ventral suture, where also the seeds are borne, e.g. Pseonia 
 and Illicium (Fig. 288) ; but sometimes (e.g. Magnolia) along 
 the dorsal suture : it is superior. 
 
 (b) The legume or pod likewise consists of but one carpel which 
 
 dehisces along buth the dorsal and ventral sutures (Fig. 288 A, 
 "transverse section Fig. 282 A) : e.g. the Vetch, Pea, Bean, and 
 
 FIG. 287.-C<zrum Carut. 
 one of the Umbellifersp. A 
 Ovary of the flower (/). 
 B Ripe schizocarp which 
 has divided into two cocci 
 or mericarps (m), a portion 
 of the median wall (a) forms 
 the carpophore.
 
 474 PART IV. CLASSIFICATION. 
 
 many other Leguminosse ; in some cases (Astragalus) a spuri- 
 ous dissepiment occurs : it is superior. 
 
 The lomentum is a modification of the legume ; it is constric- 
 ted between the seeds, and it is either indehiscent or it 
 breaks across, when ripe, at the constricted parts. It occurs 
 in the Hedysarese. 
 (c) The siliqua consists of two coherent carpels. The two carpels 
 
 FIG. 288. Dry dehiscent fruits. A The pod (legume) of the Pea : r the dorsal suture ; 6 
 the ventral ; c calyx; * seeds. B Septicidal capsule of Colchicum autumnale : ///the three 
 separating carpels. C Siliqua of Brassica ; fc the valves ; w the dissepiment and placentae 
 (replum) ; s seeds ; g style ; n stigma. D Capsule, opening by pores, of Papaver somniferum, 
 the Poppy ; n stigma; j the pores which open by the removal of the valves (<i). i'P.yxidium 
 of Hyoscyamus; d the lid; ic the dissepiment; g seeds. 
 
 when ripe separate from the base upwards into two valves, 
 leaving their margins (with the parietal placentae and the 
 spurious dissepiment) attached, as a frame or replum, to the 
 apex of the pedicel ; e.g. Eape, Mustard, and most of the 
 Cruciferse (Fig. 288 C) : it is superior. 
 
 When the siliqua is short and broad, it is termed a sillcitla, 
 as in Thlaspi and Capsella. In some cases, as in the .Radish, 
 the siliqua is jointed and indehiscent, breaking transversely
 
 GROUP V. AXGIOSPERM.E. 
 
 475 
 
 into one-seeded portions. It resembles the lomenturn, and is 
 therefore said to be lonientaceous. . 
 
 (d) The capsule is derived from a polymerous syncarpous ovary 
 which may be uni- or multilocular ; it splits into two or more 
 valves, either for a short distance only from the apex down- 
 wards, or down to the very base (Fig. 288 B). If the carpels 
 become separated from each other, and in the case of multi- 
 locular ovaries this involves the splitting of the dissepiments 
 (Fig. 289 A), the dehiscence is said to be tsepticidal ; if, on the 
 other hand, each carpel splits along its dorsal suture, the 
 dehiscence is said to be loculicirlal (Fig. 289 B). In eithe 
 form of dehiscence in a multilocular ovary the placentae may 
 either adhere to the valves (Fig. 289 B), or remain united into 
 a central column which is free from the valves ; in the latter 
 case the dehiscence is further described as being septifragal 
 (Fig. 289 O. 
 
 The capsule is 
 usually superior, 
 but sometimes, as 
 in Iridaceae and 
 Campanulacese, it 
 is inferior ; a spe- 
 cial term, diplotegi- 
 um, is applied to the 
 inferior capsule by 
 some authors. 
 
 (2) The form of capsule known 
 as a pyxidium has a transverse 
 dehiscence, e.g. in Plantago, 
 Anagallis, Hyoscyamus (Fig. 
 288 E) ; the upper part falls off 
 like a lid. 
 
 (3) The porous capsule, e.g. the 
 
 Poppy (Fig. 288 D), sheds its seeds through small holes arising from the 
 removal of small portions of the wall in certain spots. 
 
 B. SUCCULENT FBUITS. In these the pericarp is usually differentiated 
 into layers, and some portion of it retains its sap until it is ripe, and 
 usually becomes fleshy at that stage ; it is indehiscent. 
 
 (1) The drupe (Fig. 290) is superior and monomerous, e.g. the Plum, 
 Cherry ; or syncarpous, e.g. the Walnut and Coco-Nut. The most internal 
 layer, the endocarp, is very hard and sclerenchymatous (Fig. 290 e ; it is 
 commonly known as the stone in Plums, Peaches, etc., and encloses the 
 seed until germination: the mesocarp is generally succulent, and the 
 epicarp is a delicate membrane : when the fruit consists of several drupes, 
 they are commonly termed drupels (e.g. Raspberry). 
 
 (2) The berry (bacca): the endocarp is soft and juicy as well as the meso- 
 carp, so that the seeds are imbedded in the pericarp : there may be one 
 seed only, as in the Date ; or many, as in the Gourd, Currant and Grape . 
 
 FIG. 239. Diagrammatic sections of dehiassnt 
 multilocular capsules. A Septicidal, B loculi- 
 cidal, dehiscence; C loculicidal septifragal 
 dehiscence.
 
 476 
 
 PART IV. CLASSIFICATION". 
 
 the fruit may have one loculus, as in the Grape and the Gourd, or several 
 loculi, as in the Orange ; and further, it may be superior, as in the Grape, 
 Orange, and Lemon ; or inferior, as in the Currant, the Gooseberry, and 
 the Gourd ; it is, as a rule, developed from a syncarpous ovary, but a mo- 
 nomerous berry occurs in Actaea (Ranunculacese). 
 
 When the fruit is apocarpous and consists of many achenes, 
 drupels, or follicles, it is termed an etcerio ; for instance, the fruit 
 of the Buttercup, the Rose, and the Strawberry is an etaerio of 
 achenes ; that of the Raspberry and the Blackberry is an etserio 
 of drupels; that of the Tulip-Tree and 
 of the Magnolia is an etserio of follicles. 
 
 The Angiosperms are subdivided as 
 follows : 
 
 Class IX. MONOCOTYLEDONES : the 
 embryo has usually a single terminal 
 cotyledon, and the growing-point of the 
 primary stem is developed laterally : the 
 vascular bundles of the stem are closed : 
 the leaves commonly have parallel ve- 
 nation ; the flower belongs usually to 
 the pentacyclic trimerous type. 
 
 Class X. DICOTYLEDON ES : the em- 
 bryo has usually two opposite cotyledons, 
 and the growing-point of the primary 
 stem is developed terminally : the vas- 
 cular bundles of the stem are usually 
 
 open : the leaves commonly have reticulate venation: the structure 
 of the flower varies, but it frequently belongs to the pentacyclic 
 pentamerous type. 
 
 FIG. 290. Longitudin; 
 tion of the drupe of the Almond : 
 the seed attached by the fun- 
 icle(/); the hard endocarp ; 
 in the mesocarp; and x the 
 epicarp these constitute the 
 pericarp (p). 
 
 CLASS IX. MONO-GOT YLEDOXES. 
 
 Although the seed frequently contains endosperm, it contains 
 none in certain orders ; namely, the Orchidacese, most aquatic 
 Monocotyledons (Alismales, Hydrocharidacese), and in some genera 
 of Aracese. In the Scitaminese perisperm is always present in the 
 seed, either together with endosperm (Zingiberacese), or without 
 endosperm (Musacese, Marantacese). In the albuminous seeds, the 
 embryo is usually small in proportion to the endosperm (Fig. 
 291 I, e, c) 
 
 Whilst the single cotyledon of the embryo is, as a rule, terminal,
 
 GROUP V. AXGIOSPERM.K : MONOCOTYLEDONES. 
 
 477 
 
 and the growing point 
 of the stem lateral, in 
 some forms the grow- 
 ing-point of the stem 
 is terminal (apical) on 
 the longitudinal axis of 
 the embryo (e.g. Dios- 
 coreacese). The grow- 
 ing-point of the prim- 
 ary stem frequently 
 developes into a plum- 
 ule. The axis of the 
 embryo terminates pos- 
 teriorly in a short 
 radicle. 
 
 On germination, the 
 tipper end of the co- 
 tyledon commonly re- 
 mains in the seed and 
 absorbs the nutritious 
 substances deposited in 
 the endosperm (Fig. 
 291 II.-IV.} ; the lower 
 part of the cotyledon 
 elongates and pushes 
 the rest of the embryo 
 out of the seed. In 
 Grasses the cotyledon 
 has a peculiar shield- 
 like form, and is termed 
 the scutellum (Fig. 292 
 sc) : in the ripe seed it 
 almost entirely encloses 
 the embryo, and is in 
 contact by its outer 
 surface with the endo- 
 sperm ; during germin- 
 ation the cotyledon 
 absorbs the nutritious 
 matters contained in 
 the endosperm, while the stem with the other leaves grows out 
 
 FIG. 291. Germination of PTweiiu dactylifera, the 
 Date. I. Transverse section of the dormant seed. II, III, 
 IV, Different stages of (Termination (IF. the natural 
 sire). A Transverse section of the seed at x x in IF. 
 B Transverse section of the seedling at x y : C at * i. 
 e The horny endosperm ; s the sheath of the cotyledon ; 
 *< ita stalk; cits apex developed into on organ of ab- 
 sorption which gradually consumes the endosperm and 
 at length occupies its place; w the primary root; w' 
 secondary roots ; b' I" the leaves which succeed the 
 cotyledon ; (b") becomes the first foliage-leaf, in B and C 
 its folded lamina is seen cut across. (After Sachs.)
 
 478 
 
 PART IV. CLASSIFICATION*. 
 
 of the seed. In other Monocotyledons either the cotyledon is a 
 sheathing scale, or it is the first green leaf differing but little 
 from the foliage-leaves which are subsequently developed. 
 
 The primary root usually remains small and inconspicuous : in 
 Grasses generally, the radicle begins to branch before it escapes 
 through the micropyle on germination, so that the root is then 
 fibrous ; when this is the case the inadequate root-system is sup- 
 
 FIB. 292. Grain of Triticum vulgnre, the V/heat. A Cross-section thronghthe pericarp 
 and testa. Of tbese, ep is the epidermis, e the enter layers, and cM the chlorophyll. 
 layer, of the pericarp : ti remnants of the ovular integument, and n the outermost 
 thickened layer of the nucellus; these together constitute the testa: ol the alenron- 
 layer of the endosperm (x 210). JB Median longitudinal section through the lower 
 part of a ripe grain, in the plane of the furrow. At the bottom of this to the left ia 
 the embryo: the scutellum, ic ; I' the ligule of the scutellum ; rs its vascular bundle; ce 
 its layer of cylindrical epithelium: c the sheath of the plumule (coleoptile); pv the grow- 
 ing-point of the stem; hj> the hypocotyl ; I thecpiblast; r the radicle; cp the root-cap of 
 the radicle ; el the root-sheath (coleorhiza) ; m phice of exit of the radicle, corresponding 
 with the micropyle of the ovule ; p the funicle ; vp vascular bundle in the funisle : / 
 lateral surface of the furrow (x 11). (After Strasburger.) 
 
 plemented by the development of adventitious roots in succession 
 at higher and higher levels upon the stem. 
 
 The stem of Monocotyledons is traversed longitudinally (Fig. 
 99, p. 122) by scattered closed vascular bundles (Fig. 103) , it has 
 therefore no growth in thickness by the means of cambium. In 
 a few genera only, as Yucca and Dracaena, it grows subsequently
 
 GROUP V. ANGIOSPERALE : MONOCOTYLEDONES. 
 
 479 
 
 in thickness by the formation of meristem in the pericycle from 
 which additional closed vascular bundles are developed (see p. 148, 
 
 rig. in). 
 
 The axis of the embryo in many cases continues to be the main 
 axis of the plant ; at first it is thin and weak, and since no 
 secondary growth in thickness of the stem takes place, and since 
 the successive portions of the stem are thicker and more vigorous, 
 the whole stem gradually assumes the appearance of an inverted 
 cone ; but when the plant 
 has reached a certain height 
 it may then grow cylindric- 
 ally : this is the reason why 
 in Palms, in the Maize, and 
 other similar erect stems, 
 there is a diminution in 
 thickness at the lower end. 
 Frequently, however, the 
 primary axis of the plant 
 perishes when it has given 
 rise to lateral shoots. 
 
 The arrangement of the 
 leaves is at first alternate : 
 when the stem is well de- 
 
 veloped this alternate ar- 
 rangement often passes over 
 into complex spiral arrange- 
 ments, as in Fritillaria and 
 in Palms, in which plants a 
 crown of leaves is conspicu- 
 ous. In the Grasses, and a 
 few other families, the phyl- 
 
 Fio. 293. Longitudinal section of thegrain 
 of Zea Mais ( x about 6) : c pericarp ; n re- 
 mains of tbe stigma : / base of the erain ; eg 
 hard yellowish part of the endosperm ; tie 
 whiter less dense part of the endosperm ; c 
 scutellum of the embryo; an its apex; its 
 epidermis ; fc plumule ; w (below) the primary 
 root; ITS the coleorhiza: w (above) secondary 
 roots springing from the epicotyl (st). (After 
 Sachs.) 
 
 lotaxis is permanently alter- 
 nate. A whorled arrangement of the foliage-leaves occurs but rarely. 
 The leaves commonly have a well-developed sheathing leaf-base : 
 they may be described as exstipulate. The lamina is usually 
 entire, simple in outline, often long and narrow, linear or ensiform, 
 more rarely orbicular, cordate or sagittate. Branched leaves occur 
 only in a few of the Aracese : the pinnate or palmate leaves of the 
 Palms acquire this form by the splitting of the originally entire 
 laminae, and the same is the case with the perforated leaves of 
 many Aracese (see p. 37).
 
 480 PART IV. CLASSIFICATION. 
 
 The venation of the leaves is characterized by the fact that the 
 weaker veins do not usually project on the under surface. In 
 linear leaves, and in such as are inserted by a broad base, the 
 stronger veins run almost parallel ; in broader ones, e.g. Lily of 
 the Valley (Convattaria majalis\ they describe a curve which is 
 more or less parallel to the margin ; the weaker veins usually run 
 at right angles between the stronger ones. In the Scitamine* 
 and a few other plants, a number of parallel transverse veins are 
 given off at various angles (sometimes acute, and sometimes nearly 
 right angles") from the midrib. Reticulate venation of the leaves 
 is unusual ; but it occurs in Aroids, in Paris quadrifolia, etc. (see 
 p. 39). 
 
 The flower of Monocotyledons consists typically of five alternat- 
 ing and isomerous whorls, two belonging to the perianth, two to 
 the androecium and one to the gynaeceum. Thus the typical 
 formula is En, Cn, An + n, Gn, where n in most cases 3, more 
 rarely = 2, 4 or 5. 
 
 The perianth-leaves are generally all much alike, and petaloid 
 in both series : sometimes they are all sepaloid (e.g. Juncaceae) : 
 more rarely those of the external whorl are sepaloid, those of the 
 internal petaloid (e.g. Alismacese). 
 
 This type is most closely adhered to in the Liliaceae. The 
 simplest departure from it is exhibited in the suppression of the 
 inner whorl of stamens in the Iridaceae, and in the inferior position 
 of the ovary. This latter character occurs also in the Scitamineae 
 and Orchidaceae, which are further characterized by the zygomor- 
 phism of their flowers and the considerable reduction of the 
 androecium. Other various and considerable deviations by reduc- 
 tion from the Liliaceous type of flower occur among the Aracese, 
 and in the Glumales, and Typhacese, and in certain water-plants 
 (e.g. Naiadaceae, Lemnacese). On the other hand, the deviation 
 may be due to increase in number, more especially of the members 
 of the gynaeceum and to some extent of the androecium (e.g. 
 Alismaceae).
 
 GROUP V. AXGIOSPERiLE : MOXOCOTYLEDOXES. 
 
 481 
 
 I
 
 482 PART IV. CLASSIFICATION. 
 
 SUB-CLASS I. SPADICIFLORvE. 
 
 Inflorescence usually a spadix with a spathe, but flower some- 
 times solitary : flowers frequently unisexual, sometimes dioecious : 
 perianth, often wanting, never petaloid : anthers usually extrorse, 
 or dehiscing by pores : ovary superior. 
 
 Cohort I. Arales. The flowers are small and numerous ; the 
 inflorescence a spadix or a panicle with thick branches, commonly 
 enclosed in a greatly developed spathe ; the bracts of the indi- 
 vidual flowers are frequently wanting ; perianth 0, or polyphyl- 
 lous ; the flowers are usually diclinous, but both kinds of flowers 
 frequently occur in the same inflorescence : gynseceum apocarpous 
 or syncarpous : the seeds have a large endosperm : the embryo is 
 straight and minute. 
 
 Order 1. ARACE^E. Flowers monoecious or $ : perianth or 
 of 46 leaves : stamens 18, frequently coherent into a synandrium 
 in the <$ flowers : ovary inonomerous, or polymerous and multilo- 
 cular : fruit a berry : seed sometimes exal- 
 buminous. Mostly tropical. 
 
 In many of the genera the flowers are com- 
 plete and conform to the monocotyledonous 
 type, A"n, Cn, An + n G ( n ), where n may stand 
 for 2, or 3, as in Acorus (Fig. 294), in which 
 the flowers are exactly typical. In other 
 S enera > h wever, the flowers are reduced in 
 a outer, i inner peri- various ways and degrees ; not only does the 
 3ns ' * perianth disappear, but the number of the 
 stamens and carpels is frequently diminished. 
 In many ? flowers staminodia are present, either in the typical or 
 in a smaller number. An extreme case is offered by those diclinous 
 flowers of which the <$ consists of only a single stamen (e.g. 
 Arisarum), and the ? of only one monomerous ovary. These 
 much-reduced flowers are disposed in regular order on the spadix : 
 thus in Arum (Fig. 295) the numerous $ flowers, consisting each 
 of one carpel (Fig. 295 /), are inserted on the base of the spadix ; 
 and the flowers, each consisting merely of 3-4 stamens, are 
 closely packed higher up on it (Fig. 295 a). The upper part of the 
 spadix is covered with rudimentary flowers (b, c). When, as in 
 this case, the perianth of the true flowers is wholly wanting, the 
 whole inflorescence may assume the aspect of a single flower ; but
 
 GROUP V. ANGIOSPERM.E : MOXOCOTYLEDDXES. 
 
 483 
 
 irrespectively of the numerous intermediate forms which are to be 
 found, such a view is untenable when it is barne in mind that here 
 the ovaries are invariably situated below 
 the stamens, while in a flower they are 
 invariably above them. 
 
 The usually sympodial stem may be un- 
 derground, a tuber, or a rhizome, or it may 
 be aerial ; in the latter case it often climbs, 
 clinging to trees by means of aerial roots. 
 The leaves are either alternate and dis- 
 tichous or, more often, spiral with a diver- 
 gence of f . They are rarely narrow, linear, 
 or ensiform, and commonly consist of leaf- 
 base, petiole, and blade ; the venation is 
 reticulate, and the leaf often exhibits a 
 more or less complicated segmentation. 
 Laticiferous sacs or cells (see p. 99) occur 
 in some families of the order, as do also 
 sclerotic cells (see Fig. 98 A, p. 120). 
 
 The principal families are : 
 
 FIG. 295.-Spadixof ,4 runt 
 maculatum (nat. size) : / 
 macrosporangiate, a micro- 
 sporangiate, and b rudi- 
 mentary flowers ; c the up- 
 per club-shaped end of the 
 spadix. 
 
 Fam. 1. Pothoidece : without either laticiferous 
 or sclerotic cells : flowers usually $ , with or 
 without a perianth. This family includes a 
 
 number of genera, such as Pothos, Anthurium, Acorus. The only member 
 which occurs in Britain is Acorus Calamus, the Sweet Flag, which grows 
 on the margins of ponds and rivers : its subterranean rhizome bears long 
 ensiform alternate leaves, crimped at the edges ; its flowering-shoot is 
 triquetrous, bearing a terminal spadix which is, however, displaced to one 
 side by the spathe which developes so as to form a continuation of the 
 long axis of the flowering-shoot : the spadix is densely covered with 
 flowers (Fig. 294). 
 
 Fam. 2. Caltoidece: with straight rows of laticiferous cells: fli>\v.-r> 
 usually $ , with or without a perianth : leaves never sagittate. No 
 member is indigenous in Britain : Calla palustris occurs in the marshes of 
 Northern Europe; it has a white spathe and parallel- veined leaves. 
 
 Fam. 3. Philodendroidece : with straight rows of laticiferous cells: 
 flowers diclinous, without a perianth : stamens usually connate : leaves 
 generally parallel-veined. Zantedeschia (Calla or Richardia) cdhiopica, 
 with a white spathe, is commonly cultivated under the name of the 
 Trumpet Lily. 
 
 Fam 4. Aroidece: with straight rows of laticiferous cells: flowers 
 diclinous: usually without perianth. Arum maculatum, the Cuckoo-pint 
 or Lords and Ladies, is a British plant, common in wood and hedges : the
 
 484 PART IV. CLASSIFICATION. 
 
 large green spathe completely envelopes the spadix (Fig. 295). Dracun- 
 culus and Arisarum are also European genera. 
 
 Order 2. LEMNACE^E. Stem leafless. Each, inflorescence con- 
 sists of two <$ flowers and one $ flower borne on a lateral branch 
 of the stem : the flowers consist of a 
 single stamen, and the ? flower of one 
 carpel. 
 
 Lemna trisulca, L. (Synrodela) polyrhiza, minor 
 and ffibba, are known as Duck-weed ; they are 
 common in tanks and ponds, floating on the 
 water. The stem, which is leafless, is almost 
 flat, resembling a thallus : it bears two rows of 
 branches (Fig. 296), as also roots on its under 
 FIG. 296, Part of a plant surface which are suspended in the water, 
 of Lemna trisulca, seen from Hoots are, however, absent in Wdffia arrhiza, 
 above: a the young lateral which is algo devoid of vascu l ar bundles; its 
 flower has no spathe, and it bears only one row 
 of branches : it is the smallest known flowering plant. 
 
 Order 3. TYPHACE.E. Flowers diclinous ; the perianth repre- 
 sented only by scales, or 0. Stamens usually 3. Ovary usually 
 monomerous, containing one ovule. Inflorescence a spadix, without 
 a spathe,. elongated or compact. 
 
 In Sparganium, the Bur-Reed, the inflorescences are spherical spikes 
 which are borne terminally and laterally in two rows on the upper part 
 of the stem. The lower spikes bear only <j> , and the upper only J flowers : 
 the perianth consists of 3-6 scales ; stamens 3-8, free ; gynseceum some- 
 times dimerous with an ovule in each loculus. Sparganium simplex and 
 ramosum are not rare in ditches. 
 
 Typha, the Reed-Mace or Bulrush, bears its flowers on a long terminal 
 spadix ; the $ flowers are borne directly on the upper and thinner portion 
 of the main axis ; on the lower and thicker portion are borne the ? flowers, 
 partly on the main axis and partly on very short lateral shoots ; the 
 perianth is replaced by long hairs *, stamens 15, monadelphous. Typha 
 angustifolia and latifolia occur in bogs and wet places. 
 
 Cohort II. Pal males. Order 1. PALMACE^E. The dioecious 
 or monoecious, rarely moncclinous or polygamous, flowers are in- 
 serted, with or without bracts, on the spadix or on the thick axis 
 of a spicate or paniculate inflorescence (Fig. 297) : they generally 
 conform to the type -BT3, C3, ^43 + 3, G -' : in some instances a 
 larger or a smaller number of stamen's are present : anthers some- 
 times introrse : carpels rarely more or less than 3, either free or 
 connate ; when the gynseceum is apocarpous, the ovary is unilocu-
 
 GROUP V. ANGIOSPERM/E : MONOCOTYLEDONES. 
 
 485 
 
 lar: when syncarpous, the ovary has from one to three loculi. 
 Each loculus contains, typically, a single basal ovule ; but in tri- 
 merous ovaries, two of the ovules are generally abortive : frequently 
 not more than one of the carpels (whether the gynseceum be apo- 
 carpous or syncarpous) developes into the fruit: the fruit is 
 generally baccate or drupaceous, one-seeded : the seed is large, and 
 the contained endosperm is horny. 
 
 Their mode of growth is somewhat various. Most Palms bear 
 their leaves closely arranged in a crown at the top of a tall or of 
 a quite short stem, which is clothed for some distance below its 
 apex with the remains of the older withered leaves. But in some 
 genera, e.g. Calamus, the stems creep or climb and the leaves are 
 inserted at some distance from each other. The blade of the leaf 
 commonly splits in the course of its growth, 
 assuming a compound palmate or pinnate form. 
 The inflorescence is invested by bracts : there 
 is usually a large bract (spathe) which en- 
 velopes the whole inflorescence when young, 
 and other, inner, bracts which either partially 
 invest it or (when branched) its branches. 
 
 Palms chiefly inhabit the tropics, par- 
 ticularly the Moluccas, Brazil, and the region 
 of the Orinoco, and the different genera be- 
 long exclusively (at least originally) either to 
 the Old or to the New World. 
 
 FIG. 297. -Port of the 
 panicle of ? flowers of 
 Chauiaedorea: the 
 thick axis; a the ex- 
 ternal; and j) the inter- 
 nal whorl of the peri- 
 anth ;/ ovary (x 3). 
 
 PhcKnix dactt/lifera (the Date Palm) a native of 
 Asia and Africa, has pinnatifid leaves. Of the 
 three ovaries, one only developes to form the fruit 
 which is known as the Date (p. 475, Fig. 291) ; the 
 stone of the Date consists of a very thin testa en- 
 closing the large mass of hard endosperm in which 
 
 the embryo is imbedded. Chamcerops humilis is a frequently cultivated < .ma- 
 mental plant, with fan-like leaves, which belongs to the Mediterranean 
 region. Metroxylon (Ett-Sagus) Rumphii and teuc, growing in the Mo- 
 luccas, are the plants from which Sago is obtained ; it consists of thw 
 starch-grains obtained from the parenchyma of the trunk. The stems of 
 species of Calamus, in the East Indies, supply Malacca-cane. Areca 
 Catechu (Fig. 298 J) is the Betel-Palm of tropical Asia, Coco* nucifera (the 
 Coco-nut Palm) has, as is well known, many uses. The fruit itself 
 gigantic drupaceous fruit; the mesocarp is traversed by an immense 
 number of vascular bundles, which are used to make ropes, etc. In- 
 side the excessively hard innermost layer of the pericarp, the eiidocarp, 
 lies a single large seed. When the fruit is mature, the endosperm forms a
 
 486 
 
 PART IV. CLASSIFICATION. 
 
 layer only a few millimetres in thickness, which lines the hard shell ; the 
 rest of the space (the remaining cavity of the embryo-sac) is filled with 
 fluid, known as coco-nut milk. The embryo, which is small, is imbedded 
 in the firm tissue of the endosperm, tinder the spot where there is a hole 
 
 FIG. 298. A Pait of the $ inflorescence of Phoenix reclinata (nat. size): B single $ 
 flower: C two carpels: D floral diagram. J Fruit of Areca Catechu: one half of the 
 fibrous pericarp has been removed. 
 
 (corresponding in position to the style of the single fertile loculus of the 
 ovary) in the endocarp. Elaia guineensis is the Oil Palm of West Africa ; 
 the mesocarp of the plum-like fruit, yields the oil. Phytelephas grows in 
 tropical America : the hard endosperm is known as vegetable ivory. 
 
 SUB-CLASS II. GLUMIFLOBJE. 
 
 Flowers monoclinous, or unisexual and then mostly monoecious, 
 usually in heads or spikelets invested by imbricate bracts : perianth 
 absent, or scaly : ovary superior, uni- or multilocular, with one 
 ovule in the loculus : seeds with endosperm. 
 
 Cohort I. Glumales. Ovary unilocular : ovule erect. 
 Order 1. GRAMINACE^E. True Grasses. The leaves are alter- 
 nate on the stem, which is known as the haulm ; the embryo lies 
 
 on the side of the endosperm 
 (Figs. 292-3). The usually 
 monoclinous flowers generally 
 have the formula AD, CO, 
 .43 + 0, 6rl ; they are enclosed 
 by bracts here termed palecc, 
 and are arranged in com- 
 
 FIG. aW.-Diajjrams of Grass flowers. A p li ca t e d inflorescences ; the 
 P.ambusa. B Common type of Graminacece. 
 In A there are three, in B two lodicules. monomerOUS unilocular ovary
 
 GROUP V. ANGIOSPERM.E : MONOCOTYLEDOXES. 
 
 487 
 
 contains only one ovule ; the grain is the fruit, a caryopsis, to 
 which one (the inferior) or, less commonly, both, of the palese some- 
 times adhere, e.g. Barley and Oats. 
 
 The flower is sessile in the axil of a bract, which is termed the 
 inferior or outer palea, sometimes also called the flowering- glume 
 (Fig. 301 &j, & 2 ,...), and there is also a bracteole opposite to and 
 somewhat higher than this which is termed the superior or inner 
 palea (Fig. 301 ps). The two palese completely enclose the 
 flower. 
 
 Within the inferior palea are usually two small (antero-lateral) 
 scales, the lodicules (sometimes only a single anterior one, Melica), 
 
 FIG. 300. Single-flowered spikelet of 
 
 Pant'cum miftaceum (mag.); C, and C, 
 
 second and third glumes : D inferior 
 palea: E superior palea. 
 
 Fio. 301.-A spikelet of Wheat dis- 
 sected (mag.) : * axis of the spikelet ; 
 g glumes ; 6, 5, b, b. inferior palee bear- 
 ing (gr) the awn ; 6, is sterile. B, J?, B t 
 the flowers raised (as indicated by the 
 dotted lines) out of the azila of the in- 
 ferior pale* ; pt superior palea. 1 ; a an- 
 thers ; /ovaries. 
 
 and occasionally (e.g. Stipa, some Bambusese, Fig. 299 A), there is 
 a third scale situated posteriorly within the superior palea. These 
 lodicules are frequently regarded as rudimentary perianth- 
 leaves, but it is more probable that they are bracteoles, the 
 two antero-lateral lodicules representing the two halves of a single 
 bracteole, present, as such, in Melica. They grow and become 
 succulent at the time of flowering, thus forcing apart the palese 
 and the glumes. Usually two or more flowers, thus enclosed 
 by palese, are present on an axis (Fig. 301 a?), and constitute 
 the spikelet of the Grass, and beneath the lowest flower there 
 are usually two (or more) bracts which bear no flowers in their
 
 488 PART IV. CLASSIFICATION. 
 
 axils and are known as the glumes (Fig. 301 g}. Thus a spikelet 
 consists of a main axis bearing two rows of bracts of which the 
 two first and lowest are barren, while the succeeding ones bear 
 each a flower in its axil, and beneath each flower there is also 
 a bracteole (superior palea) belonging to the floral branch itself. 
 The inferior palese often have, either at the apex or else borne on 
 the midrib, a spinous process called the arista or awn (Fig. 301 gr} . 
 
 The number of flowers in each spikelet varies, however, accord- 
 ing to the genus ; often there is but one, the lowest, with rudi- 
 ments of others above it ; if, however, only one of the upper flowers 
 is developed, then the lower palese bear no flowers in their axils 
 and are regarded as glumes, several being therefore present in such 
 a case. The spikelets themselves are in many genera, e.g. Rye 
 and Wheat (Fig. 302 B), arranged in two rows on a main axis ; the 
 inflorescence may then be designated a compound spike (see p. 
 440) ; in most of the other genera the main axis of the inflor- 
 escence bears lateral branches which are slender, of various length, 
 and often branched again, and which bear the terminal spikelets ; 
 in this way a panicle is formed, as in the Oat (Fig. 302 A}. This 
 may be either loose and spreading, with long lateral branches, or 
 compressed, with very short branches, e.g. Alopecurus. The posi- 
 tion of the branches of the panicle is more or less bilateral ; dorsi- 
 ventral, when (e.g. Festuca) the branchlets of the main branches 
 of the panicle all arise on the same side (unilateral or secund 
 panicle). 
 
 The androecium consists commonly of one (Fig. 299 5) or two 
 (A) whorls of 2-3 stamens; when there is but one whorl of 
 stamens, it corresponds to the outer whorl in those flowers in 
 which two whorls are present. Sometimes (e.g. Luziola, Ochlandra, 
 Pariana) the stamens are numerous (about 18-20;, or there may 
 be but one or two. When there are normally only two stamens, 
 they are usually situated in the median plane (e.g. Anthoxanthum), 
 sometimes in the lateral plane (e.g. Coleanthus) ; but where this 
 is the result of suppression (Diarrhena, Orthoclada) they are 
 postero-lateral, the anterior stamen being suppressed : when there 
 is only a single stamen, this is generally the anterior stamen (e.g. 
 species of Festuca and Andropogon), the two postero-lateral 
 stamens being suppressed. 
 
 The monomerous gynseceum consists of a single median carpel 
 (Fig. 299), bearing 1-3 styles (see p. 467) : the single, somewhat 
 campylotropous ovule is sessile on the ventral suture of the carpel.
 
 GROUP V. ANGIOSPERM^ : MONOOOTYLEDONES. 489 
 
 The stem is generally characterised by swollen or tumid nodes, 
 to which the sheathing leaf -bases contribute. The long internodes 
 are hollow : the sheathing leaf-bases are largely developed, and 
 frequently extend over several internodes. A membranous ligule 
 is developed at the junction of leaf-base and lamina (see p. 32 ; 
 Fig. 19 A). 
 
 The more common Grasses are classified as follows : 
 
 Series A. PAXICOIDE^ : spikelet one-flowered, or sometimes two-fiowered 
 and then the lower flower is imperfect; articulated so that it falls off 
 entire after flowering ; no prolongation of the axis beyond the flower. 
 
 Tribe 1. Panicece : spikelets dorsally compressed, in compound spikes : 
 glumes 3, of which the lowest is the smallest : inferior palea without an 
 awn. 
 
 Panicum fflabrum (Digitaria humifusa), P. (Echinochloa) Crus-gaUi, and P. 
 (Setaria) viride occur occasionally on cultivated land. P. miliaceum yields 
 Millet (Fig. 300). 
 
 Tribe 2. Maydece: the diclinous flowers are in distinct spikelets; the 
 two kinds of spikelets usually form distinct inflorescences, but sometimes 
 they occur in different parts of the same inflorescence : the lowest glume is 
 the largest. 
 
 Zea Mais, the Maize Plant, cultivated in warm countries, is a native of 
 Tropical America: the $ spikelets form a loose panicle at the apex of the 
 haulm, and the ? flowers are borne laterally on a thick spadix, which is 
 ensheathed by leaves. 
 
 Tribe 3. Andropogonece : flowers monoecious or polygamous : glumes 3, of 
 which the lowest is the largest. 
 
 Saccharum Officinarum, the Sugar-cane, is a, native of the East Indies. 
 Andropoyon Sorghum, in different varieties (vulgaris. Durra, etc.), yields a 
 kind of Millet seed : the flour of this is known in Arabia and India as 
 Durra. 
 
 Tribe 4. Oryzece : spikes laterally compressed : glumes 2-4, often repre- 
 sented only by bristles : stamens generally 6. Oryza saliva is the Rice- 
 plant, from the East Indies; cultivated in marshy regions of Southern 
 Europe. Leemia oryzoides, the Cut-grass, is found in ditches in the South 
 of England. 
 
 Series B. POOIDE^: : spikelet one- or many-flowered, with distinct inter- 
 nodes between the flowers : when one-flowered, the axis of the spikelet is 
 prolonged beyond the flower : the' ripe fruits fall, leaving the glumes 
 behind. 
 
 Tribe 5. Phalaridece: spikelets pedicillate in panicles, laterally com- 
 pressed, 1-flowered : glumes 4, the inner pair being smaller. Phalaris 
 arundinacea, the Reed-Grass, is common on the banks of streams, etc. : 
 a variety with white-streaked leaves is cultivated in gardens. Anthox- 
 anfhum odoratum, Vernal-Grass, which has only two stamens and a pani- 
 culate inflorescence, is common in meadows : it gives the peculiar odour to 
 fresh hay.'
 
 490 
 
 PART IV. CLASSIFICATION. 
 
 Tribe 6. Agrostidece : spikelets l-flo\vered, in panicles : glumes 2. 
 In Agrostis, the Bent-Grass,- the axis of the spikelet is glabrous, or it 
 baars short hairs ; A. vulgaris and alba are common in meadows : Apera 
 Splca Venti is common in fields : in Calamagrostis, the Small Reed, several 
 species of which occur on the banks of rivers and in woods, the axis of the 
 spikelet is covered with long hairs. Stipa pennata, the Feather-Grass, has 
 a long hairy awn. Milium effusum, Millet-Grass, without an awn, is 
 common in woods. Amongst the forms with dense cylindrical panicles, 
 Alopecurus, the Fox-tail Grass, has the glumes coherent at the base, and 
 one rudimentary palea. Phleum, the Cat's-tail Grass, has free glumes 
 and two distinct paleae. Phleum pratense is commonly known as Timothy- 
 Grass. 
 
 Tribe 7. Avenece : the pani- 
 culate, or rarely spicate, spike- 
 lets consist of several (usually 
 two) flowers one of which is 
 sometimes $ ; the glumes (or 
 one of them at least) are as 
 long as the whole 'spikelet, 
 longer than the inferior paleae, 
 which usually have a long 
 twisted or bent awn. 
 
 A vena, the Oat-Grass, has 
 loose panicles, and a two- 
 toothed inferior palea ; of this 
 genus there are many species ; 
 A.fatua (Wild Oats, or Havers), 
 pratensis and pubescens, are 
 common in cornfields and 
 meadows. The following 
 species are cultivated : A. sa- 
 tiva, the Oat (Fig. 302.4), with 
 its panicles in various planes ; 
 A. orientalis, with its panicles 
 in one plane ; A. atrigosa, with 
 a hairy floral axis ; and A, 
 nuda, the spikelets of which 
 usually consist of three flowers. 
 Trisetum (Arena) flavescens, the 
 yellow Oat-Grass, with a free fruit, occurs in pastures. Aira (Deschampsia) 
 c.cespitosa, a.ndflexuosa, Hair-Grasses, have truncate inferior palese, and are 
 common in meadows and woods. Holcus, the Honey-Grass, has spikelets 
 consisting of two flowers, the upper of which is usually <? , and the leaf- 
 sheaths are covered with silky hairs ; it is common in damp meadows. 
 In Arrheuatherum, the False Oat-Grass, the lower of the two flowers is $ . 
 Tribe 8. Fe&tucece: the spikelets are usually many-flowered, and the 
 glumes shorter than the inferior palese which either have 110 awn or a 
 straight terminal awn. Melica, the Melic-Grass, has sometimes spikelets 
 
 FIG. 302. A Panicle of Oat, Avcna sativa : s main 
 axis; ' lateral axes; a spikelet (i nat. size). B 
 Spike of Wheat: s axis; g the depressions in 
 which the spikelets (a) lie. These are removed 
 at the lower part.
 
 GROUP V. ANGIOSPERM^E : MOXOCOTYLEDOXES. 491 
 
 consisting of a single flower only : the glumes are long ; it is common in 
 woods. Molinia ccerulea has a very long haulm, consisting for the most 
 part of a single intemode ; its spikelets are in loose purplish panicles ; it 
 occurs on moors. Briza, the Quaking-Grass, has spikelets which are com- 
 pressed laterally and are cordate at the base ; it is common in meadows. 
 Koeleria cristata has dense panicles; it is common in dry meadows. 
 Dactylis fflomerata, the Cock's-foot Grass, has dense panicles divided into 
 parts which have longer stalks ; it is common in meadows. Poa pratensis, 
 trivialis, etc. (Meadow-Grass), are common in meadows ; their spikelets are 
 compressed laterally ; the glumes have a sharp keel; P. annua is common 
 by the roadside. Other Meadow-Grasses are Glyceria aquaiica sundfluitans, 
 with obtuse unequal gJ nines, .and a lower palea with 5-7 prominent 
 parallel veins, growing in ditches; and Schlerochloa maritima, distani, etc., 
 growing in salt-marshes and by the sea-shore, with acute unequal glumes. 
 In all the Meadow-Grasses, the fruit is free from the pale*. Festuca 
 efatior, and others, the Fescue-Grasses, are common in meadows. Bromus, 
 the Brome-Grass, of which there are several species, is common in fields 
 (B. secalinus), in meadows (B. racemosus and others), by the roadside (B. 
 sterilis and mollis). Brachypodium, with shortly-stalked spikelets in a 
 simple raceme, and unequal glumes, is common in woods (B. sylva/icum) 
 and on heaths (B. pinnatum). In Phragmites the axis of the spikelet i* 
 covered with long silky hairs ; Phragmites communis, the Used, ccsurs 
 abundantly in marshes. Sesleria caerulea, the Moor-Grass, has laterally 
 compressed spikelets in dense panicles. Gynerium, the Pampas-Grass, 
 also belongs here; it is dioecious. The upper flowers in the spikelets of 
 plants belonging to this tribe are often unisexual, and <J; Phragmites is 
 peculiar in that the lower flower of the spikelet is <? . 
 
 Tribe 9. Chtoridecb : spikelets laterally compressed, usually 1-flowered, 
 sessile, in compound spikes : glumes 2. Cynodon Dactylon, the Dog's-tooth 
 Grass, is often abundant on waste ground. Spartina slricta occurs in salt- 
 marshes. 
 
 Tribe 10. Hordece : spikslets solitary, or 2 or 3 together, 1- or many- 
 flowered, situated in depressions on the main floral axis nearly always in 
 two opposite rows, forming the so-called spike : glumes 1-2. In Lolium, 
 the Rye-Grass (L. perenne, Darnel, is common everywhere), the posterior 
 surface (that is, the middle line of the posterior glume) is directed towards 
 the main axis, and this glume is usually rudimentary. In all the other 
 genera the side of the spikelet is directed towards the main axis, and 
 there are two glumes. In Agopyrum, the paleae adhere to and fall off with 
 the fruit: A. repens, the Couch-Grass, is common everywhere, and is a 
 troublesome weed on account of its spreading rhizome. Secale cereale, the 
 Rye, has 2-flowered spikelets and narrow awl-shaped glumes. In Xardus 
 stricta, the Mat-Grass, the two rows of spikelets converge laterally ; the 
 glumes are rudimentary ; there is but one stigma ; the leaves and haulms 
 are rough ; it grows on moors. Triticum, the Wheat, has 3- or more 
 flowered spikelets, with ovate glumes. Three species are cultivated, T. 
 monococcum, T. sativum and T. polonicum ; in the first species the terminal 
 spikelet is abortive. The following varieties of T. sativum are cultivated ;
 
 492 PART IV. CLASSIFICATION. 
 
 T. vulgare, the common Wheat, with long glumes, which have no keel, 
 and T. turgidum, English Wheat, with short keeled glumes; T. compact/tin. 
 the D\varf Wheat, with short, stout spikelets; and T. durum, the Hard 
 Wheat, known by its long rigid awns ; all these varieties have a wiry 
 floral axis (hence sometimes described as T. satimtm tenax), and the fruit 
 easily falls out of the glumes, and in all but T. durum there are awned 
 and un-awned (beardless) forms: T. spelta, the Spelt, which has an almost 
 quadrangular spike, and T. dicoccum', with a compact spike, have a brittle 
 floral axis, and the fruit is firmly enclosed by the glumes. In all the 
 species the length of the awn varies very much. Hordeum, the Barley, 
 has 3 single-flowered spikelets inserted together in one depression on the 
 floral axis. H. murinum is common on the roadside and on walls. The 
 following varieties of H. sativum are cultivated: H. vulyare and H. hexa- 
 stichum, with only fertile spikelets; in the latter species the spikelets are 
 all equally distant, and are therefore arranged in six rows ; in the former 
 species the median spikelets are nearer together, and the lateral ones more 
 distant, so that they are described as being in four rows : further, H. 
 distichum is the two-rowed Barley, the lateral spikelets of which are <?, 
 so that the fruits are arranged in two rows. The fruit usually adheres to 
 the palea. The genus Elymus, the Lyme-Grass (E. arenarius, British) 
 belongs to this tribe, as also Pariana, a tropical genus remarkable for its 
 numerous stamens. 
 
 Tribe 11. Bambusece : spikelets 2- or many-flowered, rarely 1- flowered, 
 in racemes or panicles, clustered at the nodes of the branches of the in- 
 florescence: glumes 2 or many, becoming larger upwards, but shorter than 
 the nearest palea : stamens generally 6 (see Fig. 299 A). Large Grasses, 
 known as Bamboos, having perennial aerial shoots with often shortly 
 petiolate leaves, growing mostly in the Tropics. The most familiar genera 
 are Arundinaria and Bambusa. 
 
 Order 2. CYPERACE^E. The leaves are arranged in three rows 
 on the stem : perianth 0, or of 3-6 or more bristles or scales : the 
 androecium consists typically of two trimerous whorls, though 
 one whorl (the inner) is absent in some genera : the gynaeceum 
 is typically trimerous, though it is sometimes dimerous : ovary 
 unilocular:. ovule erect, anatropous: the embryo is enclosed in the 
 endosperm. 
 
 Tribe 1. Scirpoidece : flowers $ ; perianth 0, or of bristles : glumes disti- 
 chous: the odd carpel is anterior. The spikelets are often arranged so as 
 to form spikes, panicles, umbels, or capitula : the flower has the formula 
 #3, C3, ,48+0 or 3, G. 
 
 Cyperus, the Galingale, has many-flowered compressed spikelets with 
 deciduous bracts or glumes: Schoenus, the Bog-Rush, has few-flowered 
 (1-4) spikelets with persistent glumes : C. tonyus and fuscus, and S. nigri- 
 cans, occur in England. Cyperus Papyrus (Papyrus Antiquorum) is an 
 Egyptian species from which the Papyrus of the ancients was made.
 
 GROUP V. ANGIOSPERMJE : MONOCOTYLEDOXES. 
 
 493 
 
 Scirpus, the Club-Hush, has a bristly perianth, cylindrical spikelets, 
 and the glumes are imbricate on all sides ; in some species the spikelets 
 are solitary, as in Scirpus ccespitosus, in others there are lateral spikelets, 
 in addition, on short stalks, as in S. lacustris (the true Bulrush), or on 
 long stalks, as in S. sylvaticus, Eriophorum polyatacJiium and other species 
 (Cotton-Grass) are common on boggy moors; the hairs of the perianth, 
 after flowering, grow to a considerable length. 
 
 Tribe 2. Caricoidece : spikelets cylindrical \ flowers unisexual ; perianth 
 0. 
 
 These plants have diclinous (sometimes dioecious) flowers. In the genus 
 Carex the $ flowers have the formula KQ, CO, 43+0, GO] they are situated 
 in the axils of bracts (glumes) (Fig. 304 B and D) and form simple spikes. 
 The ? flowers have the formula KO, CO, 40+0, G (3 > or <1> and are not sessile 
 in the axils of the glumes (6 in Fig. 304 A and C), but a short branch 
 springs from the axil of each of these leaves bearing a second bract (s in 
 
 FIG. 303. A Flower of Scirpus (magnified): FIG. 304. Flower of Carex (masr.). 
 
 p the bristly perianth ; a the three stamens ; A $ flower with (b) bract (elume) ; * 
 
 the ovary : n the three stigmata. B Its second bract (utriculus) ; / ovary ; n 
 
 floral diagram. stigma. B <J flower : st the three 
 
 stamens ; o anthers. C Diagram of the 
 9 and (D) of the S flower: r axis of the 
 spike ; b bract (glume) ; s second bract. 
 
 the Fig.) and it is in the axil of this second bract that the ? flower, which 
 consists of a trimerous, or more rarely, dimerous (in Carex dioica and 
 pulicaris, etc.) ovary, is situated. The second bract increases greatly and 
 invests the fruit (and the short branch which sometimes projects beyond 
 the fruit as a seta,}, forming the so-called utriculus : this structure has been 
 regarded as a perianth, and termed the perigynium. In Kobresia (Elyna) 
 the second bract is not tubular, and therefore does not completely invest 
 the ovary. In consequence of there being a second bract, the odd carpel 
 of the trimerous gynaeceum is posterior : when the gynseceum is dimerous, 
 the two carpels are lateral. 
 
 The genus Carex, the Sedge, contains numerous, species which grow 
 mostly in damp localities ; they have stiff leaves with sharp or saw-like 
 edges. Only a few of them are dioecious (C. dioica, scirpoidea] : in most
 
 494 PART IV. -CLASSIFICATION. 
 
 the <? and ? inflorescences occur on the same axis. In one large section 
 of them the two kinds of flowers occur on the same spike which is either 
 <? at the base and ? at the top, or vice versa. When this is the case the 
 axis bears either only one terminal spike, as in Carex pulicaris and C. 
 pauciflora, or several spikes forming a capitulum at the apex, as in C. 
 cyperoides, or a spike or a panicle, as in C. muricata, arenaria, and panicu- 
 lata. In a second section, on the other hand, each spike is unisexual, and 
 then the <J spike is almost always terminal on the axis and the ? lateral, 
 as in Carex acuta, glauca, prcecox, digitata, flava, and paludosa. 
 
 SUB-CLASS III. PETALOIDE^. 
 
 Flowers rarely unisexual ; perianth rarely wanting, usually 
 biseriate, the corolla usually petaloid, and sometimes the calyx also. 
 
 SEEIES I. HYPOGYN.E. 
 
 Ovary superior. 
 
 Sub-series. Apocarpce. 
 
 Gynseceum more or less completely apocarpous. 
 
 Cohort I. Alismales. Marsh- or water-plants; flowers fre- 
 quently unisexual ; seeds without endosperm. 
 
 Order 1. NAIADACELE. Perianth 0, or of 2-4 segments ; stamens 
 1-4 : ovaries 1-4, with usually a single erect or suspended ovule. 
 Water-plants. 
 
 In the genus Naias the flowers are solitary or in spikes, and are either 
 monoecious or dioecious: perianth of one or two gamophyllous series: $ 
 flowers with 1 stamen, ? flowers with one carpel : ovule erect. N. flexilis 
 is the only British species. In Zostera, the Grass-wrack, the flowers are 
 diclinous, and without a perianth ; they are borne in two rows on one side 
 of a flattened spike ; stamen 1, carpel 1. Zostera marina and nana are the 
 British species living in the brackish waters of estuaries. In Zannichellia, 
 the Horned Pondweed, the flowers are diclinous, and are solitary or in 
 spikes: S flower, perianth 0, stamen 1; V flower, perianth bell-shaped, 
 carpels 4-6. Z. palustris is the only British species. 
 
 In Potamogeton, the Pondweed, the flowers are monoclinous and in 
 spikes: general formula PO, A2 + A2, G x 4 : the extrorse stamens have a 
 broad leafy connective. This genus is represented in Britain by many 
 species : in some (.P. pusillus) the stem bears only submerged leaves which 
 are narrow and linear ; in others the leaves are somewhat broader (P. 
 densus), and in others again it bears a few broad leaves which float on the 
 water (P. natans). In Ruppia, the Tassel Pondweed, the flowers are gener-
 
 GROUP V. ANGIOSPERALE : MONOCOTYLEDONES. 495 
 
 ally two on a spike ; formula PO, A2, Gi. It. maritima is the British 
 species. 
 
 Order 2. JUNCAGINACEJL Flowers sometimes diclinous ; both 
 perianth-whorls are sepaloid and inconspicuous ; anthers extrorse ; 
 carpels sometimes coherent ; the outer whorl of carpels is occasion- 
 ally abortive ; ovules 1-2, anatropous, embryo straight. 
 
 Triglochin palustre, the Arrow-Grass, is common in marshes and on the 
 margin of pools : carpels coherent till mature. The monoclinous flowers 
 are disposed spirally in a long loose spike without bracts. Scheuchzeria 
 palustris is rarer ; it occurs in bogs ; the flowers are set in the axils of 
 distichous bracts : carpels free. 
 
 Order 3. ALISMACELE. Flowers sometimes monoecious; floral 
 formula K3, CS, A3 2 + or 3, or oo, G3 + 3 or oo : perianth hetero- 
 chlamydeous ; the sepals are often coherent at the base ; the petals 
 
 FIG. 305. Diagram of the Flower of 
 Trigloohin. 
 
 FIG. 3C6. Flora diagrams. A of 
 Butomus. B Of Alisma. 
 
 are white or violet ; anthers extrorse or introrse ; carpels sometimes 
 partially coherent ; ovules 1-3, campylotropous, embryo curved. 
 
 Alisma Plantago (Water Plaintain, Fig. 306 B), has the floral formula 
 K3, C3, A3 2 +Q, GQ or more ; the numerous, monomerous, one-seeded ovaries 
 are crowded on the broad receptacle. The main axis of the inflorescence 
 bears whorls of branches which have a helicoid ramification. It is rather 
 common in damp spots. Damasonium stellatum, the Star-fruit, is found in 
 ditches in the South of England : it has two-seeded ovaries. 
 
 Sagittaria sagittcefol.ia, the Arrowhead, has diclinous flowers with the 
 formula K3, C3, <J A oo, ? G J?. The flowers are disposed in trimerous 
 whorls, the <J in the upper and the ? in the lower whorls. The anthers 
 are extrorse. The ovaries, which are very numerous and one-seeded, are 
 inserted on a fleshy receptacle. Only the sagittate leaves and the inflores- 
 cence appear above the water. 
 
 Order 4. BUTOMACE^E. Flowers never unisexual ; general 
 floral formula the same as in Alismacese ; anthers introrse ; carpels 
 distinct ; ovules numerous, with superficial placentation ; embryo 
 straight or ciirved.
 
 496 
 
 PART IV. CLASSIFICATION. 
 
 FIG. 307. Butomus w/nliellttus. A Flower (nat. size). 
 B Gjnasceum (mag.) ; n stigmata. I Diagram : p p 
 perianth ; / stamens of the outer whorl duplicate : /' 
 stamens of the inner whorl ; c outer, and c' inner whorl 
 of carpels. (After Sachs.) 
 
 Butomus umlellalus is 
 the Flowering Rush 
 (Figs. 306 A, 307). The 
 flowers, which have vio- 
 let petals, have the fol- 
 lowing formula : K3, C'3, 
 A3- + 3, G 3 + 3 ; they are 
 arranged in an umbel- 
 late helicoid cyme at the 
 apex of the scape, which 
 is about 3 feet high ; 
 this and the leaves, 
 which are of about the 
 same length, spring 
 from an underground 
 rhizome. The ovules, 
 which are numerous, are 
 borne on the inner sur- 
 face of the carpels (Fig. 
 284 0) : the embryo is 
 straight. 
 
 Sub-series. Syncarpce. 
 Gynseceum syncarpous. 
 
 Cohort I. Li Hales. Perianth homochlamydeous, usually 
 petaloid ; seeds with endosperm ; general floral formula A'3, (73, 
 
 Order 1. LILIACE.E. The flowers conform generally to the 
 above formula, but 3 is replaced sometimes by 2 or 4 : they are not 
 zygomorphic : endosperm oily ; fruit a capsule or a berry. Mostly 
 rhizomatous or bulbous plants : rarely trees or shrubs. 
 
 Sub-order 1. LILIOIDE^E, with a loculicidal capsule, introrse anthers, 
 and united styles. Bulbous plants. 
 
 The family Tulipece includes the following 
 genera : Lilium, Fritillaria, Tulipa, Erythron- 
 ium, Lloydia. 
 
 Many species are cultivated, Lilium can- 
 didum is the white Lily ; L. kulbiferum, produc- 
 ing bulbils in the axils of the upper leaves; 
 I" Martagon, the Turk's Cap Lily ; L. tigrinum, 
 the Tiger-Lily ; L. speciosum, auratum, etc. 
 Fritillaria imperialis is the Crown Imperial, 
 the flowers of which are surmounted by a 
 ^^ Qf ]eaveSi TM Gesneriana is the 
 
 Tulip. Ertjthronium Dens-Canis is the Dog- 
 Tooth Violet. The following occur wild in 
 
 Fm. 308 . Flower of the 
 Hyacinth : a a a the three 
 outer; it'ithe three inner 
 segments of the perianth, 
 which is tubular at the lower 
 part (nat. size).
 
 GROUP IV. ANGIOSPERM.E : MONOCOTYLEDONES. 
 
 497 
 
 Britain : Lilium Martagan; Tulipa sylvestris, wild Yellow Tulip; Fritillaria 
 Meleayris, the Snake's Head ; Lloydia serotina. 
 
 The Scilleoi includes the following genera amongst others: Galtonia, 
 Hj'acinthus, Muscari, etc., in which the segments of the perianth cohere' 
 more or less (Fig. 308) ; Scilla, Camassia, Ornithogalum, etc., with free- 
 perianth-leaves. The following occur wild in Britain; Byacinthus non- 
 xcriptuii, the Blue Bell; Muscari racertosum, the Grape-Hyacinth; Scilla 
 
 FIG. 809. The underground part of a flowering plant of Colchicum aututnnale. A Seen, 
 in front; k the corm ; ' '' cataphyllary leaves embracing the flower-stalk; ich its base 
 from which proceed the roots, us. B Longitudinal section : h h a brown membrane 
 which envelops all the underground parts of the plant; it the flower-shoot of the 
 previous year which has <lied down, its swollen basal portion (fc) only remaining as a 
 reservoir of food-materials for the new plant now in flower. The new plant is a lateral 
 shoot from the base of the corm (fc), consisting of the axis, from the base of which proceed 
 the roots (to'), and the middle part of which (fc') swells up in the next year into a corm, the 
 old corm (fe) disappearing; the axis bears the sheath-leaves (*''') and the foliage-leaves 
 (I' I") ; the flowers (I b') are placed in the axils of the uppermost foliage-leaves, the Axis 
 itself terminating amongst the flowers. (Alter Sachs.) 
 
 M.B. K K
 
 498 PART IV. CLASSIFICATION. 
 
 verna and autumnalis, the Squills ; Ornithogalum nutans, the Star of Beth- 
 lehem. 
 
 Sub-order 2. MELANTHIOIDE^E or COLCHICOIDE^E, with a usually septicidal 
 capsule, usually extrorse anthers, and separate styles. Mostly rhizomatous 
 plants. 
 
 Not many genera are common in cultivation ; among these Gloriosa, 
 Uvularia, and Veratrum may be mentioned ; Veratrum album and niyrum 
 have broad ovate leaves. 
 
 Tofieldia palustris, the Scottish Asphodel, has ensiform radical leaves; 
 the flowers, which are pale green, are disposed in a raceme on a scape ; it 
 occurs in Scotland, in wet places on mountains, but it is rare. Narthecium 
 ossifrtigum, the Bog-Asphodel, somewhat resembles Tofieldia, but the 
 flowers are yellow and the capsule is loculicidal ; common in Scotland and 
 in the north of England. 
 
 The Colchicece are bulbous plants and have introrse anthers. Col- 
 chicum autumnale is the Autumn Crocus or Meadow Saffron ; when it is 
 flowering in the autumn, the stem is underground ; it is at this time short 
 and slender (Fig. 309 &'), attached laterally to the corm of the previous 
 year's growth (&), and bears a few imperfectly developed leaves (I' I") as 
 well as one or two flowers (V b") : the ovaries of the flowers are also sub- 
 terranean ; the six leaves of the perianth cohere and form a tube of some 
 centimetres in length, which grows far beyond the ovaries and above the 
 surface of the soil, terminating in a petaloid six-partite limb ; the stamens 
 are attached in the upper portion of the tube. In the spring the under- 
 ground stem swells at its base (&') into a corm, and grows upwards, so that 
 the developing leaves (I' I") and the capsule rise above ground ; a lateral 
 shoot is formed at its base, which, in the autumn, produces the flower. 
 
 Sub-order 3. ASPHODELOIDEJE ; rhizomatous plants, with usually radical 
 leaves, but the leaves are sometimes borne on an aerial rarely branched 
 stem ; inflorescence usually a terminal spike or raceme : perianth-leaves 
 free or connate ; anthers introrse ; fruit capsular. 
 
 Asphodelus, Eremurus, Anthericum, Hemerocallis, Phormium (Phor- 
 mium tenax is the New Zealand Flax), Kniphofia and Aloe", are cultivated. 
 The only British species is Simethis bicolor in the south of England. 
 
 Sub-order 4. ALLIOIDE^E ; generally bulbous plants : inflorescence 
 umbellate, more or less completely enclosed by two or more bracts. 
 
 Agapanthus, Nothoscordum, Milla, Brodisea, and Allium are the more 
 commonly cultivated genera. Of Allium, several species are in cultivation 
 for culinary purposes, as A. Cepa, the Onion ; A. ascalonicum, the Shalot ; 
 A. Schoenoprasum, Chives ; A. Porrum, the common Leek ; A. sativum 
 (vulyare), Garlic. Some species (Wild Garlic) are wild in Britain, such 
 as A. oleracetim, vineale, ursinum, and triquetrum in Guernsey. The leaves 
 of the various species of Allium are generally tubular and hollow ; the 
 flowers are disposed in spherical heads or umbels ; bulbils are occasionally 
 produced among the flowers. Gagea lutea is also British. 
 
 Sub-order 5. DRACJENOIDEJE, stem erect, usually arborescent, with second- 
 ary growth in thickness (see p. 148). 
 
 Species of Yucca are commonly cultivated in gardens; Cordyline and
 
 GROUP V. AXGIOSI'ERM.E ! MONOCOTYLEDONES. 
 
 499 
 
 Dasylirion in greenhouses. Dracaena Draco is the Dragon's Tree of the 
 Canary Islands, yielding a red gum-resin (Dragon's blood). 
 
 Sub-order 6. ASPARAGOIDE^, with a subterranean rhizome bearing aerial 
 leafy stems : fruit baccate. 
 
 Aspararjtis officinalis is the Asparagus ; the young shoots, which spring 
 from the underground rhizome, are eaten. Convallaria majalis is the Lily 
 of the Valley. Maianthemum bifolium has a dimerous flower. Polygonatum 
 is Solomon's Seal. Ruscus aculeatus (the Butcher's Broom), and other 
 species, are small shrubs, with leaf-like branches (phylloclades, see p. 28), 
 on which the diclinous flowers are borne in the axils of minute leaves. 
 Paris quadrifolia (Herb Paris) is poisonous : the flowers are tetramerous, or 
 exceptionally trimerous or pentamerous : they are terminal, and the stem 
 beneath bears four (or three or five) leaves in a whorl beneath the flower 
 (Fig. 310) ; the venation of the leaves is reticulate. 
 
 Maianthemum" bifolium, Paris qitadrifolia, Runcus aculeaftts, Convallaria 
 majalis, Polygonatum verticillatum, 
 mult iflor um, and officinal e, are wild 
 in England. 
 
 Sub-order 7. SMILACOIDE^E, scram- 
 bling shrubs, having 3-5 ribbed 
 leaves with reticulate venation. 
 The roots of species of Smilax con- 
 stitute Sarsaparilla. 
 
 Order 2. JUNCACE.E. Floral 
 formula, K%, C3, 43 + 3, G. 
 
 Plants of a grass-like aspect ; 
 they differ from the preceding 
 order in the dry and glumaceous 
 character of the perianth, and 
 in the starchy endosperm. The 
 leaves are linear or tubular ; the 
 inflorescence is an anthela (see p. 442). 
 
 The species of Luzula, which has a unilocular three-seeded ovary, mulii- 
 flora, pilosa, campesfris, and sylvatica, are common in woods and on heaths. 
 Juncus has a trilocular many-seeded ovary ; plants of this genus are called 
 Hushes ; J. glaucus and e/usus have a tubular stem and leaves, and a 
 terminal inflorescence which is displaced laterally by a tubular bract 
 which appears to be a prolongation of the stem ; they are common in wet 
 fields ; J. bufonius, by waysides. 
 
 FIG. 310. Diagram of the flower of Part* 
 quadrifolia. ; I the foliage-leaves ; nj) the 
 outer ; tp the ioner whorl of the perianth ; 
 an outer; in inner whorl of stamens. 
 (After Sachs.)
 
 500 PART IV. CLASSIFICATION. 
 
 SERIES II. EPIGYK2E. 
 Ovary inferior. 
 
 Cohort I. Hydrales. Order 1. HYDROCHARIDACE.E. The in- 
 florescence is at first enclosed in a spathe formed of a single bract, 
 or more commonly of two connate bracts. The flowers have a 
 perianth, the inner whorl being petaloid, and usually conform to 
 the monocotyledonous type, but with pleiotaxy in the andrcecium 
 and gynseceurn ; formula A~3, C3, AS + 3 + , G (3+ ...).- The flowers 
 are usually unisexual and dioecious ; the ? flowers have stami- 
 nodia ; the $ flowers have no gynseceum but an increased number 
 of whorls in the androecium. Seeds generally numerous ; without 
 endosperm. Water-plants. 
 
 Fam. 1. Hydrillece. Ovary unilocular. Stem elongated, with whorls of 
 small leaves. 
 
 Elodea (Anacharis) canadensis came originally from North America and 
 has spread in our waters so as even to impede navigation in canals. 
 
 Fam. 2. Vallisneriece. Ovary unilocular. Stem short, with crowded 
 leaves. 
 
 Valiisneria spiralis inhabits the lakes and ditches of the warmer parts of 
 Europe. The leaves are long, narrow, and linear. The ? flowers are 
 raised above water on long peduncles ; the $ inflorescences break away 
 from their peduncles and float about on the water to fertilize the ? 
 flowers ; the fruit ripens under water. 
 
 Fam. 3. Stratiotece. Ovary 6- (or more) chambered. Stem short, with 
 crowded leaves. 
 
 Stratiotes aloides (Water-Soldier) has stiff narrow leaves. Hydrocharis 
 Morsus Ranee is the Frog's Bit ; the plant is small and floats on the water, 
 with small roundly-cordate leaves. 
 
 Cohort II. Dioscoreales. Flowers regular : floral formula 
 A'3, (73, A3 + 3, G^ : fruit a berry or a capsule : endosperm oily. 
 
 Order 1. DIOSCOREACE^E. The ovary is trilocular, with one or 
 two ovules in each loculus : the flow r ers are dioecious. They are 
 climbing plants, with twining stems, having large above- or under- 
 ground' tubers, and usually triangular leaves with reticulate vena- 
 tion. 
 
 Dioscorea saliva, Batatas, and others, known as Yams, are largely culti- 
 vated in the tropics, their tuberous roots yielding a food rich in starch. 
 Tamus communist, the Black Bryony, is common in England. 
 
 Order 2. BROMELIACE.E. K3, C3, AS + 3, G (3). The ovary is 
 superior, inferior, or semi-inferior, trilocular, with many seeds.
 
 GROUP V., ANGIOSPERM^E : MONOCOTYLEDONE3. 501 
 
 Perianth heterochlamydeous. The leaves are usually long and 
 narrow, sharply serrate; the stem is generally very short. The 
 flowers are $ , and form spikes 
 or panicles with bracts. 
 
 Ananas saliva is the Pine-apple. 
 The fruit is a berry, and the 
 berries of each inflorescence 
 coalesce into a spurious fruit 
 (sorosis), above which the axis 
 of the inflorescence extends and 
 bears a crown of leaves (Fig. 
 311 ; see p. 472). In a state of 
 cultivation the berries contain 
 no seeds. It is a native of 
 America, and is cultivated in 
 all warm countries and in hot- 
 houses. 
 
 Cohort III. Amomales 
 
 (Scitaminese). The flowers 
 are irregular, zygomorphic or 
 asymmetrical : general for- 
 mula, ^ K3, C3, A3 + 3, G (Tt , 
 occasionally with a great re- 
 duction in the androecium. 
 Perianth wholly petaloid, or 
 clearly heterochlamydeous : VQ 311 .l FmHofthePine . apple (rednced) . 
 ovary usually trilocular : 
 
 fruit, a capsule or a berry. Usually no endosperm, but abundant 
 perisperm. They are tall herbaceous plants ; the leaves are large 
 and have pinnate venation. 
 
 Order 1. MUSACEJE. ^ A'3, (73, .43 + 2 f 1 or 0, G 1 ^. Flower 
 dorsiventral ; the anterior external member of the petaloid perianth 
 is usually very large, and the posterior always very small. In the- 
 family Musese the odd sepal is anterior ; the sepals are usually free,- 
 as are also the petals in Ravenala ; but in Strelitzia the two lateral 
 petals are connate, and in Musa the five anterior members of the- 
 perianth are connate, forming a tube which is open posteriorly : 
 the posterior stamen is sterile or absent, and the others are not 
 always fertile. The flower of the family Heliconiese differs from 
 this type in that the odd sepal is posterior, and the abortive 
 posterior stamen belongs to the outer whorl. Seeds, one (Heli- 
 conia), or many, in each loculus, without endosperm. They are
 
 502 PART IV. CLASSIFICATION. 
 
 all shrubs of colossal growth, with enormously long leaves : the 
 flowers are usually arranged in spicate inflorescences in the axils 
 of large and often coloured bracts ; sometimes several flowers 
 spring from the axil of one bract. 
 
 Mima paradisiaca (Plantain), M. Sapientum (Banana), and M. Emete are 
 natives of the tropics of the Old World ; the two former are now distributed 
 
 FIG. 312. -Diagram of flower of Musa. FIG. 313. Diagrams of the two types of flower in 
 the Zingiberaceae. A Hedychium. B Alpinia. 
 
 throughout America and applied to a great variety of purposes ; the fruit, 
 which is of the nature of a berry, is an article of food, and the vascular 
 bundles are used for making textile fabrics. The other genera are 
 Bavenala, Strelitzia, Heliconia. 
 
 Order 2. ZINGIBERACE^E. 4- #3, (73, A t 2 or + 1 f 2, G m . 
 Flower dorsiventral : calyx not always distinct. Of the inner 
 whorl of stamens the posterior alone bears a perfect anther, the 
 other two being transformed into a usually petaloid body, the 
 label lum. The outer whorl of stamens is absent, or but slightly 
 indicated, in the Zingiberese (Fig. 313 B) : but is represented in 
 the Hedychiese and Globbese by" two postero-lateral petaloid 
 staminodes (Fig. 313 A). There is a small amount of endosperm 
 in the seed, in a depression in the perisperrn. 
 
 The commoner genera are Curcuma, Hedychium ; Zingiber, Alpinia ; 
 Globba, having a unilocular ovary with three parietal placentae. 
 
 The starch which is prepared from the rhizome of Curcuma angustifolia 
 and leucorrhlza is known in commerce as East Indian arrowroot ; Turmeric 
 is obtained from the rhizome of C. lonya. Cardamoms are the fruits of 
 Eletteria Cardamomum. The dried rhizomes of Zinyiber qfficiiiale are the 
 common ginger. 
 
 Order 3. MARANTACE.E or CANNACE.E. K3, (73, AO + 1 f 1, 0, or 
 
 A f 2, + 1 f 2, Gp,. Flower asymmetric, often heterochlarnydeous. 
 The androecium is represented by a number of petaloid bodies, of 
 which one only, the posterior stamen of the inner whorl, bears a 
 bilocular anther (Fig. 314 st, an) ; of the staminodia one is larger 
 than the others, and is reflexed, forming a labcllum (Fig. 314 I) j
 
 GROUP V. AXGIOSPERALE ; MOXOCOTYLEDOXES. 
 
 503 
 
 the narrow ones vary in number in the different species (Fig. 314 a 
 and /?) : seed without endosperm ; seeds numerous in Canna, single 
 in each loculus in other genera. 
 
 Canna indlca and other species are com- 
 monly grown as ornamental plants. 
 
 Amylum Marantse, the starchy meal 
 prepared from the rhizome of Maranta 
 arundinacea.is true or West Indian arrow- 
 
 Cohort IV. Orchidales. Flower 
 irregular, dorsiventral, zygomorphic, 
 gynandrous (see pp. 455, 462), reduced 
 iii the androecium : perianth petaloid. 
 Seeds very small, without endosperm 
 or perisperm ; the embryo a minute 
 undifferentiated mass of cells. 
 
 Order 1. ORCHID ACE^E. The flowers 
 of most of the genera have the for- 
 mula ^ A'3, C3, 41 + f 2, m : those 
 of the Cypripediinse, however, have 
 the formula -^ K3, C3, A f 1 + 2, 0$ 
 (Fig. 315 A, B}. The flower is gene- 
 rally so placed, in consequence of 
 torsion of the ovary, that the posterior side of the flower, instead 
 of being uppermost, as is normally the case, comes to lie inferiorly 
 (resupinate), but there are exceptions (e.g. Liparis, Nigritella, 
 Epipogum). The posterior segment (petal) of the inner whorl called 
 the labdlum (Fig. 31 6, see also Fig. 244 I), is always larger than 
 the others, and varies greatly in form ; it frequently has a spur 
 (Fig. 316 sp) or a sac-shaped cavity (Fig. 244). The andrcecium 
 and the three stigmata are, in most Orchids, borne on a prolongation 
 of the floral axis the gyuostcmium (Fig. 244 s ; Fig. 318 B and C gs). 
 In the androecium usually three stamens are represented : in the 
 mouandrous Orchids there is a fertile anterior stamen belonging to 
 the outer whorl (Fig. 315 .4), and often two staminodes, which 
 are sometimes petaloid (e.g. Diuris) or small tooth-like prominences 
 (auriculae, stelidia) on the gynostemium (e.g. Orchis, Epipactis, 
 Fig. 244 a?), belonging generally to the inner androecial whorl, 
 but sometimes apparently to the outer : in the diandrous Orchids 
 (e.g. Cypripedium, Fig. 315 B) there are, generally, two fertile 
 stamens belonging to the inner whorl ; the outer whorl being only 
 
 Fio. 314. Flower of Caima indiea 
 (nat.size) : /inferior ovary ; pa the 
 outer; jn the inner whorl of the 
 perianth ; g style ; tt the fertile sta- 
 men, with (<ui) the anther ; I label- 
 lam ; a and ft the two staminodia. 
 (After Eichler.)
 
 504 
 
 PART IV. CLASSIFICATION'. 
 
 represented by an anterior staminode. The anther usually has 
 four pollen-sacs, but may have two (e.g. Collabium) or eight (e.g. 
 Calanthe, Bletia). In some genera the pollen- grains are separate 
 from ea.ch other ; in the majority they are united into a mass, 
 pollinium, which fills an entire pollen-sac (Fig. 244 E, F, p). The 
 pollinium may consist of tetrads with a common exine (e.g. Neottia) ; 
 or of larger groups of cells, termed massulce (e.g. Orchis), when it 
 is said to be sectile ; or of uniform tissue. In those Orchids which 
 have pollinia, it is frequently the case that the tissue of the pollen- 
 sac is prolonged, according to the position of the anther, either to 
 the lower (basitonous, e.g. Ophrydinse) or to the upper end of the 
 anther (acrotonous, e.g. Phajiinse, Oncidiinae), and here almost 
 exclusively gives rise to a mucilaginous filament, the caudiclc, 
 
 FIG. 315. Diagram of Orchidaceous 
 flowers, neglecting resnpination. A The 
 monandrous type. S The diandrous type 
 (Cypripedium) : the shaded stamens are 
 staminodia. 
 
 FIG. 316. F owerof Orchis mascula (x2) 
 / the twisted ovary a a a the three outer 
 perianth-leaves ; i i two of the inner, I the 
 third inner perianth-leaf, the labellum, with 
 (sp) the spur; 71 stigma; p pollen -sacs. 
 
 attached to the pollinium (or to the two or more pollinia of each 
 half of the anther) below or above. 
 
 The ovary is unilocular (rarely trilocular as in some Cypri- 
 pediinse), and contains numerous anatropous ovules on three 
 parietal placentae. In all the monandrous Orchids, the anterior 
 lobe of the trilobate stigma is not susceptible of pollination, and 
 is either rudimentary or develops into an organ termed the 
 rostellum (Fig. 244 ft), which is situated either above or below 
 the anther, and in the tissue of which one or two small masses 
 of sticky mucilage (retinacula) are formed, and are frequently 
 enclosed in one or two pouches (bursiculcv) formed by the rest of 
 the tissue of the rostellum. The pollinia adhere to the retinacula 
 by the caudicle, when present, and are removed, in pollination, by 
 the adhesion of the retinacula to the proboscis of the insect (see 
 p. 413).
 
 GROUP V. AXGIOSPERXLE ; MONOCOTYLEDOXES. 
 
 505 
 
 Most of the indigenous species have underground rhizomes or 
 tubers. In the latter case, two tubers are usually present : the 
 
 Fis. 317. Tubers (A) of Orchis Morio; B of Gymnndenia Conopuca : s the peduncle; 1 this 
 year's tuber ; 2 next year'* tuber; fc the bud ; w and tc' roots (nat. size). 
 
 older one, which, at the time of flowering, becomes flaccid (Fig. 317 
 
 A and S, 1), throws up the flowering scape (s) or, in young plants, 
 
 a short underground stem which produces only leaves above ground. 
 
 At the upper end of this tuber another much firmer tuber is formed 
 
 (Fig. 317, 2), bearing at its apex the bud of the next years stem (A'). 
 
 The tuber is to be regarded as a 
 
 lateral bud which coalesces with its 
 
 first root (or more than one, Fig. 
 
 3175) and then increases in bulk: 
 
 the lower end of an undivided tuber, 
 
 as well as the ends of palmate tubers, 
 
 has, in the young state at least, the 
 
 same structure as the apex of a true 
 
 root. 
 
 The genera of Orchid aceae are so nu- 
 merous and so diverse that it is impossi- 
 ble to give more than a summary of 
 those which are British. 
 
 DIANDR.E : two fertile stamens, belong- 
 ing to the inner whorl: all three lobes 
 of the stigma are susceptible of pollina- 
 
 tion: pollen-grains cohering but slightly. 
 -c, ., 7, . ,.. f. j- 
 
 Fam. 1. tVr^te. C W r,^,. 
 
 Calceolus, the Lady s Slipper, now very 
 rare, occurs in woods in the north of 
 
 FIG. 318. Flower of Cypripedium 
 Calceolus .- ji p the leaves of the peri- 
 
 *"& "" ** c l Rwav - * 8ide 
 view. B Back view. C Front view; 
 , ovftry; ^ gjno8tmilim ; . . the 
 
 two fertile 8tamen9 . staminode; n 
 btigma. (After Sachs.)
 
 506 PART IV. CLASSIFICATION. 
 
 England : it has a creeping rhizome and broad ovate leaves : the perianth 
 is of a reddish-brown colour, except the labellum which is yellow and 
 forms a shoe-like sac (Figs. 315, 318). 
 
 MONAXDR.E : one fertile stamen, the anterior, belonging to the outer 
 whorl : only the two lateral lobes of the stigma are susceptible of pollina- 
 tion : the anterior lobe is rudimentary, or is developed as the rostellum: 
 pollen-grains coherent into pollinia. 
 
 Fam. 2. Ophrydince : anther short and broad ; the waxy pollinia are 
 basitonous; a rostellum, forming retinacula to which, the caudicles of the 
 pollinia adhere. 
 
 To the sub-family Serapiadece, which is characterized by the short 
 gynostemium and the erect anther belong the genera Ophrys, Orchis, and 
 Aceras. In Ophrys there are two distinct bursicul^ and retinacula, and 
 the pollinia remain distinct : the flowers resemble insects : 0. apifera the 
 Bee Orchis, 0. aranifera the Spider Orchis, and 0. musciferathe Fly Orchis, 
 occur in chalk pastures. In Orchis there is but one bursicula, but there 
 are two retinacula, so the pollinia may be removed separately, and the 
 labellum is spurred : Orchis Morio, mascula, and militaris, have round or 
 oval tubers ; whilst O. latifolia, maculata, and pyramidalis have palmate 
 tubers. In Aceras (Aceras anthropophora is the green Man-Orchis) the 
 3-lobed lip is not spurred, and there is but one retinaculum. 
 
 To the sub-family Gymnadeniece, characterized by the absence of a 
 bursicula, and consequently bare retinacula, belong the British genera 
 Gymnadenia, Habenaria, Neotinea, Herminium (as also other interesting 
 European genera, such as Chamseorchis and Nigritella). In Gymnadenia 
 (O. Conopsea, the fragrant Orchis) the retinacula are contiguous : in Habe- 
 naria (H. albida, lifolia, viridis, Butterfly Orchis) the retinacula are 
 distant : in Neotinea (N. intacta) the pink perianth-segments are con- 
 nivent: whilst in the preceding genera the labellum is spurred, it is not 
 spurred in Herminium (H. Monorchis, the green Musk Orchis). 
 
 Fam. 3. Neotliince, : pollinia usually soft and granular, either acrotonous 
 or altogether without caudicles. 
 
 To the sub-family Cephalantherece., in which the labellum is transversely 
 segmented, belong the genera Cephalanthera, Epipactis, and Epipogum. 
 Cephalanthera (C. grandijiora, C. enzifolia, C. rubra) and Epipactis (E. 
 latifolia and E. palustris), the Helleborines, are rhizomatous leafy plants 
 with well-developed leaves on the peduncles : the labellum is not spurred, 
 and the rostellum is rudimentary. Epipogum Gmelini is a saprophyte, has 
 no roots, and its leaves are scaly and not green ; it has granular pollinia 
 with acrotonous caudicles, a rostellum producing a retinaculum, and a 
 spurred labellum ; the flower is not resupinate. 
 
 To the sub-family Spirantliece, characterized by a rostellum as long as 
 the anther, producing a retinaculum to which the granular pollinia 
 (without caudicles) adhere, belong the genera Spiranthes, Listera, and 
 Neottia. Spiranthes, Lady's tresses (8. autumnalis, cestivalis, and gemmi- 
 para) has a spike unilateral by torsion, perianth-segments connivent, no 
 spur. Listera, Tway-blade (L. cordata and ovata), has only two foliage- 
 leaves, and spreading perianth-segments, no spur. Neottia Nidus-Avis, the
 
 GROUP V. ANGIOSPERM.E ; MONOCOTYLEDOXES. 507 
 
 BirdVnest Orchid, is a saprophyte, with scaly leaves, which do not contain 
 chlorophyll ; labellum not spurred. 
 
 To the sub-family Phj/surece, characterized by the structure of the pol- 
 liniurn, which is sectile, belongs the genus Goodyera (G. repeim) in which 
 the labellum has no spur, and the pollinia have acrotonous caudicles ; the 
 inflorescence is, like that of Spiranthes, a unilateral twisted spike ; the 
 plant is rhizomatous. 
 
 Fam. 4. Liparidince : the anther produces four waxy pollinia without 
 caudicles. Liparis (Siurmia) Loeselii, has only two foliage-leaves and 
 a pseudo-bulb; the flower is not resupinate ; there are two retiuacula, to 
 each of which a pair of pollinia become attached. Malaxis (M. paludota, 
 Bog Orchis) has a short gynostemium and a single retinaculum ; repro- 
 duced by pseudo-bulbs. Corallorhiza (C. innata, the spurless Coral-root) is 
 a saprophytic plant, without roots or foliage-leaves. 
 
 There are many other families, including a large number of genera 
 which are mainly tropical and commonly epiphytic with aerial roots. 
 Man}' of these are cultivated in hot-houses such as Oncidium, Vandai 
 Dendrobium, Angrsecum, etc. Vanilla is the dried fruit' of Vanilla 
 plaiiifolia, a climbing species. 
 
 Though pollination is usually dependent upon the visits of insects (see 
 p. 413), self pollination is by no means uncommon. For instance, among 
 British Orchids, Ophrys apifera and Neotinea iiitacta are probably always 
 self-pollinated, and Neottia Nidus-Avia, Epijxidis oualis and E. latifolia, are 
 frequently self-pollinated, simply by the falling of the pollen on to the 
 stigma. Cephalanthera rubra is commonly pollinated whilst in the bud, by 
 the germination of the pollen-grains, the pollen-tubes making their way to 
 the stigma. 
 
 Cohort V. Narcissales. Flowers regular or irregular: not 
 less than three stamens in the androecium : perianth petaloid : 
 seeds with oily endosperm. 
 
 Order 1. AMARYLLIDACE^. #3, C3, ^13 + 3 or 12 to 18, 0, 5j , 
 The flower is occasionally zygomorphic and narrowly funnel- 
 shaped : anthers usually introrse. The fruit is usually a trilocular 
 loculicidal capsule, sometimes a berry. 
 
 The principal of the numerous genera are arranged in the following 
 families: 
 
 Fam. 1. Amur nil idoidece: subterranean stem, bulbous: scape leafless, 
 bearing a single terminal flower, or an umbellate inflorescence, invested 
 by one or more bracts. Amongst the genera without a corona (see p. 458) 
 are Amaryllis (.4. Belladonna, the Belladonna Lily), Vallota (V. purpurea, 
 the Scarborough Lily) with zygomorphic flowers ; Galanthus (G. nivalis, 
 the Snowdrop), and Leucojum (L. vernum, the Spring Snowflake; L. asti- 
 vum, the Summer Snowflake) with actinomorphic flowers. Amongst the 
 genera with a corona are the many species of Narcissus ; A T . (C'orbtilaria) 
 Bulbocodium, the Hooped Petticoat Daffodil ; N. (Ajax) Reudo-narciim, the
 
 508 
 
 PART IV. CLASSIFICATION. 
 
 common Daffodil ; N. (Queltia) Jonquitta, the Jonquil, and 2V. incomparalrilis 
 the Star Daffodil ; 2V. poeticus, the Poet's or Pheasant's Eye Nai-cissus ; 2V. 
 Tazetta, the Cluster Narcissus. 
 
 Fam. 2. Agavoidece : stem not subterranean, short or elongated into a 
 trunk. Here belongs the genus Agave. Agave americana, commonly 
 known as the false or American Aloe, is a native of Mexico but has been 
 naturalised in Southern Europe. The short stem bears a rosette of large 
 thick prickly leaves : when it has attained sufficient vigour in Southern 
 Europe in from 10 to 20 years it throws up a scape 20-30 feet high, which 
 branches arid bears a large number of flowers in a pyramidal panicle. 
 
 The British species of the 
 order are the common Daffo- 
 dil, the Snowdrop, and the 
 Snowflakes. 
 
 Order 2. IRIDACE.E. 
 /v3, C3, 43 + 0, Gjj,. The 
 
 flower is sometimes zygo- 
 morphic : the anthers are 
 extrorse . the fruit is 
 usually a trilocular locu- 
 licidal capsule. 
 
 Fam. 1. CROCOIDE^E : flowers 
 actinomorphic, terminal, 
 single, with sometimes other 
 axillary flowers, each in- 
 vested by a spathe : stem, a 
 corm. 
 
 To this family belong, 
 amongst others, the genera 
 Crocus and Eomulea. Many 
 species of Crocus (e.g. C. 
 aureuSj bifloriis, sjxciosus, ver- 
 nus, etc.) are cultivated ; C. 
 sativus is the Saffron Crocus, 
 the dried stigmata of which 
 are termed Saffron : the only 
 indigenous British species is 
 C. nudiflorus which is autumn- 
 flowering. Romulea (Trichonema) Columnce occurs in the Channel Islands. 
 Fam. 2. IRIDIOIDKJE: flowers mostly actinomorphic, forming many- 
 flowered inflorescences of various form with spathes, each of which invests 
 more than one flower : stem bulbous or rhizomatous. 
 
 Iris, the Flag, is the principal genus. The species of this very large 
 genus may be divided into two groups based upon the bulbous or the 
 rhizomatous character of the stem. The most familiar of the bulbous 
 Irises are, /. xiphioides (or Xiphion latifolium, or Iris anglica) the so-called 
 
 FIG. 319. Diagram of the flower of Iris, and view 
 of the same after the removal of the perianth : s 
 peduncle ;/ inferior ovary ; r tabular portion of the 
 perianth ; pa the insertion of the outer, pi of the 
 inner leaves of the perianth ; st stamen ; a anther ; 
 n n n the three petaloid stigmata (nat. size).
 
 GROUP V. AXGIOSPERM.E ; DICOTYLEDONES. 509 
 
 English Iris; /. Xiphium (Xiphion vulgare) the Spanish Iris; /. reticulala 
 and persica. The rhizomatous Irises are classified, according to the pre- 
 sence or absence of hairs (beard) on the perianth-segments, into bearded 
 (e.g. Jris yermanica,florentina,etc,.') and beardless forms (e.g. Iris Pseudacorus, 
 the Yellow Flag, andfoetidissima, both of which are British). 
 
 Fam. 3. IXIOIDE.E : the flowers, which are frequently zygomorphic, are 
 each invested by a spathe : stem, usually a corm. 
 
 In the Gladiolece, the zygomorphism of the flower is well-marked, but the 
 flower may be either straight and erect (e.g. Tritonia, Montbretia, Spar- 
 axis), or curved (e.g. Gladiolus). Gladiolus illyricus (communis\ the lesser 
 Gladiolus or Corn-Flag occurs in England. 
 
 CLASS X. DICOTYLEDONES. 
 
 The ripe seed (Fig. 245) may be albuminous, containing a mass 
 of endosperm and a relatively small embryo, as in the Umbelliferae 
 and Euphorbiaceae ; but sometimes the embryo is relatively large 
 and the endosperm occupies only a small space, as in the Labiatae : 
 more commonly the seed is exalbuminous, the endosperm being 
 wholly absent, and then the embryo, which has large and fleshy 
 cotyledons, fills the entire cavity of the testa, as in the Rosaceae, 
 the Leguminosse (Fig. 320), and the Composite. Perispenn is 
 rarely present, either together with endosperm (e.g. some Piperales 
 and Nymphaeacese), or alone (Chenopodiales, Caryophyllales). 
 
 The embryo (see p. 401) usually has distinct members, consist- 
 ing of an axis and two opposite cotyledons; in rare cases, e.g. 
 Corydalis, only one cotyledon is present, or abnormally three may 
 occur, as is occasionally the case in the Oak, the Sycamore, and 
 the Almond. In parasites and saprophytes which are devoid of 
 chlorophyll and which have very small seeds, such as Monotropa 
 and Orobanche, the embiyo is quite undifferentiated, and it con- 
 sists of only a small number of cells. 
 
 The axis of the embryo frequently persists as the main axis of 
 the plant which grows in length and produces numerous less 
 vigorous lateral shoots; but it often happens that some of these 
 lateral branches subsequently grow as vigorously as the main axis : 
 when this is the case, and when also the lower and feebler shoots 
 die off, a head, such as is common in forest-trees, is the result ; in 
 the case of shrubs, vigorous branches are formed quite low down 
 on the main stem. The branching of the stem is almost invariably 
 axillary and lateral : it is frequently monopodial (p. 19), but in 
 many forest-trees the stem (trunk) and branches form a sympo-
 
 510 
 
 PART IV. CLASSIFICATION. 
 
 dium, the uppermost lateral bud growing each year in the direction 
 of the main axis, which does not itself develop any further (p. 21). 
 When the axis of the embryo continues to be the main axis of 
 the plant, the primary root also develops greatly, and forms a 
 tap-root from which the lateral roots grow in acropetal succession. 
 In cases in which the growth in length of the tap-root is limited, 
 numerous adventitious roots spring from its older portions ; these 
 may again give rise to lateral roots, and by a repetition of this 
 process an elaborate root-system is formed. 
 
 FIG. 32 1 . Ftrta Faba, the Bean. A Seed with one of 
 the cotyledons removed ; c the remaining cotyledon ; 
 IT radicle ; fcn plumule ; s testa. B Germinating seed ; 
 s testa ; I a portion of the testa torn away ; n hilum ; 
 st petiole of one of the cotyledons; fc curved epi- 
 cotyl ; he the very short hypocotyl ; h the primary 
 root; twits apex; fcn bud in the axil of one of the 
 cotyledon*. 
 
 FIG. 321. Seedling of the Maple 
 (nat. size): c c the cotyledons; fc 
 the plumule; he the hypocotyl; 
 11- primary root; h root hairs 
 (the lower part is cut off). 
 
 The stem is almost always monostelic (see p. 117). The vas- 
 cular bundles of the stem are almost always conjoint, collateral. 
 and open, and the stem grows in thickness by the activity of the 
 cambium -ring which is formed (p. 137). When the stem grows in 
 thickness, the root does so also.
 
 GROUP V. ANGIOSPERMLE ; DICOTYLEDOXES. 511 
 
 The leaves exhibit infinite variety both in their relative position 
 and in their form. The foliage-leaves almost always consist of 
 petiole and blade ; amplexicaul leaf-bases are comparativelv rare, 
 but stipules, on the contrary, are very common. Branching or 
 segmentation of the leaves is common, and is frequently indicated 
 by the incision of the margin. The usually reticulate venation 
 of the leaves is characterized by the presence of a large number 
 of veins which project on the under surface, except in thick, 
 fleshy leaves, and which frequently anastomose ; a midrib is 
 almost always present, giving off lateral branches to right and 
 left. 
 
 The flowers, when they are lateral, are usually furnished with 
 two prophylla or bracteoles (see p. 443) : they differ very consider- 
 ably in their structure, and cannot be referred to any one type. 
 The following are the principal forms : 
 
 1. In a considerable number the perianth, which is simple, and 
 the androecium are isomerous, consisting of four, five, or six 
 members ; their arrangement is either spiral (f ), or whorled so 
 that the stamens are always superposed on the leaves of the 
 perianth ; the latter are all similar and are sepaloid. Formula 
 P5 | J5, or Pn + n, An + n, where n = 2 or 3. This structure pre- 
 vails in some of the Monochlamydeae (Urticales, Amentales). 
 
 2. In a second group, all the parts of the flower are arranged in 
 a continuous spiral, the stamens, and sometimes the carpels, being 
 generally more numerous than the leaves of the perianth : the 
 perianth may consist only of a calyx, or a corolla may be developed 
 in place of the external stamens ; when this is the case the corolla 
 alternates with the calyx, provided that it is isomerous with it, as 
 in most Ranales. 
 
 3. With these two types are connected by many intermediate 
 forms those flowers in which the biseriate perianth and the stamens 
 are in whorls : their formula is Kn, Cn, An + n, where n usually 
 = 5 or 4. This is the most common type of structure of the 
 flower ; it occurs in most Polypetalse and Gamopetalae ; it may 
 be modified either by the suppression of one (usually the inner) 
 whorl of stamens, or by their multiplication, their branching, or 
 their cohesion, or by the suppression of the corolla. 
 
 4. Finally, there remain certain flowers which cannot be directly 
 referred to any one of the above types, and they must therefore 
 be left unexplained for the present, and the relationships of their 
 families must remain uncertain.
 
 512 PART IV. CLASSIFICATION. 
 
 In all cases the structure of the gynseceum is variable : it is 
 frequently oligomerous. 
 
 The sub-divisions in which the Dicotyledons are arranged in the 
 following classification are especially characterized by peculiarities 
 in the structure of the flower. It is impossible, however, to draw 
 sharp distinctions between the sub-classes, the cohorts, the orders, 
 and sometimes even between the families, for the position of a 
 plant in the system depends, not upon any one character, but upon 
 the aggregate of its characters. 
 
 The principal orders of Dicotyledons may be arranged as 
 follows : 
 
 SUB-CLASS I. MONOCHLAMYDE^E. 
 
 Cohort I. Urticales. Cohort III. Chenopodiales. 
 
 Order 1. URTICACE^E. Order 1. CHEXOPODIACE^. 
 
 2. HORACES. 2. POLYGONACPLE. 
 
 3. CANNABINACE.E. Cohort IV. Asarales. 
 
 ,, 4. ULMACE^E. Order 1. ARISTOLOCHIACE^. 
 
 Cohort II. Amentales. Cohort V. Santalales. 
 
 Order 1. BETULACE^E. Order 1. SAXTALACE.E. 
 
 2. CORYLACE.E. 2. LORAXTHACE.E. 
 
 3. FAGACE/E. Cohort VI. Euphorbiales. 
 
 4. JUGLAXDACE.E. Order 1. EUPHORBIACE.E. 
 5. SALICACEJE. 
 
 SUB-CLASS II. POLYPETAL.E. 
 SEEIES I. THALAMIFLOJELE. 
 
 Cohort I. Ranales. Cohort III. Parietales. 
 
 Order 1. RAXUXCULACE^E. Order 1. PAPAVERACE.E. 
 
 2. MAGNOLIACELE. 2. FUMARIACE.E. 
 
 3. NYMPHJEACE^E. 3. CRUCIFER.E. 
 
 4. BERBERIDACE.E. 4. CISTACE^:. 
 
 Cohort II. Caryophy Hales. 5. VIOLACE^:. 
 
 Order 1. CARYOPHYLLACEJE. Cohort IV. Guttiferales. 
 
 Order 1. HYPERICACK<. 
 Cohort V. Malvales. 
 Order 1. TILIACE^:. 
 2. MALVACEAE.
 
 GROUP V. ANGIOSPERXLE | DICOTYLEDONE3. 
 
 513 
 
 SERIES II. DISCIFLOR^E. 
 
 Cohort I. Geraniales. 
 
 Order 1. GERANIACE.E. 
 2. LINAGES. 
 3. OXALIDACE^E. 
 4. BALSAMINACE.E. 
 
 5. 
 
 SERIES III. 
 
 Cohort I. Umbellales. 
 
 Order 1. UMBELLIFER^E. 
 
 2. ARALIACEJE. 
 Cohort II. Passiflorales. 
 
 Order 1. CUCURBITACE.E. 
 Cohort III. Myrtales. 
 Order 1. ONAGRACE^E. 
 2. LYTHRACELE. 
 3. MYRTACE^E. 
 
 Cohort II. -Sapindales. 
 Order 1. SAPINDACE^E. 
 
 2. ACERACELE. 
 
 3. POLYGALACE.E. 
 Cohort III. Celastrales. 
 Order 1. CELASTRACELE. 
 2. RHAMXACE^E. 
 3. AMPELIDACE.E. 
 
 CALYCIFLOR.E. 
 
 Cohort IV. Resales. 
 Order 1. ROSACEJS. 
 
 2. LEGUMINOS^E. 
 Cohort V. Saxifragales. 
 Order 1. SAXIFRAGACE^:. 
 2. CRASSULACE^E. 
 
 SUB-CLASS in. GAMOPETALJ:. 
 
 SERIES I. 
 
 Cohort I. Lamiales. 
 
 Order 1. LABIATE. 
 Cohort II. Personales. 
 
 Order 1. SCROPHULARIACE^E. 
 2. PLANTAGINACEJE. 
 3. OROBANCHACE^E. 
 4. LENTIBULARIACE^E. 
 Cohort III. Polemoniales. 
 Order 1. CONVOLVULACE^:. 
 2. POLEMONIACELE. 
 3. SOLANACE^:. 
 4. BORAGINACE^E. 
 
 SERIES II. 
 Cohort I. Campanales. 
 
 Order 1. CAMPANULACEL^. 
 Cohort II. Rubiales. 
 Order 1. RUBIACE.E. 
 
 2. CAPRIFOLIACE^I. 
 M.B. 
 
 HYPOGYN^E. 
 
 Cohort IV. Gentianales. 
 Order 1. GENTIANACELE. 
 
 2. OLEACELE. 
 Cohort V. Primulales. 
 Order 1. PRIMULACEL^. 
 
 2. PLCMBAGINACE^E. 
 Cohort VI. Ericales. 
 Order 1. ERICACE^:. 
 2. PYROLACELE. 
 3. VACCINIACE^. 
 
 EPIGYN^l 
 Cohort III. Asterales. 
 
 Order 1. VALERIANACELE. 
 2. DIPSACE*:. 
 3. COMPOSITE. 
 
 L L
 
 514 
 
 PART IV. CLASSIFICATION. 
 
 SUB-CLASS I. MONOCHLAMYDE.E. 
 
 The flowers have a simple, usually sepaloid, perianth, or it may 
 be absent ; they are commonly unisexual. 
 
 Cohort I. Urticales. Flowers usually diclinous, in inflor- 
 escences of various forms : perianth usually present, simple, 
 sepaloid, consisting typically of five (-) or reduced to four (2 +. 2) 
 segments ; stamens equal in number and opposite to the segments 
 of the perianth, in consequence, apparently, of the essentially 
 spiral arrangement of the floral organs (see p. 446) ; ovary 
 superior, monomerous, unilocular, or sometimes dimerous with 
 two styles, and then rarely bilocular: ovule solitary, in different 
 positions. Seed commonly containing endosperm. The inflor- 
 escences in orders 1-3 are usually situated two together at the base 
 of a leafy dwarf-shoot which springs from the axil of a leaf, and 
 they are cymose (Fig. 322). The leaves are generally hirsute. 
 Cystoliths (p. 78) are commonly present. 
 
 FIG. 322. Part of the stem of Urtica 
 urem, with a leaf (/) in the axil of which 
 is the branch (m), at the base of which 
 are the inflorescences (b), without any 
 bracts (nat. size). 
 
 FIG. 323. .4 staminal rf ; B carpellary 
 $ flowers of the Stinging Nettle, Urtica : 
 p perianth ; a stamen ; n' rudimentary 
 ovary of the <J flower ; ap outer ; i;> 
 inner whorl of the perianth ; n stigma of 
 the $ flower (mag.). 
 
 Order 1. URTICACELE. Ovary monomerous: ovule central, ortho- 
 tropous. Seed containing endosperm. They are mostly herbs or 
 shrubs without milky juice and frequently provided with stinging 
 hairs : leaves alternate, stipulate. Flowers polygamous, monoecious, 
 or dioecious, in paniculate or glomerulate inflorescences. 
 
 Urtica urens and dioica (Stinging Nettles) are known by the stinging 
 hairs which are distributed over their whole surface: perianth 2 + 2; the 
 two outer segments of the perianth of the $ flower are larger than the 
 inner segments (Fig. 323 B). In the former species the $ and ? flowers 
 are contained in the same panicle, and the floral axis is but feebly de- 
 veloped ; in the latter they are on different plants, and the axis is well
 
 GROUP V. ANGIOSPERALE ; DICOTYLEDONES. 515 
 
 developed and bears leaves. Bohmeria nivea, a native of China and Japan, 
 has strong bast-fibres used for weaving the material known in England as 
 Grass-cloth. Parietaria officinalis, Wall-Pellitory, having polygamous 
 flowers with a gamophyllous perianth, and destitute of stinging hairs 
 occurs occasionally on walls, by roadsides, etc. 
 
 Order 2. MORACE^E. Ovary generally dimerous, and sometimes 
 bilocular (Artocarpus) : ovule suspended, anatropous or campylotro- 
 pous, more rarely basal and orthotropous : seed with or without 
 endosperm ; the fruit is enveloped by the perianth (usually 2 + 2), 
 which becomes fleshy, or by a fleshy floral axis. Trees and 
 shrubs with milky juice, scattered leaves and caducous stipules. 
 
 Morus alba and n iyra (Mulberry) come from Asia ; the flowers' are dis- 
 posed in short catkins ; the catkins are borne singly on shoots, which, at 
 the time of flowering are still buds, and they contain the diclinous flowers ; 
 the $ flowers give rise, as ripening take place, to 
 a spurious fruit (sorosis, p. 472), consisting of 
 spurious drupes formed mainly by the perianths. 
 The leaves, particularly of the former species, are 
 the food of the silkworm. Brousxonetia papyrifera 
 (Paper Mulberry) has flowers like the preceding, 
 but they are dioecious : the bark is made into 
 paper in China and Japan. Madura tindoria, in 
 Central America, yields Fustic, a dye. Fiats 
 Carica is the Fig-tree of Southern Europe ; the 
 fig itself (termed a syconus) is the deeply concave 
 axis of the inflorescence, on the inner surface of 
 which the flowers and subsequently the fruits, in FIG. 32*. Longitudinal 
 the form of hard grains (achenes), are borne (Fig. 8ection of a Fi * (nat 8ize > : 
 321 /); the cavity is closed above by small ^eel""/ 1 .^ T, 
 bracts (Fig. 324 6). Ficus elastica is the India- flowers ; 6 bracts, 
 rubber tree ; it is frequently cultivated in rooms. 
 
 F. religiosa and other East Indian species yield Caoutchouc, which is their 
 inspissated milky juice (latex). Ficus indica is the Banyan. Artocarpus 
 incisa is the Bread-fruit tree of the South Sea Islands ; the large spurious 
 fruit (sorosis) of this tree is roasted and eaten as bread. Galadodendron 
 riile, the Cow-tree of Columbia, has a nutritious latex, while that of Anti- 
 aris toxicaria (Java) is poisonous. 
 
 Order 3. CANNABINACELE. Ovary dimerous, unilocular: ovule 
 suspended, campylotropous : seed with endosperm. Flowers 
 dioecious : the < flowers (Fig. 325 A) have a 5-partite perianth and 
 5 short stamens; the $ flowers have a tubular entire perianth 
 (Fig. 325 S, p\ enclosed in a bracteole (Fig. 325 B, tf). Herbs with 
 decussate leaves at least the lower ones and persistent stipules ; 
 devoid of latex.
 
 516 
 
 PART IV. CLASSIFICATION. 
 
 FIG. 325. A <J flower of the Hop : p 
 the perianth ; o stamens. B Part of ? 
 inflorescence : p perianth ; / ovary, with 
 two stigmata (i) ; each flower is enclosed 
 in its bracteole (d) ; s scale, i.e. one of the 
 two stipules, from the common axil of 
 which the branch bearing the flowers 
 springs. 
 
 Cannabis sativa, the Hemp, a native of Asia, is cultivated throughout 
 Europe. The $ inflorescences are panicled dichasia or scorpioid cymes, 
 and are disposed on both sides of a rudimentary shoot at the apex of the 
 
 plant ; the $ flowers are placed singly 
 on both sides of a similar shoot, which 
 bears secondary shoots in the axils of 
 its leaves, each having two flowers. 
 The tough bast-fibres are used in 
 weaving and for ropes ; the seeds 
 contain a great deal of oil. Humulus 
 Lupulus, the Hop, is both cultivated 
 and found wild. The stem, which 
 has the peculiarity of twining to the 
 right, bears its leaves in pairs ; each 
 leaf has a pair of membranous sti- 
 pules. In the inflorescence the leaves 
 (bracts) are placed singly, and are 
 finally represented only by their 
 stipules. In the ? inflorescence, 
 which somewhat resembles a fir-cone, 
 a rudimentary shoot is present in the 
 common axil of each pair of stipules, and bears two flowers on each side ; 
 it seems at first sight as if two flowers were developed in the axil of each 
 stipule (Fig. 325 B). All the scales and bracts are covered, especially 
 on the upper surface, with numerous yellow glands. In the $ inflores- 
 cence the shoot which bears the flowers is well developed. 
 
 Order 4. ULMACE^E. Ovary dimerous, sometimes bilocular, but 
 generally unilocular by abortion. Ovule suspended and solitary. 
 Flowers mostly monoclinous, with a 4-6-partite perianth (Fig. 326 
 A). Woody plants devoid of milky juice : leaves alternate, with 
 caducous stipules. The inflorescences (glomerules) are borne di- 
 rectly in the axils of the leaves. 
 
 In the genus Ulmus the compact dichasial inflorescences are developed 
 in the axils of the leaves (either persistent or deciduous), of the previous 
 year, and they are invested by bud-scales ; one 
 or more flowers are developed in the axil of 
 each of the more internal scales (bracts), and 
 they open before the unfolding of the leaves. 
 The ovary is sometimes bilocular. The fruit 
 is a samara, that is, an achene with a broad 
 membranous wing (Fig. 826 B}. The leaves 
 are alternate, and always oblique (p. 33). The 
 annual shoots have no terminal bud, and so 
 they form a sympodium (see p. 21). Two 
 species of Elm are indigenous in England: 
 Ulmus campeztris, the common Elm, and Ulmus 
 
 FIG. 326. 4 Flower of 
 Ulmus monlana (mag.) : d 
 bract ; p perianth ; a stamens. 
 B Fruit (samara) (nat. size) : 
 m membranous margin 
 (wing).
 
 GROUP V. ANGIOSPERM.E ; DICOT^LEDONES. 517 
 
 monlana, the broad-leafed Wych, or Scottish, or Mountain Elm. Celtis 
 australis, from Southern Europe and C. occidentalis, from North America, 
 are often cultivated as ornamental trees ; their flowers are polygamous 
 and are placed singly or several together in the axils of the oblique 
 acuminate leaves : the fruit is drupaceous. 
 
 Cohort III. Amentales. The flowers, which are either dicli- 
 nous or dioecious, are arranged in catkins (amenta). The perianth, 
 when it is present, consists typically of 5 (-f ) segments ; or it may 
 deviate from the type so as to consist of four, (i.e. 2 + 2), or six (i.e. 
 3 + 3) segments : the stamens, when their position can be determined, 
 are superposed on the segments of the perianth for the reason given 
 in the case of Urticales (see p. 514). The ovary is either superior 
 or inferior, di- or tri-merous, with few ovules. The fruit (with the 
 exception of the Salicacese) becomes by abortion one-seeded, and 
 is indehiscent : the seed has no endosperm. The flowers are fur- 
 nished with bracts which often form investments for the fruit: 
 their arrangement in most of the orders 
 is as follows : in the axil of a scaly 
 bract (the bracts being arranged spirally 
 in the amentum) is a flower (&) with 
 two bracteoles a and /?, in the axil of 
 each of which is another flower with 
 two more bracteoles a' and yS' (Fig. 327). 
 The plants are trees and shrubs. 
 
 Order 1. BETCLACE^. The flowers FI. 327 -Typical diagram o 
 
 a group of flowers in the Amen- 
 
 are monoecious, but in different catkins. taleg . d bract ; 6 the median 
 The 2 flowers have no perianth : the flower with its bracteoles, a and 
 
 r , ft ; b' V the two lateral flowers, 
 
 Ovary IS bllocillar, With two OVUles: ^th their bracteoles ' and p'. 
 
 the fruit is one-seeded, indehiscent, 
 
 without any investment : the bract is coherent with the two or four 
 bracteoles (the bracteoles a' are always absent) to form a three- or 
 five-lobed scale, which does not adhere to the fruit. 
 
 Alnus, the Alder. In the $ amenta three flowers with four bracteoles 
 (a, /3, /3', p) occur in the axil of the bract, each flower having a perianth of 
 four segments, and four unbranched stamens. In the ? amenta the me- 
 dian flower is absent ; the four bracteoles coalesce with the primary bract 
 (Fig. 328 B, v *) to form a five-lobed woody scale which persists after the 
 fall of the fruit which is not winged. The <J catkins are borne terminally, 
 and the ? laterally on the highest lateral branch, on the shoots of the 
 previous year; they are not enclosed by bud-scales during the winter, 
 and blossoming takes place before the unfolding of the leaves. The leaves 
 have usually a arrangement : in A. incana, the White Alder, the leaves
 
 518 
 
 PART IV. CLASSIFICATION. 
 
 are acuminate and gray on the under surface ; in A. glutinosa, the black or 
 common Alder, they are obovate or even emarginate, and green on both 
 surfaces. In Alnus viridis, the Mountain Alder, only the $ catkins 
 are destitute of bud-scales in the winter : the fruit is winged, 
 
 Betula, the Birch. In both kinds of catkins the three flowers have only 
 the bracteoles a and /3. In the $ flowers the perianth is usually incom- 
 plete, and there are only two stamens, the filaments of which are forked. 
 In the ? catkins, the two bracteoles cohere with the bract to form a three- 
 lobed scale which falls off together with the winged fruit. The $ cat- 
 kins are borne terminally on the shoots of the previous year, and are not 
 covered with bud-scales during the winter ; the $ catkins are borne ter- 
 minally on lateral dwarf-shoots which have only a few leaves, and they 
 are enclosed by bud-scales during the winter ; as a consequence, flowering 
 takes place after the unfolding of the leaves. The shoots of successive 
 years form sympodia, and the leaves are arranged spirally. B. verrucosa has 
 white glands on the leaves and young shoots : B. pubescens has no glands, 
 but the shoots are hairy ; it is a northern form : B. fruticosa and 
 B. natia are shrubs occurring in high latitudes : B. alba is the common 
 Birch. 
 
 FIG. 328. A Scale from a (J catkin of 
 Alnus incana : the axillary branch adheres 
 to the scale (s), it bears four bracteoles and 
 three flowers: two of the flowers are seen 
 laterally (I/ b'), the median one from above ; 
 p perianth ; a stamens. B Bract (s) of a $ 
 catkin of the same plant : its axillary branch 
 bears two lateral branches, each of which 
 bears two bracteoles (v v) and one flower ; / 
 the ovary ; n the stigmata (magnified and 
 diagrammatic). 
 
 Flo. 329. Alnus glutinosa. A Branch 
 bearing catkins (in winter). B a group of 
 <J flowers (from above). C The same after 
 removal of flowers (lateral view). E Group 
 of ? flowers, seen from within. F The 
 same after the removal of the flowers, ff 
 a scale from the ? catkin : 6 bract ; o, /3, j3' 
 bracteoles. 
 
 Order 2. CORYLACE^E. Flowers monoecious, in $ and ? cat- 
 kins. The <$ flowers have no perianth ; that of the $ flower is 
 rudimentary. The inferior ovary is bilocular ; one loculus is 
 sterile, the other contains two suspended anatropous ovules : the 
 fruit is one-seeded and indehiscent (a nut). Two flowers are borne 
 in the axil of the bract of the ? catkin, the median flower being 
 absent. The one-seeded fruit is surrounded by a leafy investment 
 (cupule) formed by the three bracteoles (a a! ft' and /fa' ft'
 
 GROUP V. ANGIOSPERJLE ; DICOTYLEDON ES. 
 
 51 9 
 
 respectively, Fig. 327) of each side. In the g catkin the median 
 flower only is developed : the filaments of the stamens are deeply 
 forked. 
 
 FIG. 330. Corylus Avellana. A Bract (s) of a 
 cj catkin, with a <J flower: stamens (/), and 
 anthers (a). B 9 catkin: the lower bracts () 
 have no flowers : the stigmata (n) project above. 
 C A single ? flower surrounded by the cupnle 
 (bracteoles) (c), with two stigmata (n) (mag. 
 and diag.) 
 
 FIG. 331. Corylus Avellana. A 
 Flowering branch. B $ flower 
 with its bract. C Bract after the 
 removal of the anthers. F Group 
 of ? flowers seen from within : 
 b bract. 
 
 In Corylus, the Hazel, the ? catkin resembles a bud, since the external 
 sterile bracts have the same structure as the bud-scales (Fig. 380.B) ; the 
 red stigmata project at the top ; the investment of the fruit is irregularly 
 cut 5 a small projection is formed on the fruit, the nut, by the remains of 
 the epigynous perianth. Each bract of the amentum bears two bracteoles 
 a and /}, and a flower consisting of four forked stamens (Figs. 330-1). 
 Both kinds of amenta are placed in the axils of the leaves of the previous 
 year, and are not enclosed by scales during the winter; hence flowering 
 takes place before the unfolding of the leaves. 
 Leaves distichous. C. Avellana is the common 
 Hazel ; a variety of C. tubuloaa, with red leaves, 
 the Purple or Blood Hazel, is cultivated as an 
 ornamental shrub. 
 
 In Carpinus, the Hornbeam, the fruit has a 
 three-lobed cupule (Fig. 332), the fruit is ribbed 
 and is surmounted by the perianth. The bract 
 of the <J catkin bears 4-10 deeply forked sta- 
 mens ; there are no bracteoles. The catkins of 
 both kinds are borne at the apex of short leafy 
 shoots of the same year, hence flowering takes 
 place after the unfolding of the leaves. Leaves 
 distichous. The annual shoots form sympodia. 
 
 C. Betuhts .has an irregular stem and serrate pinus Betulu*' with "three- 
 leaves which are plicate along the lateral veins. i bed capsule. 
 
 FIG. 332. Fruit of Car-
 
 520 
 
 PART IV. CLASSIFICATION. 
 
 In Ostrya (Southern Europe) the investmant of the fruit is an open 
 tube. 
 
 Order 3. FAGACE.E. Flowers monoecious, with a perianth of five 
 or six segments. Ovary inferior, trilocular, with two ovules in 
 each loculus ; ovules anatropous, ascending or suspended ; the fruit 
 is one-seeded and indehiscent (a nut) ; it is invested by a cupule 
 formed probably by the connate bracteoles a' /?' a' ft' (Fig. 327), and 
 having its surface covered with scales, prickles, etc. The fila- 
 ments are not forked. 
 
 In Quercus, the Oak, the $ catkins are loose ; each bract bears a single 
 flower in its axil without bracteoles : the perianth is 5-7 lobed, and the 
 stamens from 5-10 or indefinite (Fig. 3334). There is a single flower, the 
 median one, in the axil of each bract of the ? catkin ; thus the cupule in- 
 vests only a single fruit, and forms the so-called cup at its base. The 
 
 leaves are developed 
 in order, and are ag- 
 gregated towards the 
 apices of the annual 
 shoots ; the annual 
 shoots are always ter- 
 minal. The $ catkins 
 are borne in the axils 
 of the uppermost bud- 
 scales (pairs of stipules) 
 
 on b * 11 lon s and 
 dwarf - shoots of the 
 same year; the ? cat- 
 kins in the axils of the 
 foliage-leaves of the 
 terminal shoots: 
 flowering takes place 
 shortly after the un- 
 folding of the leaves. 
 The ovules are ascend- 
 ing. The hypogean cotyledons remain enclosed in the testa during 
 germination. Quercus Itobur is the English species, of which there are 
 two varieties, Quercus peduncuJata and Quercus sessiliflora : the former has 
 elongated ? catkins, so that the fruits are widely separated from each 
 other, and its pinnate! y lobed leaves are shortly stalked and cordate at 
 the base : the latter has compact ? catkins, so that the fruits form a 
 cluster, and its leaves have longer petioles, and are narrowed at the base. 
 Quercus Suber is the Cork-Oak of Southern Europe. There are also several 
 North American species. 
 
 In Fagus, the Beech, the catkins of both kinds are stalked dichasial 
 clusters, borne each in the axil of a foliage-leaf. The flowers have no 
 bracts, or bracteoles, except the cupule of the $ flower, The flowers of 
 
 c 
 
 FIG. S3?. Quercus pedunculata. A3 flower mncrnified: 
 j> perianth ; a stamens. B $ flower magnified : d bract ; c 
 cnpule ; y the epijrynous perianth; g the style; n the 
 stigma. C The same, still more magnified, in longitudinal 
 section ; / ovary ; a ovules.
 
 GROUP V. ANGI08PERlt : DICOTYLEDOXES. 
 
 521 
 
 the pendulous <J catkin are closely packed : they have a perianth of 4-7 
 segments, and 8-12 stamens. The erect $ catkin consists of two flowers 
 only, which are invested by a tetramerous cupule. The cupule is covered 
 Avith hard bristles, and when ripe splits into four valves to allow the two 
 triquetrous fruits to escape ; each fruit bears at its apex a brush-like rem- 
 nant of the perianth. The ovules are suspended. The ? inflorescences 
 are borne on erect axes in the axils of the leaves of the apical shoot of the 
 same year, the <? on pendulous axes springing from the axils of the lower 
 leaves of the shoot. Leaves distichous, approaching each other on the 
 under surfaces of the shoots, their axillary buds approaching each 
 other on the upper surface : the winter-buds are elongated and pointed. 
 The epigean cotyledons escape from the seed on germination. Fa gun 
 sylvatica is the common Beech : varieties with tinted leaves, such as the 
 Purple Beech and the Copper B^ech, are commonly cultivated. 
 
 In Castanea, the edible or Spanish Chestnut, some of the catkins consist 
 at their lower part of ? flowers and at their upper of <J flowers, whilst 
 others have only <J flowers. In the axil of each bract there are usually 
 either seven <? or three ? flowers : the latter are invested by the 
 bracteoles a and /3, and by a cupule formed by the other four bracteoles ; 
 the cupule, which is covered with prickles, completely encloses the fruit 
 until it is ripe, when it splits into four valves. Both kinds of catkins are 
 formed in the axils of leaves of shoots of the same year, the mixed catkins 
 being nearer to the apex than the <J ones. The ovules are suspended. The 
 leaves are arranged spirally on vigorous shoots ; they are distichous on the 
 less vigorous lateral shoots. C. vulyaris, from Southern Europe, is culti- 
 vated in parks ; it has undivided toothed leaves. 
 
 Order 4. JUGLAXDACE^E. Flowers monoecious, the two kinds of 
 flowers being contained in distinct catkins. Each bract bears in 
 its axil a single flower with 
 two bracteoles. The ? 
 flower has usually a peri- 
 anth : the inferior ovary is 
 dimerous, and encloses a 
 single erect orthotropous 
 ovule. The <$ flowers are 
 usually borne on the bract ; 
 
 , , Fig. 33*.^ Bract of the <J catkin of Jugian* 
 
 they may or may not have a nigra bearing a flower . p perianth and bract- 
 perianth, and the Stamens eole* ; stamens ; * axis of the catkin. B $ 
 j -A /!? QQ/4 A\ flower of the ssme plant: I bracteoles; e peri- 
 
 are indefinite (Fig. 334,1). anth; ngtigmata (magnifle d). 
 
 The fruit is drupaceous ; the 
 
 leaves are pinnate, and, like the flowers, they are aromatic. 
 
 In Juglans the $ catkins are borne on the apices of the leafless shoots of 
 the previous year, and the few-flowered ? catkins on the apices of the 
 leafy shoots of the same year. The bracteoles of the ? flowers (Fig. 8*4 /)
 
 522 
 
 PART IV. CLASSIFICATION. 
 
 grow up around the ovary. The succulent mesocarp is thin, and ruptures 
 irregularly; the hard endocarp opens on germination along the line of 
 junction of the two carpels, and then the incurved margins of the carpels 
 are seen as an incomplete longitudinal septum projecting between the two 
 cotj-ledons of the embryo which is closely invested by the endocarp. J. 
 regia, the Walnut Tree, is a native of Southern Europe : in North America, 
 J. cinerea and niyra occur ; also various species of Carya, the Hickory, re- 
 markable for its very hard wood. 
 
 Order 5. SALICACILE. The dioecious flowers are arranged in 
 amenta, and are borne in the axils of the bracts without any 
 bracteoles. There is no perianth, but each flower contains a 
 glandular disc or nectary. The ovary is dimerous and unilocular, 
 and contains a number of parietal ovules. The dehiscence of the 
 fruit is loculicidal ; the numerous seeds are furnished with a pencil 
 of silky hairs at their bases (p. 416). The catkins are developed at 
 
 the ends of lateral dwarf- 
 shoots which always bear 
 scales or even a few 
 foliage-leaves. 
 
 Salix, the Willow or Sal- 
 low, has entire bracts, a one- 
 or two-toothed nectary in 
 each flower, and usually 
 two stamens, entire shortly- 
 stalked leaves, and its win- 
 ter-buds are covered by a 
 scale which is formed by 
 the coalescence of two. Some species, such as S. alba, fragilis, and babylonica , 
 the Weeping Willow, have pendulous branches, and are arborescent : most 
 of them are shrubby, and some, such as S. reticulata, retusa, and herbacea, 
 are small decumbent shrubs occurring in the Alps and in high latitudes. 
 In S. purpurea and incana the two stamens are connate: S. triandra has 
 three stamens. Most of the species grow on the banks of rivers ; S. aurita 
 and caprea in forests, and S. repens and others on moors. 
 
 Populus, the Poplar, has toothed or lobed bracts, a cup-shaped nectary 
 (Fig. 335 C, p), and numerous (4-30) stamens ; the leaves are often lobed and 
 have long petioles ; the winter-buds are enclosed by a number of scales ; 
 the shoots have a terminal bud. 
 
 Cohort III. Chenopodiales. Flowers usually monoclinous ; 
 perianth sepaloid or petaloid : ovary monomerous or polymerous ; 
 ovule usually solitary ; embryo coiled or curved. 
 
 Order 1. CHEXOPODIACEJE. Flowers small, united to form a 
 dense inflorescence : the bracteoles are frequently suppressed. 
 
 Fig. 335.- 4 s , B ? flower of Salix -. d bract; h disc ; 
 o stamens; /ovary; n stigmata (enlarged). C De- 
 hiscent fruit of the Poplar ;s seeds : p disc.
 
 GROUP V. ANGIOSPERXLE ; DICOTYLEDON ES. 
 
 523 
 
 Fig. 330,-Flower of Cheno- 
 podium (enlaiged) ; fc peri- 
 anth ; a stamens ; / ovary ; 
 n stigma. 
 
 Stamens typically equal in number to and superposed on the 
 
 usually four (2 + 2) or five (*-) free or connate sepaloid perianth 
 
 leaves for the same reason as in the 
 
 Urticales (p. 514) (Fig. 336). Ovary 
 
 usually medially dimerous and unilocular, 
 
 with a single campylotropous, erect or 
 
 horizontal, basal ovule : seed contains 
 
 perisperm, but no endosperm. Stipules 
 
 wanting. 
 
 Clienopodium album, the Goose-foot, and (.'. 
 Bonus ffenricus, the All-good, are common 
 weeds on garden-ground and waste land. 
 Spinacia oleracea is Spinach, cultivated as a vegetable. Beta vnlgaris is 
 cultivated under the var. Cicla (Mangold) ; B. altissima is the species used 
 in the manufacture of sugar, and B. rubra is the red Beetroot ; B. mari- 
 tima is the wild Beet. Salsola, the Salt-wort, and its allies, Suseda, the 
 Sea-blite, and Salicornia, the Marsh-Samphire or Glass-wort, with fleshy 
 stems and leaves, are conspicuous in the vegetation of the sea-shore. 
 Atriplex, the Orache, is the other British genus. 
 
 Order 2. POLYGONACELE. The flowers have a simple 4, 5, or 
 6-leaved perianth which 
 may be either sepaloid 
 or petaloid, and usually 
 the same number of su- 
 perposed stamens ; but 
 occasionally the stamens 
 are more numerous or 
 some of them are sup- 
 pressed. Ovary usually 
 trimerous, unilocular, 
 with a single basal ortho- 
 tropous ovule ; the fruit 
 is frequently more or less 
 enveloped by the persist- 
 ent perianth. The leaves 
 have well-developed 
 sheaths (Fig. 337 A v} and 
 connate stipules forming 
 an ocrea (Fig. 337 A o : 
 see p. 31) which embraces 
 the stem for some distance 
 above the leaf -sheath. 
 
 Fio. 337.- A Portion of the stem () of Pulygonum, 
 with a leaf (b), its sheath (r), and the ocres (o) (nat. 
 size). B Flower of Rheum; fc external, c internal 
 perianth-whorl ; a the stamen*. C Fruit of Rumex, 
 enclosed by the inner whorl of the perianth ; t base of 
 one of the perianth -leaves; fc external rerianth-leaves, 
 D Fruit of Rheum (/); fc outer, c inmr perianth-whorl 
 (enlarged).
 
 524 PART IV. CLASSIFICATION. 
 
 Rheum, the Rhubarb, has six (three internal and three external) 
 perianth-leaves and two whorls of stamens, the outer containing six, and 
 the inner three; Rheum undulatum and other species are cultivated. 
 Rumex. the Dock, has flowers of similar structure, but the inner Avhorl of 
 stamens is absent ; the triquetrous fruits are completely enveloped by the 
 inner whorl of perianth-leaves (Fig. 337 C c) ; the leaves contain a large 
 quantity of oxalic acid. Polygonum has usually five petaloid perianth- 
 leaves and a varying number of stamens (5-8) ; P. Fagopyrum, the Buck- 
 wheat, is cultivated for the sake of its mealy seeds. 
 
 Cohort IV. Asarales. Affinities doubtful. Flowers mono- 
 clinous or unisexual : ovary inferior : ovules numerous. 
 
 Order 1. ARISTOLOCHIACELE. Flowers 3-6-merous, monoclinous : 
 perianth of three connate petaloid segments forming a three-lobed 
 tube : stamens 6 or 12, with extrorse anthers : ovary usually 
 G-locular, with numerous ovules in two longitudinal rows along the 
 inner angles of each loculus. The 
 minute embryo is enclosed in the 
 copious endosperm. They are herbs 
 or shrubs, often climbing, with large 
 leaves. 
 
 In Asarum europceuni (Asarabacca) the 
 three lobes of the perianth are equal : 
 alternating with them are three scales 
 which probably represent a corolla : the 
 twelve stamens (apparently in two whorls) 
 are free, and the connective is produced 
 Fio. 333. - Asarum ouropamm. (FJ 33^ The &nnual shoots of tfae c 
 Longitudinal section of the flower , ,, , 
 
 (maK.); P perianth. (After Sachs.) in S stem ^ar four cataphyllary leaves, 
 two large petiolate reniform foliage-leaves, 
 
 and a terminal flower. The lateral branches spring from the axils of the 
 uppermost foliage-leaf and of the scales. In Aristolochia, the Birthwort 
 (see Fig. 243, p. 412), the limb of the perianth is obliquely lipped ; the six 
 anthers are sessile and adnate to the short style (see p. 462). A. Sipho is 
 a climber frequently cultivated : A. Clematitis, though not indigenous, is 
 found wild in Britain, generally on ruins ; the flowers of the latter occur 
 usually several together in the axils of the leaves, and those of the former 
 in pairs, one above the other, together with a branch, in the axils of the 
 leaves of the shoot of the previous year. 
 
 Cohort V. Santalales. Parasitic plants : leaves, when 
 present, entire : stamens equal in number to the leaves of the 
 perianth and superposed upon them : ovary inferior, uuilocular ; 
 ovules usually devoid of integument. 
 
 Order 1. SAXTALACEJE. Parasites provided with chlorophyll :
 
 GROUP V. AXGIOSPERMvE ; DICOTYLEDOXES. 
 
 525 
 
 flowers generally monoclinous : ovules 1-4, suspended, upon a free 
 central placenta : perianth 3-5-lobed ; fruit a nut or drupe : seed 
 with endosperm. 
 
 Tliesium linophyllum, the Bastard Toad-flax, 
 is an indigenous plant which is parasitic on 
 the roots of other plants. The leaves are 
 narrow and linear. The bracts of the flowers, 
 which are disposed in racemes, are usually 
 placed high up on the pedicels, close under 
 the flowers, and in most of the species con- 
 stitute with the bracteoles a three-leaved 
 epicalyx. The stamens are filiform, inserted 
 at the base of the lobes of the perianth, 
 remaining curled up at the apex of the indehiscent fruit (Fig. 3395). 
 Santalum album, an East Indian tree, yields Sandal-wood. 
 
 FIG. 339. -A Flower ; B fruit 
 
 of Thf fin in jii ii f ii ii ii Hi .- / ovary ; 
 p perianth ; stamens ; n stigma 
 (enlarged). 
 
 The perianth is persistent, 
 
 Order 2. LORAXTHACELE. Parasites provided with chlorophyll : 
 flowers monoclinous or diclinous ; sometimes dioecious : perianth of 
 4, 6, or 8 leaves : ovary 1 2-merous : in the free central placenta, 
 which becomes more or less closely adherent to the wall of the 
 ovary, are developed several embryo-sacs, each of which probably 
 represent an ovule, but usually one only is fertile : fruit a berry : 
 seed generally with endosperm. 
 
 Viscum album, the Mistletoe, is parasitic on various trees, forming con- 
 spicuous evergreen bunches. The stem bears a pair of opposite leaves 
 (Fig. 340 b 6), from the axils of which new branches spring, each bearing 
 a pair of cataphyllary leaves and then a pair of foliage-leaves, while the 
 main axis ceases to grow, or produces a terminal inflorescence consisting 
 of three flowers (Fig. 340 hf) : branches or inflorescences may also spring 
 from the axils of the cata- 
 phyllary leaves. The 
 flowers are dioecious. The 
 fruit is a one-seeded berry 
 with a viscid pericarp, by 
 means of which the seeds 
 become attached to trees, 
 and thus effect the dis- 
 tribution of the plant. The 
 $ flowers have multilocu- 
 lar sessile anthers which F.o. 3K-A Terminal shoot of a 9 plant of the 
 i /-r.- om o \ MUtletoe, Vitcum album: s stem; bb leaves; kfc 
 are inserted (Fig. 340 B a) Minary bud8 . f three ? flower8 w , th the fruit tet . 
 
 upon the leaves of the peri- j, bracts. B <J flower (mag.) p perianth ; a anthers 
 anth. adherent to the leaves of the perianth. 
 
 Cohort VI. Euphorbiales. Flowers usually diclinous; the
 
 526 
 
 PART IV. CLASSIFICATION. 
 
 perianth sometimes consists of calyx and corolla, sometimes it is 
 simple, and occasionally it is absent : the ovary is usually trilo- 
 cular, with one or two anatropous and generally suspended ovules 
 in each loculus ; the seed contains endosperm : the structure of the 
 flowers is very various. 
 
 Order 1. EUPHORBIACE^E. The fruit is usually dry and dehis- 
 cent, a schizocarp splitting into cocci. The micropyle of the 
 solitary suspended ovule is directed outwards. They are plants 
 of very, various habit and floral structure, and they mostly contain 
 milky juice. 
 
 The genus Euphorbia has cymose umbels or dichasia, the 
 branches of which terminate in what were formerly regarded as 
 hermaphrodite flowers, but are really inflorescences, each one being 
 termed a c.yatliium. The cyathium consists of a tubular involucre 
 (Fig. 341 p\ between the five lobes of 
 which glandular appendages, often of 
 a semilunar form, are situated (Fig. 
 341 dr}. Within this involucre are 
 numerous staminate flowers in five 
 groups, each of which consists of a single 
 stamen (Fig. 341 a) and is terminal on 
 a long pedicel, and one carpellary flower 
 (Fig. 341 </), consisting of a trilocular 
 ovary (Fig. 341 /), at the base of which 
 an indication of a perianth mav in some 
 cases be detected. That the cyathium 
 is an inflorescence and not a single 
 flower is most clearly visible in some 
 foreign genera (e.g. Monotaxis), in which 
 a perianth is distinctly developed round 
 each stamen. There is a single ovule 
 in each loculus of the trilocular ovary : 
 the seed has a peculiar appendage (arilode, p. 416). 
 
 In Mercurialis the inflorescence is racemose : the staminate flowers 
 have a three-leaved perianth and numerous stamens ; the carpellary 
 flowers have a similar perianth and a bilocular ovary. The juice 
 is not milky. 
 
 Ricinus bears its monoecious flowers in a compound inflorescence, 
 in which the staminate flowers are placed below and the carpellary 
 flowers above. The perianth is simple and five-lobed, the stamens 
 numerous and much branched (Fig. 278). 
 
 FIG. 341. Part of an inflores- 
 cence of a Euphorbia: b 6 bracts 
 in the axils of which are the 
 flower bnds (fcn) ; p is the invo- 
 lucre of the cyathium ; dr the 
 g'nnds; a the male flowers; g 
 tMe pedicel of the female flower 
 (/) ; n the st'gmas (enlarged).
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDONES. 527 
 
 Of Euphorbia, the Spurge, a number of species are annual herbs, as 
 E. Peplns and helioscopia (the common Sun Spurge) occurring in gardens 
 and by roadsides ; some South European forms" are small shrubs, as E. 
 ilendroides and fruticosa. In Africa and the Canary Islands the genus is 
 represented by species which much resemble Cactese in appearance ; their 
 stems are thick and cylindrical or angular or sometimes spherical, pro- 
 ducing small leaves which usually soon fall off. Mercurial i.i aniiua and 
 perennis (Dog's Mercury) are weeds ; the first common in cultivated 
 ground, the second in woods; their flowers are dioecious. Kicinus coni- 
 munis (the Castor-oil plant) is a native of Africa, now frequently culti- 
 vated. Some species of Phyllanthus have phylloid branches which bear 
 their small flowers in the axils of minute bristle-like leaves situated in 
 indentations at the edge of the phylloclade. Manihot iitilissima, a South 
 American plant, yields the starchy meal known in commerce as tapioca. 
 From Heven guianensis, a species growing in Central America, most of the 
 caoutchouc is obtained. 
 
 SUB-CLASS II. POLYPETAL.E. 
 
 Flowers usually monoclinous : perianth usually consisting of 
 calyx and corolla, the petals being free. 
 
 SERIES I. THALAMIFLOR-E. 
 
 Sepals usually free : petals often indefinite : stamens hypogynous, 
 often indefinite : gynaeceum apocarpous or syncarpous. 
 
 Cohort I. Ranales. Flowers generally acyclic or hemicyclic : 
 perianth consisting of calyx only, or of calyx and corolla : stamens 
 usually indefinite : gynseceum apocarpous, sometimes reduced to a 
 single carpel ; very rarely syncarpous, with a multilocular ovary. 
 Seed with or without endosperm. 
 
 Order 1. RANUNCULACE.E. Perianth either consisting of a 
 petaloid calyx, or of calyx and corolla, usually spiral: stamens 
 numerous, occupying several turns of the spiral, or arranged in 
 several alternating whorls: anthers usually with lateral dehis- 
 cence, sometimes extrorse or introrse : carpels numerous, spirally 
 arranged ; rarely one only ; the ovules are disposed on the connate 
 margins of each carpel, that is, in two rows down the ventral 
 suture ; in several genera the number of the ovules in each ovary 
 is reduced to one, which then originates from either the upper or 
 the lower end of the cavity of the ovary : seed with endosperm. 
 They are almost all herbaceous plants, and are either annuals or 
 they have perrennial rhizomes ; they have no stipules, but they 
 have amplexicaul leaves. 
 
 Tribe 1. Anemonece. Petals generally replaced by stamens : sepals fre-
 
 528 
 
 PART IV. CLASSIFICATION. 
 
 quently petaloid : ovaries numerous, each, containing a single suspended 
 or ascending anatropous ovule 5 fruit consists of a number of achenes. 
 
 The genus Clematis consists of shrubs which creep, or climb by their 
 petioles, and have opposite leaves, and a petaloid usually valvate calyx. 
 Clematis Vitalba, the Old Man's Beard, is common in hedges; it has a 
 greenish-white calyx, and fruits with long feathery styles ; C. Viticella, 
 patens, and others are cultivated as decorative plants. Atragene alpirta, 
 occurring in the Alps and in Siberia, has its external stamens converted 
 into petaloid staminodes. 
 
 Thalictrum ; the species of this genus, as T. majus^ minus, flavum , and 
 
 FIG. 312. Flowers of Kanunenlaceaa : s peduncle; fc sepals; c petals; a stamens; 
 / carpels ; n stigma (all of natural size or slightly magnified). A Flower of Anemone 
 Pa.lsa.Hlla in longitudinal sn^tion ; h epicalyx ; t receptacle. B Gynaeceum of Ranunculus : 
 * receptacle with the points of insertion of the stamens which have been removed : C flower 
 seen from below. D Flower of Hclleborus viridis. E Flower of Aconitum Napellus : h 
 bracteoles ; V hooded posterior sepal the lateral sepal on this side is removed. 
 
 alpinum, the Meadow-Rues, have stems well covered with leaves, and 
 flowers with an inconspicuous, fugacious, 4-5-leaved calyx, and a flat 
 receptacle. 
 
 Anemone has an hemispherical receptacle (Fig. 342 A t), and a petaloid, 
 usually 5-6-leaved calyx. In most of the species the underground 
 rhizome elongates into an erect scape which bears a single whorl of three 
 bracteoles forming an epicalyx (p. 443), beneath the terminal flower. In
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDOXES. 529 
 
 A. nemorosa, ranunculoides, and others, these bracteoles resemble the foliage- 
 leaves, and often bear flowers in their axils; but in A. Pulsatilla, and 
 others, they differ from the foliage- leaves in that they are palmatifid 
 (Fig. 342.4 h) ; in A. Hepatica, in which the scapes spring from the axils of 
 cataphyllary leaves, the three bracteoles are simple and lie so closely 
 under the petaloid calyx that at first they appear to be the calyx of the 
 flower. 
 
 Myosurus minimus (Mouse-tail) has a very long cylindrical receptacle, 
 bearing the indefinite spirally arranged carpels: stamens 4-14; the 5 
 sepals are spurred. Adonis, the Pheasant's Eye, has completely acyclic 
 flowers ; sepals 5, petals 8 or more, not glandular at the base ; stamens and 
 carpels indefinite, arranged in ^ order: A. autumnalis is the species which 
 occurs in England. 
 
 In Ranunculus, the calyx, which is not petaloid, consists of 5 () sepals, 
 and the corolla of 5 imbricate petals which alternate with the sepals and 
 have a nectary at their base : the stamens and carpels are arranged 
 spirally ; anthers extrorse; the ovule is ascending, whereas it is suspended 
 in all the preceding genera. The genus includes water-plants with finely- 
 divided leaves and white flowers, as R. aquatilis, Water Crowfoot, jiuitans, 
 etc. ; and land- or bog-plants, usually with a yellow corolla, as It. acris, 
 the Buttercup, re pens, bulbosua, and scelerattts (all known as Crowfoot), and 
 Lingua and Flammula (the Greater and Lesser Spearworts) ; they are all 
 more or less poisonous. R. Ficaria (the Lesser Celandine) has 3 sepals and 
 usually 8 petals. 
 
 Tribe. 2. Helleborece. Perianth generally consisting of calyx and 
 corolla, the latter being occasionally suppressed ; the petals are glandular 
 at the base : ovaries usually fewer in number than the leaves of the 
 perianth ; ovules numerous, borne on the ventral suture ; fruit usually 
 consists of several follicles. 
 
 (a) With regular, generally actinomorphic, flowers : 
 
 Helleborus, with acyclic flowers ; sepals more or less petaloid in $ ar- 
 rangement; the petals, which are small and tubular, in f or & ; stamens 
 in ^ or 2 r ; ovaries usually 3-5 (Fig. 342 D) ; H. Niger is the Christmas 
 Rose ; H. viridis and fottidus are not rare. Nigella has 5 petaloid sepals 
 and usually 8 (superposed if 5) small glandular petals: its carpels cohere 
 partially or completely, forming a septicidal capsule. Trollius, the Globe- 
 flower, has 5-15 petaloid sepals, and a similar number of small petals 
 which, like the stamens and carpels, are all arranged spirally : T. europaui 
 occurs in sub-alpine regions. Caltha, the Marsh-Marigold, has 5 yellow 
 petaloid sepals, but no corolla : C. palustri* is common in damp places. 
 Eranthis, the Winter Aconite, has a 3-leaved epicalyx, and small petals 
 with long claws. Acttea has a petaloid calyx and an alternating (some- 
 times suppressed) corolla ; it has a single carpel which becomes a baccate 
 fruit : A. spicata, the Baneberry or Herb Christopher, occurs in woods. 
 Aquilegia, the Columbine, has a cyclic flower (Fig. 343) : it has 5 petaloid 
 sepals, and petals with long spurs ; there are several whorls of stamens : 
 A. vulgaris, atrata, Aklei, and others occur wild, or are cultivated as de- 
 corative plants. 
 
 M.B. * *
 
 530 PART IV. CLASSIFICATION. 
 
 (6) With irregular dorsiventral flowers. 
 
 Delphinium, the Larkspur, 'has the posterior of the 5 petaloid sepals 
 prolonged into a spur : there are typically 5-8 petals, of which only the 2 
 (Z>. Ajacis ; see Fig. 273 A) or 4 (D. Staphisagria) posterior are developed ; 
 the spurs of the two posterior petals pro- 
 ject into that of the posterior sepal : D. 
 Staphisagria has 3-5 carpels; D. Consolida 
 and D. Ajacis, common garden plants, 
 have usually but one carpel. In Aconi- 
 tum, the Wolf's-bane or Monk's-hood, the 
 posterior of the 5 petaloid sepals is large 
 and hooded ; the two posterior of the 8 
 petals have long claws and are covered by 
 the posterior sepal, the others being in- 
 conspicuous (Fig. 342 E, c). 
 
 Tribe 3. PcKoniece. The perianth con- 
 sists of calyx and corolla, and the petals 
 FIG. 343,-Diagram of flower of are not glandular : ovaries with numerous 
 Aquilegia. ovules, surrounded by a disc : fruit of 
 
 several follicles. 
 
 In Pseonia, the Peony, the flower is acyclic: the calyx consists of 5 
 sepals which gradually pass into the foliage-leaves ; the petals are 5 or 
 more. P. officinalis, corallina, and others are cultivated as decorative 
 plants ; P. Moutan has a woody stem and a tubular disc. 
 
 Order 2. MAGNOLIACELE. Perianth cyclic, consisting usually of 
 three alternating trimerous whorls, one of sepals and two of petals, 
 stamens and carpels numerous, arranged spirally : seed containing 
 endosperm. Woody trees or shrubs. 
 
 Tribe 1. Magnoliece. Carpels very numerous on an elongated cylindrical 
 receptacle : flowers invested by a spathoid bract ; stipules connate. Mag- 
 nolia grandiflora and other species, and Liriodendron tulip/era, the Tulip- 
 tree, from North America, are ornamental trees. 
 
 Tribe 2. Illiciece. Carpels in a single whorl on a flat receptacle (Fig. 
 286). Illicium anisatum, the Star-Anise, is a native of China. 
 
 Order 3. NYMPH.EACE.E. Flowers usually acyclic without any 
 sharp demarcation between the petals and the stamens : pistil 
 either apo- or syn-carpous. Water-plants, generally with broad 
 floating leaves. 
 
 Tribe 1. Nymphceina;, Carpels connate, forming a polymerous multilo- 
 cular ovary which may be either superior or inferior. Ovules numerous, 
 placentation superficial: seeds numerous, containing both endosperm and 
 perisperm, sometimes arillate (p. 415). The rhizome grows at the bottom 
 of the water and throws up broad, flat, cordate leaves with long petioles 
 which float on the surface. The flower also reaches the surface, borne on 
 a long peduncle.
 
 GROUP V. AXGIOSPERM.E ; DICOTYLEDONES. 531 
 
 Xgmphaa alba, the white Water-Lily, has four green sepals, a great 
 number of white petals which, together with the very numerous stamens, 
 are arranged spirally, and a semi-inferior ovary. Xuphar luteum, the 
 yellow Water-Lily, has a calyx consisting usually of five greenish-yellow 
 sepals ; the petals, which are smaller and yellow, are usually 18 in number, 
 and form a continuous spiral with the indefinite stamens ; the ovary is 
 superior. Victoria regia, a Brazilian species, has peltate leaves of more 
 than a j-ard in diameter. 
 
 Tribe 2. Nelunibiece. Ovaries numerous, distinct, imbedded in the fleshy 
 receptacle : seeds solitary, exalbuminous. 
 
 Nelumbium upeciosum is the Lotus of Egypt and Asia. 
 
 Tribe 3. Cabombete. Flowers cyclic. Calyx and corolla each three- 
 leaved. Stamens 3-18 or x. Ovaries 3-18, monomerous, each with two or 
 three ovules attached to its walls or to the dorsal suture of the carpel. 
 Seeds containing endosperm and perisperm. The submerged leaves are 
 much divided, the floating leaves peltate. Cabomba occurs in tropical 
 America : Brasenia is widely distributed. 
 
 Order 4. BERBERIDACE.E. The calyx, corolla, and androecium, 
 each, consist of two di- or tri-merous whorls. Gynaeeeum mono- 
 merous ; ovary with numerous marginal ovules. Fruit capsular or 
 baccate. Seed with endosperm. 
 
 Berberis vulgar is is the Barberry, its floral formula is /T3 + 3, 6*3-1-3, 
 A3+3, G ; the flowers are in pendent racemes, usually without terminal 
 Hewers; when a terminal flower is present it is acyclic and its formula is 
 Kb | Co | Ab (see Fig. 262, p. 447). Fruit an oval berry. The leaves of the 
 ordinary shoots are transformed into spines (Fig. 29), in the axils of which 
 are dwarf-shoots bearing the foliage-leaves and the inflorescences. Epi- 
 medium has a dimerous flower ; calyx of 4-5 whorls ; petals spurred. In 
 Berberis, sub-genus Mahonia. there are 3 whorls of sepals, and in Nandina 
 many whorls, the inner of which gradually become petaloid. Podophyllum 
 has sometimes 3 whorls of petals (though the number of petals varies in 
 consequence of oligomery), and shows duplication of the stamens of the 
 inner whorl. The anthers usually dehisce by valves, but in Podophyllum 
 and Nandina the dehiscence is longitudinal. 
 
 Cohort II. Caryophyllales. Flowers cyclic, generally actino- 
 imrphic and pentamerous, sometimes monochlamydeous : calyx 
 often gamosepalous : stamens usually definite : ovary unilocular, 
 with basal placenta : seed with perisperm. 
 
 Order 1. CARYOPHYLLACE.E. Flowers generally pentamerous, 
 with calyx and corolla, though the latter is suppressed in some 
 cases; sepals distinct or coherent: stamens in two whorls of 
 which the inner is often wanting; ovary 2-, 3-, or 5-merous, 
 unilocular; or multilocular at the base, with a central placenta
 
 532 
 
 PART IV. CLASSIFICATIONS 
 
 or with a single basal ovule : fruit usually a capsule : leaves 
 opposite, decussate : stems usually tumid at the nodes. 
 
 Tribe 1. Ahinea. The corolla and the inner whorl of stamens are 
 usually present ; the calyx is eleutherosepalous ; fruit a capsule ; usually 
 no stipules. 
 
 The British genera are Sagina (Pearl-Avort), Arenaria (Sand-wort), 
 Cerastium, Stellaria (Chick-weeds and Stitch-worts), Spergula (Spurrey), 
 Lepigonum, Holosteum, Moenchia ; they are mostly small herbaceous 
 plants with white petals, occurring in meadows, on roadsides, etc., but 
 species of Lepigonum (Spergularia), the Sandwort-Spurrey, and Arenaria 
 (Honckenya) peploides, Sea-Purslane, grow on the sea-coast ; they are dis- 
 tinguished from each other principally by the number of carpels present, 
 and by the mode of dehiscence of the fruit. 
 
 Tribe 2. Silenece. The 
 corolla and the inner whorl 
 of stamens are always pre- 
 sent : the calyx is gamo- 
 sepalous ; stamens 10, fila- 
 ments connate at base : the 
 fruit is a capsule (in Cucu- 
 balus a berry) : the leaves 
 have no stipules ; the floral 
 axis often elongated between 
 the calyx and the corolla 
 (Fig. 344 y} : the petals (as in 
 Lychnis and Saponaria) often 
 have ligular appendages 
 (Fig. 344 x : see p. 459). 
 
 The species of Dianthus, 
 the Pink, which commonly 
 Fie. 344.-Longitudinal section of the flower of oc eur w ild are D. deltoides, 
 Lychnis Flos Jovis-. y prolonged axis (anthophore; ^ . and D Armeria . 
 see p. 444) between the calyx and the corolla; * 
 
 ligular appendages or corona. {After Sachs.) D - Caryophyllus, the Carna- 
 
 tion, and D. chinensis, are 
 
 well-known garden flowers ; there are two styles, and the calyx is sur- 
 rounded at its base by bracteoles. The genus Saponaria has two stj-les 
 but no bracteoles; S. officinalis, the Soap- wort, occurs on the banks of 
 rivers. The genus Silene (Catchfly) has three styles; S. inflata, unions, 
 and others, are common in meadows. The genus Lychnis (Campion) has 
 five styles ; the species alba (vespertina) and diurna are dioecious; L. Githayo, 
 the Corn-cockle, is common in fields. 
 
 Tribe 3. Polycarpece. Leaves with scarious stipules : calyx eleutherose- 
 palous; the corolla is present, but the inner whorl of stamens is wanting : 
 style 3-fid. This group includes the British genus Polycarpon (Allseed) 
 and others. 
 
 Tribe 4. Paronychiece. Sepals distinct or coherent : the corolla and the
 
 GROUP v. ANGIOSPERM.E; DICOTYLEDONES. 
 
 533 
 
 inner whorl of stamens are usually wanting: style usually bifid: ovary 
 umlocular, with 1-4 ovules : fruit generally indehiscent. 
 
 The British genera are Scleranthus (KnaWel), Herniaria r Corrigiola 
 (Strap- wort), and Illecebrum : they are small inconspicuous herbs, with 
 scarious stipules (except Scleranthus). 
 
 The Paronychieae have also been placed, as a distinct natural order, 
 ILLECEBRACE^:, among the Monochlamydeae. There is no doubt that they 
 have affinities with the Chenopodiales. and that they thus connect that 
 cohort with the Caryophyllacese. 
 
 Cohort III. Parietafes. Flowers cyclic, with calyx and 
 corolla : sepals free : stamens definite or indefinite; gynaeceum of 
 two or more carpels : ovary unilocular, sometimes many-chambered, 
 with parietal placentation : seed with or without endosperm, 
 
 Order 1. PAPAVERACE^E. Flowers usually actinomorphic, A'2, 
 C2 + 2, A<x. , G ( - ] or (oc ), or rarely with trimerous whorls :. calyx 
 sepaloid, corolla peta- 
 loid : the numerous 
 whorls of stamens al- 
 ternate : ovary of two 
 lateral carpels or of 
 more (Fig. 345 a), two- 
 or more - chambered : 
 ovules numerous, at- 
 tached to the more or 
 less infolded edges of 
 the carpels : endo- 
 sperm abundant, em- 
 bryo small. The sepals 
 commonly fall off be- 
 fore the flower ex- 
 pands (Fig. 345/c). Plants with abundant milky latex. 
 
 Papaver, the Poppy, has a many-chambered ovary ; the fruit is a porous 
 capsule (Fig. 288 D): P. somniferum is cultivated for the sake of the oil 
 contained in the seeds, and for the latex obtained from its capsules, which 
 when inspissated, constitutes opium ; several species are British, such as 
 P. fiha'as, the Field Poppy ; P. Argemone, the Pale or Long Prickly- 
 headed Poppy ; P. hybridum, the Bound Prickly-headed Poppy : P. dubiuni r 
 the Long Smooth-headed Poppy ; and Meconopsis cambrica, the Yellow 
 Welsh Poppy. Chelidonium majus, the Celandine, has two carpels, a 
 siliquose fruit, and orange-coloured milky latex. Glaucium, the Horned 
 PPP3 r > has a siliquose fruit which is generally spuriously bilocular 
 
 Order 2. FUMARIACE^. Flowers isobilaterally symmetrical, 
 
 FIG. 315. Flower of Ctielidoniitr* mojijs (nat. size) ; 
 fc calj-x ; ca outer, ct inner petals ; a Btamens ; n stigma. 
 A Diagram of the flower of Chelidonium. a Many- 
 chambered ovary of Papaver.
 
 534 
 
 PART IV. CLASSIFICATION. 
 
 or zygomorphic with lateral symmetry : floral formula A"2, C'2 + 2, 
 A2 + 2, G. The three whorls of the perianth alternate ; one of the 
 outer petals (rarely both) is usually furnished with a spur : in most 
 genera there are three stamens on each side, a central one, with a 
 perfect anther (the stamen of the outer whorl, Fig. 346 B a), and 
 two lateral stamens, each with only half an anther (apparently the 
 halves of the stamens of the inner whorl ; Fig. 346 B a t a,). The 
 fruit is siliquose and many-seeded, or one-seeded and indehiscent. 
 Herbaceous plants without milky latex, sometimes climbing by 
 means of their petioles which act as tendrils (Adlumia, Fumaria). 
 Seeds containing endosperm. 
 
 The flowers of Adlumia, Dicentra, and Hypecoum are isobilateralJy 
 symmetrical. ])icentra spectabilis is a favourite ornamental plant; both 
 the outer petals are spurred, the two inner petals are hollowed at their 
 apices, so that they completely enclose the anthers. In Hypecoum the 
 petals are not spurred, and there are four stamens, two lateral forming 
 the outer whorl, and two antero-posterior forming the inner whorl : fruit 
 usually indehiscent. In Corydalis and Fumaria only one of the outer 
 
 FIG. 346<-^l Flower of Dicentra spectabilis : one of the outnr petals is removed : s pedicel ; 
 ca the outer, ci the inner petals ; / stamens. B The three stamens of one side, seen from 
 within : /filaments ; a the middle complete anther ; a, a, the lateral half-anthers. C Flower- 
 bud, with the sepals, which soon fall off, still adhering (fc)i (nat. size). Diagram of Fumi- 
 tory. 
 
 petals is spurred, and consequently the flower is irregular and laterally 
 zygomorphic (p. 455). In Corydalis the fruit is atwo-valved capsule with 
 numerous parietal seeds : some species, e.g. C. cava and solida, have a 
 tuberous rootstock ; others, as C. lutea and aurea, have rhizomes. Fumaria 
 officinalis, and others (Fumitories) are common in fields ; the ovaries 
 contain but few ovules, and of these only one ripens to a seed ; fruit 
 globose, indehiscent. 
 
 Order 3. CRUCIFER^:. Flowers regular, isobilateral : floral for- 
 mula K2 + 2, C x 4, A2 + 2 2 , 6P. The four petals form a whorl, alter-
 
 GROUP - V. ANGIOSPERM.E ; DICOTYLEDONES. 
 
 535 
 
 nating with the four sepals as if the latter formed one whorl; 
 there are, however, three perianth-whorls, as in the two preceding 
 families ; but whereas in them only the 
 outermost whorl is sepaloid, in this family 
 the two outer whorls are sepaloid, and the 
 innermost, which alone is petaloid, is a 
 whorl consisting of four instead of two mem- 
 bers. The two outer stamens are lateral, 
 as in those families ; the two inner ones, 
 which in most Fumariaceae are apparently 
 divided, are here duplicate, having longer 
 filaments (Fig. 348 B b b) than the outer 
 ones (a) ; hence they are tetradynamous. There are usually four, 
 sometimes more, nectaries at the base of the stamens (Fig. 348 B d). 
 The ovary consists of two carpels with the ovules in two longi- 
 tudinal rows on the connate margins of the carpels ; these two 
 parietal placentae are connected by a membranous growth which, 
 as it is not formed of the margins of the carpels, must be regarded 
 
 o. 317. Diagram of the 
 flower of Cruciferae. 
 
 Fi 343.- Flowers, fruits, and embryos of various Cruciferas. A Flower of Brassica (nat. 
 sizeT's pedicel; l:k calyx; c corolla. B The same after removal of the perianth ( 
 ma<O a a the two outer short stamens ; I the four longer inner ones ; / the ovary ; 
 stigma ; d gland. C Siliqua of Brassica ; v dissepiment. D Angustiseptal ailicuU ol 1 
 E Latiseptal silicula of Draba. D* and * Diagrammatic transverse section of the pi 
 ing v dissepiment s seed. F indehiscent silicula of Isatis. G Jointed siliqua of Ruj./i,i.n.* 
 KapJicmistrum : g style ; I II separate segments. H-K Diagrams of differently-fold 
 embryos, with transverse sections : r radicles ; c c cotyledons.
 
 536 PART IV. CLASSIFICATION. 
 
 as a spurious dissepiment (Figs. 348 D* E* v, 288 C w}. When 
 the fruit opens, the pericarp splits into two valves corresponding 
 to the carpels, leaving their margins, as a frame or replum, bearing 
 the placentse with the spurious dissepiment attached : the seeds 
 remain attached to them for some time (Fig. 288 C, p. 474). 
 
 The flowers are in racemes in which the bracts are suppressed ; 
 when the lower pedicels are longer than the upper ones, the raceme 
 becomes a corymb, and then the lower flowers are usually zygomor- 
 phic, the petals turned towards the periphery being larger than 
 those directed towards the axis of the inflorescence, as in Iberis. 
 
 The form of the fruit is of importance in the subdivision of this 
 order. In some genera it is much longer than it is broad, when it 
 is termed a siliqua, (Figs. 288 (7, 348 (7) ; in others, it is not much 
 longer, or about as long as it is broad, when it istermed a silicula 
 (Fig. 348 D and E}. The latter is commonly somewhat com- 
 pressed in one direction ; either parallel to the dissepiment, that is 
 to say laterally (Fig. 348 E and E*), so that the dissepiment lies 
 in the direction of the greatest diameter, when it is latiseptal ; or 
 perpendicularly to the dissepiment, that is in the median plane, 
 so that the dissepiment lies in the narrowest diameter, when it is 
 angiistiseptal (D and /)*). Fruits with only one or a few seeds, and 
 which are indehiscent, are confined to only a few genera, such as 
 Isatis (Fig. 348 F). So likewise is the jointed siliqua, which has 
 transverse dissepiments between the seeds ; when they are ripe it 
 divides transversely into segments, as in Raphanus (Fig. 348 Gr). 
 
 The seed is exalbuminous. The embryo is folded in the seed 
 in various ways ; the radicle may lie in the same plane as one of 
 flat cotyledons (Fig. 348 K), when the cotyledons are said to be 
 incumbent, Notorhizecc (the diagram being Q ||) ; or the radicle 
 may occupy the same position, the cotyledons being folded (Fig. 
 348 7), when the cotyledons are said to be incumbent and folded, 
 Orthoploceoe. (diagram of section Q ^>) ; or, thirdly, the radicle may 
 be lateral to the two cotyledons (Fig. 348 //), when the cotyledons 
 are said to be accumbent r Pleurorliizece (diagram Q =) : more 
 rarely the cotyledons are spirally rolled so that in a transverse 
 section they are cut through twice, Spirolobece (diagram Q || ||) ; 
 or, finally, they may be doubly folded, and be seen four times in 
 a section, Diplocolobem (diagram Q II II II ID- The seeds contain 
 much fatty oil. 
 
 Sub-order 1. SILIQUOS.E. Fruit a siliqua, much longer than it is 
 broad.
 
 GROUP V. ANGIOSPERM*: ; DICOTYLEDONES. 537 
 
 Tribe 1. Arabidece. Q=. Cheiranthus Cheiri, the Wall-flower, and 
 Matthiola annua and incana, the Stocks, are cultivated as garden-plants. 
 Nasturtium qfficinale is the Water-cress. Barbarea vulgaris is the Yellow 
 Rocket. Cardamine (incl. Dentaria) also belongs to this tribe. 
 
 Tribe 2. SisymbrtecK. Q \\ . Sisymbrium officinale, the Hedge-Mustard, 
 is common on rubbish heaps ; and Erysimum, the Treacle-Mustard, on 
 walls, etc. Hesperis is the Dame's Violet. 
 
 Tribe 3. Brassicecn. Q^> The species and varieties of Brassica are 
 much cultivated. Brassica oleracea is the Cabbage, with the following 
 varieties ; acephala, Scotch kale, Cow-cabbage or Borecole ; bullata, the 
 Savoy -cabbage 5 capitata, the red and white Cabbage; caulorapa, with thi 1 
 stem swollen at base, is the Kohl-rabi; Botrytis, with connate fleshy 
 peduncles and abortive flowers, is the Broccoli (asparagoides) and the 
 Cauliflower (cauliflora) ; gemmifera^ with numerous lateral leaf-buds, 
 known as Brussels-sprouts. Brassica campestris is the wild Navew; it 
 includes the following sub-species; Itapa, the wild Turnip, with bright 
 green hispid leaves and flat corymbs of flowers, among the cultivated 
 varieties of which is the var. depressa, the Turnip : Napus, the wild Rape, 
 with glabrous glaucous leaves and long racemes of flowers, several varie- 
 ties of which are cultivated for their oily seeds, and one (var. esculenta, 
 the Teltow Turnip) for its fleshy root : Napobrassica, the Turnip-cabbage, 
 including Rutabaga, the Swedish Turnip. B. campestris oleifera is the true 
 Colza or Coleseed, from the seeds of which colza-oil is obtained. Brassica 
 (Sinapis) nigra and alba are the black and white Mustard. Brn**i<-i' 
 Sinapis (Sinapis arvensis) is the Charlock or Corn-Mustard. To this tribe 
 belongs also the genus Diplotaxis. 
 
 Sub-order 2. SILICULOS.E. Fruit a silicula. 
 
 A. LatiseptcE. The dessepiment is. in the longest diameter of the silicula. 
 Tribe 4. Alyssinece. Q =. Cochlearia officinalis is the Scurvy-grass ; C. 
 
 Armoracia, the Horse-radish, has a thickened root. Alyssum cali/cinum and 
 Draba (Erophila) verna t the Whitlow-grass (Fig, 348 E), are common 
 weeds : Lunaria biennis is Honesty, 
 
 Tribe 5. Camelinece. Q || . To this tribe belong Camelina (Gold-of- 
 pleasure), and Subularia, the Awl- wort, an aquatic plant. 
 
 B. Anguntiseptce. The dissepiment is in the shortest diameter of the 
 silicula. 
 
 Tribe 6. Lepidinece. Q || . Capsella Bursa Pastoris, the Shepherd's 
 Purse, is common, as also various species of Senebiera and Lepidium 
 (Cresses). 
 
 Tribe 7. T/ilaspidece. Q =. Various species of Thlaspi, the Penny- 
 Cress, are common. To this tribe belong also the British genera Iberi* 
 (Candytuft), Teesdalia, and Hutchinsia. 
 
 Sub-order 3. NUCUMENTACEVE. Silicula indehiscent, few-seeded. 
 
 Tribe 8. Isatidece. laatis tinctoria, the Woad, has compressed, pendul- 
 ous, unilocular, one-seeded fruits (Fig. 348 F) : the leaves yield a blue 
 dye. 
 
 Sub-order 4. LOMENTACE^:. Fruit a siliqua or silicula, constricted into 
 one-seeded segments (lomentaceous) (Fig. 348 G).
 
 538 
 
 PART IV. CLASSIFICATION. 
 
 Tribe 9. CakilinecK. Silicula two-jointed. This tribe contains the 
 genera Cakile, the Sea-Rocket, and Crambe, the Sea-Kale. 
 
 Tribe 10. RaphanetK. Silicula more or less moniliform. Raphanm sati- 
 vus is the Radish ; It. Baphanistrum, the wild Radish or White Charlock, 
 is a common weed. 
 
 Order 4. CISTACE.E. Flowers usually actinomorphic and penta- 
 merous : the two external of the five sepals are generally smaller, 
 aud sometimes they are absent : stamens numerous, in consequence 
 of multiplication : carpels 3-10, forming a uni- or multilocular 
 ovary ; ovules orthotropous ; seed with endosperm. Trees or shrubs 
 with generally opposite stipulate leaves. 
 
 Cistus has 5-10 carpels forming a chambered or completely mutilocular 
 ovary. Cistus ladaniferus, creticue, ^.nd other species, grow in the south of 
 Europe : a balsam is derived from them. Helianthemum has a unilocular 
 
 trimerous ovary : Helian- 
 themum vulgare, the Bock 
 Hose, is an under -shrub 
 which grows wild on dry 
 soils. 
 
 Order 5. VIOLACELE. 
 Floral formula 7i5, Co, 
 A5, G { ~ : flowers always 
 borne laterally : ovules 
 anatropous : fruit a Iccu- 
 licidal capsule (Fig. 349 
 (7) : seed with endo- 
 sperm. The indigenous 
 species have irregular 
 dorsiventral flowers ; the 
 anterior inferior petal is 
 prolonged into a hollow spur (Fig. 349 A cs) in which the nectar 
 secreted by the spur-like appendages of the two lower stamens 
 collects (Fig. 349 Afs). The sepals are produced at the base (Fig. 
 349 A Is}. 
 
 Viola is the Violet, Pansy, or Heart's-ease : many species, as V. odorata, 
 the Sweet Violet, have only an underground stem which bears cataplryll- 
 ary leaves, and which throws up petiolate foliage-leaves, and bracteolate 
 peduncles each bearing a single flower : V. odorata has runners, but hirta 
 and collina have none : in others, as V. canina, the Dog-Violet, the main 
 stem is above ground and bears the foliage-leaves : in V. mirabilis these 
 two forms are so combined that, in the spring, flowers are developed from 
 the rhizome which have large blue petals but are always sterile ; it is not 
 
 Fis. 349 Viola tricolor. A Longitudinal section of 
 flower: v bracteole on the peduncle; I sepals; Is ap- 
 pendage; c petals; cs spur of the lower petals ; j't 
 glandular appendage of the lower stamens ; a an- 
 thers (after Sachs). B Ripe fruit ; fc calyx. C After 
 Oehiscence; p parietal placenta; steeds. (Mag.)
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDOXES. 539 
 
 till later that inconspicuous (cleistogamous, p. 410) flowers with minute 
 petals appear on the leafy stem, and these only ace fertile : in V. tricolor 
 and its allies the stipules are leafy and pinatifid. 
 
 Cohort IV. Guttiferales. Flowers usually cyclic, generally 
 actinomorphic, and pentamerous : sepals usually free, with imbricate 
 aestivation : stamens usually indefinite : gynseceum syncarpous, 
 ovary uni- or multi-locular : seed exalbuminous. 
 
 Order 1. HYPERICACE^E. Formula usually Ko, (75, .40 + 5oo. 
 G 1 - ; or ^40+ 3 oo, 6?'^. Sepals sometimes united at the base : sta- 
 mens usually indefinite and polyadelphous ; 
 when in five bundles, the bundles are super- 
 posed on the petals ; this position of the stamens 
 is generally attributed to the suppression of an 
 outer whorl of stamens which is indicated by 
 staminodes in species of all the genera : ovary 
 uni- or multi-locular, or many-chambered ; 
 capsule septicidal ; ovules numerous, anatro- 
 
 . , , ., W i_ FlG - 350. TiBgram of 
 
 pous ; placentae parietal or axile. Herbs or aypericum caiydnum. 
 
 under-shrubs with decussate entire leaves, 
 
 which are dotted over with translucent oil-glands ; exstipulate. 
 
 The following are examples of the different relative numbers of staminal 
 bundles and of carpels : 
 
 Staminal bundles 5, carpels 5: Hypericum calycinum. 
 
 Staminal bundles 3, carpels 8 : H. Humifusum, hirsutum, montanum, per- 
 
 foratum, undulatum, barbatum. 
 
 Staminal bundles 5, carpels 3: H. Androscemum, hircinum, elalum. 
 Staminal bundles 3, carpels 5 : H. peplidifolium. 
 
 All these species, except the last (St. John's Worts, or Tutsans), occur 
 wild in Britain. 
 
 Cohort V. Malvales. Flowers cyclic, generally pentamerous 
 and actinomorphic : calyx often gamosepalous, with valvate aesti- 
 vation : corolla with usually contorted aestivation : stamens typi- 
 cally in two whorls, frequently obdiplostemonous (p. 452), sometimes 
 branched, and often connate : carpels usually five and then anti- 
 petalous, often forming a multilocular ovary: seed usually with 
 endosperm- 
 Order 1. TILIACE.E. Sepals usually free : stamens 10 or indefi- 
 nite, sometimes polyadelphous ; in the indigenous species the stami- 
 nal whorl opposite to the sepals is suppressed, and there are 5 
 antipetalous staminal bundles ; anthers 4-locular, opening by pores 
 or valves : gynEeceum usually completely syncarpous ; style 1 ;
 
 540 
 
 PART IV. CLASSIFICATION. 
 
 ovary usually 5-locular, each loculus containing two ovules ; but 
 the fruit is generally only one-seeded. Mostly trees or shrubs : 
 leaves alternate, stipulate. 
 
 The only indigenous genus is Tilia, the Lime-tree. It has oblique leaves 
 with deciduous stipules; the annual shoots have not a terminal bud. The 
 inflorescence is cymose, few-flowered : the peduncle is adnate to the leafy 
 bracteole ; this is brought about in the following manner : in the axil of the 
 leaves there is usually a bud, together with an inflorescence (Fig. 351) : 
 the large bracteole ( 7t) and a bud-scale, 
 which is opposite to it, are the first 
 two leaves of the axillary shoot which 
 is terminated by the infloresence, the 
 peduncle of which is adnate to the large 
 bracteole for some distance : the bud 
 is a winter-bud developed in the axil of 
 the above-mentioned bud-scale. The 
 inflorescence itself terminates in a 
 flower ; other flowers are borne in the 
 axil of two upper bracteoles which 
 soon fall off, and other flowers again 
 may be developed in the axils of 
 their bracteoles, and so on. T. platy- 
 phyllos, the large-leafed Lime, has a 
 few-flowered inflorescence, and leaves 
 which are bright green and downy 
 on the under surface: T. cordata 
 has an inflorescence which consists of 
 a large number of flowers, and has 
 small leaves which are bluish-green 
 and pubescent with red hairs on the 
 under surface. T. vulyaris is the com- 
 mon Lime. Corchorus, in the East 
 Indies, yields Jute, which consists of 
 the bast-fibres. 
 
 Order 2. MALVACEAE. Calyx 
 usually gamosepalous, frequently 
 invested by an epicalyx (p. 443) ; 
 the corolla is adnate at the base 
 to the androecium : the typically 
 obdiplostemonous androesium is a 
 long tube (Fig. 352 A} consisting 
 of five monadelphous usually branched stamens which are opposite 
 to the petals, each branch bearing a bilocular anther ; there is 
 sometimes an inner series of staminodes opposite to the sepals : 
 carpels 5- oo ; styles many, connate ; the gynseseum is sometimes 
 
 Fio. 351. Inflorescence of the Lime : 
 n branch ; It petiole subtending an in- 
 florescence and a bud. Attached to the 
 peduncle is the large bracteole (h) : fe 
 calyx ; c corolla ; s stamens ; / ovary ; 
 fc?i flower-bud (nat. tize).
 
 GROUP V. ANGIOSPERSLE ; DICOTYLEDONES. 541 
 
 almost apocarpous (Malopeae) ; usually syncarpous with a multi- 
 locular ovary, splitting into cocci (Fig. 352 C D), with usually one 
 ovule in each coccus (p. 473), or a loculicidal capsule (Hibiscese). 
 Under-shrubs or herbs : leaves stipulate and generally palmately 
 veined. 
 
 Malva, the Mallow, has an epicalyx of three bracteoles, Hibiscus has one 
 of many bracteoles, and Althaea has one of 6-9 brocteoles : Althcea rosea is 
 the Hollyhock, and A. officinalis is the Marsh-mallow: several species 
 of Malva are indigenous, M. sylvestris, rotundifolia, and moschata : Gossij- 
 
 n 
 
 FIG. 352. A Flower of Malva Alcea (nat. size) : fc calyx ; c corolla ; s connate stamens, 
 with the anthers (a) ; 71 stigmata. B Fruit of Althcea rosea enclosed iu {fc) the calyx : ak 
 epical3-x. C The same after the removal of the calyx. D A single coccus of the same in 
 longitudinal section : seed ; w radicle ; st cotyledon of the embryo (mag.). 
 
 plum herbaceum (with the vars. religiosum and hirmtum) and G. arboreum 
 in Egypt and the East Indies, and G. barbadtnse (with var. peruvianuni) in 
 America, yield Cotton, which consists of the long hairs on the testa of the 
 
 SERIES II. DISCIFLOR.E. 
 
 Flowers typically encyclic and generally pentamerous, often 
 obdiplostemonous : sepals free and coherent : petals in a single whorl : 
 stamens usually definite, and hypogynous : a disc is usually present : 
 gynseceum generally syncarpous. 
 
 Cohort I. Geraniales. Flowers usually pentamerous through- 
 out ; formula Kb, Co \ -45 + 5, G- } ; generally obdiplostemonous; 
 the carpels are opposite to the petals : ovary usually 5-locular, with
 
 542 
 
 PART IV. CLASSIFICATION. 
 
 1 or 2 suspended ovules ; the micropyle is directed inwards : disc 
 various or wanting. 
 
 Order 1. GEBANIACE^E. Disc usually represented by a gland at 
 the base of and outside each of the antisepalous stamens : flowers 
 usually actinomorphic : stamens connate at the base : the carpels 
 are prolonged into a carpophore (Fig. 353 A a) ; two ovules in each 
 loculus ; the fruit is septicidal from 
 below upwards, the awns of the 
 separating carpels (cocci, see p. 473) 
 rolling up (Fig. 353 B}. Seed devoid 
 of endosperm. Herbs ; leaves simple, 
 stipulate. 
 
 Geranium has 10 stamens : in most 
 species the seed is expelled on the rolling 
 up of the awn: Geranium pratense, sylvati- 
 cum, sanguineum, columbinum, and other 
 species, the Crane's-bills, are wild in Eng- 
 land ; G. Robertianum, Herb-Robert, is 
 universally distributed. Erodium, the 
 Stork's-bill, has the 5 stamens which are 
 opposite to the petals transformed into 
 staminodes ; E. cicutarium is common in 
 waste places. Pelargonium, in many 
 varieties, is a well-known garden-plant ; 
 the flowers are irregular and dorsiventral ; 
 the disc is absent, but the posterior sepal 
 is provided with a glandular spur which 
 adheres to the pedicel. The cocci of Ero- 
 dium and Pelargonium are indehiscent, and are forced into the ground 
 by the movement of the hygroscopic awn. 
 
 Order 2. LINACEJE. Disc generally a whorl of 10 small extra- 
 staminal glands : formula K5, (75, ( | A f 5 + 5), G- : flowers acti- 
 nomorphic, rarely all the whorls are tetramerous : stamens mona- 
 delphous at the base ; the whorl of stamens opposite to the petals 
 is replaced by staminodes . each loculus of the ovary contains two 
 ovules, and is often divided into two by a more or less complete 
 false dissepiment : seed usually contains endosperm : capsule septi- 
 cidal. Herbs or shrubs ; leaves simple, entire, with or without 
 stipules. 
 
 Linum usitatissimum is the Flax : the strong bast-fibres are used in 
 weaving linen ; the seeds contain oil ; the walls of the outer cells of the 
 testa are mucilaginous. There are several British species of Linum. 
 Radio! a, the other British genus, has tetramerous flowers. 
 
 
 FIG. 353. Fruit of Geranium. A 
 Before, R after splitting into cocci ; 
 s pedicel ; / loculi of the ovary ; a 
 iu B the awn; n stigma ; a and b 
 carpophore (magr.).
 
 GROUP V. AXGIOSPER&LE J DICOTYLEDON KS. 543 
 
 Order 3. OXALIDACE.E. Disc present as small glands at the 
 base of the antipetalous stamens, or of all of them : flowers actino- 
 morphic; formula Ko, Co, ( | 45 + 5), G^ ; the antipetalous 
 stamens are sometimes staminodial ; those which are opposite to 
 the sepals are the longest : ovules numerous ; fruit a capsule, or 
 more rarely a berry ; seed containing endosperm. Herbs, with 
 compound (ternate), generally exstipulate leaves. 
 
 Oxalis Acetosella, the Wood-S3rrel, is frequent in woods; it contains 
 much potassium oxalate. The tuberous roots or underground stems of 
 some American species, as 0. esculenfa, crenata, and Depjyei, contain much 
 mucilage, and are used as food. Some species (e.g. O. gracilis) show tri- 
 morphic heterostylism (p. 411) : others (e.g. O. Acetosella), have cleistoga- 
 mous flowers (p. 410). The leaves of Oxalis and Averrhoa show sleep- 
 movements : those of Biophytum are sensitive to touch. 
 
 Order 4. BALSAMIXACE.E. Disc 0: flowers irregular, dorsiven- 
 tral ; formula Kb, (75, | 40 + 5, G ( - : the posterior sepal is 
 spurred, and the two anterior are small or absent : the anterior 
 petal is large : ovary 5-locular ; ovules numerous ; the fruit is 
 loculicidally septifragal, the valves separate elastically and roll 
 upwards, so that the seeds are projected to some distance ; seed 
 without endosperm. Herbs, with simple exstipulate leaves. 
 
 Impatiens Noli-me-tangere, the yellow Wild Balsam, occurs in damp and 
 shady spots ; the ripe fruit flies open with violence at a touch. Impatient 
 Balsamina, an Indian species, is cultivated. 
 
 Order 5. RuTACEjE. Disc usually annular : flowers usually 
 actinomorphic : gynseceum sometimes partially apocarpous, but the 
 styles are usually connate : seed with or without endosperm. There 
 are numerous oil-glands on the leaves and stems. 
 
 Sub-order. E.CTE.E. The placentse project into the loculi of the ovary; 
 each bears 3 or more ovules : fruit a loculicidal 
 capsule : seed with endosperm. Ruta grateolens, 
 the Hue, has pentamerous terminal flowers, and 
 tetramerous lateral flowers. Dictamnus Fraxin- 
 ella has an irregular dorsiventral flower. 
 
 Sub-order. AURANTIE^:. Gynseceum syncar- 
 pous : calyx gamosepalous : fruit a berry (p. 476) : 
 seed without endosperm. 
 
 The genus Citrus has an indefinite number of 
 bundles of connate stamens (polyadelphous) (Fig. F|G - 351.-Diapram of 
 355 A), all belonging apparently to the aiitise- 
 
 palous inner whorl : the carpels are usually more numerous than the 
 petals, and during ripening they become filled with a succulent tissue de-
 
 544 
 
 PART IV. CLASSIFICATION. 
 
 derived from their walls ; the various parts of the flower and the fruit 
 (p. 97) contain much ethereal oil : the leaf, which is typically pinnate, is 
 reduced to its terminal leaflet which is articulated to the winged petiole 
 (Fig. 23 (?); the leaf is sometimes spinous. 
 
 Fio. 355. Flower and aoral diagram of Citrus. A Open flower ; c corolla; s the partially 
 connate stamens ; n the stigma. B Bud ; fc calyx; c corolla; d oil-glands. 
 
 Citrus medico is the Citron; C. medica var. Limonum, is the Lemon; C. 
 medico var. Limetta, is the Lime; Citrus Aura nti um var. Bigaradia (or C. 
 vulyaris) is the Bitter or Seville Orange, and C. Aurantium sinense is the 
 Sweet Orange; Citrus nobilisis the Mandarin Orange ; and Citrus decumaua 
 is the Shaddock: all originally derived from tropical Asia- 
 Cohort II. Sapindales. Flowers typically pentamerous and 
 obdiplostemonous but with reduction in the andrcecium, actino- 
 morphic or zygomorphic, sometimes unisexual : gynseoeuin 
 oligomerous, usually syncarpous. Mostly trees. 
 
 Order 1. SAPIXDACE.E. Flowers usually irregular, obliquel}* 
 zygomorphic or asymmetric, in that the two petals of one side are 
 larger and of somewhat different form to the three others ; of these, 
 one, which lies in the plane of symmetry, is sometimes wanting 
 
 FIG. 350. Floral dia- 
 gram of JEsculus': but 
 the missing stamens 
 should be represented 
 us antisepalous. 
 
 FIG. 357. Fruit of A. platanoides, dividing into tv 
 mericarps in ; s pedicel ; ;! wings (nat. size).
 
 GROUP V. ANGIOSPERJOE ; DICOTYLEDONES. 545 
 
 two or three of the antisepalous stamens are usually suppressed, so 
 that the number is eight or seven ; they are inserted within the 
 disc : the ovary is trilocular ; ovules two "in each loculus : seed 
 without endosperm. 
 
 jEsculus has opposite, palmately compound, exstipulate leaves ; the 
 flowers are in terminal scorpioid racemes ; the fruit has a loculicidal de- 
 hiscence : ;E. Hippocastanum is the Horse-Chestnut, derived from Asia ; X. 
 carnea, JE. Pavia, and other species are frequently cultivated. A great 
 number of genera and species grow in warm climates; they have generally 
 scattered pinnate leaves : often climbers with branch-tendrils. The fleshy 
 fruit of Sapindus Saponaria makes a lather with water like soap. 
 
 Order 2. ACERACE^E. Flowers regular: stamens commonly 
 eight, in consequence of the suppression of the two median ones, 
 variously inserted : disc annular, rarely absent, extrastaminal or 
 intrastaminal : ovary bilocular ; ovules two in each loculus ; when 
 ripe the fruit splits into two one-seeded winged mericarps (samaras, 
 p. 473, Fig. 357) : leaves opposite, palmately lobed, sometimes com- 
 pound, exstipulate : flowers in terminal racemes, sometimes in 
 corymbs with an apical flower : seed without endosperm. 
 
 The principal species of Acer, the Maple, are A. Paeudoplatanus, the 
 Sycamore, having leaves with crenate margins, flowers in elongated pen- 
 dulous racemes, blooming after the unfolding of the leaves, and parallel- 
 winged fruits ; A. platanoides, having leaves with serrate margins, flowers 
 in short erect racemes blooming before the unfolding of the leaves, and 
 fruits with widely diverging wings (even more than in Fig. 357) ; A. cam- 
 pest re, the common Maple, which is sometimes shrubby, with a trilobate 
 leaf, short erect racemes of flowers which bloom after the unfolding of the 
 leaves, and fruits with wings which are diametrically opposite. Some 
 North American species are often cultivated, such as A. rubrum, with five 
 stamens opposite to the sepals, and a rudimentary disc; A. dasycarpum, 
 with the same number and position of the stamens, without any corolla, 
 and having dioecious flowers; A. Negundo, with compound 3-5 foliolate 
 leaves, and dioecious flowers like those of the preceding species. Sugar is 
 prepared from the sap of A. saccharinum and dasycarpum especially. 
 
 Order 3. POLYGALACE^E. Flowers irregular, dorsiventral ; the 
 two lateral sepals conspicuously large and known as " wings " (Fig. 
 358 A k') : petals three, the two lateral being absent ; the anterior 
 petal is very large and carinate : stamens usually eight, forming a 
 tube open posteriorly, to which the corolla, or at least the anterior 
 petal, is adnate (Fig. 358 B} : disc rudimentary : carpels two, 
 median, forming a bilocular ovary, each loculus containing a single 
 suspended ovule : fruit usually a capsule. The flower somewhat
 
 546 
 
 PART IV. CLASSIFICATION. 
 
 resembles that of the Papilionese, but it must be borne in mind 
 that here the two " alee " or wings belong to the calyx. 
 
 FIG. 358. Flower of Polygola gfandiflora. A Seen from outside after the removal of the 
 wing-sepal fc. B Longitudinal section : fc calyx : fc' wing ; c corolla ; s tube of stamens. 
 (After Sachs.) 
 
 The flower of the Polygalacese resembles that of the Aceraceae in the 
 suppression of two stamens in the plane of the two carpels. 
 
 Polyyala vulgar is, amara, and others, the Milkworts, are herbs, woody at 
 the base, occurring in woods and meadows. 
 
 Cohort III. Celastrales. Flowers regular, frequently actino- 
 morphic, 4-5-merous ; only one whorl of stamens, which either 
 alternates with or is opposite to the petals, is usually present : disc 
 usually within, sometimes external to, the androscium : ovules 
 usually erect : the seed nearly always contains endosperm. Trees 
 or shrubs. 
 
 Order 1. CELASTRACE^:. Formula, Ah, Cn, ^4n, G (n) or less, 
 n = 4 or 5: sepals imbricate: stamens and carpels inserted on a 
 flattened disc : stamens alternate with the petals : usually two 
 ovules in each loculus of the ovary : 
 leaves scattered, entire, stipulate. 
 
 In the genus Euonymus, the Spindle-tree, 
 the loculicidal capsule contains seeds in- 
 vested by an orange-coloured arillode (p. 416) ; 
 E. turopwa occurs both cultivated and wild. 
 
 Order 2. RHAMNACE^E. Formula, Kn, 
 Cn, | An, G-~ ; n = 4 or 5 : calyx usually 
 gamosepalous, valvate ; petals usually 
 small and often hood-shaped (Fig. 359 c), 
 enclosing the stamens which are opposite 
 to them : flowers sometimes diclinous : 
 usually a single ovule in each loculus of the ovary which is in- 
 
 Fio. 359. Flower of Ehnminis 
 Frangula (mag.) : fc sepals con- 
 nate at the base iuto a tube (d) ; 
 c hood-shaped petals enclosing 
 the stamens (a) .
 
 GROUP V. AXGIOSPERM^E ; DICOTYLEDONES. 547 
 
 vested by a disc : leaves usually scattered, entire, stipulate : fruit 
 a drupe or a capsule. 
 
 Rhamnns catharttca, the Buckthorn, has opposite leaves and thorny 
 twigs : the berries of R. infectoria, in Southern Europe, yield a green or 
 yellow dye : R. Frangula has scattered leaves ; its wood produces a par- 
 ticularly light charcoal. 
 
 Order 3. AMPELIDACEJS. Formula same as in Rhamnacese : 
 sepals small ; the corolla is often thrown off before it opens (Fig. 
 360 A c) : a glandular disc between the androecium and the gynse- 
 ceum : ovules one or two in each loculus : fruit baccate. Climbing 
 plants, with stem-tendrils ; leaves palmate, exstipulate or stipulate. 
 
 Vitis vinifera, the Grape-Vine, probably derived from the East, is culti- 
 vated in endless varieties ; other species, such as V. vulpina and Labrnsca, 
 as also Ampelopsis hederacea, the Virginian Creeper, are also frequently 
 cultivated. The tendrils of the Vine (Fig. 15 A) are branches bearing 
 scaly leaves in the 
 
 axils of which other , 
 
 branches arise : their 
 peculiar position op- 
 posite to the foliage- 
 leaves may be ex- 
 plained as follows : the 
 ordinary shoots are 
 sympodia, and each 
 
 tendril is the terminal 
 
 , , FIG. 360. Flower of Vitis vinifera, and diagram. A At 
 
 segment of a member the moment of opening B Open . fc ca]yx . c corolla . d 
 
 of the sympodmm ; the glands . , 8t a men s ; /ovary ; n stigma (slightly mag.), 
 following member is a 
 
 shoot springing from the axil of the foliage-leaf which is opposite to the 
 tendril. Every third leaf has no tendril opposite to it, that is to say, 
 the members of the sympodium alternately bear one or two leaves. The 
 inflorescences occupy the same positions as the tendrils. Each leaf has 
 also a bud in its axil, which either remains undeveloped or gives rise to a 
 dwarf-shoot: from the axil of the cataphyllary leaf of the dwarf-shoot 
 an ordinary shoot is developed. In some species of Ampelopsis (e.g. A. 
 Veitchii and Roylei) the tendrils attach themselves to flat surfaces by 
 means of discoid suckers developed at their tips. 
 
 SEEIES III. CALYCIFLOR-E. 
 
 Flowers epigynous or perigynous : calyx usually gamosepalous : 
 stamens definite or indefinite : gynseceum syncarpous or apocar- 
 pous. 
 
 Cohort I. Um be Hales. Flowers regular, sometimes actino- 
 morphic, epigynous, with generally a single whorl of stamens
 
 548 
 
 PART IV. CLASSIFICATION. 
 
 opposite to the sepals : calyx inconspicuous : ovary bilocular, with 
 one ovule in each loculus : a disc between the stamens and the 
 styles : inflorescence usually umbellate : seed containing endosperm : 
 leaves exstipulate. 
 
 Order 1. UMBELLIFERJE. Flowers generally regular, but 
 with oligomery in the gynseceum ; formula, K6, (75, Ab, G& : 
 the calyx is generally very small, often hardly visible, though 
 sometimes well developed (e.g. Eryngium, Astrantia) : the corolla 
 consists of five rather small white or yellow petals ; occasionally 
 the outermost petals of the flowers at the circumference of the 
 umbel are larger than the others, and the umbel is then termed 
 radiant : stamens five ; ovary inferior, bilocular : the base of 
 
 rr 
 
 FIG. 361. A Flower of Foeniculum (mag.) : / ovary; c corolla; s stamens; d disc. B 
 Fruit of Heracleum : p pedicel ; g style ; r r r ridges (costa?) : rr marginal ridges ; o oil- 
 ducts (vittae) (mag.). C Transverse section of mericarp of Carwro Cantt (Orthosperine*) : 
 w surface that comes into contact with the other mericarp; o vittse; e endosperm. D 
 Transverse section of mericarp of Conium (Campylospermece). S Fruit of Coriandrum, 
 (Ccelospermece) : k margin of the surface along which the two mericarps are in contact ; r 
 ridges; n secondary ridges : F section of a mericarp. (Mag.) 
 
 the two styles is fleshy and thickened, forming an epigyuous 
 disc (Fig. 361 A d) ; one suspended ovule in each loculus of the 
 ovary (Fig. 284 E) : the fruit, when ripe, splits into two meri- 
 carps, each loculus of the ovary being permanently closed by a 
 median septum (Fig. 362 B a; see p. 473). The structure of the 
 pericarp is an important characteristic for the classification of the 
 family. The fruit is commonly either oval in form, or compressed 
 (Fig. 361 B\ or nearly spherical (Fig. 361 E] : its surface generally 
 bears longitudinal ridges (costce or juga primarid) enclosing vas-
 
 GROUP V. ANGIOSPERMJE ; DICOTYLEDONES. 
 
 541> 
 
 cular bundles, five generally on each mericarp ; of these, two run 
 along the margins (Fig. 361 B, C, D, rr\ and the other three along 
 the dorsal surface (Fig. 361 B, <7, Z), r). In the spaces between 
 the ridges which form furrows, lie oil-ducts or receptacles (vittce) 
 (Fig. 361 B, C, o), and sometimes other secondary ridges (juga. 
 sccundaria) (Fig. 361 E, F, n), which do not enclose vascular 
 bundles. The mericarp when ripe is filled by the seed, which 
 consists of the abundant endosperm (Fig. 361 C, D, F, e~) enclosing 
 a small embryo. According to the form assumed by the endosperm, 
 the following groups may be distinguished : the OrthospcrmecK r in 
 which the surface of the endosperm, which is directed towards the 
 plane of junction of the two mericarps, is flat or convex, as in 
 Carum (Fig. 361 C) : the Campylospermece, 
 in which the endosperm is concave to- 
 wards the same plane, as in Conium (Fig. 
 361 D], and the Coelospermece, in which 
 the whole endosperm is curved, so that it 
 is seen to be concave towards this plane 
 both in longitudinal and in transverse 
 section, as in Coriander (Fig. 361 F). 
 
 The flowers, with few exceptions (Hy- 
 drocotyle, Astrantia, Eryngium, where the 
 umbels are simple), are in compound um- 
 bels (p. 440) ; in some few cases, as in 
 Caucus, the umbel has a distinct terminal 
 flower which is black in colour: an in- 
 volucre and involucels are largely de- 
 veloped in some species, in others they are 
 wholly wanting. The hollow stem bears 
 large leaves with generally well-developed 
 sheathing bases and much divided laminae : 
 rarely the leaves are simple, as in Hydro- 
 cotyle and Bupleurum. 
 
 The British genera are arranged as follows : 
 Sub-order I. ORTHOSPERMK.E. 
 
 A. Umbels simple. 
 
 Tribe 1. Hydrocotylece. Fruit laterally compressed. The genus Hy< In. - 
 cotyle consists of marsh-plants with peltate leaves (Fig. 22). 
 
 Tribe 2. Saniculece. Fruit nearly cylindrical. This group includes 
 the genera Astrantia, Eryngium, and Sanicula. 
 
 B. Umbels compound. 
 
 Tribe 3. Amminece. Fruit without secondary ridges, laterally com- 
 
 Fia. 362. Fmit of Caram. 
 Carui. A Ovary of the flower 
 (/). B Ripe Fruit. The two 
 carpels have separated go a* 
 to form two mericarps (m). 
 Part of the septum consti- 
 tutes the carpophore (a).
 
 550 PART IV. CLASSIFICATIOX. 
 
 pressed : Ammi, Bupleurum, Petroselinum, Apium, ^Egopodium, Carum 
 (Figs. 361 C, and 362), Cicuta, Slum, Pimpinella, Trinia, Conopodium, 
 Sison. 
 
 Tribe 4. Seselinetv. Secondary ridges absent, or if present (Siler) not so 
 prominent as the primary : fruit not compressed : ^Ethusa, Foeniculum, 
 (Enanthe, Seseli, Meum, Ligusticum, Silaus, Crithmum, Siler. 
 
 Tribe 5. An<jelicei.v. Fruit without secondary ridges, dorsal ly com- 
 pressed, the lateral primary ridges winged, the wings of the two mericarps 
 divergent ; Angelica, Archangelica. 
 
 Tribe 6. Peucedaneiv. Fruit without secondary ridges, dorsally com- 
 pressed, the lateral primary ridges winged, the wings of the two meri- 
 carps apposed : Peucedanum (inch Imperatoria), Pastinaca, Heracleum, 
 Tordylium. 
 
 Tribe 7. Daucinew. The secondary ridges are spinous : Daucus. 
 
 Sub-order II. CAMI>YLOSI>ERME.. 
 
 Tribe 8. Caucalinece. Secondary ridges spinous : Caucalis (incl. Torilis). 
 
 Tribe 9. Smyrniece. Fruit without secondary ridges : Anthriscus, 
 Myrrhis, Conium (Fig. 361 Z>), Smyrnium, Physospermum. 
 
 Sub-order III. C<ELOSPERMK.E. 
 
 Tribe 10. Scandicece. Fruit sub-globose, without secondary ridges : 
 Scandix, Chserophyllum, Echinophora. 
 
 Tribe 11. Coriandrecn. Fruit spherical ; secondary ridges more pro- 
 minent than the wavy primary ridges : Coriandrum (Fig. 361 F, E). 
 
 Anthriscus siliestris, the Cow-Parsley ; Carum Carui, the Caraway ; Herac- 
 leum Sphondylium, the Cow-Parsnip ; jEgopodium Podayraria, the Gout- 
 Weed ; Pastinaca sativa, the Wild Parsnip, are common in meadows and 
 woods : Crithmum, the Samphire, grows on rocks by the sea : Echinophora, 
 the Prickly Samphire, growing on sandy sea-shores, has been exter- 
 minated in Britain. The following are cultivated: Apium graveolens, 
 Celery; Petroselinum sativum, Parsley; Daucus Carota, the Carrot; Pasti- 
 naca oleracea, the Parsnip ; Anthriscus Cere/Mum, the Chervil. The follow- 
 ing are poisonous: Conium maculatum, the Hemlock; Cicuta virosa, the 
 Water-Hemlock ; jEthusa Cynapium, Fool's-Parsley. 
 
 Order 2. ARALIACE^E. Flowers generally pentamerous; stamens 
 sometimes more numerous ; carpels more or less numerous : fruit, 
 a berry or a drupe. Shrubs, sometimes root-climbers, with 
 scattered palmate leaves. 
 
 Hetlera Helix, the Ivy, does not blossom till it is some years old : the 
 mmbels are borne on erect branches, the leaves of which are entire. Fatsia 
 papi/rifera is used in Japan for making a kind of paper known as rice- 
 paper ; it is made from the pith. 
 
 Cohort II. Passiflorales. Flowers frequently unisexual, 
 regular ; epigynous, perigynous or hypogynous ; pentamerous : 
 stamens in one or two whorls, or indefinite : gynseceum syncarpous ;
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDOXES. 
 
 551 
 
 ovary usually trimerous and unilocular ; ovules numerous, on 
 parietal placentae. 
 
 Order 1. CUCURBITACEJE. Flowers diclinous -or polygamous, 
 often irregular : corolla of five petals, often gamopetalous : stamens 
 epipetalous, five, but they frequently cohere, either in pairs, so 
 that there appear to be but three (Fig. 363, diagram), or all com- 
 pletely into a single continuous ring (Cyclanthera) ; the anthers 
 are commonly long and sinuous : ovary inferior, unilocular, becom- 
 ing spuriously multilocular, with one or (more often) many ovules ; 
 it is, however, often described as multilocular (usually 3) with 
 projecting axile placentas : 
 fruit baccate, a pepo or a 
 succulent berry (p. 476), 
 often of great size, with a 
 relatively thick and solid 
 pericarp : seed without 
 endosperm. Herbs with 
 scattered leaves, mostly 
 climbers, with tendrils 
 growing by the side of the 
 leaves. 
 
 There is considerable dif- 
 ference of opinion as to the 
 morphological nature of the 
 tendril in this order, but it 
 appears to be essentially a 
 leaf, in fact the first leaf of 
 the flowering-shoot which 
 arises in the axil of the re- 
 lated foliage-leaf : the vegeta- 
 tive branch, which is always 
 developed by the side of the 
 flowering - shoot, seems to 
 spring from the axil of the 
 tendril. The tendril often bears a number of branches at its distal end, but 
 whether simple or branched, its structure shows that the proximal portion 
 corresponds in structure to a petiole, whilst the distal irritable portion 
 (including the branches) has a bilateral structure which suggests corre- 
 spondence with a lamina. 
 
 Cm-urbita Pejx> is the Pumpkin : the genus Cucumis has free stamens ; 
 Cucumis sativa is the Cucumber, and Cucumis Melo is the Melon: Cilrullus 
 vuifjaris is the Water Melon. The genus Bryonia has a small white 
 corolla : the loculi of the ovary are 2-seeded, and the fruit is a succulent 
 berry ; B. dioica is common in shrubberies and hedges. 
 
 FIG. 363. A Longitudinal section of $ flower of 
 Cucumis: /ovary; sfc ovules ; t calyx ; C corolla; 
 n stigma ; st' rudimentary stamens. B Longitudi- 
 nal section of <J flower; st stamens ; n' rudimentary 
 ovary ; the corolla (c) is not alt shown (somewhat 
 mag.). Floral diagram of Cncurbita.
 
 552 
 
 PART IV. CLASSIFICATION. 
 
 Cohort III. Myrtales. Flowers usually actinomorphic, 
 encyclic, epigynous or perigynous, with usually two whorls of 
 stamens, typically obdiplostemonous : gynseceum syncarpous, with 
 usually a single style : leaves usually opposite. 
 
 Order 1. OXAGRACE.E. Flowers usually tetramerous through- 
 out, generally epigynous : antipetalous stamens sometimes sup- 
 pressed : ovary multilocular, with generally numerous ovules on 
 axile placentae : fruit a berry or a capsule ; seed without endo- 
 sperm. Calyx often petaloid, forming a long tube (Fig. 364 A, r). 
 
 C 
 
 FIG. 364. .4 Flower of Fnchsia : s pedicel ; / inferior ovary ; fc sepals, connate at the 
 base, forming a tube (r) ; a stamens ; g style; n stigma. B Flower of Epilobtum hirsutum 
 (letters as before). C Fruit of Epilobium after dehiscence ; w outer wall ; m columella 
 formed by the septa ; so seed with tufts of hairs (nat. size). 
 
 (Enothera biennis, the Evening Primrose, occurs on river banks: the seed 
 has not a tuft of hairs, and the flowers are yellow. Epilobium is the 
 Willow Herb, of which many species are common ; E. angustifolium, 
 hirsutum, and montanum occur in fields, hedges, and ditches; the seeds 
 have a tuft of long hairs (see p. 416) ; flowers red ; fruit a septifragal 
 capsule. Ciraxa lutttiana (Enchanter's Nightshade) has dimerous flowers 
 K2 C2, A2, G(y (Fig. 270 B) ; common in damp and shady spots. Isnardia 
 palustris has no corolla ; its fruit is a septicidal capsule. Fuchsia (Figs. 
 364 A, 270 A), many species of which are cultivated as ornamental plants, 
 is a native of South America ; fruit a berry. 
 
 Trapa natans, the Water-Chestnut, a not vei-y common water-plant 
 of Central Europe, has a stem bearing a rosette of leaves which float
 
 GROUP V. ANGIOSPERM^E ; DICOTYLEDONES. 
 
 553 
 
 on the surface of the water ; in the axils of these leaves the flowers are 
 borne singly : their formula is K, (74, A4, <?<?), and they are perigynous : 
 the fruit is indehiscent, and the sepals remain adherent to it in the form 
 of four horns : it contains two seeds. 
 
 Order 2. LYTHRAOE^E. Flowers perigynous, with usually both 
 whorls of stamens : formula Kn, On, | ^4n + n, G (2 - ) , where n = 3 
 16 : ovary free in the hollow receptacle : an epicalyx formed by 
 connate stipules is often present : seed without endosperm. 
 
 Lythrum tialicaria, the Loosestrife, occurs in bogs and ditches : flower 
 usually pentamerous or hexamerous : the stamens of the two whorls are 
 unequal in length, and the length of the style also varies ; three forms of 
 flowers are thus produced (trimorphism ; see p. 412). The other British 
 genus is Peplis ; P. Portula is the Water-Purslane ; it has usually hexa- 
 merous flowers and an indehiscent fruit: gynaeceum dimerous in both 
 genera. 
 
 FIG. 365. Longitudinal section of 
 the flower of Calorhamnus ; /ovary; 
 s calyx; p corolla; st antipetalous 
 bundle of stamens; g style. (After 
 Sachs). 
 
 FIG. 366. Flower-bud of Jamboa 
 Caryophyllus, the Clove, in longitudi- 
 nal section ; / the inferior ovary, with 
 the oil-glands (<!>) ; sk the ovules ; k 
 calyx ; c corolla ; st stamens ; a an- 
 thers ; g style (enlarged) . 
 
 Order 3. MYRTACEJE. Flowers 4- or 5-merous, epigynous : sta- 
 mens often very numerous, free, or connate in usually antipetalous 
 bundles (Fig. 365) ; sometimes few and obdiplostemonous : ovary 
 1 oo-locular ; seeds 1-x in each loculus, without endosperm: 
 placentation and fruit various : leaves usually opposite, dotted 
 with oil-glands. Shrubs or trees. 
 
 Myrtus communis is the Myrtle of Southern Europe ; the genus Eugenia 
 includes a number of ornamental shrubs, among which is E. (Jambosa) 
 Ceiryopkytttit, the buds and flowers of which yield the spice known as 
 cloves (Fig. 366). Eucalyptus Globulus, from Australia, is much planted
 
 554 PART IV. CLASSIFICATION. 
 
 in marshy districts, which it tends to dry up by its active transpiration. 
 Berthdletia excelsn grows in tropical America; its seeds are known as 
 Brazil nuts. 
 
 Punica Granatum, the Pomegranate, grows in Southern Europe ; flowers 
 5-8-merous ; receptacle petaloid ; stamens indefinite ; in the ovary there 
 are two whorls of loculi, an external superior of which the loculi are as 
 numerous as and are opposite to the petals, and an internal inferior 
 consisting of three loculi. 
 
 Cohort IV. Resales. Flowers actinomorphic or zygomorphic, 
 usually monoclinous and perigynous : stamens rarely fewer in 
 number than the petals or equal to them, generally indefinite in 
 numerous whorls : gynseceum more or less completely apocarpous : 
 ovules anatropous, suspended or erect : seed generally without 
 endosperm. 
 
 Order 1. ROSACELE. Flowers actinomorphic, rarely zygo- 
 morphic, perigynous : gyngeceum generally apocarpous ; carpels 
 1- oo ; ovules 1 or few, anatropous : fruit various ; seed generally 
 without endosperm : leaves scattered, stipulate ; the odd sepal is 
 posterior (see Fig. 267). 
 
 Tribe 1. Roseau. Carpels numerous, attached to the base and sides of 
 the hollow receptacle, which is narrow above (Fig. 367 C) ; each contains 
 a, single suspended ovule ; when ripe, they are achenes enclosed in the 
 fleshy receptacle : the sepals are frequently persistent at the top of 
 it. Shrubs with imparipinnate leaves; the stipules are adnate to the 
 petiole. 
 
 Many species of Rosa, the Rose, are wild, such as R, arvensis, canina, 
 and rubiyinosa (Sweet-Briar or Eglantine) ; and many others are culti- 
 vated, as R. centifolia, damascene/,, indica, gallica, etc. 
 
 Tribe 2. Spirceece. Carpels usually 5, each containing two or more 
 suspended ovules ; they are inserted upon the floor of the flat open 
 receptacle, and becomfe follicles ; the calyx is persistent till the fruit 
 is ripe. 
 
 Spircea Ulmaria, Meadow-sweet, and S. Filipendula, Dropwort, occur in 
 woods, meadows, etc.; Sp. sorbifoiia, media, ulmifolia, and other species, 
 Kerria japonica, and Rhodoty pus (with drupes), are ornamental shrubs. 
 
 Tribe 3. Prunece. The single carpel, containing two suspended ovules, 
 is inserted on the floor of the receptacle (Figs. 367 A and 368 A) ; the 
 receptacle and the calyx fall off when the fruit is ripe: stamens usually 
 in three whorls of 5 or 10 ; fruit a drupe (p. 475, Fig. 290) ; only one seed 
 is usually present. 
 
 Prunus is the principal genus of the tribe. In the sub-genus Amyg- 
 dalus the fruit has a furrowed coriaceous endocarp ; Prunus Amygdalus 
 (A. communis), the Almond-tree, and nana, are trees of Southern Europe ; 
 P. Persica is the Peach. In the sub-genus Prunophora, the fruit has a 
 smooth, stony endocarp ; P. communis (spinoya) is the Sloe or Blackthorn ;
 
 GROUP V, ANGIOSPERM^E ; DICOTYLEDONES. 
 
 555 
 
 P. Armeniaca is the Apricot; P. domestica is the Wild Plum, it has an 
 ovoid fruit and glabrous shoots : P. insititia is the Bullace, it has a globoid 
 fruit and hirsute shoots. In the. sub-genus Cerasus, P. Cerasus, the Dwarf 
 or Morello Cherry, has foliage-leaves at the base of its umbellate inflor- 
 
 FIG. 367. Diagrammatic longitudinal sections of Rosaceous flowers. A Prunes. 
 B Potentillese. C Roseae. J> Pomea? : fc calyx ; c corolla; /ovaries ; n stigmata. 
 
 escences ; P. Avium, the Wild Cherry or Gean, has only scales at the base 
 of its inflorescences. In the sub-genus Laurocerasus, P. Mahaleb, the 
 Damson, has fragrant bark; P. Padus, the Bird-Cherry, has elongated 
 racemose inflorescences ; P. Laurocerasus, the Cherry-Laurel, has evergreen 
 leaves which somewhat resemble those of the true Laurel ; P. lusitanica is 
 the Portugal Laurel. 
 
 Tribe 4. Poteriecn. Flowers often diclinous : corolla often absent : 
 ovaries few, often but one, monomerous, enclosed in the cavity of the 
 receptacle : ovules solitary, suspended: fruit, a dry receptacle bearing 
 one or more nut-like achenes. 
 
 The genus Alchemilla has tetramerous flowers destitute of a corolla 
 the stamens (4 or fewer) alternate with the sepals ; an epicalyx is present : 
 A. vulgaris, the Lady's Mantle, and A. arvensis, are common. In the 
 genus Poterium, the flowers of the sub-genus Sanguisorba (P. officinale, 
 the great Burnet), have no corolla, the four stamens are opposite the 
 sepals, and they have no epicalyx : the flowers of the sub-genus Poterium 
 (P. Sanyuisorba, the Salad Burnet), resemble those of the preceding, but 
 the stamens are indefinite, and they are polygamous. The flower of 
 Agrimonia is pentamerous ; it has 
 a corolla and indefinite stamens : 
 the outer surface of the receptacle 
 is beset with bristles. 
 
 Tribe 5. PotenlillecK. The ova- 
 ries, which are numerous, are 
 inserted upon a prolongation of 
 the axis into the cavity of the 
 receptacle (Tigs. 367 B and 368 B) ; 
 each usually contains one ovule. FIG. 368. A Flower of the Cherry: pe- 
 
 The calyx is often surrounded by duncle c corolla : a """"ens ; 9 style, pro- 
 , , , , -i jectinjT out of the cavity of the receptacle. 
 
 an epicalyx formed by the con- B Fruit of the Blackberry . EvbutfnticMW , 
 nate stipules of the sepals (Fig. fc calyx; /fleshy ovaries.
 
 556 PART IV. CLASSIFICATION. 
 
 275 C). The stamens are usually indefinite, each whorl consisting of 
 as many or twice as many stamens as there are petals. These flowers 
 are distinguished from those of the Ranunculacese, which they somewhat 
 resemble, by the whorled arrangement of the stamens and by the 
 presence of the hollow receptacle; for in Ranunculaceous flowers the 
 stamens are arranged spirally and the sepals are quite free. 
 
 Of the genus Potentilla, the fruit of which is an etserio of achenes on a 
 dry receptacle, many species are common, such as P. anserina, the Silver- 
 weed, reptans, Tormentilla, and others: the sub-genus Sibbaldia includes 
 the species P. procumbens, which is found on Scottish mountains : the 
 sub-genus Comarum includes the species P. Comarum, the Marsh Cinque- 
 foil. Fragaria is the Strawberry ; the receptacle becomes succulent as 
 the fruit ripens and bears the small achenes on its surface 5 F. vesca 
 and elatior are found in woods ; F. virginiana and other North American 
 species are cultivated. In the genus Rubus there is no epicalyx, the 
 ovary contains two ovules, and the fruit is an etserio of drupels ; Rubu* 
 Jd<xtis is the Raspberry ; its fruits separate from the dry receptacle when 
 they are ripe : in R. fruticosus, the Blackberry, and It. ceesius, the Dew- 
 berry, the upper part of the receptacle separates together with the fruits 
 when ripe. Dryas octopetala, the Mountain Avens (without epicalyx) 
 is a procumbent Alpine shrub with an oval long-tailed fruit (resembling 
 that of Clematis Vitalba). An epicalyx is present in most species of Geum ; 
 Geum urbanum and rivale (Avens) occur in woods and damp fields; the 
 long style is hooked. 
 
 Tribe 6. Pamete. Ovaries five or fewer, contained in the cavity of the 
 receptacle, connate, and adnate to the wall of the receptacle (Fig. 367 D). 
 The spurious fruit is surmounted by the calyx. The individual fruits 
 either become hard and are like small drupes imbedded in the fleshy 
 receptacle, or they have only a thin wall, so that they are more like 
 capsules and seem to be loculi of the whole fruit, as in the apple for 
 instance, where the succulent portion is derived from the receptacle, and 
 the core consists of the fruits enclosing the seeds, which are basal, gener- 
 ally two in each carpel. Stamens indefinite : no epicalyx. Shrubs or 
 trees with deciduous stipules. 
 
 I. With stony fruits. 
 
 In the genus Cotoneaster, the fruits project above the receptacle : in 
 Cratsegus, the Hawthorn, they are completely enclosed ; C Oxijacantha, 
 the May, and its var. monogyna, the common White Thorn, are common : 
 Mespilus, the Medlar, has a large fruit which is surmounted by the five 
 large sepals. 
 
 I. With coriaceous fruits. 
 
 The genus Cydonia, the Quince, has numerous ovules on the ventral 
 suture of each carpel ; the outer layers of cells of the testa are mucila- 
 ginous. The genus Pyrus has two basal ovules : P. communis and others 
 are the Pear-trees ; the loculi of the spurious fruit, seen in transverse 
 section, are rounded towards the exterior ; the fruit is not hollowed at the 
 base : the sub-genus Malus includes P. Mains and others, the Apple-trees ; 
 the fruit is hollowed at the base, and the loculi, seen in transverse
 
 GROUP V. ANGIOSPERM^E ; DICOTYLEDONES. 557 
 
 section, are pointed towards the exterior : the sub-genus Sorbus resembles 
 the preceding, but has pinnatifid leaves ; it includes P. Aucuparia, the 
 Mountain Ash or Rowan-tree, also P. domestica, the true Service-tree, and 
 P. torminalis, the Wild'Service-tree : the sub-genus Aria, includes P. Aria, 
 the White Beam. The genus Amelanchier includes the European A. 
 vulgaris, and A, canadensis, the June-Berry. The genera Raphiolepis 
 and Photinia (incl. Eriobotrya, the Loquat), include well-known culti- 
 vated flowering shrubs. 
 
 Order 2. LEGDMINOS^E. Flowers usually dorsiventral, perigy- 
 nous, pentamerous, with calyx and corolla : stamens ten or more : 
 ovary of a single anterior carpel ; ovules borne on the ventral 
 suture : fruit a legume or a loinentum : flowers always lateral : 
 leaves nearly always compound. 
 
 The Leguminosae, more particularly the Papilionese, are remarkable 
 physiologically by the presence of tubercles on their roots, caused by the 
 attack of a Fungus, and by their extraordinary faculty of nourishing in 
 soils poor in combined nitrogen (see p. 191). 
 
 Sub-order 1. PAPILIONE^E. Flowers 
 dorsiventral, papilionaceous (Fig. 272 A). 
 The five sepals, the odd one being an- 
 terior, are usually connate, forming a 
 tube above the insertion of the corolla 
 and the androecium : the five lobes are 
 usually unequal and sometimes form 
 two lips, the lower of three and the 
 upper of two teeth : petals five, alternate 
 
 with the sepals, imbricate so that the 
 
 , , , FIG. 369. Flower of Lotus covjucu- 
 
 anterior petals are overlapped by those , atug (gomewhat ma ^ A With one 
 
 behind them ; the posterior petal is a ia removed ; k calyx ; fa vexillum ; 
 much enlarged, and is called the vex- fl ala; s carina. B With the corolla 
 ilium (Fig. 369.4, /a); the two lateral removed; rtube formed by the nine 
 
 petals, which are much smaller, are *" 8tamen; ' 
 
 termed the alai (Fig. 369 A, fl) ; the two 
 
 anterior petals are connate or sometimes simply apposed, and form a hollow 
 boat-shaped body, the keel, or carina (Fig. 369 A, *). In a few cases the 
 corolla is entirely or partially suppressed ; thus in Amorpha, only the 
 vexillum is present. The ten stamens belong to a single whorl, with 
 direct diplostemony ; they are either connate and monadelphous, forming 
 a tube, or the posterior stamen may be free, so that the tube consists of 
 nine stamens, and is incomplete posteriorly (Fig. 3695), in which case the 
 androecium is diadelphous (9-1) ; rarely the stamens are all free ; they 
 mostly curve upwards, and diminish in length from in front backwards. 
 The ovary, enclosed by the staminal tube, consists of a solitary anterior 
 carpel ; it is often divided into chambers by a spurious longitudinal 
 septum, or by transverse septa into several chambers. The fruit is 
 usually a legume or a lomentum (Fig. 288 A), rarely one-seeded, and
 
 558 PART IV. CLASSIFICATION. 
 
 indehiscent : the seed frequently contains scanty endosperm. The flowers 
 are solitary and axillary, or in racemes. The leaves are only rarely 
 entire, usually palmately or pinnately compound (Fig. 23), with often large 
 stipules (Fig. 19 (7), which are sometimes spines (Robinia). The following 
 are the principal tribes : 
 
 Tribe 1. Genistece. Stamens usually monadelphous : leaves simple, or 
 compound ternate. 
 
 In Ulex the Whin, Gorse or Furze, Genista the Green-weed, Cytisus 
 (Sarothamnus) the Broom, and Lupinus, the stamens are monadelphous ; 
 in Genista the leaves are simple ; in Cytisus the leaves are ternate ; in 
 Ulex the leaves are ternate in seedlings, but in mature plants they are 
 scaly or spinous ; in Lupinus the leaves are palmately compound. Cytisus 
 Laburnum is a well-known flowering tree. 
 
 Tribe 2. Tri/oliece. The posterior stamen is usually free ; leaves 
 ternate, and leaflets with serrate margins. 
 
 In Medicago (Medick), Melilotus, and Trifolium, the stamens are dia- 
 delphous : in Ononis, the Best-harrow, they are monadelphous. Trifolium 
 is the Clover: the stamens are partially adnate to the corolla; the 
 withered corolla persists and encloses the small legume : flowers in 
 capitula; T. pratense, the Red Clover, T. repens, the White Clover, and 
 T. hybridum, the Alsike Clover, which are common in meadows, and T. 
 incarnatum, from the East, are cultivated. Medicago has usually a 
 spirally-wound legume, and a deciduous corolla ', M. falcata and lupulina 
 are common; M. saliva, Lucerne, is cultivated. Melilotus (Melilot) has a 
 globular legume ; M. alba and altissima are common on the banks of 
 streams. Trigonella is the Fenugreek. 
 
 Tribe 3. Lotece, Stamens diadelphous, the posterior stamen being free : 
 leaves pinnate ; leaflets sessile, entire. 
 
 Lotus corniculatus, the Bird's-foot Trefoil, with a beaked carina and 
 nearly straight legume, is common in meadows. In Anthyllis, the 
 Kidney-Vetch, the stamens are monadelphous at first, the posterior 
 stamen becoming more or less separate: Anthyllis Vulneraria, Ladies' 
 Fingers or Woundwort, is common in dry pastures. 
 
 Tribe 4. Galegece. Stamens diadelphous : leaves multijugate impari- 
 pinnate ; leaflets stalked. 
 
 Indigofera tinctoria, in the East Indies, produces Indigo. Glycyrrhiza 
 is the Liquorice. Robinia Pseudacacia. the false Acacia, is a native of 
 North America, but it has become naturalized. Astragalus has a legume 
 with a spurious longitudinal dissepiment : very many species of it occur, 
 especially in the East. 
 
 Tribe 5. Hedysarece. Leaves imparipinnate ; stamens diadelphous : 
 fruit a lomentum, with transverse septa, dividing into segments. Coty- 
 ledons leafy, epigean. 
 
 Hippocrepis,the Horse-shoe Vetch, and Coronilla arecommon in meadows ; 
 Onobrychis saliva, the Sainfoin, is cultivated. Arachis hypoguia, the Earth- 
 Almond or Ground-Nut of tropical America, ripens its fruits in the earth. 
 Desmodium gyrans, the Telegraph-plant, has motile leaflets. 
 
 Tribe 6. Video*. Stamens diadelphous : legume unilocular ; cotyledons 
 hypogean ; leaves paripinnate and usually cirrhose (see Fig. 19 C).
 
 GROUP V. ANGIOSPERM-rE | DICOTYLEDOXES. 
 
 559 
 
 Vicia sativa, the Vetch, and V. Faba, the Bean, are cultivated ; other 
 species occur wild. Plsum sativum and aroense, the Pea, are cultivated. 
 Lens esculenta, the Lentil, belongs to Southern Europe. Various species of 
 Lathyrus (inch Orobus) occur wild in woods : L. odoratua and others are 
 cultivated. 
 
 Tribe 7. Phaseolece. Stamens diadelphous: legume unilocular: coty- 
 ledons usually epigean, but not leafy : leaves usually imparipinnate, fre- 
 quently ternate. Mostly climbing plants with twining stems. 
 
 Phaseolus vulgaris, the French Bean, and P. multiflorus, the Scarlet 
 Runner, are cultivated. Wistaria (Glycine) chinensis is an ornamental 
 climber. Physostigma is the Calabar Bean. 
 
 Sub-order 2. CJESALPINIE.S:. Flower dorsiventral, but not papilionaceous 
 (Fig. 272 B and Fig. 870) ; petals imbricate so that the posterior petal is 
 overlapped by those anterior to it; stamens ten or fewer, free, more rarely 
 connate : the legume is frequently divided by transverse septa, and is in- 
 dehiscent : flowers in panicles or racemes : seeds often albuminous. 
 
 Gleditschia triacanthos and other species are cultivated for ornament. 
 Cercis Siliquastrum, the Judas tree, has rounded leaves. The wood of 
 
 FIG. 370. Flower of a Cassia: 
 fc calyx ; c corolla ; o stamens ; ' 
 the central shorter ones ; /ovary. 
 
 FIG. 371. Flower of an 
 Acacia (mag.) : fc calyx ; c 
 corolla; tt stamens, with 
 (an) anthers; n stigma. 
 
 CcesaJpinia braziliensis is known as Pernambuco or Brazil wood. Hsema- 
 toxylon, Cassia, Bauhinia, Tamarindus, and Ceratonia (C. Siliqua, the 
 Carob-tree) are other well-known genera. 
 
 Sub-order 3. MIMOSEJE. Flowers regular ; petals with valvate aestiva- 
 tion: stamens ten, rarely fewer, frequently very numerous, free (Fig. 371), 
 usually much longer than the perianth : legume sometimes divided by 
 transverse septa : seed rarely albuminous : flowers usually grouped in 
 spikes or capitula. 
 
 Mimosa pudica, the Sensitive Plant, has irritable leaves (see Part III). 
 Species of Acacia are mimerous in Africa, Asia, and Australia. In the 
 Australian species the leaves are represented by flattened petioles (phyl- 
 lodes, p. 32) which are extended in the median plane. 
 
 Cohort V. Saxifragales. Flowers generally monoclinous 
 and actinomorphic ; hypogynous, perigynous or epigynous ; eu-
 
 560 
 
 PART IV. CLASSIFICATION. 
 
 cyclic ; stamens usually in two whorls, with obdiplostemony ; 
 ovary generally syncarpous, multilocular, with more than one 
 style or stigma ; ovules usually numerous in each loculus ; seed 
 with or without endosperm. 
 
 Order 1. SAXIFRAGACE^E. Flowers usually 4-5-merous, epigy- 
 nous or perigynous, completely actinomorphic only when there are 
 five carpels : stamens usually in two whorls ; carpels less numer- 
 ous, usually connate below and free above ; seeds numerous, con- 
 taining endosperm. 
 
 Tribe 1. Saxifragece. Flowers perigynous or epigynous, regular, but 
 generally with oligomery in the gynaeceum : petals with imbricate aesti- 
 vation, sometimes suppressed : two whorls of stamens, but one or other 
 of the whorls is suppressed in some genera and species : cai-pels usually 
 
 FIG. 372. Longitudinal section of the 
 ovary of Bergenia ; g style ; n stigmata ; 
 p placentae (mag.). (After Sachs.) 
 
 FIG. 373. Floral diagram of Parnassia 
 but the whorl of antipetalous staminodei 
 should be represented as external to th 
 whorl of stamens. 
 
 two, diverging above (Figs. 281 D, 372) : inflorescence of racemose cymes : 
 fruit a capsule : leaves alternate. 
 
 The British genera are Saxifraga and Chrysosplenium : Saxifraga has 
 an oblique bilocular ovary; the receptacle invests the lower connate 
 portion of the ovary : many species occur in mountainous districts, and in 
 several of them there is a deposit of carbonate of lime on the margins of 
 the leaves (see pp. 96, 203) ; only a few species, such as S. tridactylites and 
 granulata, occur in the plains : Chrysosplenium, the Golden Saxifrage, has 
 a tetramerous flower destitute of a corolla ; the two species are small 
 plants, somewhat resembling a Euphorbia, occurring in damp places. 
 
 Tribe 2. Parnassiece. Fowers perigynous, often actinomorphic ; the five 
 stamens opposite to the petals are transformed into glandular staminodes ; 
 petals with imbricate aestivation : ovary 4-5-merous, unilocular : fruit a 
 loculicidal capsule : leaves alternate.
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDONES. 
 
 561 
 
 Parnassia palustris, Grass of Parnassus, has a whorl of radical leaves, 
 and terminal and lateral peduncles each bearing a single flower and 
 adnate to a bracteole : it is frequently found in damp localities. 
 
 Tribe 3. Ribesiece. Flowers epigynous, incompletely actinomorphic, 
 pentamerous (Fig. 374) : stamens five, opposite to the sepals ; carpels 
 usually two, usually median, sometimes lateral : fruit a berry : leaves 
 scattered : inflorescence racemose. Shrubs. 
 
 Several species of Eibes, the Currant, are cultivated : R. rubrum is the 
 Bed Currant; R. nigrum, the Black Currant; R. Grossularia, the Goose- 
 berry : the spines of the last species are developed from the pulvinus. 
 
 Apparently allied to the Saxifragacese is the order DHOSERACE.E, which 
 includes a number of insectivorous plants. Drosera has a scorpioid in- 
 florescence borne on a scape without bracteoles; the leaves are radical 
 and are fringed with glandular appendages, each of which is traversed by 
 a nbro-vascular bundle (Figs. 33, 34, p. 48). D. rotundifdia and inter- 
 media, the Sun-dews, are found on wet heaths. Aldrovanda vesiculosa, is a 
 floating rootless water-plant of Southern Europe ; its whorled leaves fold 
 up when stimulated ; flowers solitary, axillary. Dioncea muscipula, Venus' 
 Fly-trap, occurs in North America ; it has leaves which likewise fold to- 
 gether when touched ; flowers with 10-20 stamens and basal ovules. 
 
 Fia. 374. Flower of Ribes (mag.) : 
 
 pedicel; fc calyx; c corolla ; st stamens ; FIG. 375. Flower of Sedum acre (x 3). 
 
 . b disc ; g styles. 
 
 Order 2. CRASSULACE^E. Formula A"h, (7n, | An 4- n, (?n, where 
 n = 3 30 : flowers actinomorphic, perigynous or hypogynous, 
 with two (rarely one) whorls of stamens : gynseceum, generally 
 completely apocarpous ; carpels opposite to the petals, with a scale 
 (disc) external to each carpel : ovules numerous, marginal : fruit 
 a follicle : seed with endosperm : inflorescence usually cymose. 
 Plants with entire fleshy leaves, arranged spirally, often in rosettes. 
 
 The genus Sedum has usually pentamerous flowers ; Sedum acre, the 
 Stonecrop, is common on walls and rocks ; S. Rhodiola has dioecious 
 flowers. S. Telephium, the Orpine and others are common. The genus 
 Sempervivum has at least 6-merous flowers ; S. Tectorum, the Houseleek, 
 and other species, as also species of Echeveria, Crassula, etc., are, fre- 
 quently cultivated. 
 
 M.B. O O
 
 562 
 
 PART IV. CLASSIFICATION. 
 
 SUB-CLASS II. GAMOPETAL^E. 
 
 Flowers usually monoclinous : perianth differentiated into calyx 
 and corolla : calyx usually gamosepalous ; corolla generally gamo- 
 petalous, in some cases suppressed : ovary usually syncarpous. 
 
 SERIES I. HYPOGYKE. 
 
 Ovary superior (except in Vacciniacese; : stamens epipetalous, or 
 free and hypogynous. 
 
 Cohort I. Lamiales. Flower pentamerous, usually dorsiven- 
 tral : the formula is generally -f K (5) [C (5) A 5] G ; corolla 
 usually bilabiate, the two posterior petals being connate and form- 
 ing a frequently helmet-shaped (galeate) projecting upper lip ; the 
 anterior petal, with the two lateral petals, forming the under lip : 
 stamens epipetalous ; 
 the posterior stamen 
 is usually suppressed 
 or is a staminode ; the 
 two lateral stamens 
 
 are generally shorter m \jj* < x \ \ I Ij / /-] 
 
 than the two anterior */* ,\\A\\\ \\ V / ^~7l 
 
 ones, so that they are ^ 
 
 didynamous : the two 
 
 median carpels form a 
 
 usually bilocular 
 
 ovary which some- 
 
 times becomes sub- 
 divided into four lo- 
 
 FIB. 376. A Flower of Lamium, side view : fc calyx ; o 
 upper ; 11 under lip. B Flower of Leonurus opened : o 
 upper ; M divided under lip ; s lateral lobes of the 
 Culi : leaves Scattered, corolla; // short, /'/long stamens (mag.). C Gynsu- 
 
 or opposite decussate ceum ; " Wobed ovary : g style taa *' ) - 
 exstipulate : the leafy shoots have no terminal flower. 
 
 Order 1. LABIATE. Stamens four, didynamous (Fig. 376 B) ; 
 rarely, as in Salvia and its allies, only the two anterior stamens 
 stamens are developed : the bicarpellary ovary becomes subdivided 
 by spurious dissepiments into four loculi (Fig. 376 (7), which part, 
 as the seed ripens, into four nutlets (as also in the Boraginacese, 
 see Fig. 383) ; style gynobasic : the ovule in each loculus is solitary 
 and erect : seed without endosperm. Herbs with decussate leaves 
 and quadrangular stem. The flowers are disposed apparently in 
 whorls round the stem, but the inflorescence is in fact made up of
 
 GROUP V. ANGIOSPERALE ; DICOTYLEDONES. 563 
 
 compound cymes or dichasia, termed verticillasters, developed in 
 the axil of each of the two opposite leaves. 
 
 Tribe 1. Ocimoidece. Stamens 4, descending. 
 
 Ocimum basilicum, the Sweet Basil, from India, and Lavandula, the 
 Lavender from Southern Europe, are cultivated as pot-herbs: several 
 species of Coleus are cultivated. 
 
 Tribe 2. Mentlwidece. Stamens 4, equal, ascending, divergent: corolla 
 almost regular, 4- or 5-lobed. 
 
 Many species of Mentha, Mint, are common. Pogostemon Patchouli yields 
 oil of Patchouli. Lycopus has only 2 fertile stamens, the two posterior 
 ones being abortive. 
 
 Tribe 3. Satureinece. Stamens 4, with broad connective, ascending, 
 either almost equal (Thymus, Origanum), or didynamous and remote at 
 base, conniving under the upper lip. 
 
 Origanum vulgare is the Wild Marjoram; the Sweet Marjoram which is 
 cultivated is an exotic species. Thymus Serpyllum is the wild Thyme ; the 
 garden Thyme is T. vulgaris, from Southern Europe. Satureia hortensis 
 (exotic) is the Summer Savory. Various species of Calamintha (stamens 
 not divergent) are common, such as C. arvensis, the Common Basil, and C. 
 Clinopodium, the Wild Basil. 
 
 Tribe 4. Melissinets. Stamens 4, didynamous, with narrow connective, 
 remote at base, conniving under upper lip. 
 
 Melissa offtcinalis, the Balm, and Hyssopus, the Hyssop, are cultivated as 
 pot-herbs. 
 
 Tribe 5. Monardew. Stamens 2, ascending:- one theca of each anther is 
 either wanting or it is widely separated from the other (see Fig. 276 C). 
 
 Salvia verbenacea, the Wild Sage or Clary, is common. Rosmarinus 
 officinalis, the common Rosemary, is exotic. 
 
 Tribe 6. Nepetece. Stamens 4, didynamous, ascending parallel ; the 
 posterior two are the longer. 
 
 Nepeta Cataria, the Catmint, occurs in hedges ; and Nepeta Glechoma, the 
 Ground Ivy, is very common. 
 
 Tribe 7. Stachydece. Stamens 4, didynamous, ascending, parallel ; the 
 anterior two are the longer : upper lip of corolla usually arched (rin- 
 cjent). 
 
 Lamium album, the Dead-Nettie, and pitrpureum, are very common (Fig- 
 376). Various species of Galeopsis (Hemp-Nettle), Stachys (Woundwort 
 or Betony), Marrubium (Horehound), Ballota, Melittis, and Leonurus 
 (Mother-wort) are found in England. 
 
 Tribe 8. Scutellariece. Stamens 4, didynamous, ascending, parallel ; 
 calyx closed when the fruit is ripe. 
 
 In the genus Scutellaria, the anthers of the anterior pair of stamens 
 have but one theca ; S. galericulata, the common Skullcap, and 5. minor, 
 the Lesser Skullcap, are common. In the genus Prunella each filament 
 has a small tooth below the anther : P. vulgaris is common. 
 
 Tribe 9. Ajugoidece. Stamens 4, didynamous, ascending, parallel ; the 
 posterior two are the shorter: upper lip of corolla very short.
 
 564 PART IV. CLASSIFICATION. 
 
 Ajuga reptans, the Creeping Bugle, and Teucrium Scorodonia, the Wood 
 Germander, are common. 
 
 Cohort II. Personales. Flowers pentamerous, usually dorsi- 
 ventral : stamens epipetalous : the posterior stamen is usually 
 suppressed, or appears as a staminode : carpels 2, median : ovules 
 usually indefinite. 
 
 Order 1. SCROPHULARIACE^E. Ovary bilocular, with numerous 
 auatropous ovules borne on axile placentae : seed with endosperm : 
 stamens four, didynamous, often with a rudimentary fifth posterior 
 stamen (Fig. 378 B, st) ; sometimes only the two lateral stamens are 
 present ; rarely all five are fertile : corolla with imbricate (cochlear) 
 aestivation : general floral formula as in Lamiales. 
 
 Sub-order 1. PSEUDOSOLANE^E. Flower nearly regular : the two pos- 
 terior petals are external, the anterior internal ; stamens usually 5 : 
 leaves scattered. The genus Celsia has only four stamens, whilst in the 
 genus Verbascum (Mullein) there are five. 
 
 Fie. 377. Flcral diagrams, A of most Scrophulariacese ; B of Veronica ; C of the Lenti- 
 bulariacese : o npper, under lip. 
 
 Sub-order 2. AHTIRRHOIDE-E. Flowers irregular : corolla as in the pre- 
 ceding, the two posterior petals forming the upper lip of the corolla : 
 stamens 4 : leaves opposite. Antirrhinum, the Snapdragon, has a pro- 
 jection on the lower lip of the personate corolla, termed the palate ; the 
 corolla is gibbous at the base; stamens 4 (Fig. 378 A, B~) : A. majus, the 
 great Snapdragon, is a well-known garden plant. Linaria has a spurred 
 personate corolla ; stamens 4 : L. vulgaris, the yellow Toad-Flax, is com- 
 mon in fields. In Gratiola the two anterior stamens are represented by 
 staminodes. Paulownia imperialis is an ornamental flowering tree from 
 Japan. Limosella (L. aquatica, the Mudwort) has a sub-campanulate 
 corolla with a short tube. Mimulus (M. luteus, the Yellow Monkey-flower) 
 has a sub-campanulate corolla with a two-lipped limb ; the two lobes of the 
 stigma close together on being touched. Maurandia and Rhodochiton are 
 genera of plants climbing by means of sensitive petioles. Many species of 
 Mimulus (Musk), Calceolaria, Chelone, and Pentstemon, are cultivated. 
 
 Sub-order 3. RHINANTHOIDE^E. Flower irregular : the two posterior 
 petals are overlapped by the lateral petals : stamens 4, or 2. Digitalis,
 
 GROUP V. ANGIOSPERJLE ; D1COTYLEDONES. 56fr 
 
 the Foxglove, has an obliquely campanulate (digitaliform) corolla ; sta- 
 mens 4- D, purpurea is common in woods; the yellow D. grandiflora is- 
 cultivated. Scrophularia has a globose corolla; S. nodosa (Figwort) and 
 S. aquatica are common. Veronica, the Speedwell, has only the 2 postero- 
 lateral stamens, and the two lobes of the upper lip of the rotate corolla 
 are united ; the posterior lobe of the calyx is suppressed (Figs. 377 J?, 378 C) : 
 V. Anagallin and V. Beccabunga are common in ditches ; V. arvensis, agrestis, 
 serpyllifolia, Chanuedrys. and others in pastures and fields. Sibthorpia has 
 a sub-rotate 5-8-fid corolla, and four stamens ; S. europcea is the Cornish 
 Moneywort. 
 
 Pedicularis, the Lousewort, has a 5-toothed calyx, and the upper lip of 
 the corolla is galeate : Euphrasia, the Eyebright, has a 4-toothed calyx, 
 the upper lip of the corolla has two spreading or reflexed lobes : Bartsia 
 has a 4-toothed calyx, upper lip of the ringent corolla entire or only 
 
 PIG. 378. Flowers of Scrophulariaceas. A Antirrhinum : k calyx ; r tube of the personate 
 corolla, gibbous at the base (h) : o upper, u under lip of the corolla ; g prominence (palate) 
 of the under lip. B Upper lip of the Bame, seen from within: the two longer anterior 
 stamens ; s' the short lateral ones ; *t rudimentary posterior one. C Flower of Veronica ; 
 k calyx ; u u u the three lobes of the lower lip of the rotate corolla : o the upper lip ; c the 
 two stamens ; n stigma. 
 
 notched : Rhinanthus, the Battle, has a four-toothed inflated calyx : 
 Melampyrum, the Cow-wheat, has a 4-toothed tubular calyx, and the cap- 
 sule is few-seeded : all these plants possess chlorophyll, but they are more 
 or less parasitic upon the roots of other plants. 
 
 Order 2. PLANTAGIXACE.E. Flowers regular, isobilateral, and 
 apparently tetramerous, but the true interpretation of them is de- 
 duced from those of Veronica (Figs. 377 B and 379) : the posterior 
 sepal is suppressed, as also the posterior stamen ; the two posterior 
 petals cohere to form an upper lip which is quite similar to one of 
 the lobes of the three-lobed lower lip (Fig. 379) : stamens four, the 
 two anterior not being suppressed: ovary dimerous, bilocular, or 
 sometimes unilocular or spuriously 4-locular : ovules solitary and
 
 566 
 
 PART IV. CLASSIFICATION. 
 
 basal, or numerous : fruit a capsule with transverse dehiscence, or 
 a nutlet : seed with endosperm. 
 
 Plantacjo lanceolata (Ribwort), major, media, the Plantains, are weeds 
 universally distributed. P. Coronopus, the Buck's-horn Plantain, and P. 
 maritima, grow in dry places and on sandy sea-shores. The leaves form a 
 rosette just above the root, and the long scapes spring from their axils, 
 bearing simple spikes. In P. Cynops, Psyllium, and others, the main stem 
 is elongated : the testa of the seed is mucilaginous. In Littorella lacustris 
 the flowers are monoscious ; fruit 1-seeded, indehiscent ; stamens hypogyn- 
 ous : it grows on the bottom in shallow waters. 
 
 Order 3. OROBANCHACE^E. Plants which are destitute of chlo- 
 rophyll, with scaly leaves, parasitic on the roots of other plants ; 
 the flower resembles that of the Scrophulariacese, but the ovary is 
 unilocular with 2 or 4 parietal placentae. 
 
 B 
 
 FIG. 379. Flower of Plantago: a axis of 
 the inflorescence (scape) ; d bract ; fc calyx; 
 c corolla; st stamens; n stigma (mag.). In 
 the diagram, o is the upper, and u the 
 under lip. 
 
 FIG. 380. Bladders of Utricularia. 
 A Outside view : s pedicel ; o entrance ; 
 i and b bristly appendages. B Section ; 
 v a valve opening inwards and prevent- 
 ing the exit of the imprisoned animal 
 (mag.). 
 
 The commoner species of Broomrapes, occuring in Britain, are Orobanc/ie 
 major and minor, parasitic on Leguminosae, elatior on the Greater Knap- 
 weed, Hederce on Ivy, ramosa on Hemp ; mostly of a brownish or whitish 
 hue. Lathrcea Squamaria, the Greater Toothwort, is generally parasitic on 
 the roots of the Hazel: it is of a pale rose colour with slightly bluish 
 flowers : the subterranean scaly leaves each form a kind of pitcher. 
 
 Order 4. LENTIBULARIACELE. Only the two antero-lateral 
 stamens are developed (Fig. 377 C) : ovary unilocular : ovule 
 numerous on a free central placenta : seed without endosperm. 
 
 The British species of Utricularia are floating water-plants with 
 finely divided leaves bearing bladder-like appendages (modified leaflets) 
 which serve to catch small aquatic animals (Fig. 380). Pinrjuicula vul- 
 (jaris and alpina (Butter-worts) are small plants growing in damp
 
 GROUP V. ANGIOSPERM^E ; DICOTYLEDOXE.S. 5G7 
 
 places, with rosettes of radical leaves which catch insects by their viscid 
 secretion. 
 
 Cohort III. Polemoniales. Flowers generally regular, but 
 with oligomery in the gynaeceum ; pentamerous : stamens epipetal- 
 ous : ovary of two, rarely five, carpels : leaves usually scattered 
 and exstipulate : the inflorescence is often cymose, with a terminal 
 flower: formula K (5) [C (5) A5] G to (-). 
 
 Order 1. CONVOLVULACE^E. Usually two median carpels 
 forming a bilocular ovary, with 1-2 anatropous ovules in each locu- 
 lus : the corolla has usually a contorted aestivation, twisted to the 
 right: fruit a septifragal capsule, or a berry: seed with endo- 
 sperm. Commonly plants climbing by twining stems : with milky 
 latex. 
 
 Convulvus arvensis, the lesser Bindweed (Fig. 274 A\ 
 and Calyxtegia Sepium, the larger Bindweed, the 
 former with two small bracteoles, the latter with 
 two large bracteoles which invest the calyx, and 
 C. Soldandla. the Sea-Bindweed, are common wild 
 plants. Batatas edulis is cultivated in Tropical 
 America for its edible tuberous rhizome, the Sweet 
 Potato. 
 
 The genus Cuscuta consists of parasites destitute 
 of chorophyll, with filiform twining stems, which 
 attach themselves to other plants by means of 
 haustoria (see p. 48), and derive their nourishment 
 from them : the small flowers are arranged in p- IO- 3^ _ Stem of 
 fascicles (Fig. 381 b) : the corolla has imbricate Cuscuta europcea(g), with 
 aestivation: fruit a capsule with transverse dehis- inflorescence (b) twining 
 
 round a stem of Hop (a), 
 cence. 
 
 C'ascuta europaxi, the greater Dodder, which occurs commonly on Nettles 
 and Hops, is widely distributed : C. Epilinum is the Flax Dodder, and C. 
 Epilhymum, the lesser Dodder, occurs on various low-growing plants; C. 
 Trifolii attacks Clover, which it often destroys. 
 
 Order 2. POLEMONIACE/E. Ovary usualy trimerous and trilo- 
 cular, with one erect or several oblique ovules in each loculus ; 
 capsule loculicidal : seed with endosperm. Mostly herbs. 
 
 Polemonium cceruleum is Jacob's Ladder ; various species of Phlox and 
 Gilia are common garden plants. Cobaea is a genus of plants climbing by 
 means of leaf-tendrils. 
 
 Order 3. SOLANACEJE. Ovary usually consists of two obliquely 
 placed carpels, bilocular, with numerous ovules in each loculus : 
 the axile placentae sometimes project so far into the loculi that
 
 568 
 
 PART IV. CLASSIFICATION. 
 
 the ovary appears to be quadrilocular, as in Datura : ovules 
 campylotropous ; fruit a capsule with various dehiscence, or a 
 berry : seed with endosperm. Herbs, occasionally woody plants, 
 sometimes climbers by irritable petioles (e.g. species of Solanum) ; 
 without milky latex. Inflorescence cymose, but complicated by 
 the displacement of the bracts : Fig. 382 B, for instance, is a dia- 
 gram of the inflorescence of Atropa ; the main axis which termin- 
 ates with the flower 1, bears a bracteole la and a lateral shoot 
 terminating in the flower 2 ; this springs from the axil of a bract 
 I/?, which, however, is not inserted at the base of its axillary 
 
 shoot (the point of 
 the arrow indicates 
 its proper position), 
 but is displaced up- 
 wards until it is 
 close under the 
 bracteole 2a ; this 
 displacement is re- 
 peated throughout 
 the whole system of 
 the cyme, so that in 
 Atropa there are 
 always two leaves 
 below each flower, a 
 larger one (Fig. 382 
 A la, 2a, and so on) 
 which is the brac- 
 teole of the flower, 
 and a smaller one 
 (Fig. 382 A, Oft, 1ft, 
 2ft, etc.), which is 
 the bract from the 
 axil of which the 
 flowering-shoot springs. In other of the Solaneae similar arrange- 
 ments are found. Most plants of this order are poisonous. 
 
 Tribi 1. Solanece. Fruit a berry : embryo curved. In the genus Sol- 
 anum the anthers are syngenesious : S. Dulcamara, the Bittersweet or 
 Woody Night-shade, has a blue flower, and S. nigrum has a white flower ; 
 both are common : S. tuberosum is the Potato-plant. Physalis Alkekengi, 
 the Winter Cherry, has an inflated red calyx which encloses the berry. 
 Lycopersicum esculentum is the Tomato. The fruits of Capsicum longum and 
 
 B 
 
 Fie. 382, A Upper portion of a flowering stem of Atropa 
 Belladonna. B Diasrram of the same stem : 1 2 3 the 
 flowers; a and /3 the bracteoles and bracts. From the 
 axils of ft spring the new floral axes, along which the bract 
 p is displaced.
 
 GROUP V. ANGIOSPERHLE ; DICOTYLEDONES. 
 
 569 
 
 annuum are known as Chili Peppers. Atropa Belladonna (Fig. 382) is the 
 Deadly Nightshade 5 the anthers are not syngenesious, and the corolla is 
 campanulate ; the berries are black and very poisonous. Lycium barbarum 
 is a shrub belonging to Southern Europe which has become wild in places 
 in the North. Hyoscyamus niger is the common Henbane: the capsule 
 dehisces transversely (pyxidium). 
 
 Tribe 2. Daturas. Capsule almost quadrilocular in consequence of the 
 outgrowth of the placenta, 4-valved : embryo curved. Datura Stramonium 
 is the Thorn-apple. 
 
 Tribe 3. Cestrece. Embryo straight : all five stamens fertile. Nicotiana 
 Tabacum is the Tobacco plant (Fig. 274.B): Petunia is commonly cultivated. 
 
 Order 4. BORAGINACE^E. Ovary consisting of two median car- 
 pels, spuriously quadrilocular in consequence of a dissepiment along 
 the dorsal suture of each carpel (Fig. 383 C, r) : the single style 
 usually arises from the incurved apices of the carpels (gynobasic), 
 
 FIG. 383. A Flower of Anchnsa (slightly mag.) : 
 
 fc calyx; c corolla; b the scaly appendages. B Fie. 384 Corolli of Ery- 
 
 Fruit of Myosotis (mag.); t the receptacle ; m m thrcea Centaurinmspreadout 
 
 the four achania ; g the gynobasic style. C Dia- r tube ; limb ; a stamens, 
 gram of the quadrilocular ovary in trans, section : 
 r the dorsal sutures ; p p the placenta ; s the ovules. 
 
 and is surrounded at its base by the four loculi (Fig. 383 B) : each 
 loculus contains a single suspended anatropous ovule : when the 
 fruit is ripe the loculi separate completely, and appear to be four 
 nutlets : seed without endosperm : the corolla usually has five 
 scaly ligular appendages at the junction of the limb with the tube 
 (Fig. 383 A 6) : inflorescence scorpioid (see p. 441), often very com- 
 plicated. Herbs or shrubs generally covered with harsh hairs and 
 only rarely glabrous, e.g. Myosotis palustris. 
 
 Myosotis is the Scorpion-grass ; M. palustris, the Forget-me-not, occurs in 
 damp places, M. sylcatica in woods, and M. arcensis and others in fields. 
 Lithospermum arvense (Gromwell), L. offirinede, Echium vulgar e (Viper's Bu- 
 gloss), with an irregular flower, Symphytum officinale the Comfrey, Lycop&is
 
 570 PART IV. CLASSIFICATION. 
 
 arvensis (Common Bugloss), Cynoglossum officinale (Hound's-tongue), and 
 Borago ojficinalis, the Borage, are common. Anchusa officinalis, the Alkanet ; 
 Mertensia maritima, the smooth Gromwell or Sea-Bugloss ; and Pulmonaria 
 anyustifolia, the Lung- wort, are rare in Britain. 
 
 Cohort IV. Gentianales. Flowers regular, but with oli- 
 gomery in the gynseceum : perianth and androecium usually 4- or 
 5-merous : corolla with frequently contorted aestivation (to the 
 right) : stamens inserted on the tube of the corolla : carpels two : 
 leaves commonly decussate and exstipulate : formula J5T(5) [C(5) 
 Ao] G. 
 
 Order 1. GTENTIANACE.E. Carpels are perfectly connate, forming 
 a uni- or incompletely bi-locular ovary : ovules parietal, numerous, 
 anatropous : seed with endosperm. Usually herbs without milky 
 latex : leaves almost entire. 
 
 Sub-order 1. GENTIANEJE. Leaves decussate : corolla with contorted 
 aestivation. 
 
 Gentiana the Gentian, has a bilobed stigma ; it occurs in mountainous 
 districts. Erythrsea has a capitate stigma ; E. Centaurium, the common 
 Centaury, is common in pastures (Fig. 384). Species of Cicendia and Chlora 
 also occur in Britain. 
 
 Sub-order 2. MENYANTHE^E. Leaves spiral: corolla with valvate sesti- 
 vation. 
 
 Menyanthes trtfoliata, Buck-bean or Bog-bean, with ternate leaves, is 
 common in marshes : Vittarsia nymphceoides (or Limnanthemum peltatum) is 
 found in ponds and rivers. 
 
 Order 2. OLEACE.E. Calyx and corolla usually 4-merous, some- 
 times wanting ; stamens and carpels two, alternate : ovary bilo- 
 cular : ovules 2 in each loculus : fruit a capsule, a berry, a drupe, 
 
 FIG. 385. A Flower of Fraxinus Omus (enlarged): 7: calyx; c corolla; st stamens; 
 /ovary; n stigma. B 9-flower of Fraxinus excelsior, the common Ash; an anthers; 
 / ovary ; n stigma (enlarged). Floral diagram of the Oleacese.
 
 GROUP V. ANGIOSPERM^E ; DICOTYLEDONES. 
 
 571 
 
 or a samara : seeds 1-4, usually with endosperm : stem woody : 
 leaves always decussate. 
 
 Ligustrum has a baccate fruit ; L. vulgare, the Privet, is a common 
 shrub. Olea has a drupaceous fruit ; 0. europcea is the Olive-tree of the 
 East and of Southern Europe. The genus Fraxinus has a winged fruit ; 
 in F. excelsior, the common Ash, the perianth is suppressed and the 
 flowers are polygamous ; in F. Ornus, the Manna-Ash of Southern Europe, 
 the perianth is complete, and the corolla is deeply cleft (Fig. 385 A). The 
 genus Syringa has a tubular corolla with a 4-lobed limb ; & vulgaris 
 is the Lilac. 
 
 The flowers of Jaaminum grandiflorum and other species belonging to 
 Southern Europe, contain a very fragrant ethereal oil. 
 
 Cohort V. Primulales. Flowers actinomorphic, usually pen- 
 tamerous : formula K(o) [C(5) -40 + 5] 67-' : stamens inserted on 
 the tube of the corolla and opposite to its lobes : gynseceum con- 
 
 \\ 
 
 FIG. S86. Heterostyled flowers of Primula elatior in longitudinal section. A Short- 
 styled, B long-styled form; fc calyx; c corolla; a anthers ;/ ovary ; g style; n stigma. 
 Floral diagram of Primula. 
 
 sisting of five connate carpels which are opposite to the sepals ; 
 ovary unilocular, with a free, central placenta or a single central 
 ovule : seed with endosperm. 
 
 Order 1. PRIMULACE^E. Style single : ovules indefinite, on a 
 free central placenta (Fig. 284 G) : the corolla is gamopetalous, 
 tubular below, expanding above into a 5-lobed limb ; it is sup- 
 pressed in the genus Glaux: the stamens (Fig. 386 a) are 
 generally adnate to the tube of the corolla and are opposite to its 
 lobes ; this position of the stamens is explained by assuming the 
 suppression of an outer antisepalous whorl of stamens which is re- 
 presented in some genera (e.g. Soldanella) by petaloid staminodes : 
 fruit a capsule. Herbaceous plants with conspicuous flowers.
 
 572 
 
 PART IV. CLASSIFICATION. 
 
 The genus Primula has a 5-valved dehiscent capsule, and a 5-cleft calyx, 
 Primula vulgaris is the Primrose ; Primula elatior and P. veris are the Oxlip 
 and the Cowslip or Paigle ; they are remarkahle in that they are hetero- 
 styled (see p. 411). The capsule of Anagallis arvensis, the Pimpernel, de- 
 hisces transversely (pyxidium). Cyclamen europceum, the Sow-bread, has 
 an underground tuber ; the lobes of the corolla are reflexed. Lysimachia, 
 the Yellow Loosestrife, has a deeply 5-cleft calyx. Trientalis, the Chick- 
 weed Winter-green, has usually a 7-merous flower. The other British 
 genera are Hottonia (H. palustris, the Water- violet), Samolus (S. Valerandi, 
 the Brookweed), and Glaux (G. maritima, the Sea Milk-wort). 
 
 Order 2. PLUMBAGINACE^E. Styles five : there is a single basal 
 ovule in the cavity of the ovary, pendulous on a long funicle : 
 flowers often small, in dense inflorescences with numerous bracts : 
 no trace of an external antisepalous whorl of stamens. 
 
 In the genus Armeria the flowers are in capitula of scorpioid cymes, 
 which are surrounded by an involucre formed of the lower scarious bracts 
 with downward prolongations embracing the peduncle ; A. maritima, the 
 Thrift, occurs on sandy soils. Statice Limonium, the Sea-Lavender, with 
 racemose cymes, occurs on sandy sea-shores. Plumbago occurs in South- 
 ern Europe and in the East Indies. 
 
 FIG. 387. A Flower of Erica: pedicel; fc calyx; c corolla; a anthers. B Fruit of 
 Pyrola rotundifolia : s pedicel ; fc calyx ; / fruit, the loculi of which alternate with the sepals ; 
 g style ; n stigma. C Flower of Foecinium afyrtiUus : /ovary (inferior); fe calyx ; c corolla. 
 Floral diagram of Erica : the stamens opposite to the petals are faintly shaded. 
 
 Cohort VI. Ericales. Flowers 4-5-merous, actinomorphic : 
 stamens usually in two whorls and then obdiplostemonous, usually 
 hypogynous: carpels opposite to the petals: formula K(ri), C(n), 
 I An + n, 6r(n), where n = 4 or 5: ovary superior or inferior, 
 multilocular, with large recurved axile placentse : seed with en- 
 dosperm : anthers sometimes appendiculate (Fig. 277 }. 
 
 Order 1. ERICACEAE. Anthers generally opening by two pores 
 at the top (Fig. 387 A\ often furnished with appendages : pollen 
 in tetrads : fruit a capsule, or succulent : a well-developed disc.
 
 GROUP V. ANGIOSPERALS: ; DICOTYLEDONES. 573 
 
 Sub-order 1. RHODODENDROIDE^:. Fruit a septicidal capsule, corolla fuga- 
 cious : anthers without appendages. 
 
 Rhododendron ferrugineum and Mrsutum, the Alpine Roses, are wild on 
 the continent : other species of Rhododendron (incl. Azalea), from the 
 mountains of Asia and North America, as also species of Kill m ia from 
 North America, are cultivated. Daboecia polifolia, the Irish Menziesia or 
 St. Dabeoc's Heath, Phyllodoce taxifolia, the Scottish Menziesia, and 
 Loiseleuria procumbens, the trailing Azalea, represent the sub-order in the 
 British Flora. 
 
 Sub-order 2. ARBUTOIDEJE. Fruit a berry, or a drupe, or a loculicidal 
 capsule : corolla fugacious : anthers usually appendiculate. 
 
 Andromeda Polifolia, the marsh Andromeda or Wild Rosemary, occurs 
 in peat-bogs, and Arctostapliylos Uva Ursi and alpina, the red and the black 
 Bearberry, on the mountains of Scotland. Arbutus Unedo is the Straw- 
 berry-tree of Southern Europe, and Gaultheria is the Aromatic Winter- 
 green. 
 
 Sub-order 3. ERICOIDE.E. Fruit usually a loculicidal capsule : corolla 
 persistent : anthers usually appendiculate. 
 
 Calluna Erica, the Ling or Heather, with a septicidal capsule and a 
 deeply 4-partite coloured calyx, is common on moors : the principal British 
 species of Erica, are E. mediterranea (or carnea), the Irish Heath; E. 
 Tetralix, the cross-leaved Heath ; E. cinerea, the grey or fine-leaved Heath ; 
 and E. vagans, the Cornish Heath. Very many species belong to the 
 Mediterranean region, and to the Cape. 
 
 Order 2. PYROLACRffi. Sepals more or less distinct : petals 
 commonly connate at the base only : anthers without appendages, 
 dehiscing generally transversely or by pores : fruit a loculicidal 
 capsule (Fig. 387 B} : seeds minute, with an extremely small 
 embryo consisting of only a few cells, and a relatively massive 
 integument. Saprophytes containing chlorophyll. 
 
 Pyrola rotundifolia, secunda, minor, and uniflora, the Winter-greens, are 
 found in woods. 
 
 The MONOTROPE^E are saprophytes devoid of chlorophyll, with scale-like 
 leaves. Monotropa Hypopitys (Hypopitys multiflora), the Bird's nest, is 
 not very common in England. 
 
 Order 3. VACCINIACE^E. Ovary inferior (Fig. 387 C] : anthers 
 with appendages (Fig. 277 B\ usually opening by two pores : fruit 
 a berry. 
 
 Vaccinium Vitis-ldcea is the red Whortleberry or Cowberry ; it usually 
 blossoms and bears fruit twice in the year : V. Myrtillus is the Bilberry, 
 Blaeberry, or Whortleberry, with deciduous leaves : V. Oxycoccos (Oxycoccos 
 pal-ustris, or Schollera Oxycoccos) is the Cranberry : and V. uliginosum, the 
 gieat Bilberry or Bog-Whortleberry. They are all low shrubs occurring 
 on moors. .
 
 574 
 
 PAET IV. CLASSIFICATION. 
 
 SEEIES II. EPIGYN^I. 
 Ovary inferior. 
 
 Cohort I. Campanales. Flowers actinomorphic or zygo- 
 morphic, pentamerous ; formula K($) (7(5) .4(5) G& to ^, : sepals 
 leafy and narrow : stamens usually free from the corolla, but often 
 connate : ovary multilocular, of two to five carpels, inferior. 
 
 Order I. CAMPANULACE^E. Flowers regular (Figs. 263, 389) : 
 stamens five, often connate at the base ; ovary usually trilocular, 
 with numerous ovules ; placentation axile : fruit a capsule : seed 
 with endosperm. Mostly herbs with milky latex. 
 
 The gynaeceum is often oligomerous, and then usually trimerons (e.g. 
 most species of Campanula, Fig. 389, and Phyteuma), sometimes bilocular 
 (Jasione, species of Phyteuma): when isomerous, the carpels are either 
 antisepalous and therefore opposite to the stamens (e.g. a few species of 
 Campanula, Fig. 263), or antipetalous and therefore alternate with the 
 stamens (e.g. Musschia, Platycodon). 
 
 FIG. 339. Andrcecinm and gynseeeum cf 
 Campanula : / inferior ovary ; c insertion 
 of the corolla ; o anthers ; b expanded base 
 of the stamens ; n stigmata (mag.). 
 
 Fis. 399. 4 Floral diagram of a spe- 
 cies of Campanula with a trimerous 
 ovary (e.g. C. persicifolia) -. a gynseceum 
 of Lobelia. 
 
 Campanula rotundifolia, the Hare-bell, glomerata, and other species are 
 common in fields, on heaths, etc., etc. : C. Medium is the Canterbury-bell 
 cultivated in gardens. Phyteuma orbiculare and spicatum, the Hampions, 
 are indigenous in parts of England ; the flowers are in capitula, and the 
 calyx is deeply 5-cleft with spreading teeth : nearly allied is the genus 
 Jasione ; J. montana, the Sheep's-bit, is common in England. Specularia 
 has a rotate corolla ; S. Speculum, Venus's Looking-glass, is cultivated. 
 
 Cohort II. Rubiales. Flowers generally regular, actinomor- 
 phic or zygomorphic : calyx generally present : stamens epipetalous : 
 gynseceum 2-5-merous : ovary uni- or multi-locular ovules 2 x ; 
 leaves generally opposite.
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDON ES. 
 
 Order 1. RUBIACILE. Flowers regular, 4- or 5-merous : calyx 
 leafy or suppressed : corolla with valvate aestivation : ovary 1- or 
 2-locular, consist- 
 ing of 2 carpels, 1- 
 or many - seeded : 
 seed usually con- 
 taining endosperm : 
 leaves decussate, 
 stipulate : stipules 
 (see p. 30) often 
 similar to the true 
 leaves (Fig. 390 A, 
 n n) : the true 
 leaves are distin- 
 guished by the 
 branches which 
 arise in their axils 
 (Fig. 390 4 //,**). 
 
 FIG. 390. A Portion of a stem of Bubia Ttnctorum : ff the 
 decussate leaves with the yonng shoots (s ) in their axils ; 
 n n the free stipules resembling the leaves (nat size). B 
 Flower (mag.) : /ovary ; k calyx (rudimentary) ; c corolla; a 
 anthers ; n stigma. 
 
 Sub-order 1. STEL- 
 LATE. Stipules large 
 and leafy: loculi 1- 
 seeded. 
 
 Galium, Bedstraw, 
 has a rotate 4-lobed 
 corolla and an in- 
 conspicuous calyx, 
 usually tetramerous : 6. verum, Mollugo, Aparine, and others are com- 
 mon in hedges and pastures. Asperula has an infundibuliform corolla, 
 but in other respects the flower resembles that of Galium ; A. odorata, the 
 Wood-ruff, is common : A. cynanchica is the Squinancy-wort. Rubia Tinc- 
 torum, the Dyer's Madder, has a pentamerous flower, a rotate 5-lobed 
 corolla, and a baccate fruit ; it is used in dyeing and largely cultivated ; 
 it is indigenous in Southern Europe and the East ; it is closely allied to 
 the British species R. peregrina, the Wild Madder. Sherardia has a 
 tubular 4-lobed corolla, and a conspicuous calyx with a 4-6 toothed limb 
 which persists on the top of the fruit ; S. arvensis, the Field Madder, is 
 found in cultivated and waste places. 
 
 Sub-order 2. COFFEEJE. Stipules scaly : loculi 1-seeded. 
 
 Coffea arabica, the Coffee-tree of Africa, is grown in the tropics ; the fruit, 
 a berry, contains one or two seeds ; the so-called coffee-bean is the seed, 
 which consists of hard endosperm and contains a small embryo. Cephaelis 
 yields Ipecachuana. 
 
 Sub-order 3. CIXCHOXE.E. Stipules scaly ; loculi many-seeded. 
 
 Various species of Cinchona, indigenous to the eastern slopes of the
 
 576 
 
 PART IV. CLASSIFICATION. 
 
 Andes, but cultivated in Java and the East Indies, yield the cinchona bark 
 from which Quinine is prepared. Bouvardias are ornamental greenhouse 
 plants from Central America. 
 
 Order 2. CAPRIFOLIACE.E. Flowers usually pentamerous, actino- 
 morphic or zygomorphic : corolla usually with imbricate aestiva- 
 tion ; gynseceum 2-5-merous : ovules suspended : fruit baccate ; 
 seed with endosperm : leaves opposite, usually exstipulate. Mostly 
 trees or shrubs. 
 
 Tribe 1. Sambucece. Flower regular, sometimes completely actmomor- 
 phic, corolla rotate (Fig. 274 C) : one ovule in each loculus. 
 
 Sambucus has a 5-partite corolla, and 3-5 seeds in the berry ; S. nigra is 
 the Elder ; S. Ebulus is the Dwarf Elder or Banewort. Viburnum has a 
 5-partite corolla, and one seed in the trimerous berry, two carpels being 
 
 FIG. 391. Floral diagram of 
 Caprifoliaceee, A Leycesteria : 
 a gynseceum of Lonicera ; b of 
 Symphoricarpus. 
 
 FIG. 392. Flower of Lonicera. Caprifolium : /ovary ; fc calyx; r corolla-tube ; c c the five 
 lobes of the limb ; st stamens ; g style ; n stigma. 
 
 abortive; V. Lantana and V. Opulus, the Guelder Hose, are common; a 
 form of the last species is cultivated in which all the flowers (and not 
 merely those at the circumference of the corymb as in the original species) 
 have a large corolla, and are barren ; V. Tinus is the Laurustinus. Adoxa 
 nioschatellina-j the Moschatel, is a small plant occurring in damp woods: its 
 flowers are 4- or 5-merous ; it appears that there is no calyx, that which is 
 regarded as the calyx being probably an involucre of bracteoles and bract ; 
 the stamens are each divided into two, so that there are 8-10 bilocular 
 anthers. 
 
 Tribe 2. Lonicereae. Flowers more or less irregular, zygomorphic ; 
 corolla tubular : loculi containing several ovules. 
 
 Lonicera, the Honeysuckle, has a somewhat bilabiate corolla (Fig. 392), 
 and a 2-3-locular ovary ; L, Caprifolium and Periclynienum, with a climb- 
 ing stem, are well-known garden shrubs ; in many species the fruit of two
 
 GROUP V. AXGIOSPERM.E ; DICOTYLEDONES. 
 
 577 
 
 st 
 
 adjacent flowers grow together to form a single berry (e.g. L. alpiyena}. 
 Sf/mphoricarptts racemosus, the Snowberry, has 4-5-locular ovary with 
 white berries ; it is a common ornamental shrub. Diervilla (or Weigelia) 
 has a bilocular capsule ; D. florida and rosea are ornamental shrubs. 
 Linttcea borealis is a small creeping plant in Scotland ; it has 4 unequal 
 stamens, the posterior being suppressed, and a trilocular ovary. 
 
 Cohort III. Asterales. Flower either irregular or regular, 
 pentamerous, with oligomery in the gynaeceum : calyx inconspicu- 
 ous, often, wanting : stamens epipetalous, alternating with the seg- 
 ments of the corolla : ovary 
 unilocular, ovule solitary. 
 
 Order 1. VALERIAXACE.E. 
 Flower irregular : calyx rudi- 
 mentary, sometimes eventu- 
 ally assuming the form of a 
 hairy crown of ten rays, 
 called a pappus, which is 
 not developed until after 
 flowering (Fig. 393 , p) ; 
 during flowering it remains 
 short and infolded (Fig. 393 
 A, k) : stamens 1-4, usually 
 three : carpels three, of which, 
 however, usually only one 
 developes, so that the fruit 
 is unilocular (Diagram A, 
 Fig. 393) ; ovule single, 
 suspended: seed without en- 
 dosperm : leaves decussate, 
 exstipulate. 
 
 Of the genera occurring in 
 Britain, Valeriana and Centran- 
 thus have a pappus, whilst Vale- 
 rianella has not. Valeriana 
 officinal is, and dtoiccr, are com- 
 mon in damp places. Valerianella has a toothed calyx-limb ; many 
 species are common in fields: Vaterianella olitorict, Corn-salad, or Laml>'>- 
 lettuce, is eaten. Centranthns ruber is an ornamental plant ; only one 
 stamen and one carpel are developed (Fig. 893, Diagram ); at the base 
 of the tube of the corolla is a spur which is indicated in Valeriana by a 
 protuberance. 
 
 FIG. 393. .4 Flower, B Fruit of Valerian : 
 ovary ; t calyx ; c corolla ; a spur ; st stamens 
 g style ; p pappus. Floral diagram*, A of 
 Valerian; abortive carpels x x : B of Cen- 
 trantbus. 
 
 Order .2. 
 
 M.B. 
 
 DIPSACE.E. 
 
 Flower more or less dorsiventral, sur- 
 p P
 
 578 
 
 PART IV. CLASSIFICATION. 
 
 rounded by an epicalyx (Fig. 394 /c') formed of connate bracteoles : 
 calyx often plumose or bristly (Fig. 394 fc): corolla usually bila- 
 biate : stamens only four, the posterior one being suppressed : 
 ovary apparently dimerous, one carpel being more or less com- 
 pletely suppressed, unilocular, with one suspended ovule: seed 
 with endosperm: leaves decussate, exstipulate: flowers in a dense 
 capitulum surrounded by an involucre of bracts: the outer florets 
 are usually ligulate : the Receptacle may or may not bear scaly 
 bracts (palese) : fruit invested by the epicalyx which is cleft longi- 
 tudinally. 
 
 Fto. 394. Flower of 
 Scabiosa (mag.) : / ovary; 
 k' epiculyx (long sect.) ; 
 fc calyx ; c corolla ; t sta- 
 men * ; n stigma. 
 
 FIG. 395. Floral dia- 
 gram of Composite 
 (tubular floret). 
 
 Fis. 396. Flower of Arnica (mag.). A Tubular floret from the centre (disc) (longitudinal 
 sect.). B Ligulate marginal floret (ray): /ovary; p pappus; c corolla; a anthers; st 
 stamen ; n stigma ; g style ; ovule. 
 
 Dipsacus, the Teazle, has a calyx without bristles; the capitula of 
 Dipsacus Fullonum are used in finishing woollen cloth, for the sake of the 
 strong hooked spines of the paleae : D. si/lvestris is common on waste ground. 
 In the genus Scabiosa, the paleae, which are usually present, are not 
 spinous : in the sub-genus Asterocephalus, the epicalyx (or involucel) is 
 8-furrowed, and its projecting limb is dry and scarious ; S. Columbaria, 
 with a 5-lobed corolla, is common in dry pastures: in the sub-genus 
 Succisa, the limb of the 8-furrowed epicalyx is herbaceous ; S. succisa, with 
 a 4-lobed corolla, occurs in damp meadows: in the sub-genus Knautia, 
 there are no paleae but the receptacle is hairy, and the epicalyx is 4- 
 furrowed ; S. arvenais is common in fields.
 
 GROUP V. ANGIOSPERMJS ; DICOTYLEDOXES. 579 
 
 Order 3. COMPOSITE. The flowers are always collected into 
 many-flowered capitula (sometimes only 1 -flowered) ; different 
 kinds of flowers ( $ , ? , or sterile) generally present in the same 
 head: ovary dimerous, unilocular, with a basal, erect, anatropous 
 ovule : the calyx is rarely present in the form of small leaves or 
 scales (Fig. 397 D, p) ; more commonly it is a crown of simple or 
 branched hairs (pappus; Figs. 396 p', 397.4, E, p}, and is not 
 developed till after the flowering is over ; sometimes the calyx 
 is wholly wanting : corolla tubular, either regular, and 5-toothed 
 (Figs. 396 A, c ; 397 C, w, c), or irregular and expanded at the 
 upper end into a lateral limb with 3 or 5 teeth (Figs. 396 B ; 397 
 B, ra ; 397 .4, c), when it is said to be ligulate : the stamens are 
 short, inserted upon the corolla (Fig. 396 A, st) ; the anthers are 
 elongated and syngenesious, forming a tube through which the 
 style passes (Figs. 396 A, a) : this is bifid at its upper end (Fig. 
 396 A, n ; 397 A and (7, n) : on each of these branches the stig- 
 matic papillae are arranged in two rows : in the wholly ? flowers 
 the styles are usually shorter (Fig. 396 B, g~) : fruit a cypsela (p. 
 473), crowned by the pappus (Fig. 397 A, E, D, p) when it is 
 present (Fig. 397 F, /) : sometimes the fruit has its upper end 
 prolonged into a beak, and its surface is covered with ridges or 
 spines (Fig. 397 E) : seed without endosperm. 
 
 Usually herbs with scattered (more rarely decussate), exstipulate 
 leaves, often with milky latex. The capitula are always surrounded 
 by a number of bracts forming an involucre (Fig. 397 B, C, i). 
 The scaly bracteoles of the individual florets (paleae) may be present 
 or wanting (Fig. 397 C, d). 
 
 The Composite are classified according to the form of the 
 flowers and to the distribution of the different kinds of flowers in 
 the inflorescence. 
 
 Sub-order I. TDBCLIFLOBJE. The capitula either consists entirely of 5 
 tubular florets (by tubular flowers are meant those with a regular 5- 
 toothed corolla); or the central florets (florets of the disc) are tubular and 
 ? (Fig. 396 A), whereas the florets of the ray are ligulate and ? or sterile 
 and form one or two rows (Figs. 396 B ; 397 B and C, ra). 
 
 Tribe 1. Eupatoriece. Leaves mostly opposite : flowers all tubular, ? 
 the branches of style narrow ; papillae extending to the middle. 
 
 Eupatorium cannabinum, the Hemp Agrimony, is common in damp 
 places. 
 
 Tribe 2. Asteroldece. Leaves alternate : ray-florets ? or sterile, gener- 
 ally ligulate: branches of the style hairy above, papillae extending to 
 where the hairs begin. Many species of Aster, belonging chiefly to North
 
 580 
 
 PART IV. CLASSIFICATION. 
 
 America, are cultivated as ornamental plants, as also Callisteplius hortensis, 
 commonly known as the China Aster. Erigeron acre, alpinum, and cana- 
 dense occur in England ; the last is an imported weed. Bellis perennis, the 
 Daisy, has no pappus. Solidago virgaurea is the Golden Rod. 
 
 Tribe 3. Senecionidece. Leaves alternate : ray-florets in one row, ligulate 
 $ , rarely absent : branches of the style tufted at the tips. 
 
 Senecio vulyaris, the common Groundsel, has no ray-florets. Arnica mon- 
 tana occurs in Alpine woods. Two species of Doronicum (D. Pardalianches 
 and plantagineuini) have become naturalized in England. Petasitesvulgaris, 
 the Butter-bur, and Tussilago Farfara, the common Coltsfoot, are common 
 in damp fields. 
 
 FIG. 397. Flowers of Compositae : / fruit or ovary ; fc its beak ; p pappus ; c corolla ; s 
 stamens ; o anthers ; n stigmata. A Ligulate flower of Taraxacum, with a 5-toothed corolla- 
 limb, $ . B Capitnlum of Achillea: ra floret of the ray, with ligulate 3-toothed corolla, ? ; 
 in $ florets of the disc, with a 6-toothed tubular corolla ; t involucre. C Longitudinal 
 section more highly magnified ; r receptacle ; t involucre ; d bracteoles (paleae) ; ra floret 
 of the ray ; m florets of the disc ; n' stigmata of the ? flowers. D Fruit of Tanacetum 
 with a scaly pappus : E of Taraxacum, with a hairy pappus ; Ji beak : F of Artemisia with- 
 out a pappus (mag.). 
 
 Tribe 4. Anthemidece. Leaves alternate: ray-florets $ , ligulate or tubu- 
 lar : branches of style tufted at the tips : involucral bracts scarious : 
 pappus 0, or minute. 
 
 Artemisia Absinthium, Wormwood, A. vulyaris and campestris are common : 
 Chrysanthemum Leucantkemum, the Ox-eye Daisy, is common in fields : 
 Matricaria Chamomilla, the Wild Chamomile, has a hollow conical recep-
 
 GROUP V. ANGIOSPERM.E ; DICOTYLEDONES. 581 
 
 tacle destitute of palese : Anthemis nobilis, the Common Chamomile, has a 
 receptacle bearing paleae, as also A. arvensis, the Corn Chamomile: Achillea 
 Millefolium is the Milfoil, or Yarrow : Tanacetum vulgare is the Tansy : 
 Diotis maritima is the sea-side Cotton-weed. 
 
 Tribe 5. Helianthoidece. Leaves opposite : ray-florets or ligulate 
 yellow, $ or sterile : branches of style as in Asteroidese. 
 
 Bidens is common in wet places. Galinsoga is naturalized in England. 
 Helianthus annuus is the Sunflower; oil is extracted from the seeds: the 
 tubers of H. tuberosus, a AVest Indian species, are rich in inulin (p. 83), 
 and serve as a vegetable (Jerusalem Artichoke). Species of Zinnia, Bud- 
 beckia, Dahlia, and Coreopsis are cultivated. 
 
 Tribe 6. Helenioidece. .Resemble the Helianthoidese, but the receptacle 
 is without paleae. Species of Helenium, Tagetes, Gaillardia, are commonly 
 cultivated as garden flowers. 
 
 Tribe 7. Inuloidece. Leaves alternate : ray-florets frequently ligulate, 
 ? , yellow : anthers appendiculate at base. 
 
 In Inula (7. ffelenium, the Elecampane), Pulicaria (P. dyssnterica, the 
 Fleabane), and others, the ray-florets are ligulate ; whereas, in other genera, 
 Gnaphalium (the Cudweed), Filago, Antennaria, the ray-florets are fili- 
 form ; Antennaria is dioecious. 
 
 Tribe 8. Cynarece. Flowers all tubular, the outer ones sometimes $ or 
 sterile: style thickened below the branches: anthers often appendiculate 
 at base : leaves generally armed with spines, alternate. 
 
 Arctium Lappa (A. majus), the Burdock, is common by roadsides ; the 
 leaves of the involucre are hooked and spinous. Carduus nutans and crispus 
 are the common (true) Thistles; Cnicus lanceolatus, palustris, pratensis 
 (Plume-Thistles), are common in damp districts. Carlina vulgaris is the 
 Carline-Thistle ; the inner leaves of the involucre, which are white, fold 
 over the flower-head under the influence of moisture, but in drought spread 
 widely open. Onopordon Acanthium is the Scottish or Cotton Thistle. Cen- 
 taurea Scabiosa and nigra, the Knapweeds, are common everywhere: C. 
 Cyanus is the Corn-flower or Bluebottle, occurring in wheat-fields. Cynara 
 Scolymus is the Globe-Artichoke ; the flower-buds are eaten as a vegetable. 
 Carttiamus tinctorict, the Safflower, is used in dyeing. In Echinops, the 
 Globe-Thistle, numerous one-flowered capitula are collected into one large 
 spherical head. Saussurea and Serratula are the Saw-worts. 
 
 Tribe 9. Calendulece. Kay-florets ? and usually ligulate : disc-florets 
 usually sterile. 
 
 Calendula officinalis, the Pot-Marigold, is a familiar garden plant. 
 
 Sub-order II. LABIATIFLOR.E. The $ disc-florets have a regular or a 
 bilabiate corolla; the ray-florets have usually a bilabiate corolla. 
 
 Tribe 10. Mulisiece. This tribe includes all the Composite with a bila- 
 biate corolla : they come mostly from South America. Mutisia is one of 
 the few climbing genera : it climbs by means of leaf-tendrils. 
 
 Sub-order III. LIGULIFLOR.E. All the florets are $ ; limb of the corolla 
 5-toothed and ligulate (Fig. 397 A). 
 
 Tribe 11. Cichoriece. Mostly herbs, all containing latex in laticiferous 
 vessels (Fig. 80, p. 99).
 
 582 PART IV. CLASSIFICATION. 
 
 Taraxacum officinale, the Dandelion, is the commonest of wild flowers. 
 Lactuca sativn is the Lettuce : L. Scariola, virosa, and others are common in 
 waste places. Scorzonera hispanica is eaten as a vegetable. Trayopoyon 
 porrifolius is the Salsafy; T. pratensis, the Goafs-beard, is common. Cicho- 
 rium Intybus, the Chicory, is found by roadsides; the roasted roots are 
 mixed with Coffee : C. Endivia (Endive) is a vegetable. To this tribe be- 
 long also the British genera Hypochseris (Cat's-ear), Arnoseris (Lamb's 
 Succory), Leontodon (Hawkbit), Hieracium (Hawkweed), Sonchus (Sow- 
 Thistle), Crepis (Hawk's-beard), Lapsana (Nipplewort), Picris.
 
 INDEX. 
 
 PART I. MORPHOLOGY, ANATOMY, AND PHYSIOLOGY. 
 
 Abscission-layer, 156. 
 Absorption, 158, 177. 
 
 of gases, 178. 
 
 of liquids, 178. 
 Accumbent, 536. 
 Achene, 473. 
 Achlamydeous, 457. 
 Acicular leaves, 32, 433. 
 
 crystals, 81. 
 Acids, organic, 187. 
 Acrocarpous, 333. 
 Acropetal development of members. 
 9. 
 
 of tissue, 126. 
 Acrotonous, 504. 
 Actinomorphic symmetry, 453. 
 Acuminate, 37. 
 Acute, 37. 
 
 Acyclic flower, 445 (Fig. 262), 527. 
 Adhesion, 21, 462. 
 Adnate, 460. 
 
 Adventitious members, 9, 136. 
 .Ecidiospore, 300. 
 .Ecidium, 300 (Fig. 178). 
 Aerial roots, 45, 109 (Fig. 87). 
 Estivation, 43. 
 Air-bladders, 269. 
 Air-cavity, 108 (Fig. 88), 115. 
 Air-chamber, 89, 321 (Fig. 199). 
 Al, 546 (Fig. 358), 557 (Fig. 369). 
 Albuminous seed, 414 ^Fig. 245). 
 Alburnum, 143, 165. 
 Aleuron, 80 (Figs. 54, 55), 201. 
 Alkaloids, 186, 201. 
 Alternation of generations, 2, 234. 
 Aluminium, 189. 
 Amentum, 442, 517. 
 Amides, 186, 196, 199, 201. 
 Ammonia, 190. 
 Amoeboid stage, 283. 
 Amphigastria, 319. 
 Amphithecium, 136, 316, 337. 
 Amplexicaul, 30. 
 Amygda'lin, 187. 
 
 Amy 1 in, 187. 
 Amylolytic enzyme, 198. 
 Amyloplastic function, 70. 
 Amyloses, 187. 
 Anabolism, 193. 
 Anatomy, 63. 
 
 Anatropous ovule, 399 (Fig, 237). 
 Androscium, 443, 460. 
 Androspore, 258. 
 Anemophilous, 410. 
 Angiocarpous sporophore, 303. 
 Angustiseptal silicula, 535 (Fig. 
 
 348). 
 Annual plants, 417. 
 
 rings, 141 (Figs. 112-3). 
 shoots. 23. 
 
 Annular vessels, 74 (Fig. 44). 
 Annulus, 302 (Fig. 182), 343 (Fig. 
 
 208), 363 (Figs, 215-7), 
 Anterior, 448. 
 Anthela, 442. 
 
 Anther, 395, 460 (Figs. 276, 279), 
 Antheridial cell, 406. 
 Antheridiophore, 310 (Fig. 198). 
 Antheridium, 60, 243, 310, 350, 369 
 
 (Figs. 139, 140, 147, 148, 150, 
 
 158, 160, 192, 193. 222), 
 Anthocyanin, 83. 
 Anthophore, 444, 532 (Fig. 344). 
 Anticlinal, 102. 
 Antipetalous, 447. 
 Antipodal cells, 408 (Fig. 212) 
 Antisepalous, 446. 
 Apex, 4. 
 Apical cell, 101, 104 (Figs. 85, 86), 
 
 132 (Fig. 106), 133, 324 (Fig. 
 
 200). 
 
 Aplanogamete, 240. 
 Apocarpous, 465 (Fig. 281), 472. 
 Apophysis of Moss-capsule, 388. 
 
 of Pmus, 435. 
 Apostrophe, 172 (Fig. 124). 
 Apothecium, 294 (Fig. 177). 
 Aqueous tissue, 115.
 
 584 
 
 IXDEX, PART I. 
 
 Archegoniophore, 310 (Fig. 198). 
 Archegonium, 60, 235, 311, 350, 409 
 
 (Figs. 194, 195, 223, 241, 252). 
 Archesporium, 53, 136 (Figs. 197, 
 
 206, 210, 216). 
 Archicarp, 60, 237, 278. 293 (Fig. 
 
 172). 
 Aril (or arillus), 415 (Figs. 246, 
 
 258). 
 
 Arillode, 415, 546. 
 Arista, 488. 
 Arrangement of lateral members, 
 
 10. 
 
 Ascidium, 41 (Fig. 28), 175. 
 Ascocarp, 62, 277, 280, 293 (Figs. 
 
 171, 173, 175). 
 
 Ascogenous hyphse, 293 (Fig. 175). 
 Ascogonium, 278, 291, 296 (Fig. 
 
 175). 
 Ascospore, 290, 294 (Figs. 173, 175, 
 
 176). 
 Ascus, 278, 293 (Figs. 171, 175, 
 
 176). 
 Asexual formation of spores, 50, 
 
 230. 
 
 reproductive cells, 2, 50. 
 reproductive organs, 2, 51. 
 Ash, 188. 
 
 Asparagin, 186, 199. 
 Assimilation, 158, 193. 
 Asymmetry, 456 (Fig. 273). 
 Auriculate", 31 (Fig. 20), 326 (Fig. 
 
 202). 
 
 Autumn-wood, 142 (Figs. 112-3). 
 Auxospore, 265. 
 Awn, 487 (Fig. 301). 
 Axial placentation, 468. 
 Axil, 11. 
 
 Axillary branching, 11. 
 Axile placentation, 468 (Fig. 284). 
 Axis, 4, 18. 
 
 Bacca, 475. 
 
 Bacterioids, 191. 
 
 Balsam, 97. 
 
 Bark, 153 (Fig. 119). 
 
 Basal wall, 314, 346. 
 
 Base, 4. 
 
 Basidiospore, 303 (Figs. 183, 184). 
 
 Basidium, 303 (Figs. 183, 184). 
 
 Basifixed anther, 460. 
 
 Basitonous, 504. 
 
 Bast, 121 (Figs. 100-5), 130, 143. 
 
 hard. 143. 
 
 soft, '143. 
 
 Bast-fibres, 130, 143 (Fig. 111). 
 Berry, 475. 
 Biennial plants, 418. 
 Bifurcation, 19. 
 Bijugate, 35. 
 
 Bilabiate, 455. 
 Bilateral Symmetay, 6. 
 Bilocular anther, 4^63. 
 Bipinnate, 35. 
 Biseriate perianth, 457. 
 Bisexual, 61. 
 Biternate, 37. 
 Blade of leaf, 29, 32. 
 Bleeding, 182. 
 Bloom on plants, 107. 
 Body, I, 63. 
 
 septate or unseptate, 63. 
 Bordered pits, 74 (Figs. 48, 49). 
 Bostrychoid dichotomy, 19 (Fig. 9). 
 Bostryx, 441. 
 Bract, 57, 442. 
 
 function of, 175. 
 Bracteole, 57, 443. 
 Branches, development of, 9, 132. 
 Branching, 3. 
 
 axillar3 r , 11. 
 
 dichotomous, 18 (Fig. 9). 
 
 cymose, 19 (Fig. 11) 
 
 racemose, 19. 
 
 of leaf, 34. 
 
 of root, 45 (Fig. 30), 133 (Fig. 107). 
 
 of shoot, 12, 132. 
 Branch-systems, 18 (Figs. 9-11). 
 Bromine," 189. 
 Bud, 11. 
 
 adventitious, 136. 
 Budding, 229. 
 Bud-scales, 42. 
 Bulb, 25 (Fig. 13), 50. 
 Bulbil, 25, 50, 332. 
 Bundle, vascular, 121. 
 
 bicol lateral, 123. 
 
 cauline. 122. 
 
 closed, 127. 
 
 collateral, 123. 
 
 common, 122. 
 
 concentric, 123, 125 (Fig. 101). 
 
 conjoint, 121. 
 
 medullary, 123. 
 
 open, 127. 
 
 phloem-, 125. 
 
 xylem-, 125. 
 
 longitudinal course of, 122 
 I (Fig- 99). 
 
 structure of, 129. 
 
 termination of, 130. 
 Bursicula, 504. 
 
 Calcium, 188, 192. 
 
 carbonate, 78 (Fig. 52). 81. 202. 
 
 oxalate, 78 (Fig. 51), 81 (Figs. 
 
 57, 58), 202. 
 Callus, 137, 155 (Fig. 121). 
 
 of sieve-tubes, 95 (Figs. 75, 76). 
 Calyculus (epicalyx), 445.
 
 MORPHOLOGY, ANATOMY, AXD PHYSIOLOGY. 
 
 585 
 
 Calyptro, 62, 313 (Figs. 196. 206, 
 
 211). 
 
 Calyx, 58, 443. 
 Cambium, 127, 130 (Fig. 105), 137 
 
 (Figs. 108, 109). 
 Cambium-ring, 137 (Fig. 110). 
 Campanulate, 458. 
 Campy lotropous ovule, 399 (Fig. 237). 
 Cane-sugar, 187, 198. 
 Caoutchouc, 167. 
 Capillitium, 283 (Fig. 164). 
 Capitate hairs, 46. 
 Capitulate raceme, 440. 
 Capitulum of Charoideae, 261. 
 
 inflorescence, 439 (Fig. 259). 
 Capsule of Bryophyta, 52, 314, 337 
 
 (Figs. 197, 206, 208-11). 
 Capsule, a fruit, 475 (Figs. 288, 289). 
 Carbohydrates, 186, 201. 
 Carbon, 189. 
 Carbon, dioxide, absorption of, 189. 
 
 193. 
 
 evolution of, 200. 
 Carcerule, 473, 541 (Fig. 352). 
 Carina, 557 (Fig. 369). 
 Carinal cavity, 383 (Fig. 230). 
 Carpel ,56, 395, 465. 
 Carpellary flower, 56, 395. 
 Carpogamy, 241, 277. 
 Carpogonium, 242, 272 (Fig. 160). 
 Carpophore, 466 (Fig. 287). 
 Carposporangium, 244, 273 (Figs. 
 
 160, 161). 
 Carpospore, 274. 
 Caruncle, 416, 526. 
 Caryopsis, 473. 
 Catabolism, 158, 185, 197. 
 Cataphyllary leaves (Cataphylls), 
 
 42, 175. 
 
 Catkin, 442, 517 (Figs. 327-31). 
 Caudicle, 504. 
 Caulicle, 377. 
 
 Cauline vascular bundles, 122. 
 Cell, 1. 63, 66 (Fig. 36). 
 Cell-contents, 78. 
 C^ll-division, 83 (Fig. 60). 
 Cell-formation, 83 (Figs. 60-85). 
 Cell-sap, 66, 82. 
 Cell-wall, 63, 66, 72, 76. 
 
 growth of. 73. 
 Cellular structure, 64. 
 Cellulose, 66, 72, 76, 187, 201. 
 Chalaza, 399 (Fig. 237). 
 Chalk-glands, 96, 202. 
 Chambered ovary, 466 (Fig. 282). 
 Chemical composition of plants. 
 
 185. 
 
 Chemical effects of light, 161. 
 Chemiotaxis, 220, 232. 
 Chlamydospore, 277, 286, 304. 
 
 Chlorine, 188. 
 Chlorophyll, 
 
 -corpuscle, 71, development of 
 161, 192. 
 
 function of, 194. 
 Chloroplastids, 69 (Figs. 88, 40, 41). 
 
 functions of, 70. 
 
 movements of, 172 (Fig. 124). 
 Chlorotic, 192. 
 Chromatin, 69. 
 
 Chromatophore, 69 (Figs. 41, 42). 
 Chromoplastid, 69 (Fig. 42). 
 Cincinnal dichotomy, 19. 
 Cincinnus, 441. 
 Cilium, 72, 207 (Fig. 62). 
 Circinate vernation, 43. 
 Circulation of protoplasm, 204, 206. 
 Citric acid, 187. 
 Classification, 233. 
 Claw, 458 (Fig. 275). 
 Cleistogamous flowers, 410. 
 Cleistothecium, 294 (Fig. 173). 
 Climbing plants, 27 (Fig. 15), 212, 
 
 223. 
 
 Closed vascular bundles, 127. 
 Cobalt, 189. 
 Coccus, 472. 
 Coenobium, 239, 253. 
 Coenocyte, 64, 100(Fig.81), 25a(Figs. 
 
 140-2), 252 (Fig. 143), 276. 
 Cohesion, 21 (Fig. 12), 462. 
 Coleoptile, 478 (Fig. 292). 
 Coleorhiza, 479 (Fig. 293). 
 Collateral vascular bundles, 123 
 
 (Figs. 97, 100). 
 
 Collenchyma, 91 (Fig. 69), 111. 
 Colleter, 101, 167. 
 Colony, 238. 
 
 Colouring-matters, 83, 186. 
 Columella, 285 (Fig. 165), 817 (Figs. 
 
 197, 208). 
 Column, 444. 
 
 Combined effects of stimuli, 222. 
 Common bundles, 122. 
 Companion-cell, 95 (Fig. 74), 166. 
 Compound inflorescences, 439, 441. 
 Compound leaves, 35 (Fig. 23). 
 Concentric arrangement of bundles, 
 
 123 (Fig. 101). 
 Conceptacle, 269 (Fig. 157). 
 Conditions of movement, 223. 
 Conducting tissue of style, 467. 
 
 -sheath, 184. 
 
 Conduplicate vernation, 43. 
 Cone, 55, 382, 386, 421, 433 (Figs. 
 
 228, 231, 254, 255). 
 Conical root, !">_ 
 Conidiophoro. -Ji'.'. 
 Coniferin, 187. 
 Coniin, 186.
 
 586 
 
 INDEX, PART I. 
 
 Conjoint bundle, 121. 
 
 Conjugation, 58, 87 (Fig. 65), 240 
 
 255, 256 (Fig. 146), 286 (Fig. 
 
 166). 
 
 Conjunctive tissue, 118, 144. 
 Connate, 32 (Fig. 20). 
 Connective, 460 (Fig. 276). 
 Contorted vernation, 43. 
 Contractile vacuoles, 206. 
 Convolute vernation, 43. 
 Copper, 189. 
 Cordate, 37. 
 Cork, 151 (Fig. 118). 
 Corm, 25, 50 (Fig. 309). 
 Corolla, 58, 443. 
 Corona, 48, 458. 
 
 of Characese, 262 (Fig. 150). 
 Cortex, 111, 149, 260. 
 Corymb, 442. 
 Costse, 548. 
 Cotyledon, 28, 403 (Figs. 238, 239), 
 
 414 (Fig. 245), 476 (Figs. 291-3), 
 
 509 (Figs. 320-1). 
 Crenate, 37. 
 Cross-fertilisation, 232. 
 Cross-pollination, 409. 
 Cruciate tetraspores, 271. 
 Crumpled aestivation, 43. 
 Crystalloids, 81 (Fig. 54). 
 Crystals, 78 (Fig. 51), 81 (Figs. 57,58). 
 Culm, 28. 
 
 Cupule, 49, 313, 323 (Fig. 198), 337. 
 of Phanerogams, 472, 518, 520 
 
 (Fif 
 
 Cuticle, lU,. 
 Cuticularisation of cell-wall, 76, 91. 
 Cutin, 76. 
 
 Cyathium, 526 (Fig. 341). 
 Cyclic flower, 445. 
 Cyclosis, 204, 205, 260. 
 Cyme, 441. 
 
 helicoid, 21 (Fig, 11), 441. 
 
 scorpoid, 21 (Fig. 11), 441. 
 Cymose branching, 19 (Fig. 11). 
 
 inflorescence, 441. 
 Cypsela, 473. 
 Cystocarp, 62, 241, 273 (Figs. 160, 
 
 161). 
 
 Cystolith, 78 (Fig. 52), 202. 
 Cytoplasm, 68. 
 
 Daily periodicity of growth, 214. 
 
 Day-position, 174. 
 
 Deciduous, 10. 
 
 Decussate arrangement of leaves, 
 
 13. 
 
 Definite inflorescences, 441. 
 Definitive nucleus, 408. 
 Dehiscence of anther, 396, 463. 
 of fruits, 473. 
 
 Dehiscence of sporangium, 54, 364. 
 Dehiscent fruits, 416, 473. 
 Dentate, 35, 37. 
 
 Dermatogen, 102 (Figs. 83, 84). 
 Development of body, 8. 
 
 of branches of roots, 133. 
 
 of branch-systems, 18. 
 
 of leaves, 133. 
 
 of secondary members, 132. 
 
 of hairs, 135. 
 
 of emergences, 135. 
 
 of reproductive organs, 135. 
 
 of adventitious members, 136. 
 Dextrin, 187, 198. 
 Dextrose, 198. 
 Diadelphous, 462. 
 Diageotropism, 171, 218. 
 Diagonal plane of flower, 448. 
 Diagram, floral, 447. 
 Diaheliotropism, 171, 215. 
 Diaphragm, 379, 393 (Fig. 233). 
 Diastase, 198. 
 Diastole, 206. 
 Dichasial cyme, 442. 
 Dichasium, 20 (Fig. 10), 441. 
 Dichlamydeous, 457. 
 Dichogamy, 411. 
 Dichotomy, 9, 18 (Fig. 9), 132 (Fig. 
 
 106). 
 
 Diclinous, 61, 310, 395. 
 Dicyclic, 450. 
 Didynamous, 462. 
 Differentiation of tissues, 65, 101, 
 
 125, 145. 
 
 Digestive sac, 135. 
 Dimorphism, 411. 
 Dioecious, 61, 310. 
 Diplotegium, 475. 
 Diplostemonous, 450. 
 Directive effect of light, 162, 214. 
 
 of gravity, 217. 
 Disc, 470. 
 
 Dissected leaves, 37. 
 Dissemination of seed, 416. 
 Dissepiment, 466. 
 
 false or spurious, 466. 
 Dissipation of energy, 203. 
 Distractlle anther, 460 (Fig. 276). 
 Distribution of water and other 
 substances, 181. 
 
 of organic plastic substances, 
 
 184. 
 Diurnal and nocturnal positions, 
 
 173 (Figs. 125, 126). 
 Divergence, 12. 
 Dorsal suture, 465. 
 Dorsifixed anther, 460 (Fig. 276). 
 Dorsiventral arrangement, 17. 
 Dorsiventrality, 7 (Fig. 2), 13, 454 
 (Figs. 271, 272).
 
 MORPHOLOGY, ANATOMY, AND PHYSIOLOGY. 
 
 587 
 
 Double flowers, 452. 
 Drepanium, 441. 
 Drape, 475 (Fig. 290). 
 Drupel, 475'. 
 Duct, 98. 
 Duplication, 450. 
 Duramen, 143, 165. 
 Dwarf-males, 258 (Fig. 147). 
 Dwarf-shoots, 23. 
 
 Egg-apparatus, 408 (Fig. 242). 
 
 Elater, 316, 383. 
 
 Elementary constituents of the food 
 of plants, 188. 
 
 Eleutheropetalous, 458. 
 
 Eleutherophyllous, 458. 
 
 Eleutherosepalous, 458. 
 
 Emarginate, 37. 
 
 Embryo, 8. 
 
 Embryo-cell, 401. 
 
 Embryogeny of Bryophyta, 314, 319, 
 337 : of G3 r mnosperms, 424 
 (Figs. 249-251): of Phanero- 
 gams, 401 (Dicotyledons, Fig. 
 238 ; Monocotyledons, Fig. 
 239) : of Pteridophyta, 346, 
 366 (Figs. 218-220), 377, 385, 
 387, 393 (Figs. 233, 235). 
 
 Embryonal tubes, 427 (Fig. 250). 
 
 Embryo-sac, 51, 400 (Figs. 241-2), 
 
 Emergences, 48, 135. 
 Endocarp, 472 (Fig. 290). 
 Endodermis, 111, 115, 134 (Figs. 94, 
 
 96). 
 Endogenous development, 9, 44, 134 
 
 (Fig. 107). 
 Endopleura, 415. 
 Endosperm, 407 (Fig. 241), 414. 
 Endospore, 50. 
 
 Endothecium, 136, 316 (Fig. 197). 
 Energy of growth, 209. 
 
 absorption of, 194. 
 
 dissipation of. 203. 
 
 kinetic, 194. 
 
 potential, 197. 
 Ensiform, 32, 479. 
 Entire, 35. 
 Entomophilous, 410. 
 Enzyme, 189, 197. 
 Epibasal cell, 314, 346, 387. 
 Epiblast, 478 (Fig. 292). 
 Epiblema, 106. 
 Epicalyx, 57, 175, 443, 57a 
 Epicarp, 472 (Fig. 290). 
 Epicotyl, 404. 
 
 Epidermis, 106 (Figs. 87-90, 92). 
 Epigean cotyledons, 405. 
 Epigynous, 444 (Fig. 261). 
 Epinasty r 211 (Fig. 131). 
 
 Epipetalous, 462. 
 Epiphragm, 344. 
 Epiphyllous, 462. 
 Epiplasm, 294. 
 Epipodium, 29, 32. 
 Episporitim <Epispore), 287, 376. 
 Epistrophe, 172 (Fig. 124). 
 Equitant, 43. 
 
 Erect ovule, 469 (Fig. 284). 
 Erythrophyll, 83. 
 Etaerio, 476. 
 
 Etiolated plants, 162, 213. 
 Etiolin, 161. 
 Encyclic, 449. 
 Eusporangiate, 53, 349. 
 Evolution of oxygen from water- 
 plants, 195 (Fig. 128). 
 Exalbuminous seed, 414. 
 Excretion, 202. 
 Exine, 50. 
 
 Exodermis, 111 (Fig. 87). 
 Exogenous development, 9. 
 Exospore, 50. 
 Exstipulate, 30. 
 External conditions, 159. 
 Extra-floral nectaries, 96, 166. 
 Extra-seminal development, 401. 
 Extrorse, 464. 
 
 False dichotomy, 20 (Fig. 10). 
 
 foot, 315, 339. 
 Fascicle, 442. 
 Fascicular cambium, 138. 
 Fats, 80, 187, 201. 
 Fat-enzyme, 198. 
 Feeder, 393. 
 Female organ, 60. 
 
 pronucleus, 414. 
 Ferment, organised, 198. 
 Fermentation, alcoholic, 198. 
 Fertilisation, 59. 
 Fibres, 92. 
 
 woody, 140. 
 Fibrous cells, 92, 140. 
 
 root, 45. 
 
 Fibro-vascular bundle, 121. 
 Filament, 88, 395. 
 Filtration under pressure, 182. 
 Fixed light-position, 173. 
 
 oils, 187. 
 Flanks, 6. 
 Floral diagram, 447. 
 
 formula, 448. 
 
 leaves, 55, 175, 445. 
 
 organs, 456. 
 Flower, 25, 55, 894. 
 
 accessory organs of, 470. 
 
 irregular, 454. 
 
 macrosporangiate, 56, 395. 
 
 microsporangiate, 56, 395.
 
 588 
 
 INDEX, PART I. 
 
 Flower, opening and closing of, 176. 
 
 regular, 453. 
 
 reproductive organs of, 176, 395. 
 
 symmetry of, 453. 
 
 phyllotaxy of, 445. 
 Fluorine, 189. 
 Foliage-leaves, 39 (Figs. 18-28), 114 
 
 (Fig. 92), 171. 
 Follicle, 473. 
 Food of plants, 188. 
 Foot, 314, 319, 337 (Fig. 206), 347 
 (Fig. 218-220), 393 (Fig. 234). 
 Form of leaves, 28 (Figs. 18-29). 
 
 root, 45 (Fig. 30). 
 
 shoots, 23 (Figs. 13-15). 
 
 stems, 27 (Figs. 16,17). 
 Forms of tissue, 90. 
 Formation of chlorophyll, 161. 
 Formation of tissue in consequence 
 
 of injury, 155. 
 Formative region, 208. 
 Fovea, 356 (Fig. 213). 
 Foveola, 356. 
 Free cell-formation, 87. 
 Freezing, effects of, 160 (Fig. 122). 
 Fruit, 61, 232, 414, 471. 
 
 dehiscence of, 473. 
 
 dry dehiscent, 473. 
 
 dry indehiscent, 473. 
 
 succulent, 475. 
 Frustule, 265 (Fig. 152). 
 Function of chlorophyll, 194. 
 Functions of the members, 167. 
 
 of plants, 157. . 
 
 of the tissues, 162. 
 Funicle, 53, 399. 
 Fusiform root, 45. 
 
 Galeate, 562. 
 
 Gallotannin, 187. 
 
 Gametangium, 58, 60, 242 (Fig. 146), 
 
 278, 285 (Fig. 166). 
 Gametes, 2, 58, 240. 
 Gametophore, 58, 310. 
 Gametophyte, 2, 229, 234. 
 Gamopetalous, 458. 
 Gamophyllous, 458. 
 Gamosepalous, 458. 
 Gamostelic, 117. 
 Gemmse, 49, 240, 313, 337, 352. 
 Gemmation, 49, 276. 
 Generations, alternation of, 2, 234. 
 Genetic spiral, 14 (Fig. 8). 
 Generative cell, 406, 429. 
 Genus, 235. 
 Geotropism, 217 (Fig. 132). 
 
 negative, 171, 218. 
 
 positive, 169, 218. 
 
 Germination of seed, 199, 401 (Figs. 
 251, 291, 320). 
 
 Gibbous, 564 (Fig. 378). 
 Glandular hairs, 100 (Fig. 82). 
 Glandular tissue, 96 (Figs. 76-79), 
 
 166. 
 
 Glans, 473. 
 Globoid, 80 (Fig. 54). 
 Glochidia, 376. 
 Glomerule, 442. 
 Glucoses, 187. 
 Glucoside, 187. 
 Glucoside-enzyme, 198. 
 Glume, 442, 487 (Figs. 300, 301). 
 Glycerin, 198. 
 Glycogen, 294. 
 
 Gonimoblastic filaments, 273. 
 Gonophore, 444. 
 Graft-hybrids, 229. 
 Grafting, 229. 
 
 Grand period of growth, 209. 
 Grape-sugar, 187. 
 Ground-tissue, 110. 
 Growing-point, 8 (Fig. 3\ 102 (Figs. 
 
 83-86). 
 Growth, 8, 207. 
 
 in length, 207. 
 
 in thickness of stem and root, 
 137. 
 
 limited, 9. 
 
 of cell-wall, 73. 
 
 of leaf, 29. 
 
 sliding, 147. 
 Guard-cells of stomata, 107 (Fig. 
 
 88), 179. 
 Gum, 97, 187. 
 
 Gymnocarpous sporophore, 303. 
 Gynandrosporous, 258. 
 Gynandrous, 462. 
 Gynseceum, 443, 465. 
 Gynobasic style, 467. 
 Gynophore, 444. 
 Gynostemium, 444, 503 (Fig. 318). 
 
 Hairs, 3, 109 (Fig. 90), 135. 
 
 internal, 92. 
 Hapteron, 48, 240. 
 Hastate, 37. 
 Haulm, 28. 
 
 Haustorium, 48, 190, 276. 
 Heart-wood, 143. 
 Heat, influence of, 160. 
 
 production of, 203 (Fig. 129). 
 Helicoid cyme, 21 (Fig. 11), 441. 
 
 dichotomy, 19 (Fig. 9). 
 Heliotropism, 162, 169, 171, 214. 
 
 negative, 169, 216. 
 
 positive, 171, 216. 
 Hemiangiocarpous, 303. 
 Hemicyclic, 445. 
 Herbaceous. 27. 
 Hermaphrodite, 61, 395.
 
 MORPHOLOGY, ANATOMY, AXD PHYSIOLOGY. 
 
 589 
 
 Heterochlatnydeous, 457. 
 Heteroclinous, 335. 
 Heterocyclic, 449. 
 Heterocyst, 245 (Figs 135, 136). 
 Heteroecism, 299. 
 Heterogamy, 58, 241, 277. 
 Heteromerous lichen-thallus, 306. 
 
 floral whorls, 449. 
 Heterophylly, 41, 
 Heterosporous, 51, 349, 394. 
 Heterostylism, 411. 
 Hilum, 79, 399. 
 
 Histological differentiation, 65. 
 Histology, 63. 
 
 of Gymnospermae, 419. 
 
 of Phanerogamia, 400. 
 
 of Pteridophyta, 365, 377, 383, 
 387, 391. 
 
 of the development of secondary 
 
 members, 132. 
 Homochlamydeous, 457. 
 Homoiomerous lichen-thallus, 306. 
 Homospprous, 51, 349, 380. 
 Hook-climbers, 171. 
 Hormogonium, 244 (Fig. 136). 
 Humus, 190. 
 Hybrid, 232. 
 Hybridisation, 232. 
 Hydrogen, 186, 188, 190. 
 Hydrotropism, positive, 169. 
 Hy menial layer, 293. 302. 
 Hymenophore, 302 (Fig. 183). 
 Hymenium, 302 (Fig. 183). 
 Hypha, 275. 
 
 Hypobasal cell, 314, 346. 
 Hypocotyl, 404. 
 Hypoderma, 111. 
 Hypogean cotyledons, 405. 
 Hypogynous, 444 (Fig. 261). 
 Hyponasty, 211. 
 
 Hypophysis, 403 (Figs. 238, 239). 
 Hypopodium, 29, 30. 
 Hypsophyllary leaves, 55, 57 (Fig. 
 27), 175. 
 
 Ice, formation of, 161 (Fig. 122). 
 
 Imparipinnate, 35 (Fig. 23). 
 
 Incubous leaves, 326 (Fig. 202). 
 
 Incumbent, 536. 
 
 Indefinite inflorescences, 439. 
 
 Indehisceut fruits, 473, 475. 
 
 Induced movements, 211. 
 
 Indusium, 348, 361. 
 
 Inferior ovary, 444 (Fig. 261). 
 
 Inflorescence, 54, 394, 439. 
 
 Infundibuliform, 458. 
 
 Initial cells, 101. 
 
 Innate, 460. 
 
 Innovation, 23, 333. 
 
 Insertion-of leaves, 11. 
 
 Integument, 415. 
 
 Intercalary growth, 239 (Fig. 138). 
 Intercellular spaces, 89 (Fig. 67). 
 Interfascicular cambium, 138. 
 
 conjunctive tissue, 118, 120. 
 Internal hairs, 92. 
 Internode, 11, 261. 
 Interruptedly pinnate, 85. 
 Intine, 50, 897. 
 
 Intra-seminal development, 401. 
 Introrse, 464. 
 Inulin, 83 (Fig. 59), 187. 
 Invert-enzyme, 198. 
 Involucel, 440. 
 Involucral leaves, 384. 
 Involucre, 57, 810, 334, 440 (Fig. 
 
 259), 579 (Fig. 397). 
 Iodine, 189. 
 Iron, 188, 192. 
 Irregular spontaneous variations in 
 
 rate of growth, 209. 
 Irritability, 158. 
 
 conditions of, 223. 
 localisation of, 220. 
 to differences in the degree of 
 moisture in the surrounding 
 medium (hydrotropism), 169, 
 219. 
 
 to direction of incidence of the 
 rays of light (heliotropism), 
 169,171,214. . 
 to mechanical stimuli, 211. 
 to the directive influence of 
 gravity (geotropism), 169, 171 , 
 217 (Fig. 182). 
 to variations in the intensity 
 
 of light, 213. 
 to variations of temperature, 
 
 212. 
 Isobilateral arrangement, 17. 
 
 symmetry, 4, 6 (Fig. 2fl), 454. 
 Isocyclic, 449. 
 Isogamy, 58, 240, 277. 
 Isomerous, 449. 
 
 Juga primaria, 548. 
 Juga secundaria, 549. 
 
 Kinetic energy, 194, 197. 
 Knight's machine, 218. 
 
 Labellum, 418 (Fig. 244), 503 (Fig. 
 
 814). 
 
 Lsevulose, 198. 
 Lamella, 302 (Fig. 183). 
 Lamina, 29, 32. 
 Lanceolate, 87. 
 Lateral branching, 19. 
 
 buds, 11. 
 
 members, development of, 9, 182.
 
 590 
 
 INDEX, PART I. 
 
 Lateral plane of flower, 448. 
 Latex, 99, 167. 
 
 Laticiferous crenocytes 100 (Fig. 
 81). 
 
 tissue, functions of, 167. 
 
 vessels, 99 (Fig. 80). 
 Latiseptal silicula, 536 (Fig. 348). 
 Leaf, 3, 28 (Figs. 18-29). 
 
 apex of, 37. 
 
 -base, 29, 30, 37. 
 
 -blade, 29, 32. 
 
 cataphyllary, 42, 175. 
 
 compound, 35. 
 
 coriaceous, 40. 
 
 epipodium, 29, 32. 
 
 fall of, 10, 156. 
 
 floral, 43, 55, 175, 394, 457. 
 
 foliage, 39. 
 
 functions of, 171. 
 
 form of, 33. 
 
 herbaceous, 40. 
 
 hypopodium, 29, 30. 
 
 margin of, 37. 
 
 hypsophyllary, 43, 175. 
 
 mesopodium, 29, 32. 
 
 minute structure of. 114 (Fig. 
 92). 
 
 oblique, 33. 
 
 outline of, 37. 
 
 phyllopodium, 28. 
 
 pitchered, 41 (Fig. 28), 175. 
 
 prefloration, 43. 
 
 scaly, 42, 175. 
 
 -scar, 10 
 
 segmentation of, 28, 35 (Fig. 
 28). 
 
 -spine, 42 (Fig. 29), 175. 
 
 sporophyllary, 43, 55, 176, 348, 
 395. 
 
 -stalk, 29. 
 
 succulent, 40. 
 
 -tendrils, 32, (Fig. 19), 41, 175. 
 
 -traces, 122. 
 
 venation of, 38. 
 
 vernation of, 43. 
 
 -wing, 29. 
 Leaflet, 35. 
 Leafy shoot, 22. 
 
 annual, 23. 
 
 creeping, 26. 
 
 dwarf-, 23. 
 
 Legume, 473 (Fig. 288). 
 Lenticels, 154 (Fig. 120). 
 Leptosporangiate, 53, 349. 
 Leucin, 186, 199. 
 Leucoplastid, 69, 70 (Fig. 39). 
 Life-history, 2, 233, 309, 346, 417. 
 Light, chemical effects of, 161. 
 
 mechanical effects of, 161. 
 Light-position, 173, 215, 223. 
 
 Lignification of cell-wall, 77. 
 
 Lignin, 77. 
 
 Ligulate corolla, 579 (Figs. 396, 
 
 397). 
 Ligule, 32 (Fig. 19), 48, 357 (Fig. 
 
 1 213). 
 
 Limb, 458 (Fig. 274). 
 Linear, 37. 
 Linolein, 187. 
 Lithium, 189. 
 Lobed, 35, 37. 
 
 Localisation of irritability, 220. 
 Loculicidal, 475 (Fig. 289). 
 Loculus, 465. 
 Lodicule, 487 Fig._299). 
 Lomentaceous, 475, 537. 
 Lomentum, 474. 
 Longitudinal axis, 4. 
 
 section, 4. 
 Lysigenous, 89, 97. 
 
 Macrosporangiate flower, 56, 395. 
 Macrosporangium, 52, 349, 398. 
 Macrospore, 51, 349, 400, 438. 
 Macrosporophyll, 56, 349, 395, 423. 
 Macrosporophyllary flower, 56. 
 Magnesium, 188, 192. 
 Male organ, 60. 
 
 pronucleus, 413 (Fig. 249). 
 
 reproductive cells (gametes), 59. 
 Malic acid, 187. 
 Maltose, 187, 198. 
 Mannite, 187. 
 
 Manubrium, 261 (Fig. 150). 
 Massula, of Azolla, 376. 
 
 of Orchids, 504. 
 Mastigopod-stage, 283. 
 Mechanical effects of light, 161. 
 Mechanism of movements, 224. 
 Median plane of flower, 448. 
 Medulla, 117, 119. 
 Medullary bundles, 123. 
 
 conjunctive tissue, 118. 
 
 rays, 117, 118 (Fig. 97), 144 
 (Figs. 114, 115). 
 
 sheath, 128. 
 Megaspore, 400. 
 Members, 1, 3, 167. 
 
 development of, 8, 132. 
 Mericarp, 472 (Fig. 287). 
 Meristele, 118. 
 Meristem, 90. 
 Mesocarp, 472 (Fig. 290). 
 Mesophyll, 112. 
 Mesopodium, 29, 32. 
 Metabolism, 185. 
 Metallic elements of food, 188. 
 Microcysts, 277, 285. 
 Micropyle, 398. 
 Microsporangiate flower, 56, 395.
 
 MORPHOLOGY, ANATOMY, AND PHYSIOLOGY. 
 
 591 
 
 Microsporangium, 52, 349, 396. 
 Microspore, 51, 349, 396. 
 Microsporophyll, 56, 349, 395. 
 Microsporophyllary flower, 56. 
 Middle lamella, 88 (Fig. 66). 
 Midrib,. 34. 
 Mineral matters in cell-wall, 77 
 
 (Figs. 51, 52). 
 Monadelphous, 462. 
 Monocarpous, 417. 
 Monochlamydeous, 457. 
 Monoclinous, 61, 310, 394. 
 Monocyclic, 450. 
 Monoecious, 61, 310, 395. 
 Monomerous ovary, 465. 
 Monopodial branch-system, 19. 
 Monosiphonous, 266, 271. 
 Monostely, 102. 
 Monosymmetrical, 7, 454. 
 Morphin, 186. 
 Morphology, 1. 
 
 of asexual reproductive organs, 
 
 51. 
 
 sexual organs, 58. 
 of the tissue-systems, 101. 
 Morphological differentiation, 3. 
 Motile region, 225. 
 Motility of protoplasm, 225. 
 Movement, 158, 204, 205. 
 conditions of, 223. 
 induced, 205, 211. 
 mechanism of, 224. 
 of cellular members, 207. 
 of growth, 207. 
 of protoplasm, 206. 
 of variation, 207 
 spontaneous, 206. 
 Mucilage, 187. 
 
 conversion of cell-wall into, 77, 
 
 109. 
 
 secretion of, 98, 101, 167. 
 Mucro, 36 (Fig. 23). 
 Mucronate, 37. 
 Multijugate, 35. 
 
 Multilateral symmetry, 4 (Fig. 1). 
 Multilocular ovary, 466 (Fig. 282). 
 Mycelium, 275. 
 Mycorhiza, 275. 
 Myrmecophilous plants, 166. 
 Myrosin, 187. 
 Myronate of potash, 187. 
 Myxopod-stage, 283. 
 
 Napiform root, 45. 
 
 Neck, of archegonium, 311 (Fig. 
 
 194), 350, 429. 
 Nectary, 96, 166, 202, 470. 
 Negative geotropism, 171, 218. 
 
 heliotropism, 169, 216. 
 
 pressure, 180. 
 
 Nicotin, 186. 
 
 Night-position, 173, 213. 
 
 Nitrogen, 188, 190. 
 
 Nitrogenous organic substances 
 
 reserve materials, 201. 
 
 Node, 11, 29. 
 
 Non-metallic elements of food, 188. 
 
 Non-nitrogenous organic sub- 
 stances, 186. 
 reserve materials, 201. 
 
 Nucellus, 398, 469. 
 
 Nuclear division, 84. 
 
 Nucleo-hyaloplasm, 69. 
 
 Nucleolus, 66, 69. 
 
 Nucleus, 63, 66, 68 (Fig. 37). 
 
 Nut, 473. 
 
 Nutation, 211. 
 
 Nutritive properties of protoplasm, 
 Io8. 
 
 Nyctitropic movements, 173 (Fig. 
 125), 213. 
 
 Obcordate, 37. 
 
 Obdiplostemonous, 452 (Fig. 268). 
 Oblique leaf, 8, 33. 
 
 plane of flower, 448. 
 zygomorphy, 7. 
 Oblong, 37. 
 Obovate, 37. 
 Obtuse, 37. 
 
 Ocrea, 31, 523 (Fig. 337). 
 Octant-wall, 314, 347, 366 (Fig. 218). 
 Oidium-cells, 277, 304. 
 Oil-drops, 80. 
 Oil-gland, 97 (Fig. 76). 
 Oils, fixed, 187. 
 Oily seeds, 80, 201. 
 Oleic acid, 187, 198. 
 Olein, 187, 198. 
 Oligomery, 449. 
 Oligotaxy, 452. 
 Ooblastema-filatnents, 273. 
 Oogamy, 241, 277. 
 Oogonium, 60, 237, 241, 278, (Fig* 
 
 139, 140, 147, 148, 150, 158, 
 
 167). 
 Oosphere, 59, 241, 277 (Figs. 147, 
 
 242, 311 (Fig. 194), 351 (Fig. 
 
 223). 409 (Fig. 242). 
 Oospore, 59, 241, 277 (Fig. 167), 312, 
 
 851, 414. 
 
 Opening and closing of flowers, 176. 
 Operculum, 317, 820, 338, 843 (Figs. 
 
 208, 210). 
 
 Opposite members, 13. 
 Optimum-temperature, 160. 
 Orbicular, 479. 
 Organs, 1, 157. 
 
 reproductive, 51, 58, 894, 459.
 
 592 
 
 INDEX, PART I. 
 
 Organic acids, 187. 
 Organised ferments, 198. 
 Orthostichy, 13 (Figs. 7, 8). 
 Orthotropic members, 222. 
 Orthotropous ovule, 399 (Fig. 237), 
 
 469 (Fig. 284). 
 Osmosis, 178. 
 Oval, 37. 
 
 Ovary, 57, 395, 465 (Fig. 282). 
 Ovate, 37. 
 Ovule, 52, 396, 424, 468 (Fig. 285). 
 
 anatropous, 399 (Fig. 237), 469 
 (Fig. 284). 
 
 ascending, 469. 
 
 campylotropous, 399 (Fig. 237). 
 
 erect, 469. 
 
 horizontal, 468. 
 
 orthotropous, 399 (Fig. 237), 
 469 (Fig. 284). 
 
 pendulous, 468. 
 
 suspended, 468 (Fig. 284). 
 Oxalate, calcium, 78 (Fig. 51), 81 
 
 (Figs. 57, 53). 
 Oxalic acid, 187. 
 Oxygen, 188, 190, 197. 
 
 absorption of, 197, 200. 
 
 evolution of, 193 (Fig. 128). 
 
 Palea of Composite, 579. 
 
 of Ferns, 364. 
 
 of Grasses, 486. 
 
 Palisade-tissue, 112 (Fig. 92), 172. 
 Palmate, 33 (Fig. 21). 
 Palmatifid, 36 (Fig. 23). 
 Palmitic acid, 187. 
 Palmitin, 187. 
 Panicle, 442. 
 Pappus, 416, 577 (Fig. 393), 579 
 
 (Figs. 396, 397). 
 Paracorolla, 458. 
 Paraheliotropism, 174. 
 Paraphvsis, 269 (Fig. 158), 294, 303, 
 
 (Fig. 183), 335. 
 Parasites, 189, 275. 
 Parastichy, 15. 
 
 Paratonic effect of light, 162, 213. 
 Parenchyma, 90. 
 
 functions of, 163. 
 Paripinnate, 35 (Fig. 23). 
 Partite, 37. 
 
 Passage-cells, 112, 116 (Fig. 96). 
 Pedate, 33 (Fig. 21). 
 Pedicel, 55, 439. 
 Pedicellate, 55. 
 Peduncle, 55. 
 Peloria, 456. 
 Peltate, 33 (Fig. 22). 
 Pentacyclic, 451. 
 Pentamerous, 449. 
 Peptone, 198. 
 
 Perfoliate, 32 (Fig. 20). 
 Perianth, 55, 394, 457. 
 
 -leaves, 57. 175, 443, 458. 
 Periblem, 102 '(Fig. 83). 
 Pericarp, 472 (Figs. 290, 56). 
 Perichsetial leaves, 334. 
 Periclinal, 102. 
 Pericycle, 116, 118 (Figs. 97, 107), 
 
 119. 
 
 Periderm, 150, 151 (Fig. 118). 
 Peridium, 303. 
 Perigynium of Carex, 493. 
 
 of Liverworts, 312 (Fig. 194). 
 Perigynous. 444 (Fig. 261). 
 Perinium, 287, 376. 
 Periodicity of growth, 214. 
 Periplasm, 287. 
 Perisperm, 400, 414 (Fig. 245), 501, 
 
 523, 531. 
 
 Peristome, 338 (Figs. 208-210). 
 Perithecium, 291, 294 (Fig. 176). 
 Permanent tissue, 90. 
 Personate, 455. 
 Petal, 58, 176, 443. 
 Petaloid, 57. 
 Petiole, 29, 32. 
 Petiole-climbers, 175 (Fig. 127), 
 
 212. 
 
 Phelloderm, 150, 154. 
 Phellogen, 150. 
 Phloem, 121, 130. 
 Phosphorescence, 204. 
 Phosphorus, 188, 191. 
 Phototaxis, 214. 
 Phototonic effect of light, 162, 
 
 224. 
 
 Phototonus, 162, 224. 
 Phycocyanin, 238. 
 Phycoerythrin, 71. 238. 
 Phycopbgein, 71, 238. 
 Phycoxanthin, 71. 
 Phylloclade, 28 (Fig. 17). 
 Phyllode, 32. 
 Phyllopodium, 28. 
 Phyllotaxis, 12. 
 
 of flower, 445. 
 Physiology, 1, 157. 
 Pileus, 302 (Figs. 182, 183). 
 Piliferous layer, 109. 
 Pinna, 35. 
 
 Pinnate, 33 (Fig. 21). 
 Pinnule, 35. 
 Pistil, 465. 
 
 Pitcher, 32, 41 (Fig. 28), 175. 
 Pith, 118, 119 (Fig. 97). 
 Pitted wall, 74 (Figs. 45-49). 
 Placenta, 53, 348, 398. 
 Placental scale, 423. 
 Placentation, 468 (Fig. 284). 
 
 axial, 468.
 
 MORPHOLOGY, ANATOMY, AXD PHYSIOLOGY. 
 
 593 
 
 Placentation. axile or axillary, 468. 
 
 basal, 469. 
 
 free-central, 469. 
 
 marginal, 468. 
 
 parietal, 468. 
 
 superficial, 468. 
 Plagiotropic members, 222. 
 Plane of symmetry of flower, 448. 
 Planogametes, 59, 240, 256 (Fig. 
 
 146), 268 (Fig. 155). 
 Plasmodium, 63, 276, 283 (Fig 164). 
 Plastic products, 184, 201. 
 Plastic!, 68, 69. 
 Pleiomery, 449. 
 Pleiotaxy, 451. 
 Plerome, 102 (Fig. 83). 
 Pleurocarpous, 333 
 Pleurogynous stigma, 467. 
 Plumule, 404. 
 Pod, 473. 
 Podium, 18. 
 Pollen, development of, 85 (Fig. 61). 
 
 -grain, 51, 396 (Figs. 235, 236). 
 
 -sac, 52, 396 (Figs. 254, 279). 
 
 -tetrads, 396. 
 
 -tube, 407 (Fig. 240), 410 
 Pollination, 409. 
 
 Pollinium, 396, 413 (Fig. 244), 504. 
 Pollinodium, 60, 278, 291 (Fig. 172), 
 
 296, (Fig. 175). 
 Polyadelphous, 462. 
 Polyandrous, 462. 
 Polyaxial, 438. 
 Polycarpous, 418. 
 Polycyclic, 451 (Fig. 267). 
 Polyembryony, 401, 427. 
 Piilviramous, 335, 395. 
 Polyhedron-stage, 253. 
 Polvmerous, 465. 
 Polymorphism, 2, 247. 
 Polypetalous corolla, 458. 
 Polyphyllous, 458. 
 Polysepalons calyx, 458. 
 Polystely, 117. 
 Pol v-vmmetrical, 6, 453. 
 Polysiphonous, 266, 271. 
 Polytomy, 18. 
 Pome, 471. 
 Pom 322 (Fig. 199). 
 Porous capsule, 475 (Fig. 288). 
 Positive geotropism, 169, 218. 
 heliotiopism, 171, 216. 
 hydrotropism, 169, 220. 
 Posterior, 448. 
 Potassium, 188, 192. 
 Potential energy, 197. 
 Prefloration, 43. 
 Prefoliation, 43. 
 Prickle, 48 (Fig. 32). 
 Primary bast, 130. 
 
 M.B. 
 
 Primary bundle, 129. 
 
 differentiation of, 1 :Ti. 
 
 cortex, 102. 
 
 members, 8. 
 
 meristem, 101. 
 
 vascular tissue, 121. 
 
 wood, 129. 
 Primordial cell, 67. 
 Procambium, 116, 126. 
 Procarp, 60, 237, 272 (Figs. 160, 161). 
 Products of metabolism, 200. 
 Proliferation, 55. 
 Promycelium, 299 (Figs. 179, 181). 
 Prophyllum, 57, 443. 
 Prosenchyma, 90 (Fig. 68). 
 Protandrous, 411. 
 Proteids, 186, 201. 
 Proteid crystalloids, 81. 
 
 grains, 80 (Figs. 54-56). 
 Proteolytic enzyme, 198. 
 Prothallium, 2," 349 (Figs. 221, 226, 
 
 233), 405, 407 (Figs. 240, 241). 
 Protogynous, 411. 
 ! Protonema, 309 (Fig. 191). 
 Protophloem, 126 (Fig. 103). 
 Protoplasm, 1, 63, 66, 68. 
 
 continuity of, 65 (Fig. 35). 
 
 properties of, 158. 
 Protoxylem, 126 (Figs. 100-105). 
 Pseudaxis, 19, 441. 
 Pseudo-bulb, 27. 
 Pseudocarp, 414, 471. 
 Pseudo-plasmodium, 283. 
 Pseudopodium, 206, 288. 
 
 of Bryophyta, 312, 339 (Fig. 
 
 206). 
 
 Pulvinus, 30, 220, 225. 
 Pycnidium, 279, 291. 
 Pyrenoid, 71 (Fig. 41), 252 (Fig. 143). 
 Pyxidium, 475 (Fig. 288). 
 
 Quadrant-wall, 314, 346. 
 Quadrilocular anther, 463. 
 Quincuncial, 48. 
 Quinin, 186. 
 
 Raceme, 439. 
 
 Racemose, branching, 19. 
 
 inflorescences, 439 (Fig. 259). 
 Radial arrangement, of members, 12 
 (Figs. 4-8). 
 
 of bundles. 125. 
 
 longitudinal section, 4. 
 
 symmetry, 4 (Figs. 1 and 2), 
 
 453. 
 
 Radiant umbel, 548. 
 Radicle, 404. 
 Ramenta, 364. 
 Raphe, 399 (Fig. 237). 
 Raphides, 81 (Fig. 58), 202. 
 
 Q Q
 
 594 
 
 IXDEX, PART I. 
 
 Bate of growth, 208. 
 Receptacle, 54, 271, 310, 443. 
 Receptive spot, 241. 
 .Region of elongation, 208. 
 Regular flower, 453. 
 Rejuvenescence of cells, 87 (Fig. 62). 
 Replura, 474 (Fig. 288), 536. 
 Reproduction, 49, 227. 
 Reproductive organs, 49, 459. 
 
 asexual, 51. 
 
 sexual, 58. 
 
 property of protoplasm, 158. 
 Reserve materials, 201. 
 Resin-ducts, 98 (Fig. 77), 421. 
 
 -sac, 98 (Fig. 79). 
 Respiration, 197, 200. 
 Resupinate, 455, 503. 
 Retardation of growth by light, 162. 
 Reticulate vessels, 74. 
 Retinaculum, 413, 504. 
 Rhachis, 54. 
 Rhipidium, 441. 
 Rhizine, 276, 307 (Fig. 188). 
 Rhizogenic cells, 135, 347, 364. 
 Rhizoid, 309. 
 Rhizome, 26 (Fig. 14). 
 Rhizophore, 390. 
 Rib, 34. 
 
 Ricinolein, 187. 
 
 Ring, 57, 302 (Fig. 182), 343 (Figs. 
 208, 210), 363 (Fig. 215), 382 
 (Fig. 228). 
 Ringent, 563. 
 Rise of temperature in germinating 
 
 seeds, 203 (Fig. 129). 
 Roots, 3, 44. 
 
 adventitious, 9, 136. 
 
 aerial, 45, 106 (Fig. 87). 
 
 branching of, 45, 133 (Fig. 107). 
 
 functions of, 167. 
 
 growing-point of, 102 (Figs. 84, 
 86). 
 
 growth in thickness of, 138 
 (Figs. 109, 110). 
 
 primary, 44, 347. 
 
 structure of, 109 (Fig. 91), 115 
 
 (Figs. 94-96), 125 (Fig. 102). 
 Root-cap, 44, 104 (Figs. 84, 86), 109. 
 Root-hairs, 46, 110 (Fig. 91) 168 
 
 (Fig. 123). 
 Root-pressure, 182. 
 Root-tubercles, 191. 
 Rostellum. 413 (Fig. 244), 504. 
 Rotate, 458 (Fig. 274). 
 Rotation of protoplasm, 204. 
 Runner, 26. 
 
 Sac, 98 (Figs. 58, 78, 79). 
 Sagittate, 37. 
 Salicin, 187. 
 
 Samara, 473, 516 (Fig. 326\ 545 (Fig. 
 
 357). 
 
 Saprophyte, 189, 275. 
 Scalariform vessels, 74. 
 Scaly leaves, 42, 175. 
 Scape, 442. 
 
 Scattered development, 10. 
 Schizocarp, 473 (Fig. 287). 
 Schizogenous, 89, 98. 
 Scion, 229. 
 
 Sclerenchyma, 92, 111, 120, 140. 
 Sclerenchyinatous tissue, function 
 
 of, 164. 
 
 Sclerotic cells, 92 (Figs. 70, 71). 
 Sclerotium, 277, 285, 290 (Fig. 176). 
 Scorpioid cyme, 21 (Fig. 11), 441. 
 
 dichotomy, 19 (Fig. 9). 
 Scutellum, 477 (Fig. 292). 
 Scutiform leaf, 377. 
 Secondary bast, 139, 143. 
 
 conjunctive tissue, 144. 
 
 cortical tissue, 149, 154. 
 
 members, 8, 132. 
 
 sclerenchyma, 140. 
 
 tegumentary tissue, 149, 151. 
 
 tissues, differentiation of, 145. 
 formation of, 137. 
 
 tracheal tissue, 140. 
 
 wood, 140 (Fig. 111). 
 
 wood-parenchyma, 140. 
 Secretion, 166. 
 Secretum, 101 (Fig. 82). 
 Sectile pollinium, 504. 
 Seed, 53, 62, 394, 414 (Fig. 245), 431. 
 Segmentation of apical cell, 104 
 
 (Figs. 85, 86). 
 Segmentation of body, 3. 
 Self-pollination, 409. 
 Semi-amplexicaul, 30. 
 Sensitive petiole, 175 ^Fig. 127). 
 
 plant, 174 (Fig. 126), 212, 221, 
 
 226. 
 
 Sepal, 58, 175, 443. 
 Septate body, 63. 
 
 Septicidal dehiscence, 475 (Fig. 289). 
 Septifragal dehiscence, 475 (Fig. 
 
 289)T 
 
 Septum, 1, 63, 84. 
 Serrate, 35, 37. 
 Sessile, 32 (Fig. 20), 55, 439. 
 Seta, 54, 315, 319, 337 (Figs. 208, 
 
 211). 
 
 of Carex, 493. 
 Sex, 231. 
 Sexual form, 2. 
 
 organs, 60. 
 
 process, 50, 232. 
 
 system, 233. 
 Sexuality, 230. 
 Shield, 261.
 
 MORPHOLOGY, ANATOMY, AN'D PHYSIOLOGY. 
 
 595 
 
 Shoot, 3, 22. 
 Sieve-plates, 94. 
 
 -tissue, 94 (Figs. 74, 75), 165. 
 
 -tubes, 94. 
 Silicon. 189, 193. 
 Silicula, 474, 535 (Fig. 348). 
 Siliqua, 474, 535 (Fig. 348). 
 Simple conidiophore, 279, 291 (Fig. 
 170). 
 
 hair, 46 (Fig. 31). 
 
 leaf, 35. 
 
 inflorescences, 439, 441. 
 
 sporophore, 54, 285 (Fig. 165). 
 Simultaneous whorl, 10. 
 Sleep-movements, 213. 
 Sliding growth, 147. 
 Sodium, 189, 193. 
 Soft bast. 143. 
 Soredium, 306 (Fig. 186). 
 Sorosis, 472, 501 (Fig. 311). 
 Sorus, 52, 348. 
 Spadix, 439. 
 Spathe, 439. 
 Species, 235. 
 Spermatium, 242, 272 (Fig. 160), 278, 
 
 292, 300. 
 
 Spermatozoid, 59, 241 (Figs. 147, 150, 
 158), 311 (Figs. 192, 193), 351 
 (Fig. 222), 407. 
 Spermogonium, 292, 300 (Fig. 178), 
 
 305 (Fig. 185). 
 Sphaerocrystal, 83 (Fig. 59). 
 Spicate capitulum, 441. 
 
 raceme, 441. 
 Spike, 439 (Fig. 259). 
 Spikelet, 439. 
 Spine, 42 (Fig. 29), 112. 
 Spiral vessels, 74 (Fig. 44). 
 Spire, 14. 
 Spongy parenchyma, 114 (Fig. 92), 
 
 172. 
 
 Spontaneous movement, 206. 
 Sporangium, 51, 243, 278, 374, 396, 
 
 Spore, 2, 50, 230. 
 
 asexually produced, 51, 230. 
 
 development of, 85. 
 
 -reproduction, 50, 227, 230. 
 
 -sac, 338. 
 
 sexually produced, 58, 230. 
 Sporidium, 299, 300 (Figs. 179, 181). 
 Sporocarp, 373 (Figs. 224, 225). 
 Sporogonium,309, 315 (Fis- 196), 319, 
 
 337 (Figs. 206. 208-11). 
 Sporophore. 51, 54, 279, 302. 
 Sporophyll, 43, 51, 55, 56, 176, 348, 
 
 395, 421. 
 
 Sporophyte, 2, 229. 
 Spur, 455. 
 Spurious fruit. 414, 471. 
 
 Spurious tissue, 88. 
 
 whorl, 11. 
 Stamen, 56, 395. 
 Staminate flower, 56, 395, 459. 
 Staminode, 462. 
 Starch, 79, 187, 201. 
 
 -grains, 78 (Fig. 58). 
 -sheath, 185. 
 Stearin, 187. 
 Stele, 101, 116. 
 Stem, 3, 27. 
 
 function of, 169. 
 herbaceous, 27. 
 monostelic, 102, 117. 
 polystelic, 117. 
 -tendril, 27 (Fig. 15), 171. 
 trunk, 27. 
 
 twining, 27 (Fig. 15), 171. 
 winged, 28. 
 
 Stereom, 92, 120 (Fig. 98), 164. 
 Sterigma, 291, 292, 300, 303 (Fig. 
 
 184). 
 
 Stichidium, 271 (Fig. 159). 
 Stigma, 395, 467 (Fig. 283). 
 Stimulus, 211, 222. 
 Stipe, 302. 
 Stipel, 31. 
 
 Stipule, 30 (Fig. 19), 42. 
 Stock, 229. 
 Stolon, 26. 
 Stomata, 107 (Figs. 88, 89) 
 
 function of, 163, 179. 
 Stomium, 364 (Fig. 215). 
 Stratification of cell-wall 74 (Fig. 
 
 46). 
 
 Streaming of protoplasm, 206. 
 Striation of cell-wall, 74 (Fig. 50). 
 Stroma, 291 (Fig. 176). 
 Strophiole, 416. 
 Strychnin, 186. 
 Style, 395, 466 (Fig. 283). 
 Sub-hymenial layer, 303 (Fig. 183). 
 Successive whorls, 10. 
 Succulent fruits, 475. 
 Succubous leaves, 326 (Fig. 201). 
 Sucroses, 187. 
 Sugars, 187, 201. 
 Sulphur, 188, 191. 
 Superficial placentation, 468. . 
 
 Superior ovary. III. 
 Superposed members, 13, 446. 
 Supply of energy, 194. 
 Suppression. 1".-'. 
 
 Suspensor, 347, 887, 393 (Fig. 284), 
 401 (Figs. 238, 239), 425 (Figs, 
 249, 250). 
 Svconus, 472. 
 Symbiosis, 190. -J7:.. 
 Symmetry of body, 4 (Figs. 1,2). 
 of flower, 458 (Figs. 269-278).
 
 596 
 
 INDEX, PART I. 
 
 Sympodium, 19, 519. 
 Synangium, 52, 349, 389. 
 Syncarpons, 465 (Fig. 281), 472. 
 Syncyte, 64. 
 
 Synergidaj, 408 (Fig. 242). 
 Syngenesious anthers, 462. 
 Systems of classification, 233. 
 Systole, 206. 
 
 Tangential longitudinal section, 4. 
 
 Tannin, 187. 
 
 Tapetum, 53, 363, 396, 463. 
 
 Tap-root, 44, 419. 
 
 Tartaric acid, 187. 
 
 Tegumentary tissue -system, 101. 
 
 function of, 162. 
 
 primary, 106. 
 
 secondary, 149. 
 
 Teleutospore, 299 (Figs. 178, 179). 
 Temperature, 160. 
 Tendril, 27 (Fig. 15), 41 (Fig. 19), 
 
 171, 175, 212. 
 
 Tentacle, 48 (Figs. 33, 34), 189. 
 Terminal bud, 11. 
 Termination of A T ascular bundle, 
 
 130. 
 
 Tern ate, 37 (Fig. 23). 
 Testa, 415. 
 Tetracyclic, 450. 
 Tetradynamous, 462, 535. 
 Tetrasporangium, 244. 
 Tetraspore, 244, 271 (Fig. 159). 
 Thalloid shoot, 22. 
 Thallophyte, 3. 
 Thallus, 3, 22, 132, 237. 
 Theca of Bryophyta, 52, 54, 337 
 (Figs. 208-210). 
 
 of anther, 463. 
 Thein, 186. 
 Theobromin, 186. 
 Thorn, 27 (Fig. 16), 171. 
 Tissue, 65, 88. 
 
 aqueous, 115. 
 
 conjunctive, 116, 118, 140. 
 
 cuticularised, 91 (Fig. 69). 
 
 embryonic, 90. 
 
 forms of, 90. 
 
 functions of, 162. 
 
 glandular, 96 (Figs. 76-82), 147, 
 166. 
 
 ground-, 101, 110. 
 
 heterogeneous, 65. 
 
 homogeneous, 65. 
 
 permanent, 90. 
 
 prosenchymatous, 90. 
 
 sclerenchymatous, 92 (Fig. 70), 
 164. 
 
 pecondary, 137 (Figs. 108-117). 
 
 sieve-, 94 (Figs. 74, 75), 165. 
 
 spurious, 88. 
 
 Tissue-systems, 101. 
 
 tegumentary, 101, 149, 162. 
 
 thick-walled parenchymatous, 
 91. 
 
 thin-walled parenchymatous, 
 90 (Fig. 69), 163. 
 
 tracheal, 93 (Fig. 73), 121, 164. 
 
 vascular, 121, 126. 
 Torus of flower, 55, 443. 
 Trabecute, 52, 357 (Fig. 213). 
 Tracheae, 94 (Fig. 73). 
 Tracheal tissue, 93, 140, 164. 
 Tracheid, 93 (Fig. 73). 
 Trama, 303 (Fig. 183). 
 Transfusion-tissue, 119, 420. 
 Transition from root to stem, 128. 
 Transmission of stimuli, 221. 
 Transpiration, 179. 
 
 -current, 181, 183. 
 Transverse section, 4. 
 Trichogyne, 61, 242, 259 (Fig. 148), 
 272 (Figs. 160, 161), 291 (Fig. 
 172). 
 
 Trimorphic flowers, 412. 
 Tripinnate, 35. 
 Truncate, 37. 
 Trunk, 27. 
 
 Tuber, 25 (Fig. 13), 505 (Fig. 317). 
 Tubercles of roots, 191. 
 Tuberous root, 45. t 
 Tumid, 28. 
 Turgid, 159. 
 Turgidity, 159, 179, 225. 
 Twining of climbing-stems, 223. 
 
 of tendrils, 212. 
 Tyloses, 94. 
 Tyrosin, 186, 199. 
 
 Umbel, 440 (Fig. 259), 548. 
 Umbellule, 440. 
 Umbo, 435. 
 Uniaxial, 23, 438. 
 Unijugate, 35. 
 Unilocular ovary, 465. 
 
 sporangium, 52. 
 Unisexual, 61, 395. 
 Unit of protoplasm, 63. 
 Unseptate body, 63. 
 Uredospore, 299 (Fig. 178). 
 Urn, 343. 
 Utriculus, 493 (Fig. 304). 
 
 Vacuole, 66 (Fig. 36). 
 
 contractile, 206. 
 Vaginula, 315. 
 
 Vallecular cavities, 383 (Fig. 230). 
 Valve of Diatoms, 265. 
 
 of fruits, 475. 
 Valvular dehiscence of anther, 463.
 
 MORPHOLOGY, ANATOMY, AND PHYSIOLOGY. 
 
 597 
 
 Variation, movements of, 207. 
 
 in direction of growth, 209. 
 
 in rate of growth, 208. 
 Variety, 235. 
 Vascular bundles, 121 (Figs. 99-105). 
 
 tissue-system, 101, 121. 
 Vegetative cell, 393, 406. 
 
 reproduction, 49, 227. 
 
 reproductive organs, 49, 228. 
 Velamen, 93, 106 (Fig. 87). 
 Velum, 302 (Fig. 182), 356 (Fig. 213). 
 Venation, free, 38 (Fig. 24). 
 
 furcate, 38. 
 
 parallel, 38 (Fig. 25). 
 
 reticulate, 39 (Fig. 26). 
 Venter, 311, 350. 
 Ventral, 7. 
 
 canal-cell, 311 (Fig. 194). 
 
 scales, 319. 
 
 suture, 465. 
 Vernation, 43, 211. 
 Versatile anther, 461 (Fig. 276). 
 Verticillaster, 442. 
 Vessel, 94, 147. 
 Vexillum, 557 (Fig. 369). 
 Vital functions of the tissues, 162. 
 Vittse, 549 (Fig. 361). 
 Volva, 303. 
 
 Wart, 48. 
 
 Waste products, 158, 201. 
 Water-culture, 192. 
 Water, absorption of, 178. 
 
 distribution of, 181. 
 
 -stoma, 97 (Fig. 89), 108. 
 Wax, 107. 
 
 Whorl, 10, 12 (Figs. 4, 5), 445. 
 Wing, of flower, 545. 
 
 of fruits, 473, 545 (Fig. 357). 
 
 Wood, 121/129, 139 (Figs. 112-115), 
 
 Wood-parenchyma, 129, 140. 
 Woody fibre, 140 (Fig. 111). 
 
 Xylem,121, 164. 
 
 Zinc, 189, 193. 
 Zonate tetraspores, 271. 
 Zoogloea-stage 281 (Fig. 163). 
 Zoospore, 51, 67, 72, 85 (Fig. 62), 230, 
 
 247, 257 (Fig. 147), 201. ->-i 
 
 (Fig. 169> 
 
 Zygomorphic symmetry, 4, 7, 454. 
 Zygospore, 58, 240, 249, 254, 257, 277, 
 
 285 (Figs. 145, 146, 165, 166).
 
 PART II.- CLASSIFICATION AND NOMENCLATURE. 
 
 Abies, 422 (Fig. 247), 434 ! 
 
 (Fig. 255). 
 Abietineae, 434. 
 Acacia, 559 (Fig. 371). 
 Acer, 545 (Fig. 357). 
 Aceraceae, 513, 545. 
 Acer as, 506. 
 Acetabularia, 251 (Fig. i 
 
 141). 
 
 Achillea, 581 (Fig. 397). 
 Achlya, 289 (Fig. 169). 
 Aconitum, 465 (Fig. 281), 
 
 528 (Fig. 342), 530. 
 Acorus, 482 (Fig. 294). 
 Acrocarpse (Musci), 345. 
 Acrogynse (Hepaticse), 
 
 330. 
 
 Acrostichese, 361. 
 Actaea, 529. 
 Adder's-tongue Fern, 
 
 355. 
 Arliantum, 360, 366 (Fig. 
 
 219), 368 (Fig. 222), 
 
 371. 
 
 Adlumia, 534. 
 Adonis, 529. 
 Adoxa, 576. 
 
 JEcidiomycetes, 280, 298. 
 JEcidium, 300. 
 jEgopodium, 550. 
 jEsculus, 545 (Fig. 356). 
 jEthalium, 284. 
 jEthusa, 550. 
 Agapanthus, 498. 
 Agaricinae, 303. 
 Agaricus, 277, 301 (Fig. 
 
 182), 302 (Fig. 183). 
 Agave, 508. 
 Agavoideae, 508. 
 Agopyrum, 491. 
 Agrimonia, 555. 
 Agrostideae, 490. 
 Agrostis, 490. 
 Aira, 490. 
 Ajuga, 564. 
 Ajugoidese, c63. 
 Alaria, 265. 
 Alchemilla, 555. 
 Alder, 517. 
 
 Aldrovanda, 561. 
 
 Algse, 234, 237. 
 
 Alisma, 403 (Fig. 239), 
 
 495 (Fig. 306). 
 Alismacese, 481, 495. 
 Alismales, 481, 494. 
 Alkanet, 570. 
 All-good, 523. 
 AllioideEe, 498. 
 Allium, 461 (Fig. 277), 
 
 498. 
 
 All-seed', 532. 
 Almond-tree, 554. 
 Alnus, 518 (Figs. 328, 
 
 329). 
 
 Aloe, 498. 
 
 Alopecurus, 488, 490. 
 Alpine Hose, 573. 
 Alpinia, 502 (Fig. 313). 
 Alsineae, 532. 
 Alsophila, 361, 372. 
 Althsea, 541 (Fig. 352). 
 Alyssinese, 537. 
 Alyssum, 537. 
 Amanita, 303 (Fig. 182). 
 Amaryllidacese, 481, 507. 
 Amaryllidoideae, 507. 
 Amaryllis, 507. 
 Amelanchier, 557. 
 Amentales, 512, 517 (Fig. 
 
 327). 
 
 American Aloe, 508. 
 Ammi, 550. 
 Ammineae, 549. 
 Amomales, 481, 501. 
 Amorpha, 557. 
 Ampelidacese, 513, 547. 
 Ampelopsis, 547. 
 Amygdalus, 554. 
 Amylum Marantse, 503. 
 Anabsena, 245 (Fig. 136). 
 Anacharis, 500. 
 Anacrogynae, 329. 
 Anagallis, 572. 
 Ananas, 501 (Fig. 311). 
 Anaptychia, 305 (Fig. 
 
 185). 
 
 Anchusa, 569 (Fig. 383). 
 Andromeda, 573. 
 
 i Andropogon, 489. 
 
 i Andropogoneae, 489. 
 
 I Aneimia, 358, 372. 
 
 ! Anelaterese, 329. 
 
 ! Anemone, 528 (Fig. 342). 
 
 Anemoiiese, 527. 
 
 Aneura, 327, 329, 330. 
 
 Angelica, 550. 
 
 Angelicese, 550. 
 
 Angiopteris, 349, 355. 
 
 Angiospermae, 234, 438. 
 
 Angrsecum, 507. 
 
 Angustiseptse, 537. 
 
 Antennaria, 581. 
 
 Anthemideae, 580. 
 
 Aiithemis, 581. 
 
 Anthericum, 498. 
 
 Anthoceros, 330 (Fig. 
 203). 
 
 Anthocerotaceae, 330. 
 
 Anthoxanthuro, 489. 
 
 Anthriscus, 550. 
 
 Anthurium, 483. 
 
 Arithyllis, 558. 
 
 Antiaris, 515. 
 
 Antirrhinum, 564 (Fig. 
 378). 
 
 Antirrhoidese, 564. 
 
 Apera, 490. 
 
 Aphanomyces, 289. 
 j Apiocystis, 248. 
 i Apium, 550. 
 
 Aplanes, 289. 
 
 Apple-tree, 556. 
 
 Apricot. 555. 
 
 Aquilegia, 529 (Fig. 343). 
 
 Arabideae, 537. 
 
 Aracea-, 481. 482. 
 
 Arachis, 558. 
 
 Arales, 481, 482. 
 
 Araliaceae, 513. W). 
 
 Arbutoideae, 573. 
 
 Arbutus, 573. 
 
 Archangelica, 550. 
 
 Arctium, 581. 
 
 Arctostaphylos, 573. 
 
 Arcyria, 284 (Fig. 164). 
 ; Areca, 486 (Fig. 298). 
 i Arenaria 532.
 
 CLASSIFICATION AND NOMENCLATURE. 
 
 590 
 
 Aria, 557. Awl-wort, 537. 
 
 Bittersweet, 568. 
 
 Arisarum, 482, 484. Azalea. 579. 
 
 Blackberry, 556 (Fig. 
 
 Aristolochia 412 (Fig. Azolla, 373, 380. 
 
 368). 
 
 243), 524. 
 
 
 Black Bryony, 500. 
 
 Aristolochiaceae, 512, 524. 
 
 Bacillus, 281 (Fig. 163). 
 
 Black Pine, J:',\ 
 
 Arraeria, 572. 
 
 Bacterium, 281 (Fig. 162). 
 
 Black Thorn, 554 
 
 Armillaria, 303. 
 
 Ballota, 563. 
 
 Bladder-Fern, 372. 
 
 Arnica, 580 (Fig. 396). 
 
 Balm, 563. 
 
 Blaeberry, 573. 
 
 Arnoseris, 582. 
 
 Balsaminacese, 513, 543. 
 
 Blasia, 825, 330. 
 
 Aroidese, 483. 
 
 Bamboo, 492. 
 
 Blerhnum, 359, 371. 
 
 Arrhenatherum, 490. 
 
 Bambusa, 486 (Fig. 299), 
 
 Blue bell, 497. 
 
 Arrow-grass, 495. 
 
 492. 
 
 Blue-bottle, 581. 
 
 Arrow-head, 495. 
 
 Bambusese, 492. 
 
 Blyttia, 328. 
 
 Arrow-root, 502. 
 
 Banana, 502. 
 
 Bog-Asphodel, 498. 
 
 Artemisia, 580 (Fig. 397). 
 
 Baneberry, 529. 
 
 Bog-bean, 570. 
 
 Artichoke, 581. 
 
 Bangia, 272. 
 
 Bog-Orchis, 507. , 
 
 Artocarpus, 515. 
 
 Bangiaceae, 271. 
 
 Bog-Rush, 492. 
 
 Arum, 483 (Fig. 295). 
 
 Banyan, 515. 
 
 Bohmeria, 515. 
 
 Arumlinaria, 492. 
 
 Barbarea, 537. 
 
 Boletus, 303. 
 
 Asarabacca, 524. 
 
 Barberry, 531. 
 
 Borage, 570. 
 
 Asarales, 512, 524. 
 
 Barbula, 339, 345. 
 
 Boraginacese, 513, 569. 
 
 Asarum, 524 (Fig. 338). 
 
 Barley, 492. 
 
 Borago, 570. 
 
 Ascobolus, 278, 290. 
 
 Bartsia, 565. 
 
 Borecole, 537. 
 
 Ascolichenes, 306. 
 
 Basidiolichenes, 306. 
 
 Boschia, 3-JI. 
 
 Ascomycetes, 280, 290. 
 
 Basidiomycetes, 280, 301. 
 
 Botrychium, 354 (Fig. 
 
 Ascophyllum, 268. 
 
 Bastard Toad-flax, r,-_>r>. 
 
 212). 
 
 Ash, 570. 
 
 Batatas, 567. 
 
 Botrydium, 251 (Fig. 
 
 Asparagoideae, 499. 
 
 Batrachospermum, 272. 
 
 144). 
 
 Asparagus, 499. 
 
 Bauhinia, 559. 
 
 Botryococcus, 248. 
 
 Aspergillus, 291. 
 
 Bean, 559. 
 
 Botrytis, 291. 
 
 Asperula, 575. 
 
 Bearberry, 573. 
 
 Brachypodium, 491. 
 
 Asphodeloideae, 498. 
 
 Bed-straw, 575. 
 
 Brachythecium, 346. 
 
 Asphodelus, 498. 
 
 Beech, 520. 
 
 Bracken, 371. 
 
 Aspidieae, 372. 
 
 Bee Orchis, 506. 
 
 Brasenia. r>:il. 
 
 Aspidium, 361 (Fig. 215), 
 372. 
 
 Beetroot, 523. 
 Belladonna Lily, 507. 
 
 Brassica, 537 (Fig. 348). 
 Brassiceae, 537. 
 
 Asplenieae, 371. 
 
 Bcllis, 580. 
 
 Brazil Nut. .V.I. 
 
 Asplenium, 360(Fig. 214), 
 
 Bent-Grass, 490. 
 
 Bread-fruit, 515. 
 
 371. 
 
 Berbendaceae, 512, 531. 
 
 Briza, 491. 
 
 Aster, 579. 
 
 Berberis, 531. 
 
 Broccoli, 537. 
 
 Asterales, 513, 577. 
 
 Bergen ia, 560 (Fig. 372). 
 
 Brodissa, 498. 
 
 Asterocephalus, 578. 
 
 Bertholletia, 554. 
 
 Brome-Grass, 491. 
 
 Asteroideae, 579. 
 
 Beta, 523. 
 
 Bromeliaceae, 481, 500. 
 
 Astragalus, 558. 
 
 Betel-Palm, 485. 
 
 Bromus, 491. 
 
 Astrantia, 549. 
 
 Betony, 563. 
 
 Brookweed, r>7 
 
 Athyrium. 371. 
 
 Betula, 518. 
 
 Broom, 558. 
 
 Atragene, 528. 
 
 Betulaceae, 512, 517. 
 
 Broomrape, 566. 
 
 Atrichum, 339. 
 
 Biclens, 581. 
 
 Broussonetia. .M">. 
 
 Atriplex, 523. 
 
 Bilberry, 573. 
 
 Brussels-sprouts, 537. 
 
 Atropa, 568 (Fig. 382). 
 Aulacomnium, 334, 337. 
 
 Bindweed, 567. 
 Biophytum, 543. 
 
 Bryineae, 338, 842. 
 Bryonia, 551. 
 
 Aurantiese, 543. 
 
 Biota, 436 (Fig. 256). 
 
 Bryophyta, 234, 809. 
 
 Auricularia, 304. 
 
 Birch, 518. 
 
 Bryum. 884. 
 
 Auriculariege, 303. 
 
 Bird-Cherry, 555. 
 
 Buck-bean, 57' . 
 
 Autobasidiomycetes,305. 
 Autumn Crocus, 498. 
 
 Bird's-foot Trefoil, 558. 
 Bird's nest, 573. 
 
 Buckthorn, 547. 
 Buckwheat , :>-!l. 
 
 Avena, 490 (Fig. 302). 
 
 Bird's-nest Orchid, 507. 
 
 Blllborh..-!.-. -'^. 
 
 Aveneae, 490. 
 
 Birthwort, 524. 
 
 Bulgaria, 297. 
 
 Avens, 556. 
 
 Bitter or Seville Orange, 
 
 Bulgarieae, 2ii<. 
 
 Averrhoa,.543. 544. ' Bui lace, 555.
 
 600 
 
 IXDEX, PAKT II. 
 
 Bulrush, 484 ; 493. 
 Bupleurum, 550. 
 Burdock, 581. 
 Bur-reed, 484. 
 Butcher's Broom, 499. 
 Butomacese, 483,, 495. 
 Butomus, 398, 495 (Fig. 
 
 306). 496 (Fig. 307). 
 Butter-bur, 580. 
 Buttercup, 529. 
 Butterfly Orchis, 506. 
 Butterwort, 566. 
 
 Cabbage, 537. 
 Cabomba, 531. 
 Cabombeae, 531. 
 Caesalpinia, 559. 
 Caesalpiniese, 559. 
 Cakile, 538. 
 Cakilineae, 538. 
 Calabar Bean, 559. 
 Calamagrostis, 490. 
 Calamintha, 563. 
 Calamus, 485. 
 Calceolaria, 564. 
 Calendulese, 581. 
 Calendula, 581. 
 Calla, 483. 
 Callistephus. 580. 
 Callithamnion, 271. 
 Calloidese, 483. 
 Calluna, 573. 
 Calocera, 304. 
 Calothamnus, 553 (Fig. 
 
 365). 
 
 Caltha, 529. 
 Calyciflorse, 513, 547. 
 Calypogeia, 329. 
 Calystegia, 445; 567. 
 Camassia, 497. 
 Camelina, 537. 
 Camelineae, 537. 
 Campanales, 513. 574. 
 Campanula, 574 (Figs. 
 
 388, 389). 
 
 Campanulaceae, 513, 574. 
 Campion, 532. 
 Campy lospermese, 550. 
 Candytuft, 537. 
 Canna, 503 (Fig. 314). 
 Cannabinaceae, 512, 515. 
 Cannabis, 516. 
 Cannaceae, 502. 
 Canterbury-bell, 574. 
 Caprifoliaceae, 513, 576 
 
 (Fig. 391). 
 Capsella, 402 (Fig. 238), 
 
 537. 
 Capsicum, 568. 
 
 Caraway, 550. 
 Cardamine, 537. 
 Cardamom, 502. 
 Carduus, 581. 
 Carex, 493 (Fig. 304). 
 Caricoideae, 493. 
 Carlina, 581. 
 Carline Thistle, 581. 
 Carnation, 532. 
 Carob-tree, 559. 
 Carpmus, 519 (Fig. 332). 
 Carrot, 550. 
 Carthamus, 581. 
 Carum, 473 (Fig. 287), 
 
 549 (Fig. 362). 
 Carya, 522. 
 
 Caryophyllacese, 512,531. 
 Caryophyllales, 512, 531. 
 Cassia, 559 (Fig. 370). 
 Castanea, 521. 
 Castor-oil Plant, 527. 
 Catchfly, 532. 
 Catmint, 563. 
 Cat's Ear, 582. 
 Cat's-tail Grass, 490. 
 Caucalinese, 550. 
 Caucalis, 550. 
 Cauliflower, 537. 
 Cedar, 435. 
 Cedrus, 435. 
 Celandine, 529, 533. 
 Celastraceae, 513, 546. 
 Celastrales. 513, 546. 
 Celery, 550.' 
 Celsia, 564. 
 Celtis, 517. 
 Centaurea, 581. 
 Centaury, 570. 
 Centranthus, 577 (Fig. 
 
 393). 
 
 Cephaelis, 575. 
 Cephalanthera, 506. 
 Cephalantherese, 506. 
 Cerastium, 532. 
 Cerasus, 555. 
 Ceratodon, 316 (Fig. 197), 
 
 345. 
 
 Ceratonia, 559. 
 Ceratozamia, 432. 
 Cercis, 456 (Fig. 272), 
 
 559. 
 
 Cestreae, 569. 
 Ceterach, 372. 
 Cetraria, 307. 
 Chaerophyllum, 550. 
 Chsetocladieae, 285. 
 Chsetomorpha, 252. 
 Chsetopteris, 239 (Fig. 
 
 133). 
 Chamsecj'paris, 436. 
 
 Chamsedorea, 485 (Fig. 
 
 297). 
 
 Chamaeorchis, 506. 
 Chamserops, 485. 
 Chamomile, 580. 
 Chantransia, 272. 
 Chara, 260 (Figs. 149, 
 
 150, 151). 
 
 Characese, 246, 260. 
 Characium 248. 
 Charese, 263. 
 Charlock, 537. 
 Charoidese, 248, 260. 
 Cheilanthes, 362, 371. 
 Cheiranthus, 537. 
 Chelidonium, 533 (Fig. 
 
 345). 
 
 Chelone, 564. 
 Chenopodiacese, 512. 522. 
 Chenopodiales, 512, 522. 
 Chenopodium, 523 (Fig. 
 
 336). 
 
 Cherry Laurel, 555. 
 Chervil, 550. 
 Chick weed, 532. 
 Chickweed Winter- 
 green, 572. 
 Chicory, 582. 
 Chili Pepper, 569. 
 Chiloscyphus 324. 
 China Aster, 580. 
 Chives, 498. 
 Chlamy domo n a d a c e se, 
 
 249. 
 
 Chlamydomonas, 249. 
 Chlora, 570. 
 Chlorideae, 491. 
 Chlorochytrium, 248. 
 Chlorococcum, 2 is. 
 Chlorophyceae, 238, 246. 
 Chlorospheera. 24s. 
 Chondriopsis, 272. 
 Chorda, 265. 
 Chordaria, 266. 
 Christmas Rose, 529. 
 Chroococcacea?. 2 1 t. 
 Chrysanthemum, 580. 
 Chrysodium, 361. 
 Chrysosplenium, 560. 
 Cibotium, 372. 
 Cicendia, 570. 
 Cichorieae, 581. 
 Cichorium, 582. 
 Cicuta, 550. 
 Cinchona, 575. 
 Cinchonese, 575. 
 Cinquefoil, 556. 
 Circaa, 454 (Fig. 270), 
 
 552. 
 Cistaceae, 512, 538.
 
 CLASSIFICATION AND NOMENCLATURE. 
 
 601 
 
 Cistus, 538. 
 
 Colchicese, 498. I Cotton. 541. 
 
 Citron, 544. 
 Citrullus, 551. 
 
 Colchicoideae, 498. 
 Colchicum,474(Fig.288), 
 
 Cotton-Grass, 493. 
 Conch-Gran, 491. 
 
 Citrus, 544 (Fig. 355). 
 Cladonia, 307. 
 Cladophora, 252 [Fig. 
 
 497 (Fig. 309). 
 Coleanthus, 488. 
 Coleochaete, 246, 259 
 
 Cowberry, 573. 
 Cow-Parsley, 550. 
 Cow-Parsnip, 550. 
 
 143). 
 
 (Fig. 148). 
 
 Cowslip. r>7J. 
 
 Cladophoraceae, 246, 252. 
 
 Coleochae.taceae, 253, 258. 
 
 Cow-tree, 515. 
 
 Cladophorese, 252. 
 
 Coleosporium, 299. 
 
 Cow Wheat, 565. 
 
 Cladostephus, 264, 266 
 
 Coleus, 563. 
 
 Crambe, 538. 
 
 (Figs. 153, 154). 
 
 Collabium, 504. 
 
 Cranberrv, 573. 
 
 Clary, 5(33. 
 
 Collema, 306 (Fig. 187). 
 
 Crane's- 1. 'ill. M2. 
 
 Classification of Algae, 
 
 Collemaceae, 306. Crassula, 561. 
 
 238. 
 
 Colt's Foot, 580. 
 
 Crassulacae, 513, 561. 
 
 of Angiospermae, 476. 
 
 Columbine, 529. 
 
 Crat83gus, 556. 
 
 of Ascomycetes, 294. 
 of Basidiomycetes, 305. 
 
 Colza, 537. 
 Comarum, 556. 
 
 Creeping Bugle, 564. 
 Crepis, 582. 
 
 of Bryophyta, 317. 
 of Chloropliyceae, 247. 
 
 Comfrey, 569. 
 Common Basil, 563. 
 
 Cress, 537. 
 Crithmum, 550. 
 
 of Coniferaj, 434. 
 
 Common Bugloss, 570. 
 
 Crocoidese, 508. 
 
 of Dicotyledones, 512. 
 of Filicinse, 352. 
 of Fungi, 280. 
 
 Composite, 513, 579 
 (Fig. 395). 
 Conferva, 257. 
 
 Crocus, 508. 
 Cross-leaved Heath, 573. 
 Crowfoot, 529. 
 
 of Gymnospermae, 431. 
 
 Confervoidese, 248, 253. 
 
 Crown Imperial, 496. 
 
 of Hepatic*, 320. 
 
 Conifer*, 432. 
 
 Crucifera?, 512, 535 (Figs. 
 
 of Monocotyledones, 
 
 Conium, 548 (Fig. 361). 
 
 347, 348). 
 
 481. 
 
 Conjugatse, 247, 253, 254. 
 
 Cryptogamia. 2:il. 
 
 of Musci,340. 
 of Phseophycese, 264. 
 
 Conopodium, 550, 
 Convallaria, 499. 
 
 Cryptogrammc. ::7'J. 
 Cryptonemimi', 271. 
 
 of Plianerogamia, 418. 
 
 Convolvulacese, 513, 567. 
 
 Cuckoo-pint, 483. 
 
 of Phycomycetes, 285. 
 
 Convolvulus, 458 (Fig. 
 
 Cucubalus, 532. 
 
 of Plants, 233. 
 
 274), 567. 
 
 Cucumber, 551. 
 
 of Pteridophyta, 352. 
 Clavaria, 305. 
 
 Copper Beech, 521. 
 Coprinus, 277, 303. 
 
 Oucumis, 551 (Fig. 863). 
 Cucurbita, 397 (Fig. 235), 
 
 Clavariere, 303. 
 
 Coral linaceae, 272. 
 
 551 (Fig. 363). 
 
 Claviceps, 277, 290, 297 
 
 Coral lorhiza, 507. 
 
 Cucurbitaceae, 513, 551. 
 
 (Fig. 176). 
 
 Coral Boot, 507. 
 
 Cudweed, 581. 
 
 Cleistocarpae, 338, 343. 
 Clematis, 528, 556. 
 
 Corchorus, 540. 
 Cordyceps, 279, 296. 
 
 Cupressus, 436. 
 Cupressinae, 4W. 
 
 Closterium, 254 (Fig. 
 
 Cordyline, 498. 
 
 Cupressinese, 486. 
 
 144). 
 
 Coreopsis, 581. 
 
 Curcuma, 502. 
 
 Clostridium, 282. 
 
 Coriandreae, 550. 
 
 Currant, 561. 
 
 Clover, 558. 
 
 Coriandrum, 548 (Fig. 
 
 Cuscuta, 567 (Fig. 381). 
 
 Club Moss, 386. 
 
 361). 
 
 Cut-grass, 489. 
 
 Club Rush, 493. 
 
 Cork-oak, 520. 
 
 Cutleria, 265. 267. 
 
 Cluster Narcissus, 508. 
 
 Corn Cockle, r,:(-J. 
 
 Cutleneceae,2<>i. 2i.\ 
 
 Cluster Pine, 435. 
 
 Corn Flag, 509. 
 
 Cyanophvceae, 288, 244. 
 
 Cnicus, 581. 
 
 Corn-flower, 581. 
 
 Cyathea/361. ;72 
 
 Cobsea, 567. 
 
 Cornish Heath, 578. 
 
 Cyatheacese, 352. 872. 
 
 Coccus, 281 (Fig. 162). 
 Cochlearia, 537. 
 
 Cornish Money wort, 565. 
 Corn-salad, 577. 
 
 Cyathus, 804, ::.. 
 Cycadacese, 481. 
 
 Cock's Foot Grass, 491. 
 
 Coronilla, 558. 
 
 Cycas, 482 (Fijr. 258). 
 
 Coco-nut Palm, 485. 
 
 Corrigiola, 533. 
 
 Cyclamen. 572. 
 
 Cocos, 485. 
 
 Corsinia, 324. 
 
 Cydonia, 556. 
 
 Codium, 251. 
 
 Corsinie;*'. :vj|. 
 
 Cynara, 581. 
 
 Coelospermese, 550. 
 
 Corydalis, 534. 
 
 Cynarese, 581. 
 
 Cosnogonium, 306. 
 
 Corvlaceae, 512, 518. 
 
 Cynodon, 491. 
 
 Coffea, 575. 
 
 Corylus, 519 (Figs. 330, 
 
 Cynoglossum. .">7<i. 
 
 CofFeese, 575. 
 
 881). 
 
 Cyperace*, 4M. I!J. 
 
 Coffee-tree, 575. 
 
 Cotoneaster, 556. | Cyperus, 492.
 
 G02 
 
 INDEX, PART II. 
 
 Cypress, 436. 
 
 Diontea, 561. 
 
 Cypripedium, 505 (Figs. 
 
 Dioscoreacese, 481, 500. 
 
 315, 318). 
 
 Dioscorea, 500. 
 
 Cypripediince, 505. 
 
 Dioscoreales, 481, 500. 
 
 Cystopteris, 372. 
 
 Diotis, 581. 
 
 Cystopns, 287. 
 
 Diplocolobese, 536. 
 
 Cystoseira, 269. 
 
 Diplotaxis, 537. 
 
 Cytisus, 558. 
 
 Dipsacese, 513, 577. 
 
 
 Dipsacus, 578. 
 
 Daboecia, 573. 
 
 Disciflorse, 513, 541. 
 
 Dacryomvces, 304. 
 Dactylis. 491. 
 
 Discomycetes, 296. 
 Dock, 524. 
 
 Daffodil, 508. 
 
 Dodder, 567. 
 
 Dahlia. 581. 
 
 Dog's Mercury, 527. 
 
 Daisy, 580. 
 Damasonium, 495. 
 
 Dog's-tooth Grass, 491. 
 Dog's-tooth Violet, 496. 
 
 Dame's Violet, 537. 
 
 Dog-Violet, 538. 
 
 Damson, 555. 
 
 Doronicum, 580. 
 
 Dansea, 355. 
 
 Dothideacese, 296. 
 
 Dandelion, 582. 
 
 Draba, 537 (Fig. 348). 
 
 Dane wort, 576 
 
 Dracunculus, 484. 
 
 Daphne, 458 (Fig. 274). 
 
 Dracaena, 499. 
 
 Darnel, 491. 
 
 Dracsenoidese, 498. 
 
 Dasya, 272 (Fig. 159). 
 
 Dragon's Tree, 499. 
 
 Dasylirion, 499. 
 
 Dropwort, 554. 
 
 Date, 477 (Fig. 291). 
 
 Drosera, 561. 
 
 Date Palm, 485. 
 
 Droseracese, 561. 
 
 Datura, 569. 
 
 Dry as, 556. 
 
 Daturese, 569. 
 
 Duck-weed, 484. 
 
 Daucineae, 550. 
 
 Dudresnaya, 271. 
 
 Daucus, 550. 
 
 Durra, 489. 
 
 Davallia, 360 (Fig. 214). 
 
 Dwarf Elder, 576. 
 
 Deadly Nightshade, 569. 
 
 Dwarf Wheat, 492. 
 
 Dead Kettle, 563. 
 
 
 Delphinium, 457 (Fig. 
 
 
 273), 530. 
 
 Earth -almond, 558.. 
 
 Dendrobium, 507. 
 
 Echeveria, 561. 
 
 Dentaria, 537. 
 
 Echinocloa, 489. 
 
 Desmidieaa, 246, 254. 
 
 Echinophora, 550. 
 
 Desmids, 254 (Fig. 144). 
 
 Echinops, 581. 
 
 Desmodium, 558. 
 
 Echium, 569. 
 
 Dewberry, 556. 
 
 Ectocarpacese, 264. 
 
 Diandra?, 505. 
 
 Ectocarpus, 264, 266 (Fig. 
 
 Dianthus, 459 (Fig. 275), 
 
 155). 
 
 532. 
 Diarrhena, 488. 
 
 Eglantine, 554. 
 Elais, 486. 
 
 Diatomaceas, 263, 265. 
 
 Elaterese, 330. 
 
 Dicentra. 584 (Fig. 346). 
 
 Elder, 576. 
 
 Dicksonia, 360, 372. 
 
 Elecampane, 581. 
 
 Dicotyledones, 234, 509. 
 
 Eletteria, 502. 
 
 Dicranum, 345. 
 
 Elm. 516. 
 
 Dictanmus, 452 (Fig. 
 
 Elodea, 500. 
 
 268), 543 (Fig. 354). 
 
 Elymus, 492. 
 
 Dictyosphserium, 248. 
 Dictyosteliaceee, 284. 
 Didymium, 284 (Fig. 
 
 Elyna, 493. 
 Encalypta, 344. 
 Enchanter's Nightshade. 
 
 164). 
 
 552. 
 
 Diervilla. 577. 
 
 Endive, 582. 
 
 Digitalis, 564. 
 
 Endocarpon, 306. 
 
 Digitaria, 489. 
 
 Endospheera, 248. 
 
 Endosporete, 283. 
 English Wheat, 492. 
 Eiiteromorpha, '257. 
 EntyJoma, 801. 
 Ephedra. 437. 
 Epbemerum, 332, 339, 
 
 343 (Fig. 207). 
 Epilobium, 464 (Fig. 
 
 _ 280), 552 (Fig. 364). 
 Epimedium, 531. 
 Epipactis, 413 (Fig. 244), 
 
 506. 
 
 Epipogium, 506. 
 Equisetacese, 353, 380. 
 Equisetina?, 234. 358, !>0. 
 Equisetum, 380 (Fjgs. 
 
 227-230). 
 Eranthis, 529. 
 Eremascus, 278, 290, 293 
 
 (Fig. 171). 
 Eremurus. 498. 
 Ergot, 290, 297 (Fig. 17i). 
 Erica, 573 (Fig. 387). 
 Ericaceae, 513, 572. 
 Ericales, 513, 572. 
 Ericoidese, 573. 
 Erigeron, 580. 
 Eriobotrya, 557. 
 Eriophornm, 493. 
 Erodium, 542. 
 Eryngium, 549. 
 Erysimum, 587. 
 ErysipheJB, 278, 280, 295 
 
 (Fig. 173). 
 Erythrsea. 569 (Fig. 
 
 384). 
 
 Erythronium, 496. 
 Erythrotrichia. 27h. 
 Euastrum, 254 (Fig. 144). 
 Eucalyptus. 553. 
 Eugenia, 553. 
 Euonymus, 546. 
 Eupatoriese, 579. 
 Eupatorium, 57! *. 
 Euphorbia, 526 (Fig. 
 
 311). 
 
 Euphorbiacea\ 512. 526. 
 Euphorbiales, 512, 525. 
 Euphrasia. 565. 
 Eurhynchium, 346. 
 Eurotium, 290, 296 (Fig. 
 
 175). 
 
 Eusagus, 485. 
 Eusporangiatse, 354. 
 Evening Primrose. 552. 
 Evernia, 307. 
 Exidia, 304. 
 Exoascus, 294. 
 Exosporese, 284. 
 Eyebright, 565.
 
 CLASSIFICATION' AND NOMENCLATURE. 
 
 Fagaeeae. 512, 520. 
 
 Fungi, 234, 275. 
 
 Gnetum, 437. 
 
 Fagus, 520. 
 
 Furze, 558. 
 
 Goafs-beard, 582. 
 
 False Oat-grass, 490. 
 
 Fustic, 515. 
 
 Golden Hod, 580. 
 
 Fatsia, 550. 
 Feather-grass, 490. 
 
 Gagea, 498. 
 
 Gold-of-pleasure, 587. 
 Goody era, 507. 
 
 Fegatella, 324. 
 
 Gaillardia, 581. 
 
 Gooseberry, 561. 
 
 Fenugreek, 558. 
 
 Galactodendron, 515. 
 
 Goose-foot, 523. 
 
 Ferns, 359. 
 
 Galanthus, 507. 
 
 Gorse, 558. 
 
 Fern-Royal. 372. 
 
 Galegeae, 558. 
 
 Gossypium, 541. 
 
 Fescue-grass, 491. 
 
 Galeopsis, 563. 
 
 Gout- Weed, 550. 
 
 Festuca, 488, 491. 
 
 Galingale, 492. 
 
 Graminaceae, 481, 486. 
 
 Festuceae, 490. 
 Ficus, 515 (Fig. 324). 
 
 Galinsoga, 581. 
 Galium, 575. 
 
 Grape-Hyacinth, 4!i7. 
 Grape-Yinr. 547. 
 
 Field Poppy, 533. 
 Fig, 515. 
 Figwort, 565. 
 
 Galtonia, 497. 
 Gamopetalae, 513, 562. 
 Garlic, 498. 
 
 Graphidea?, 307. 
 Graphis, 308 (Fig. 190). 
 Grasses, 486. 
 
 Filago, 581. 
 
 Gasteromycetes, 303, 305. 
 
 Grass of Parnassus, c61. 
 
 Filices, 358. 
 
 Gaultheria, 573. 
 
 Grass- Wrack, 494. 
 
 Filicinse, 234, 352, 354. 
 
 Gean, 555. 
 
 Grateloupia. 271. 
 
 Filicinae Eusporangi- 
 
 Geaster, 305. 
 
 Gratiola, 564. 
 
 ata?, 352, 354. 
 
 Gelidiacese, 274. 
 
 Great Burnet. .",:>:.. 
 
 Filicime Leptosporangi- 
 
 Genista, 558. 
 
 <;ivcn-\v 1. K6. 
 
 atae, 352, 358. 
 
 Genistese, 558. 
 
 Grimmia, 345. 
 
 Fir, 435. 
 
 Gentian, 570. 
 
 Gromwell, 569. . 
 
 Fistulina, 304. 
 
 Gentiana, 570. 
 
 Ground Ivy, 563. 
 
 Flag, 508. 
 
 Gentianaceae, 513, 570. 
 
 Ground-nut. :,.\s. 
 
 Flax, 542. 
 
 Gentian ales, 513, 570. 
 
 Groundsel, 580. 
 
 Flax Dodder, 567. 
 
 Gentianeae, 570. 
 
 Guelder Eose, 576. 
 
 Fleabane, 581. 
 
 Georgiaceae, 343. 
 
 Guttiferales, 512, 539. 
 
 Floridese, 271. 
 
 Geraniaceae, 513, 542. 
 
 Guttulinese, 284. 
 
 Flowering Hush, 496. 
 Fly Orchis, 506. 
 
 Geraniales, 513, 541. 
 Geranium, 542 (Fig. 353). 
 
 Gymnadenia, 505 (Fig. 
 317). 
 
 Fcenicuhini.548{Fig.361). 
 
 Geum, 556. 
 
 Gymnadenieae, 506. 
 
 Fontinalis.333(Fig.204), 
 
 Gigartinaceae, 273. 
 
 Gymnoascese, 294. 
 
 344 (Fig. 209). 
 
 Gilia, 567. 
 
 Gymnoascus, 290, 294. 
 
 Fool's-Parsley, 550. 
 
 Ginger, 502. 
 
 Gymnogramme. 364. 
 
 FI >rir*'t-me-not, 569. 
 
 Ginkgo, 406 (Fig. 240), 
 
 Gj'mnospermse, 234, 419 
 
 F.<ombronia. 825, 330. 
 
 437. 
 
 Gymnostomuii). :\\ 1. 
 
 Foxglove, 565. 
 
 Gladiolus, 509. 
 
 Gynerium, 491. 
 
 Foxtail-grass, 490. 
 
 Gladioleee, 509. 
 
 Gyromitra, 297. 
 
 Frasaria. 556. 
 
 Glass- Wort, 528. 
 
 
 Fraxinus, 570 (Fig. 385). 
 
 Glaucium, 533. 
 
 Habenaria, 506. 
 
 French Bean, 559. 
 
 Glaux, 572. 
 
 Haematococcus, 246, 249. 
 
 Fritillaria, 496. 
 
 Gleditschia, 559. 
 
 Haematox3-lon, 559. 
 
 Frog's Bit, 500. 
 
 Gleichenia/872. 
 
 Hair-grass, 490. 
 
 Frullania, 324, 326 (Fig. 
 
 tjrleicheniacese, 352, 361, 
 
 Halarachnion, 271. 
 
 202), 330. 
 
 372. 
 
 Halidrys, 269. 
 
 Fucaceae, 265, 268. 
 
 Globba, 502. 
 
 iraL.sphsera, 248. 
 
 Fuchsia, 454 (Fig. 270), 
 
 Globbese, 502. 
 
 HalymeniA, 271, 278. 
 
 552 (Fig. 364). 
 
 Globe-flower, 529. 
 
 Haplomitrium, 324, 330. 
 
 Fucus, 269 (Fig. 156), 
 
 Globe-Thistle, 581. 
 
 Iliinl K.-rii. :;:.!'. ::71. 
 
 27n Figs. 157, 158). 
 Fuligo. -JN(. 
 
 Glceocapsa, 244 (Fig. 134). 
 Gloeosiphonia, 271. 
 
 Hard Wh.-at. !"_'. 
 Hare-bell, 574. 
 
 Fumaria. 534. 
 
 Gloriosa, 498. 
 
 Hart's-tongue Fern, 371. 
 
 Fumariaceae, 512, 533. 
 
 Glumales, 481, 486. 
 
 Havers, 490. 
 
 Fumitorv, 584. 
 
 Glumiflora?, 481, 486. 
 
 Hawks-beard, 582. 
 
 Fonaria, 310 (Fig. 191), 
 
 Glyceria. li'i. 
 
 Haw kbit, 582. 
 
 311 (Fig. 192), 313 
 
 Glycyrrhiza, 558. 
 
 Hawkweed, 582. 
 
 (Figs. 195, 196), 344 
 
 Gnaphalium, 581. 
 
 Hawthorn, 556. 
 
 (Figs. 208, 210). | Gnetacese, 431, 437. 
 
 Hazel, 519.
 
 604 
 
 INDEX, PART II. 
 
 Heart's-ease, 538. 
 
 Hormotila, 248. 
 
 Ipecachuana, 575. 
 
 Heather, 573. 
 
 Hornbeam, 519. 
 
 Iridacese, 481, 508. 
 
 Hedera, 550. 
 
 Horned Pondweed, 494. 
 
 Iridioideas, 508. 
 
 Hedge-Mustard, 537. 
 
 Horned Poppy, 533. 
 
 Iris, 508 (Fig. 319). 
 
 Hedychiese, 502. 
 
 Horse Chestnut, 545. 
 
 Irish Heath, 573. 
 
 Hedvchium, 502 (Fig. 
 
 Horse-radish, 537. 
 
 Isaria, 291. 
 
 313). 
 
 Horse-shoe Vetch, 558. 
 
 Isatidese, 537. 
 
 Hedysarese 558. 
 
 Horse-tail, 380. 
 
 Isatis, 537 (Fig. 348). 
 
 Heleiiioideae, 581. 
 
 Hottonia, 572. 
 
 Isnardia, 552. 
 
 Heienium, 581. 
 
 Hound's-tongue, 570, 
 
 Isoetaceae, 352, 355. 
 
 Helianthemum, 538. 
 
 House-leek, 561. 
 
 Isoetes, 348, 355 (Fig. 213). 
 
 Helianthoideae, 581. 
 Helianthus, 581. 
 
 Humulus, 516 (Fig. 325). 
 Hutchinsia, 537. 
 
 Ivy, 550. 
 Ixioidese, 509. 
 
 Heliconia, 501. 
 
 Hyacinth, 496 (Fig. 308). 
 
 
 Heliconieae, 501. 
 
 Hyacinthus, 497. 
 
 Jacob's Ladder, 567. 
 
 Helleboreae, 529. 
 
 Hydneae, 303. 
 
 Jambosa, 553 (Fig. 366). 
 
 Helleborines, 506. 
 
 Hydnum, 305. 
 
 Jasione, 574. 
 
 Helleborus,469(Fig. 284), 
 
 Hydrales, 481, 500. 
 
 Jasrninum, 571. 
 
 529 (Fig. 342). 
 
 Hydrilleae, 500. 
 
 Jerusalem Artichoke, 
 
 Helminthora, 271. 
 
 Hydrocharidaceae, 481, 
 
 581. 
 
 Helminthostachvs, 354. 
 
 500. 
 
 Jonquil, 508. 
 
 Helvella, 297. ' 
 
 Hydrocharis, 500. 
 
 Judas-tree, 559. 
 
 Helvellacese. 296. 
 
 Hydrocotyle, 549. 
 
 Juglandaceae, 512, 521. 
 
 Hemerocallis, 498. 
 
 Hydrocotyleae, 549. 
 
 Juglans, 521 (Fig. 334). 
 
 Hemitelia, 372. 
 
 Hydrodictyacese, 250,253. 
 
 Juncaceee, 481, 499. 
 
 Hemlock, 550. 
 
 Hydrodictyon, 253. 
 
 Juncaginaceae, 481, 495. 
 
 Hemp, 516. 
 
 Hydropterideae, 373. 
 
 Juncus, 499. __ 
 
 Hemp-Agrimony, 579. 
 Hemp-Nettle, 563. 
 
 Hylocomium, 346. 
 Hymenogaster, 304. 
 
 June Berry, 557. 
 Jungermannia, 330. 
 
 Henbane, 569. 
 
 Hymenomycetes, 305. 
 
 Jungermanniaceae, 320, 
 
 Hepaticae, 234, 317, 320. 
 
 Hymenophyllaceae, 352, 
 
 324. 
 
 Heracleum, 455 (Fig. 271), 
 
 371. 
 
 Juniper, 436. 
 
 548 (Fig. 361). 
 
 Hymenophyllum. 361, 
 
 Juniperinae, 436. 
 
 Herb Christopher, 529. 
 
 371. 
 
 Juniperus, 433, 436 (Fig. 
 
 Herb Paris, 499. 
 
 Hymeriostomum, 344. 
 
 257). 
 
 Herb Robert, 542. 
 
 Hyoscyamus, 569. 
 
 Jute, 540. 
 
 Herminium, 506. 
 
 H3 r pecoum, 534. 
 
 
 Herniaria, 533. 
 
 Hypericaceae, 512, 539. 
 
 Kalmia, 573. 
 
 Hesperis, 537. 
 
 Hypericum, 539 (Fig. 
 
 Kaulfussia, 355. 
 
 Hevea, 527. 
 
 350). 
 
 Kerria, 554. 
 
 Hibisceae, 541. 
 
 Hypnum, 346. 
 
 Kidney- Vetch, 558. 
 
 Hibiscus, 541. 
 
 Hypochaeris, 582. 
 
 Knapweed, 581. 
 
 Hickory, 522. 
 
 Hypocreaceas, 296. 
 
 Knautia, 578. 
 
 Hieracium, 582. 
 
 Hyssop, 563. 
 
 Knawel, 533. 
 
 Hildenbrandtia, 275. 
 
 Hyssopus, 563. 
 
 Kniphofia, 49a 
 
 Himanthalia, 268. 
 
 Hysterium, 279. 
 
 Kobresia, 493. 
 
 Hippocrepis, 558. 
 
 
 Koaleria, 491. 
 
 Holcus, 490. 
 
 Iberis, 537. 
 
 Kohl-rabi, 537. 
 
 Holly Fern, 372. 
 
 Iceland Moss, 307. 
 
 
 Hollyhock, 541. 
 
 Illecebracese, 533. 
 
 Labiatiflorae, 581. 
 
 Holosteum, 532. 
 
 Illecebrum, 533. 
 
 Labiatae, 513, 562. 
 
 Honesty, 537. 
 
 Illicieae, 530. 
 
 Laboulbeniaceae, 278, 
 
 Honey-grass, 490. 
 
 Illicium, 472 (Fig. 286), 
 
 291. 
 
 Honeysuckle, 576. 
 
 530. 
 
 Lactarius, 276. 
 
 Hooped-Petticoat Daffo- 
 
 Impatiens, 543. 
 
 Lactuca, 582. 
 
 dil, 507. 
 
 Imperatoria, 550. 
 
 Ladies' Fingers, 558. 
 
 Hop, 516 (Fig. 325). 
 
 Indigo, 558. 
 
 Lady Fern, 371. 
 
 Hordese, 491. 
 Hordeum, 492. 
 
 Indigofera, 558. 
 Inula, 581. 
 
 Lady's Mantle, 555. 
 Lady's Slipper, 505. 
 
 Horehound, 563. 
 
 Inuloideae, 581. 
 
 Lady's Tresses, 506.
 
 CLASSIFICATION AND NOMENCLATURE. 
 
 600 
 
 Lamb's-Jettuce, 577. 
 
 Liliales, 481, 496. 
 
 Lysimachia, 572. 
 
 Lamb's Succory, 582. 
 
 Lilioideae, 496. 
 
 Lythracea?, 518, 553. 
 
 Lamiales, 513, 562. 
 
 Lilium, 461 (Fig. 276), 
 
 Lythrum, 553. 
 
 Laminaria, 265. 
 
 496. 
 
 
 Laminariaceae, 265. 
 Lam mm, 562 (Fig. 376), 
 
 Lily, 467 (Fig. 238), 496. 
 Lily of the Valley, 499. 
 
 Mace. 415. 
 Madura, 515. 
 
 563. 
 
 Lime, 544. 
 
 Macrocystis, 268. 
 
 Lapsana, 582. 
 
 Lime-tree, 540. 
 
 Madder, 575. 
 
 Larch, 435. 
 
 Limnanthemum, 570. 
 
 Magnolia, 530. 
 
 Larix, 435. 
 
 Limosella, 564. 
 
 Magnoliacese, 512, 530. 
 
 Larkspur, 530. 
 
 Linacese, 513, 542. 
 
 Magnoliese, 530. 
 
 Lastraea, 372. 
 
 Linaria, 564. 
 
 Mahonia. .",:;!. 
 
 Lathrsea, 566. 
 
 Ling, 573. 
 
 Maianthemum, 499. 
 
 Lathams, 559. 
 
 Linnsea, 577, 
 
 Maiden-hair Jern,371. 
 
 Latiseptae, 537. 
 
 Linum, 542. 
 
 Maiden-hair Tree, 437. 
 
 Laurustinus, 576. 
 
 Liparidinae, 507. 
 
 Maize, 489. 
 
 Lavaudula, 563. 
 
 Liparis, 507. 
 
 Malaxis, 507. 
 
 Lavender, 563. 
 
 Liriodendron, 530. 
 
 Male Fern, 372. 
 
 Lecanora, 307. 
 
 Listera, 506. 
 
 Mallow, 541. 
 
 Lecanoreae, 307, 
 
 Lithoderma, 268. 
 
 Malopese, 541. 
 
 Lecidea, 307. 
 
 Lithospermum, 569. 
 
 Mai us, 556. 
 
 Lecideaceae, 307. 
 
 Litorella, 566. 
 
 Malva, 541 (Fig. 352). 
 
 Leek, 498. 
 
 Liverworts, 317, 818. 
 
 Malvacese, 512. r,|n. 
 
 Leers ia, 489. 
 
 Lloydia, 496. 
 
 Mai vales, 512, 539. 
 
 L<><iuminosse, 513, 557.' 
 
 Lobelia, 574 (Fig. 389). 
 
 Mandarin Orange, 544. 
 
 Lejeunia, 327, 330. 
 
 Loiseleuria, 573. 
 
 Mangold, 523. 
 
 Lemanea, 272, 
 
 Lohum, 491. 
 
 Manihot, 527. 
 
 Lemna, 484 (Fig. 296). 
 
 Lomaria, 371. 
 
 Manna-ash, 5< 1. 
 
 Lemnacea?, 481, 484. 
 
 Lomentacese, 537. 
 
 Man Orchis, 506. 
 
 Lemon, 544. 
 
 Lomentaria. 271. 
 
 -Maple, 510 (Fig. 821), 
 
 Lens, 559. 
 
 Lonicera, 576 (Fig. 392). 
 
 545 (Fig. 357). 
 
 Lentibulariacese, 513, 
 
 Lonicereae, 576. 
 
 Maranta, 508. 
 
 564 (Fig. 377), 566. 
 
 Loosestrife, 553. 
 
 Marantacese, 481, 502. 
 
 Lentil, 559. 
 
 Lophocolea, 324. 
 
 Marattia, 355. 
 
 Leontodon, 582. 
 
 Loquat, 557. 
 
 Marattiacese, 852, 855. 
 
 Leonurus, 563. 
 
 Loranthacese, 512, 525. 
 
 Marchantia, 311 (Fir. 
 
 Lepidinese, 537. 
 
 Lords and Ladies, 483. 
 
 198), 812 (Fig. 194), 
 
 Lepidium, 537. 
 
 Loteae, 558. 
 
 820 (Fijr. 198), 822 
 
 Lepidozia, 329, 330. 
 
 Lotus, 531; 557 (Fig. 369). 
 
 (Fig. 199). 
 
 Lepigonum, 532. 
 
 Louse wort, 565. 
 
 Marchantiacesp, 820. 
 
 Lepiota, 303. 
 
 Lucerne, 558. 
 
 Marchantiea?, 324. 
 
 Leptolegnia, 289. 
 
 Lunaria, 537. 
 
 Marjoram, 563. 
 
 Leptosporangiatae, 352, 
 358, 373. 
 
 Lung-wort, 570. 
 Lunularia, 323. 
 
 Marrubium, 563. 
 Marsh Andromeda. ">7:; 
 
 Leptothrix, 2s-J. 
 
 Lupinus, 558. 
 
 Marsh Ciiiqucfoi!, 556. 
 
 Lesser Celandine, 529. 
 
 Luziola, 488. 
 
 Marsh-mallow, 541. 
 
 Lesser Dodder, 567. 
 
 Luzula, 499. 
 
 Marsh-marigolil. .V_'M. 
 
 Lettuce, 582. 
 
 Lychnis, 532 (Fig. 344). 
 
 BCanb-Munmure, "'_':;. 
 
 Leucobryum, 342, 345. 
 
 Lycium, 569. 
 
 Marsi I.-;.. :;::,< Fi-. 225). 
 
 Leucodon. :U<i. 
 
 Lycoperdon, 305. 
 
 Marsileaceaa, 352, H7H. 
 
 Leucojum, 507. 
 
 Lycopersicum, 568. 
 
 880. 
 
 Leuconostoc, 281. 
 
 Lycopodiaceffi, 353, 386. 
 
 Mat-grass, 491. 
 
 Leycesteria, 576 (Fig. 
 
 Lycopodinae, 234, 358, 
 
 Matricaria, 580. 
 
 391). 
 
 386. 
 
 Matthiola. Tw<7. 
 
 Lichenes, 30.">. 
 
 Lycopodium, 886 (Fig. 
 
 Maurandia, 564. 
 
 Liguliflorae, 581. 
 
 ' - ::K 
 
 May, 556. 
 
 Ligusticum, 550. 
 Lisustrum, 571. 
 
 Lycopsis, 569. 
 Lycopus, 563. 
 
 Maydese, 489. 
 
 Meadow-grass. I'M. 
 
 Lilac, 571. 
 
 Lvgodium, 358, 372. 
 
 M.-:\.|.. \v-l-iif. 528. 
 
 Liliacete, 481, 496. 
 
 Lyme-grass, 492. 
 
 Meadow Saffron, 498.
 
 603 
 
 IXDEX, PART II. 
 
 Meadow-sweet. 554. Moon-wort, 355. : Nemalion. 272 <"Fiy. 160). 
 
 Meconopsis, 533. 
 
 Moor-grass, 491. Nemastoma. 271. 
 
 Medicago, 558. 
 
 Moracese, 512, 515. Neotinea, 506. 
 
 Medlar, 556. 
 
 Morchella, 297. 
 
 Neottia, 506. 
 
 Melampsora, 299 (Figs. Morell, 297. 
 
 Neottiinae, 506. 
 
 179, 180). 
 
 Morello Cherry, 555. Nepenthes, 41 (Fig. 28). 
 
 Melampvrum, 565. 
 
 Morus, 515. Nepeta, 563. 
 
 Melanthioidese, 498. 
 
 Moschatel. 576. Nepetese, 563. 
 
 Melica. 487, 490. 
 
 Mosses, 332. ; Nephrodium, 360 (Fig. 
 
 Melic-grass, 490. 
 
 Mother-wort, 563. 214), 372. 
 
 Melilotus. 465 (Fig. 281), 
 
 Mould, 275, 295. ; Nereocystis, 268. 
 
 558. 
 
 Mountain Ash, 557. New Zealand Flax, 498. 
 
 Melissa, 563. 
 
 Mountain Avens, 556. ; Nicotiaiia, 458 (Fig. 274), 
 
 Melissinefe.563. 
 
 Mouse-tail, 529. 569. 
 
 Melittis, 563. 
 
 Mucor, 279, 287 (Figs, i Nigella, 529. 
 
 Melobesia, 240, 271. 
 
 165, 166). 
 
 Nigritella, 506. 
 
 Melon, 551. 
 
 Mucoracese, 285. 
 
 Nipplewort, 582. 
 
 Mentha, 563. 
 
 Mucorinse, 285. 
 
 Nitellese, 263. 
 
 Menthoidese, 563. 
 
 Mudwort, 564. 
 
 Nostoc, 244 (Figs. 135. 
 
 Menyanthese. 570. 
 
 Mulberry, 515. 136). 
 
 Menyanth.es, 570. ' 
 
 Mullein, 564. Notorhizese, 536. 
 
 Menziesia, 573. 
 
 Musa, 502 (Fig. 312). Nothoscordum, 498. 
 
 Mercurialis, 526. 
 
 Musacese, 481, 501. 1 Nucumentacese, 537. 
 
 Merismopedia, 244. 
 
 Muscari, 497. j Nuphar, 531. 
 
 Mertensia, 570. 
 
 Musci, 234, 332. Nutmeg, 415 (Fig. 246). 
 
 Mespilus, 556. 
 
 Muscinese, 317. Nux Vomica, 414 (Fig. 
 
 Metroxvlon, 485. 
 
 Musese. 501. 245). 
 
 Metzgeria, 324 (Fig. 200), 
 
 Mushroom, 279, 301. Nyctalis, 304. 
 
 330. 
 
 Musk, 564. Nymphsea, 530. 
 
 Meum, 550. 
 
 Musk Orchis, 506. 
 
 Nymphaeaceae, 512, 530. 
 
 Mildew, 295. 
 
 Musschia, 574. 
 
 NymphaeinGe, 530. 
 
 Milfoil, 581. 
 
 Mustard, 537. 
 
 
 Milium, 490. 
 
 Mutisia, 581. 
 
 Oak, 520. 
 
 Milkwort, 546. 
 
 Mutisiese, 581. 
 
 Oat, 490. 
 
 Milla, 498. 
 
 Mycorhiza, 275. 
 
 Oat-grass. 490. 
 
 Millet, 489. 
 
 Myosotis, 569. 
 
 Ochlandra, 488. 
 
 Millet-grass, 490. 
 
 Myosurus, 529. 
 
 Ocirnoidese. 5(33. 
 
 Millet-seed, 489. 
 
 Myrionema, 266. 
 
 Ocimum, 563. 
 
 Mimosa, 559. 
 
 Myristica, 415 (Fig. 246). 
 
 Octaviana, 304. 
 
 Mimosese, 559. 
 
 Myrrhis, 550. 
 
 (Edogoniaceaj. 253. 257. 
 
 Mimulus, 564. 
 
 Myrtaceaj, 513, 553. 1 (Edogonium, 246, 257 
 
 Mint, 563. 
 
 Myrtales, 513, 552. (Fig. 147). 
 
 Mistletoe, 525 (Fig. 340), 
 
 Myrtle, 553. 
 
 CEnanthe, 550. 
 
 Moenchia, 532. 
 
 Myrtus, 553. 
 
 (Enothera. 552. 
 
 Mohria, 361 (Fig. 216), 
 
 Myxomycetes, 280, 283. 
 
 Oil Palm, 48(i. 
 
 372. 
 
 
 Old Man's Beard. 528. 
 
 Molinia, 491. 
 
 Naiadacese, 481, 494. 
 
 Olea, 571. 
 
 Monandrse, 506. 
 
 Naias, 396, 494. 
 
 Oleaceae, 513. 570. 
 
 Monardese, 563. 
 
 Nandina, 531. 
 
 Olfersia, 360. 
 
 Monk's-hood, 530. 
 
 Napobrassica, 537. 
 
 Oligoporus, 304. 
 
 Monochlamydese, 512, 
 
 Napus, 537. 
 
 Olive, 571. 
 
 514. 
 Monocotvledones, 234, 
 
 Narcissales, 481, 507. 
 Narcissus, 507. 
 
 Onagracese. 513, 552. 
 Oncidium, 507. 
 
 418, 476. 
 
 Nardus, 491. 
 
 Onion, 498. 
 
 Monogramme, 370. 
 
 Narthecium, 498. 
 
 Onobrychis, 558. 
 
 Monospora, 271. 
 
 Nasturtium, 537. 
 
 Onoclea, 359, 372. 
 
 Monostroma, 257. | Navew, 537. 
 
 Ononis, 558. 
 
 Monotropa, 573. Neckera, 346. 
 
 Onopordon, 581. 
 
 Monotropese, 573. i Xelumbieae, 531. 
 
 Oocvstis, 248. 
 
 Montbretia, 509. ! Nelumbium, 531. 
 
 Oomycetes, 278, 280, 287.
 
 CLASSIFICATION AND NOMENCLATURE. 
 
 007 
 
 Ophioglossaceae, 352, 354. 
 Ophioglossum, 354. 
 Ophrydinae, 506. 
 Ophrys, 506. 
 Orache, 523. 
 Orange, 544. 
 Orchidaceae, 481. 503. 
 Orchidales, 481, '503. 
 Origanum, 563. 
 Orchis, 504 (Figs. 315, 
 
 316). 
 
 Ornithogalum, 497. 
 Orobanchaceae, 513, 566. 
 Orobanche, 566. 
 Orobus, 559. 
 Orpine, 561. 
 Orthoclada, 488. 
 Orthoploceae, 536. 
 Orthospermeae, 549. 
 Orthotrichum, 339, 345. 
 Oryza, 489. 
 Oryzeae, 489. 
 Oscillaria, 244 (Fig. 135). 
 Oscillariaceae, 244. 
 Osmunda, 359, 372 (Fig. 
 
 261), 406. 
 Osmundacete, 352, 364, 
 
 372. 
 
 Ostrya, 520. 
 Oxalidacese, 513, 543. 
 Oxalis, 543. 
 Ox-eve Daisy, 580. 
 Oxlip. 572. 
 Oxycedrus, 436. 
 Oxymitra, 324. 
 
 Paeon ia, 530. 
 Paeonieae, 530. 
 Paigle, 572. 
 Palm, 485. 
 Palmace*, 481, 484. 
 Palmales, 481, 484. 
 Palmella, 247. 
 Palmodictyon, 248. 
 Palmophyllum, 248. 
 Pampas Grass, 491. 
 Pandorina. 249 (Fig. 138). 
 Panicea?, 489. 
 Panicoidese, 489. 
 Panicum, 487 (Fig. 300). 
 Pannaria, 306. 
 Pansy. BBS. 
 Papaver. 474, 533. 
 Papaveracpae, 512, 5H3. 
 Paper Mulberry, 515. 
 Papilionese, 557. 
 Papyrus, 492. 
 Pariana, 488, 492. 
 Parietales, 512, 533. 
 Parietaria, 515. 
 
 Paris, 461 (Fig. 277), 499 Phegopteris, 372. 
 
 (Fig. 310). Philodendroi.l,,.. IKJ. 
 
 Parmelia, 307. 
 
 Parnassia, 561 (Fig. 373). 
 
 Parnassieae, 560. 
 
 Paronychieae, 532. 
 
 Parsley, 550. 
 
 Parsley Fern, 372. 
 
 Parsnip, 550. 
 
 Passiflorales, 513, 550. 
 
 Pastinaca, 550. 
 
 Patchouli, 563. 
 
 Paulou-nia, 564. 
 
 Pea, 559. 
 i Peach, 554. 
 I Pearl- wort, 532. 
 ! Pear-tree, 556. 
 | Pediastrum, 253. 
 
 Pedicularis, 565. 
 
 Pelargonium, 542. 
 
 Pellia, 324, 330. 
 
 Peltigera, 306, 307. 
 
 Pelvetia, 268. 
 
 Penicillium. 278, 291 
 (Fig. 170), 295. 
 
 Penny-cress, 537. 
 
 Pentstemon, 564. 
 
 Peony, 530. 
 
 Peplis, 553. 
 
 Perisporiacese, 295. 
 
 Perisporieae, 295. 
 
 Peronospora, 279, 287. 
 
 Peronosporaceae, 277, 287. 
 
 Personates, 513, 564. 
 
 Pertusaria, 308 (Fig. 
 190). 
 
 Petaloidea, 481, 494. 
 
 Petasites, 580. 
 
 Petroselinum, 550. 
 
 Petunia, 569. 
 
 Peucedaneae, 550. 
 
 Peucedanum, 550. 
 
 Peziza,277,297(Fig.l77). 
 
 Pezizaceae, 296. 
 
 Phacidiese, 297. 
 
 Phacotus, 249. 
 
 Phjeogamse, 265, 268. 
 
 Phseophycese, 238, 263. 
 
 Phseosporae, 264, 265. 
 
 Phalarideae, 489. 
 
 Phalans, 489. 
 
 Phalloidefe, 304. 
 
 Phallus, 305. 
 
 Phanerogamia, 234, 394. 
 
 Phascum, 339. 312. 
 
 Ph as. .,>!.*, 559. 
 
 Phaseolus, 559. 
 
 Pheasant's Eye, 529. 
 
 Pheasant's Eye Narcis- 
 sus, 508. 
 
 Phleum, 490. 
 
 Phlox, 567. 
 
 Ph. mix, 477 (Fig. 291). 
 485 (Fig. -j 
 
 Phormium, 498. 
 
 Photinia, 557. 
 
 Phragmites, |:>1. 
 
 j Phycochromacese, 244. 
 
 Phycomycetes, 280, 285. 
 
 Phyllantluis. :,-_'7. 
 : Phyllobium, 21*. 
 
 Phyllocladus. |:;7. 
 | Phyllodoce, .",7:;. 
 
 Phylloglossum, 386. 
 ! Physalis, 568. 
 
 Physcia, 307. 
 
 Physospermum, 550. 
 
 Physostigma, 559. 
 
 Physureae, 507. 
 
 Phytelephas, 4*0. 
 
 Phyteuma, 571. 
 
 Phytophthora, 287 (Figs. 
 167, 168), 2>*. 
 
 Picea, 425 (Fig. 249), 426 
 (Fig. 250), 428 (Fig. 
 252), 435. 
 
 Picris, 582. 
 
 Pilacre, 304. 
 
 Pilacreae, 804. 
 
 Pilularia, 373, 380. 
 
 Pimpernel. .".,-_'. 
 
 Pimpinella, 550. 
 
 Pinaster, 435. 
 
 Pine, 435. 
 
 Pinea, 435. 
 
 Pine-apple, 501 (Fig. 
 311). 
 
 Pinguicula, 566. 
 
 Pink, 532. 
 
 Pinnularia, 265 (Fig. 
 152). 
 
 Piuoideae, 433. 
 
 Piiius.-|M7,Fiir.2U!.-l-w 
 (Fig. 21* . l-'7 Fi-. 
 251), 433 (Fig. 254), 
 435. 
 
 Piptocephalideae, 285. 
 
 Pisum, 559. 
 
 Pithophora, _'"._ 
 
 Plagiochila. 326 (Fig. 
 201), 330. 
 
 Plantaginacese, 513, 565. 
 ' Plantago, 565 (Fig. 879;. 
 j Plantain, 50-J : 
 ; Platycerium, 860. 
 
 Platvcodon. ~>7l. 
 \ Pleospora. 27 
 i Pleurocarp*, 345.
 
 608 
 
 IXDEX, PART II. 
 
 Pleurocladia, 268. Primulacese, 513, 571. Raphiolepis, 557. 
 
 Pleurococcacese, 248. Primulales, 513, 571. Raspberry, 556. 
 
 Pleurococcus, 248 (Fig. Privet, 571. Rattle, 565. 
 
 137). 
 
 Protobasidiomycetes, i Ravenala, 501. 
 
 Pleiirorhizea?, 536. 
 
 304, 305. ' i Reed, 491. 
 
 Plocamium, 271. Protococcacese, 248. Reed-grass, 489. 
 
 Plumbaginacea?,513,572. ; Protococcoidete, 247, 248. 
 
 Reed-mace, 484. 
 
 Plumbago, 572. Protomvces. 301. 
 
 Reindeer Moss, 307. 
 
 Plume-thistle, 581. Pruned, 554 (Fig. 367). 
 
 Rest-harrow, 558. 
 
 Poa, 491. 
 
 Prunella, 563 ; _ 
 
 Rhamnaceae, 513, 546. 
 
 Podophyllum, 531. 
 
 Prunophora, 554. 
 
 Rhamnus. 465 (Fig. 281), 
 
 Pogostemon, 563. 
 
 Prunus. 554. 
 
 546 (Fig. 359). 
 
 Polemoniacese. 513, 567. 
 
 Psalliota, 303. 
 
 Rheum, 469 (Fig. 284). 
 
 Polemoniales, 513, 567. 
 Polemonium, 567. 
 
 Pseudoneura, 327. 
 Pseudosolanese, 564. 
 
 524 (Fig. 337). 
 Rhinanthoidese, 564. 
 
 Polybotrya, 361. 
 
 Psilotacese, 353, 389. 
 
 Rhinantlms, 565. 
 
 Polycarpeae, 532. 
 
 Psilotum, 389. 
 
 Rhizocarpa?, 373. 
 
 Polvcarpon, 532. 
 
 Pteridese, 371. 
 
 Rhizoclonium, 253. 
 
 PolVgala, 546 (Fig. 358). 
 
 Pteridium, 371. 
 
 Rhizomorpha, 305. 
 
 Pol ygalacese, 513, 545. 
 
 Pteridophvta, 234, 346. 
 
 Rhizopogon, 305. 
 
 Polygonacese, 512, 523. 
 Polygonatum, 499. 
 
 Pteris, 360 (Fig. 214). 3(36 Rhodochiton. 564. 
 (Fig. 218), 367 (Fig. Rhododendroidese. 573. 
 
 Polvgonum, 523 (Fig. 
 
 220), 371. Rhododendron, 573. 
 
 337). 
 
 Puccinia, 279, 298 (Fig. Rhodomelacese, 271. 
 
 Polypetalse, 512, 527. 
 
 178). Rhodophvcea?, 238, 271. 
 
 Polypodiacese, 352, 371. 
 
 Puffball, 301, 305. Rhodotypus, 554. 
 
 Polypodieae, 372. 
 
 Pulicaria, 581. Rhodymeniacese, 273. 
 
 Polypodium. 358, 360 ; Pulmonaria, 570. Rhubarb, 524. 
 
 (Fig. 214), 369 (Fig. 
 
 Pumpkin, 551. | Rhytisma, 297. 
 
 223), 372. 
 
 Punica, 554. 
 
 Ribes, 561 (Fig. 374). 
 
 Polyporese, 303. 
 
 Purple Beech, 521. 
 
 Ribesieae, 561. 
 
 Polyporus, 303. 
 
 Pvcnophj-cus, 268. 
 
 Ribwort, 566. 
 
 Polvsiphonia, 271. 
 
 Pylaiella, 266. 
 
 Riccia, 324. 
 
 Polytrichum, 339, 344 
 
 Pj T renomvcetes, 295. 
 
 Ricciete, 322, 324. 
 
 (Fig. 211). 
 
 Pyrola, 572 (Fig. 387). 
 
 Rice-plant, 489. 
 
 Pomea?, 556 (Fig. 367). 
 
 Pyrolacese, 513, 573. 
 
 Richardia. 442, 483. 
 
 Pomegranate, 554. 
 
 Pyronema, 278, 293 (Fig. 
 
 Ricinus, 462 (Fig. 278), 
 
 Pond weed, 494. 
 
 172). 
 
 526. 
 
 Pooidefe, 489. 
 
 Pyrus, 556. 
 
 Riella, 324. 329. 
 
 Poplar, 522 (Fig. 335). 
 
 Pythium, 287, 288. 
 
 Riellese, 329. 
 
 Poppv, 533. 
 
 
 Rivulariacese, 244. 
 
 Populus, 522. 
 
 Quaking-grass. 491. 
 
 Robin i a, 558. 
 
 Portugal Laurel, 555. 
 
 Quercus, 520 (Fig. 333). 
 
 Roccella, 307. 
 
 Potamogeton, 49-1. 
 
 Quince, 556. 
 
 Rock-rose, 538. 
 
 Potato Plant, 568. 
 
 
 Romulea, 508. 
 
 Potentilla, 459 (Fig. 275), 
 
 Racodium, 306. 
 
 Rosa, 451 (Fig. 267), 554. 
 
 556. 
 
 Radiola, 542. 
 
 Rosacese, 513, 554. 
 
 Potentilleee,. 555 (Fig. 
 
 Radish, 538. 
 
 Rosales. 513. .V>1. 
 
 367). 
 
 Rarlula, 324, 330. 
 
 Rose. ::> I. 
 
 Poteriese, 555. 
 
 Ramalina, 307. 
 
 Rosea;, 555 (Fig. 367). 
 
 Poterium, 555. 
 
 Rampion, 574. 
 
 Rosemary, 563. 
 
 Pothoideae, 483. 
 
 Ranales, 512, 527. 
 
 Rosmarinus, 563. 
 
 Pothos, 483. 
 
 Ranunculaceee, 512. .V27. 
 
 Rowan-tree, 557. 
 
 Pot-Marigold, 581. 
 
 Ranunculus, 528 (Fig. 
 
 Rubia, 575 (Fig. 390). 
 
 Pottia, 344. 
 
 342), 529. 
 
 Rubiacese, 513. 574. 
 
 Preissia, 322. 
 
 Rapa, 537. 
 
 Bubiales. 513. 574. 
 
 Prickly Samphire, 550. 
 
 Rape, 537. 
 
 Rubus. 555 (Fig. 368), 
 
 Primrose. r>72. 
 
 Raphanese, 538. 
 
 556. 
 
 Primula, 453 (Fig. 269), 
 
 Raphanus,' 535 (Fig. 348), 
 
 Rudbeckia, 581. 
 
 571 (Fig. 386). 
 
 538. 
 
 Rue, 543.
 
 CLASSIFICATION AND NOMENCLATURE. 
 
 609 
 
 Rumex, 523 (Fig. 337). 
 Ruppia, 405, 494. 
 Ruscus, 499. 
 Rush, 499. 
 Rust, 275, 298, 299. 
 Ruta, 543. 
 Rutacese, 513, 543. 
 Rutese, 543. 
 Rye, 491. 
 Rye-grass, 491. 
 
 Sabina, 436. 
 Saccharoniyces, 295 (Fig. 
 
 174). 
 
 Saccharomycetes, 295. 
 Saccharum, 489. 
 Safflower, 581. 
 Saffron Crocus, 508. 
 Sage, 563. 
 Sagina, 532. 
 Sagittaria, 495. 
 Sago, 485. 
 Sainfoin, 558. 
 Salad Burnet, 555. 
 Salicace*, 51 r,22. 
 Salicornia, 523. 
 Salisburia, 437. 
 Salix, 522 (Fig. 335). 
 Sallow, 522. 
 Salsafy, 582. 
 Salsola, 523. 
 Salt-wort. r,-j:-5. 
 Salvia, 461 (Fig. 276), 
 
 . 562. 
 Salvinia, 347, 374 (Fig. 
 
 224), 379 (Fig.- 226). 
 Salviniacese, 352, 373, 
 
 380. 
 
 Sambucese, 576. 
 Sambucus, 458 (Fig. 274), 
 
 463 (Fig. 279), 576. 
 Sainolus. :>72. 
 Samphire, 550. 
 Sanaa! -wood, 525. 
 Sand- wort, 532. 
 Sanguisorba, 555. 
 Sanicula, 549. 
 Saniculese. M!i. 
 Santalacese, 512, 524. 
 Sautalales, 512, 524. 
 Sautalum. 52.\ 
 Sapindacese, 544. 
 Sapindales, 513, 544. 
 Sapindus, 545. 
 Saponaria, 532. 
 Saprolegnia, 289. 
 Saprolegniacese, 278, 289. 
 Sarciua, 281. 
 Sargassum l 269. 
 Sarothamnus, 558. 
 
 M.B. 
 
 Sarsaparilla, 499. 
 
 Satureia, 563. 
 
 Satureineae, 563. 
 
 Saussurea, 581. 
 
 Savoy-cabbage, 537. 
 
 Saw-wort, r,si. 
 
 Saxifraga, 465 (Fig. 281), 
 
 560. 
 I Saxifragacese, 513, 560. 
 
 Saxifragales, 513, 559. 
 I Saxifrage*, 560. 
 
 Scabiosa, 578 (Fig. 394). 
 I Scandiceae, 550. 
 
 Scandix, 550. 
 
 Scapania, 327. 330. 
 
 Scarborough Lily, ">"<. 
 
 Scarlet-runner, 559. 
 
 Scenedesmus, 248. 
 
 Scheuchzeria, 495. 
 
 Schistostega, 344. 
 
 Schizsea, 359, 365, 372. 
 
 _ 
 Schizomycetes, 2 Hi. 2<<i. 
 
 280. 
 
 Schizophyta, 246, 283. 
 Schlerochloa, 491. 
 Schoenus, 492. 
 Schollera, 573. 
 Sciadium, 248. 
 Scilla, 497. 
 Scilleaj, 497. 
 Scirpoideae, 492. 
 Scirpus, 493 (Fig. 303). 
 Scitaminese, 481, 501. 
 Scleranthus, 533. 
 Sclerotiuieee, 277. 
 Scolopendrium, 359, 362 
 
 (Fig. 217), 371. 
 Scorpion-grass, 569. 
 Scorzonera, 582. 
 Scots Pine, 435. 
 Scottish Asphodel, 498. 
 Scrophularia, 565. 
 Scrophulariaceae, 518, 
 
 564 (Fig. 377), 565 
 
 (Fig. 378). 
 Scurvy-grass, o37. 
 Scuteflaria, 563. 
 Scutellarieae, 563. 
 Scytonema, 244. 
 Scytonemacese, 244. 
 Scytosiphon, 267. 
 1 Sea-blite, 523. 
 Sea-bugloss, 570. 
 Sea-kale, 538. 
 Sea-lavender. ">7 
 Sea-milkwort. r.72. 
 Sea-purslane, 532. 
 Sea-rocket, 538. 
 Secale, 491. 
 
 Sedge, 493. 
 
 Sedum, 561 (Fisr. 876 
 
 St-laginella, 390 (Fig. 
 82 . 391 (Fig. 233), 
 2 Fig. 234). 
 
 Selagineilaoen, 353, 889 
 
 Sempervivum, 561. 
 
 Senebiera. .",:',7. 
 I Seneci... 
 
 j Senecionideae, 580. 
 i Sensitive Plant, 559. 
 ' Serapiadea;, ^ i. 
 
 Serratula. .\si. 
 
 Service-tree, 557. 
 I Seseli, 550. 
 
 Seseliueae, 550. 
 
 Sesleria. T.'l. 
 
 Shaddock. .Ml. 
 
 Shalot, 498. 
 
 Shwp's-l.ii. :.7I. 
 
 Shi-plifi-d's Purs.-, 537. 
 
 Sherardia. '<> >. 
 
 Shield-Fern, 372. 
 
 Sibbaldia. .V.i. 
 
 Sibthorpia, 565. 
 
 Silaus. .Vid. 
 
 8ilene,682. 
 
 Sileneae, 532. 
 
 Siler, 550. 
 
 Siliculosit-. .">:;, . 
 
 Siliquosse, 536. 
 
 Silver Fir, 435. 
 
 Silver-weed, 556. 
 
 Siniethis, 498. 
 
 Sinapis, 537. 
 
 Siphonacese, 250. 
 
 Siphonoideae, 246, 248 
 250. 
 
 Sirogonium, 255. 
 
 Sison, 550. 
 
 Sisymbriese, Tvi^ 
 
 Sisymbrium, 537. 
 
 Sium, 550. 
 
 Skullcap, 563. 
 
 Sloe, 554. 
 
 Small Reed, 490. 
 
 Sin ilaooidew, 499. 
 
 Smilax, 499. 
 
 Smut, 275, 298, 300. 
 
 Smyrniese, 550. 
 i Smyrnium, 550. 
 
 Snak.-V ll.-a.l. l!>7. 
 
 Snapdragon, 564. 
 
 Snowlx-rry. ")7.. 
 
 Snowdrop, 507. 
 
 S.ai-\v..rt. M--'. 
 
 Solanacese, 51: 
 
 Solanat 
 
 Solanin. 
 Soldanella, 571. 
 
 K R
 
 610 
 
 IXDEX f PAKT II. 
 
 Solidago, 580. Staurastrum, 254. 
 Solomon's Seal, 499. , Stegocarpse, 338, 343. 
 Sonchus, 582. Stellaria, 532. 
 
 Sorbus, 557. 
 
 Stellatee, 575. 
 
 Sordaria, 278. 
 
 Sticta, 307 (Fig. 188). 
 
 Sow-bread. 572. \ Stinging Kettle, 514. 
 
 Sow-thistle, 582. Stipa, 487, 490. 
 
 Spadiciflorse, 481, 482. Stitch-wort, 532. 
 
 Spanish Chestnut, ,521. St. Dabeoc'sJSeath, 573. 
 
 Sparaxis, 509. i St. John's Wort, 539. 
 
 Sparganium, 484. Stocks, 537. 
 
 Spartina, 491. 
 
 Stone Pine, 435. 
 
 Spearwort, 529. 
 Specularia, 574. 
 
 Stonecrop, 561. 
 Stork's-bill, 542. 
 
 Speedwell, 565. 
 
 Strap-wort, 533. 
 
 Spelt, 492. 
 
 Stratioteee, 500. 
 
 Spergula, 532. 
 
 Stratiotes, 500. 
 
 Spergularia, 532. 
 
 Strawberry, 556. 
 
 Spermaphyta, 234, 394. 
 
 Strelitzia, 501. 
 
 Spermothamnion, 274 
 
 Sturm ia, 507. 
 
 (Fig. 161). 
 
 Stypocaulon, 239 (Fig. 
 
 Sphacelaria, 263, 264. 
 
 133). 
 
 Sphserella, 249. 
 
 Suaada, 523. 
 
 Sphaeriacese, 296. 
 
 Subularia, 537. 
 
 Sphaerocarpus, 327, 329. 
 
 Succisa, 578. 
 
 Sphseroplea, 247, 252. 
 
 Sugar-cane, 489. 
 
 Sphseroplese, 252. 
 
 Summer Savory, 563. 
 
 Sphserotheca, 293. 
 
 Summer Snowflake, 507. 
 
 Sphagnacese, 312, 316, 
 
 Sundew, 561. 
 
 340. 
 
 Sunflower, 581. 
 
 Sphagnum, 332, 341 
 
 Sweet Basil, 5'63. 
 
 (Figs. 205, 206). 
 
 Sweet Briar, 554. 
 
 Spider Orchis, 506. 
 
 Sweet Flag, 483. 
 
 Spinach, 523. 
 
 Sweet Orange, 544. 
 
 Spinacia, 523. 
 
 Sweet Potato, 567. 
 
 Spindle-tree, 546. 
 
 Sycamore, 545. 
 
 Spiraea, 554. 
 
 Symphoricarpus, 577. 
 
 Spirseese, 554. 
 
 Symphyogyna. 327. 
 
 Spiranthese, 506. 
 
 Symphytum, 569. 
 
 Spiranthes, 506. 
 
 Syringa, 571. 
 
 Spirillum, 281 (Fig. 162). 
 
 
 Spirochsete, 281. 
 
 Tagetes, 581, 
 
 Spirogyra, 246, 255 
 
 Tamarindus, 559. 
 
 (Fig. 145). 
 
 Tamus, 500. 
 
 Spirolobeae, 536. 
 
 Tanacetum, 581 (Fig. 
 
 Splachnum, 338. 
 
 397). 
 
 Spring Snowflake, 507. 
 
 Tansy, 581. 
 
 Spruce Fir, 435. 
 
 Tapioca, 527. 
 
 Spurge, 527. 
 
 Taraxacum, 582 (Fig. 
 
 Spurrey, 532. 
 
 397). 
 
 Squamariacese, 272. 
 
 Tassel Pondweed, 494. 
 
 Squinancy-wort, 575. 
 
 Taxes-, 437. 
 
 Stachydeae. 563. 
 
 Taxoideae, 433, 436. 
 
 Stachys, 563. 
 
 Taxus, 396, 437{Fig. 258). 
 
 Stangeria, 432. 
 
 Teazle, 578. 
 
 Star-Anise, 530. 
 
 Teesdalia, 537. 
 
 Star Daffodil, 508. 
 Star-fruit, 495. 
 
 Telegraph-plant, 558. 
 Tetraphis, 337, 345. 
 
 Star of Bethlehem. 498. 
 
 Tetraspora, 248. 
 
 Statice, 572. ! Teucrium, 564. 
 
 : Thalamiflorge, 512, 527. 
 
 Thalictrum, 528. 
 
 Thallophyta, 234. 237. 
 
 Thelidium, 306. 
 
 Thesium 525 (Fig. 339). 
 
 T-histle, 581. 
 
 Thlaspi, 537 (Fig. 348). 
 
 Thlaspidete, 537. 
 
 Thorn-apple, 569. 
 
 Thrift. 572. ' 
 i Thuidium, 346. 
 
 Thuja,' 436 (Fig. 256). 
 
 Thyme, 563. 
 
 Thymus, 568. 
 
 Tiger-lily. 496. 
 
 Tilia, 461 (Fig. 276), 540 
 (Fig. 351). 
 
 Tiliaceae, 512, 539. . 
 
 Tilletia, 300 (Fig. 181). 
 
 Timothy-grass. 490. 
 i Tmesipteris, 389. 
 ! Toad-flax, 564. 
 
 Toadstool, 301. ' 
 
 Tobacco-plant, 569. 
 
 Todea, 372.' 
 
 Tofieldia, 498.. 
 
 Tomato, 568. 
 
 Tprdylium, 550. 
 
 Torilis, 550. 
 
 Tragopogon, 582. 
 
 Trapa, 552. 
 
 Treacle mustard, 537. 
 
 Tree-fern, 358, 372. 
 | Tremella, 303 (Fig. 184). 
 
 Tremellinese. 303. 
 
 Trentepohlia, 306. 
 
 Trichomanes, 360 (Fig. 
 214), 371. 
 
 Trientalis, 572. 
 
 Trifoliese, 558. 
 
 Trifolium, 558. 
 
 Triglochin,495 (Fig. 305) 
 
 Trigonella, 558! 
 
 Trinia, 550. 
 
 Triticum, 478 (Fig. 292), 
 491. 
 
 Tritonia, 509. 
 
 Trollius, 529. 
 
 Tropseolum, 457 (Fig. 
 273). 
 
 Trumpet Lily, 483. 
 
 Tubuliflorse, 579. 
 
 Tuburcinia, 301. 
 
 Tulip, 496. 
 
 Tulipa, 496. 
 
 Tulipese, 496. 
 
 Tulip-tree, 530. 
 
 Tulostoma, 304. 
 
 Turk's Cap Lily, 496. 
 
 Turmeric, 502.
 
 CLASSIFICATION AND NOMENCLATURE. 
 
 611 
 
 Turnip, 537: 
 
 Venus' Looking-glass, 
 
 Wild Garlic, 498. 
 
 Tussilago, 580. 
 
 574. 
 
 Wild Oats, 490. 
 
 Tutsans, 539. 
 
 Veratrum, 498. 
 
 Wild Parsnip, 550. 
 
 Twayblade, 506. 
 
 .Verbascum, 564. ' 
 
 Wild Plum. r,:,.-,. 
 
 Typha, 484. 
 Typhacete, 481, 484. . 
 Typhula, 277, 304. 
 
 Vernal grass, 489. 
 Veronica, 564 (Figs. 377, 
 378). 
 
 Wild Rosemary, 573. 
 
 Wild Siijro. 563. 
 
 
 Vetch, 559. 
 
 Willow'Herb, 562. 
 
 
 Viburmim v 576. 
 
 Winter Aconite, 529. 
 
 Ulex, 558. . 
 
 Vicia, 456 (Fig. 272), 510 
 
 Winter Cherr.x 
 
 Ulmaceae, 512, 516. 
 
 -(Fig. 320), 559. 
 
 Winter-green. .".:-!. 
 
 Ulmus, 516 (Fig. 326). 
 Ulothricaceae, 253, 256. 
 
 Vicieae, 558.' 
 Victoria, 531. 
 
 Wistaria, 559. 
 Woad, 537. 
 
 Ulothrix, 246, 256 (Fig. 
 
 Villarsia. 570. 
 
 Wolffia, l".\ 
 
 146). 
 
 Viola, 538 (Fig. 349). ' 
 
 W..lfs-bane, 530. 
 
 Ulva, 246, 257. 
 
 Violacese, 512, 538. 
 
 Wood Germander, 564. 
 
 Ulvaceae, 253, 257. 
 
 Violet, 538. 
 
 Woodruff, 575. 
 
 Umbel lales, 513, 547. 
 
 Viper's Bugloss, 569. 
 
 Woodsia, 372. 
 
 Umbelliferse, 513, 548. 
 
 Virginian Creeper, 547. 
 
 Wood-sorrel, 5l:s. 
 
 Uncinula, 295 (Fig. 173). 
 
 Viscum,525(Fig. 340). 
 
 Woody Nightshade, 568 
 
 Uredinese, 299 (Fig. 179). 
 
 Vitis, 547 (Fig. 360). 
 
 Wormwood, 580. 
 
 Uredo, 299. 
 
 Vittaria, 370. 
 
 Wound wort, 558. 
 
 Urocystis, 301. 
 
 Volvocaceae, 249. 
 
 WychElm, 517. 
 
 Urospora,- 253. 
 
 Volvocoidese, 247, 249. 
 
 
 Urtica" 514 (Figs. 322, 
 
 Volvox, 246, 249 (Fig. 
 
 Xiphion, 508. 
 
 323). . 
 
 139). 
 
 
 Urticacese, 512, 514. 
 
 
 Yam, 500. 
 
 Urticales, 512, 514. 
 
 
 Yarrow, 581. 
 
 Usnea, 307 (Figs. 186, 
 
 Wall-flower, 537. 
 
 Yeast, 295 (Fig. 174). 
 
 189). 
 
 Wall-Pellitory, 515. 
 
 Yellow Flag, 509. 
 
 Ustilaginese, 298, 300. ' 
 Ustilago, 300 (Fig. 181). 
 
 Wall-Rue; 371. 
 Walnut, 522. 
 
 Yellow Loosestrife, 572. 
 Yellow Monkey-flower , 
 
 Utricularia, 566 (Fig. 
 
 Water-Chestnut, 552. 
 
 564. 
 
 380). 
 
 Water-cress, 537. 
 
 Yellow Rocket, 537. 
 
 Uvularia, 498. 
 
 Water Crowfoot, 529. 
 
 Yellow Welsh Poppy, 
 
 
 Water-Hemlock, 550. 
 
 533. 
 
 
 Water-Lily, 531. 
 
 Yew, 437 (Fig. 258). 
 
 Vacciniaceae, 513, 573. 
 
 Water Melon, 551. 
 
 Yucca, 498. 
 
 Vaccinium,461(Fig.277), 
 
 Water Plantain, 495. 
 
 
 572 (Fig. 387). 
 Valerian, 577 (Fig. 393). 
 
 Water-Purslane, 553. 
 Water-Soldier, 500. 
 
 Zamia, 432 (Fig. 253). 
 Zanardinia, ~2>^. 
 
 Valeriana, 577. 
 
 Water- Violet, 572. 
 
 Zannichellia, 494. 
 
 Valerianacese, 513, 577. 
 
 Weeping Willow, 522. 
 
 Zantedeschia. 483. 
 
 Valerianella, 577. 
 Valisneria, 500. 
 
 Weigelia, 577. 
 Welwitschia, 437. 
 
 Zea, 479 (Fig. 293), 489. 
 Zingiber, 502. 
 
 Valisneriese, 500. 
 
 Wheat, 487 (Fig. 301), 
 
 Zingiberacea?, 481, 502. 
 
 Vallota, 507. 
 
 490 (Fig. 302). 
 
 Ziiigiberese, 502. 
 
 Vanda, 507. 
 
 Whin, 558. 
 
 Zinnia, 581. 
 
 Vanilla, 507. 
 
 White Beam, 557. 
 
 Zostera, 494. 
 
 Vascular Cryptogams, 
 Vaucheria,250(Fig. 140). 
 
 White Thorn, 556. 
 Whitlow-grass, 537. 
 Whortleberry, 573. 
 
 Zygnema, 255 (Fig. 144). 
 Zygnemese, 254. 
 Zvgogonium, 256. 
 
 Venus' Fly-trap, 561. 
 
 Wild Balsam, 543. 
 
 Zygomycetes, 280, 285. 
 
 :r, The Selwood Printing Works, Frome, and London.

 
 
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