RUAN SCN bh ii i aU MHL Uplate My Hh Ui I “ea i ik Blas pupatlenah eae iat " iF vere Mil 0 ni Hi ah ye HR ily en) VENOM AME lL a Mi iH H i venus si ay st y Dare nt ae stil Seay ik Le I Hi 1s i i ane ey te oh Senet fl ead bat ALL aa PUGH OTE DMEM Hea, Pethies, MI Ae He aieaaa ti Nita He HM RHR ue ae ay ia PU BRE alae’ HE La AnE, ea i ae i iets PA eerie Natt aida) Bria Hea be ta HE i pat it M1 He Cornell Mniversity Library BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF Henry W. Sage 1891 | OO occas tienen ay ne ules benoit wi NOTES ON THE LIFE HISTORY OF BRITISH FLOWERING PLANTS Notes on ‘The Life History of British F lowering Plants BY THE RIGHT HON. LORD AVEBURY, P.C. Pres. of the Soc. of Antiquaries ; Trustee British Museum; For. Sec. Roy. Acad. ; German Ord. Pour le Mérite ; Com. Legion of Honour; D.C.L. (Oxon.), LL.D. (Cantab, Dubl, et Edin.), M.D. (Wiirzb.), F.R.S., F.L.S.,F.G.S.,F.Z.S., F.S.A., F.E.S.; Assoc. Acad, Roy. des Sci. Brux.; Hon. Mem. R. Irish Acad., Amer. Ethnol. Soc., Anthrop. Soc. Wash. (U.S.), Brux., Firenze, Anthrop. Verein Graz, Soc. Entom. de France, Soc. Géol. de la Suisse, and Soc. Helvét. des Sci. Nat. ; Mem. Amer. Phil. Soc. Philad., and Soc. ’Ethn. de Paris ; Corresp. Mem. Soc. Nat. des Sci. Nat. de Cherb., Berl. Gesell. ftir Anthrop., Soc. Romana di Antrop., Soc. d’Emul. d’Abbeville, Soc. Cient. Argentina, Soc. de Géog. de Lisb., Acad. Nat. Sci. Philad., Numis. and Ant. Soc. Philad., Amer. Entom. Soc, ; For. Assoc. Mem. Soc. d’Anthrop. de Paris ; For. Mem. Amer. Antig. Soc. ; For. Mem. Soc. Espafiola de Hist. Nat. ; For. Mem. Roy. Swedish Acad. of Sci. Upsala; For. Mem. Danish Acad. of Sci. and Lit. ; Hon. Mem. New Zealand Inst.; Hon. Sec. Soc. Biol. Paris. London MACMILLAN AND CO.,, Limirep NEW YORK : THE MACMILLAN COMPANY L985 a ee All rights reserved PREFACE SowerBy, Bentham, Hooker, Babington, and others have given us good, and in some cases excellent works, enabling us to determine and name our British plants, but they mostly confine themselves to technical details, with such additional particulars as enable the student to distinguish one species from another. To these, how- ever, in the main they confine themselves, and, no doubt, in great measure, from considerations of space, omit other points often of great interest, nor does it fall within their intention to enter much into the economy and life-history of plants. Even Sowerby did not to any great extent fill up the gap. He does not, I think, mention the remark- able work of Sprengel, and the interesting researches of Darwin, H. Miiller, Hildebrand, Delpino, and others have been made since he wrote. Kerner’s admirable work deals with plants gener- ally, and comparatively little space, therefore, can be devoted to British species. Knuth’s Handbuch der Blutenbiologie relates mainly to the relations of flowers and insects, as also does my smaller work, British Wild Flowers, Con- sidered in Relation to Insects. Vv vi BRITISH FLOWERING PLANTS In another book, Flowers, Fruits, and Leaves, 1 have dwelt on the structure and forms of plants, but from a general point of view. In the present work I endeavour to supplement the various excellent ‘“ Floras’’ which we already possess, not in any way to compete with them: to describe points of interest in the life-history of our British plants; to explain, as far as possible, the reasons for the structure, form, and colour; and to suggest some of the innumerable problems which still remain for solution. I have followed the arrangement adopted in Bentham’s Handbook of the British Flora, as being one in very general use. Dr. Rendle has been so kind as to see the proofs through the press for me. This is a guarantee of accuracy, and he has also made many valuable sugges- tions. Hicu Extms, Down, Kernv, October 5, 1905. InrRopUCTION FLOWER FRUITS AND SEEDS LEAVES STEM SENSE ORGANS DicoryLEDons CONIFER MonocorTyLeDons INDEX CONTENTS Vil PAGE 15 20 34 42 47 381 389 445 18. 19. 20. 21. 22. 23. 24. 25. 26. ILLUSTRATIONS Geranium sylvaticum (after Bentham) Lamium amplexicaule: cleistogamous flower Section of do, Shoot of Rose Whorl of Bramble leaves . Longitudinal section through the growing onal of a winter bud of Abies pectinata ig Sachs) . Twig of Beech . Twig of Chestnut . Twig of Norway Maple . Shoot of Black Poplar . Transverse section of leaf of Empetrum (after Kerner) . Leaf of Clover (Trifolium repens): position by day Do. do. position by night . Group of Dead and Stinging Nettles . Twig of Lime . Young shoot of Hornbeam . Longitudinal section through the Jienetian of stem wal leaf of Horse Chestnut in autumn (after Sachs) Seedling of Glauctum corniculatum Frond strengthened by rolling (after Spencer), ; Portion of a grass stem; showing internodes surrounded by leaf-sheaths (after Spencer) Frond strengthened by mid-rib (after aseneen) Relation of stem and leaf in Dicotyledons (after Spencer) Single girder Double girder Multiple girder Section of a one-year-old shoot of Lime, i woody frundies separated by broad bands of soft (parenchymatous) tissue (after Kerner) ix « PAGE 12 13 21 22 22 22 23 28 30 30 30 31 32 33 34 35 36 36 38 38 38 39 FIG. 27. 28. 29. 30. 31. 34. 35. 36. 37. 38. 39. 40. 41. 42, 43. 44. 45. 46. 47, 48. 49. 50. 51. 52. 53. 54, BRITISH FLOWERING PLANTS Diagram of a young Dicotyledonous stem, showing approxima- tion of the distinct bundles Arrangement of leaves of Carex Ranunculus aquatilis (after Bentham) é Do. also enlarged petal, showing fies basal honey-gland ; . Ranunculus bulbosus: flower, with different views of petal, showing nectary : : : ‘ 33. Helleborus fetidus: flowers in the first (female) condition, the sepals partly removed, and the second (male) condition (after Knuth) Longitudinal section of seed of Daphne Santana gria Transverse do. do. ‘ Delphinium elatum. a, Young flower, seen from the front, and after removal of the calyx. 8, Section of a similar flower, seen from the side; the right half of the calyx and of the corolla has been removed. y, An older flower, seen from the front, after removing the calyx. 6, Section of a similar flower, seen from the side, after removing the right half of the calyx. (After H. Miller) Aconitum Lycoctonum. A, Flower in the second (female) con- dition, seen from the side. B, Longitudinal section. (After H. Miiller) ‘ 4 Shoot of Berberry (Berberis vulgaris), sical three spines Flower of do. do. seen from above Pistil and two stamens of do. after the visit of an insect Capsule of Poppy é Seedling of Glauctum Sen a z Fumaria officinalis: flower (after Hildebrand} Do. do. from which the sepals have is removed (after Hildebrand) Sections of seed of Hesperis matronalis Do. of Wallflower (Chetranthus Chetrt) : Sisymbrium oficinale: flowers in the first and second stages (after Knuth) Seedling of Cress (Lepidiwm ceoleaba Section of seed of Lepidium graminifolium Do. do. sativum . Raphanus sativus: seedling . Do. germinating seedling Do. outline of seed and various views of embryo Shoot of Helianthemum vulgare PAGE 40 41 47 60 61 61 62 66 67 67 68 72 73 74 75 76 77 81 89 89 89 91 91 91 93 FIG. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74, 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. ‘ 90-93. Sarothamnus (Broom): flower, ‘ituatrating explosive action LIST OF ILLUSTRATIONS Shoot of Helianthemum elandicum Polygala vulgaris: section of flower (after H. Miiller) . Do. flower opened out (after H. Miiler) Viola canina: section of flower ; and stamen Do. capsule with seed Do. do. after ejecting the seeds Do. with cleistogamous flower Viola lirta, with fruit Malva sylvestris, with stamens and stigmas fatten H. Miiller) Do. rotundifolia, do. do. Carpel of Malva moschata Fruits and bract of Lime Embryo of Lime Seedling of Lime Geranium pratense (after Bentham) Do. young flower Geranium sylvaticwm (after Bentham) Herb Robert (@. Robertianwm) : Geranium dissectum: dispersal of fruit Do. Robertianum: do. Seedling of Geranium sanguineum Section through embryo of Geranium, showing the “acelle of folding of the cotyledons . ‘ Awned fruit of Erodiwm glaucophyllum Oxalts Acetosella: leat by ae and by sight (after Darwin) . : Transverse section of the motile organ of a leaflet of Butte carnea (after Sachs) Longitudinal section of same, and leaf-stalk (after Sachs) Oxalis Acetosella: arrangement of the chlorophyll grains in a cell of the leaf: a, in diffuse light; 6, in sunlight; ¢, in long-continued sunlight (after Sachs) Flower of Balsam, in two stages (after Knuth) Seedling of Acer Pseudo-platanus Fruit and rolled cotyledons of do. Transverse section of seed of Euonynus Longitudinal do. do. Embryo of Bean Pod of Common Vetch, illustrating dehiscence Lathyrus Nissolia : seedling in pollination (after H. Miller) xl PAGE 93 95 95 96 97 97 98 100 120 120 121 122 123 124 125 126 126 128 129 129 130 130 132 135 136 137 138 140 143 144 145 145 147 149 150 xii BRITISH FLOWERING PLANTS FIG. 94. Shoot of Broom, showing bud protected by pedestal of last year’s leaf 95. Lotus corniculatus (after Hewthant).. ; : ‘ 96-100. Do. flower, illustrating position of parts in pollination 101-103. Flower of Genista tinctoria, illustrating method of 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. pollination Furze seedling : : : Trifolium pratense: head of flower-buds with the pair of protecting leaves Trifolium repens: end of creeping host ‘ Do. — subterranewm: shoot showing buds at end, and three older flower-heads which are turned down and beginning to bury themselves ‘ Trifolium subterraneum : flower-head slightly magnified Fruit of Hippocrepis Staminal tube of Lathyrus . Do. of Vicia Stipules of Lathyrus maritimus : s Do. do. with one of the stipules turned back, revealing the rest of the leaf and bud Stipule of Lathyrus grandiflorus Do. do. pratensis Stipules of do. 3 ‘ Do. do. with one of the lower stipules turned back, and exposing the next younger leaf with its stipules . Stipules of Lathyrus latifolius Do. do. with the lower stipule ‘euraved, and exposing the whole of the stipule of the next higher leaf 4 : : ; Stipules of Lathyrus ditties A, before the unfolding of the leaf, in the natural position; B, with one stipule turned back to show the leaf and shoot inside 121-124. Gewm urbanwm: style in three stages of dendloyment, and ripe fruit 125-130. Scales of bud of Rose, ae successively ie first, 131. 132. 133. 134. third, fourth, fifth, sixth, and ninth scale Stem of Rose bearing expanding lateral bud Epilobium angustifolium: flowering shoot Epilobium parviflorum: flowering shoot Inflorescence of Lythrum Salicaria PAGE 154 155 156 161 162 164 164 166 167 167 168 168 169 169 170 170 170 170 171 183 183 187 188 191 LIST OF ILLUSTRATIONS FIG. 135-1387. Long-styled, mid-styled, and short-styled flowers of Lythrum Salicaria 138. Drosera rotundifolia (after Bentham) 139, Do. anglica (after Bentham) 140. Do. rotundifolia: leaf enlarged, with the tentacles on one side inflected (after Darwin) 141. Wild Chervil (Cherophyllum sylvestr e) (after Banta 142, 143. Flowers of Wild Chervil in male and female state 144. Eryngium maritimum: petal seen in front and from the side 145. Lenticel from a branch of Sambucus nigra in the summer of the second year 146. Viburnum Opulus: shoot, with flower and fruit (after Bentham) 147, Viburnum Lantana: shoot, with flower and young and ripe fruit (after Bentham) 148. Seedling of Valerianella coronata 149. Chrysanthemum Partheniwm (after Bentham) 150-152. = Do. do. successive stages in the life of the flower i ‘ 153-155. Seeds of Calendula: side and front views and section of hooked form, winged form, and grub-like form 156-158. Taraxacum officinale: section of part of a leaf grown in shade, in diffused light, and in sunshine (after Peck) 159-161, Campanula Medium : section of bud, and of flower in first (male) condition and in second (female) condition é 162. Arctostaphylos Uva-Ursi.: stamen seen from the side (after H. Miller) ; ; 163. Arctostaphylos alpina: section of flower (after H. Miiller) 164, 165. Erica Tetrali«: section of flower and stamen (after Ogle) 166. Pyrola wniflora: section of flower 167. Primula elatior: section through the wall of a capsule tafe Leclere du Sablon) 168. Primula farinosa : long-styled form and pollen 169. Do. short-styled do. 170-172. Cyclamen europewm: three stages in position of the flower (after Kerner) 173. Anagallts arvensis: wall of capsule (after Leclere du Sibi: 174, Utricularia vulgaris: plant with flower and parts (after Bentham) 3 5 ; 175. Utricularia vulgaris: flower and parts illustrating pollina- tion mechanism (after Hildebrand) 176. Utricularia vulgaris: bladder much enlarged, containing a small Crustacean which has been captured (after Darwin) . xiii PAGE 192 201 202 203 204 205 207 219 220 221 228 231 233 234 250 256 261 262 262 265 267 268 268 271 273 275 275 276 xiv BRITISH FLOWERING PLANTS FIG. 177. Utricularia vulgaris: opening of bladder, seen in front, much enlarged ‘ ; ‘ : 178. Utricularia vulgaris: mouth of bladder, seen sideways 179-180, Pinguicula alpina: transverse sections through leaf 181. Do. piece of epidermis of leaf, showing the two kinds of gland (after Kerner) 182, 183. Fraxinus excelstor: samara with half removed and the seed pulled out, and longitudinal section of seed . 184-186. Vinca minor: flower after the removal of the front part of the corolla, with pistil and stamen : 187, 188. Menyanthes trifoliata: short-styled, and forms of flower of long-styled (after Knuth) 189, 190. Myosotis versicolor: young and older dias 191. Anther of Borage , ‘ ‘ 192, 193. Lathrea: piece of an underground aboot anid longi- tudinal section through the same (after Kerner) 194. Lathrea: longitudinal section through a leaf (after Kerner) 195, 196. Lathrea: piece of the wall of a cavity, and plasmic threads radiating from the cells of the little heads (after Kerner). 197. Verbascum nigrum (after Beniliam) . 198. Scrophularia nodosa do. 199-201. Degitalis purpurea: section of flower, showing the anthers in three stages (after Ogle) 202. Veronica Chamedrys (after Bentham) 203-205. Bartsva alpina: subterranean bud, cross-section through part of the bud, and the margin of a bud scale in section . 206, 207. Bartsta Odontites: flowers with short and long pistil (after H. Miiller) 208. Seed of Melampyrum and chrysalis of Formica fusca 209. Kuphrasia officinalis: shoot, with flower, pistil, and fruit (after Bentham) . 2 ; 210. Huphrasia officinalis: partial section of flower, enlarged 211-213, Lamium albwm (White Dead-nettle) (after Bentham) with flower and section of flower 214, Group of Dead-nettles and Stinging-nettles . 215. Diagram to show arrangement of stamens in Nepeta . 216. Diagram to show position of stamens in most Labiates 217, 218. Scutellaria galericulata: side and front views of flower (after Knuth) 219, Teucrium Scorodonia: flower in ie first state: with ninithers erect PAGE 277 278 280 280 282 285 288 296 297 303 304 305 306 310 313 314 318 318 319 322 322 326 328 330 330 331 336 LIST OF ILLUSTRATIONS FIG. 220. Teucriwm Scorodonia: flower in the second state, with re- curved anthers and exposed stigmas 221, Salvia officinalis: section of a young flower 222, Do. flower visited by a bee 223. Do. older flower : 224, 225. Do. stamens in their natural position ail when moved by a bee . . 226. Plantago media (after Bentham) . 227. Leaf of Empetrum in transverse section (after jae j 228, 229. Male and female flowers of Callitriche . ; 230-232. Urtica dioica: vertical section through part of the leaf of a Stinging-nettle, showing two hairs, from the lower one of which the head has been broken, and tops of hairs more magnified (after Kerner) 233, End of shoot of Hop 234. Flower of Elm (after Grenier and Godron) 235-248, Terminal bud of Elm, with analysis showing ihe com- ponent scales 249, Branch of Beech 250. Branch of Spanish Chestnut 251. Fruit of Oak opened 252, Fruit of Nut opened 253. Winter bud of Beech 254-256. First, sixth, and eleventh pair of stipules of same 257. Diagrammatic transverse section of pair of stipules of same, showing the extent to which they overlap 258. Bud of same after eleven pairs of stipules have been removed 259-261. Twelfth, shichean th: and fourteenth pairs of stipules of same, with leaf . 262. Stipule of the fifteenth pair with leaf 263. Last leaf discernible, occupying the centre of the bud 264. Junction of the wood of two seasons’ growth of same, showing scars of the outer pairs of stipules that covered the winter bud and which were unaccompanied by leaves 265, 266. Transverse sections of Beech leaf grown in sunshine we shade respectively (after Pfeffer) . 267. Root-tip of Beech with closely adherent vayectial mantle (after Kerner) ; 268, 269. Bud of Spanish Ghovtant and second scale depachel 270. Oak shoot 271. Oak bud xv PAGE 336 338 338 338 338 342 353 354 368 368 368 368 368 370 371 371 372 372 xvi BRITISH FLOWERING PLANTS FIG. 272-292. Quercus pedunculata: pairs of stipules forming the scales of the winter bud, sketched in the first week of May 293, Young female flower of Oak with involucre of scales 294. The same, cut lengthwise 295, Cone-scale of Birch . 296. Diagram of a three-flowered group from the female eatiein at Birch (after Eichler) 297. Pair of fruits of Hornbeam . 298. Diagram of a pair of female flowers of enous (utter Eichler) 299. Pair of fruits of Hazel, pia in its involucre 300. Plan of arrangement of a male flower of Hazel (Gtter Eichler) 301, 302. Female and male flowers of Hival 303. Populus nigre: terminal winter bud, showing a pair of persistent stipules belonging to a leaf of last season 304. Black Poplar shoot ‘ 305. Pinus sylvestris: fragment of terminal bud representing seven tiers of scales of the winter bud 306. Pinus sylvestris: a detached scale-base 307. Do. analysis of terminal bud 308. Do. apex of branch 309. Picea excelsa: apical and two lateral buds showing pedestals of leaves after the green portion has been removed 310-315. Picea excelsu: normal and perfect leaf, and successive modifications to form scales 316-318. Picea excelsa: inner scales after iiiew have Alsiiediina about the middle of April 319. Diagrammatic section of Arum 320. Flower of Lemna trisulca (after Le Maout ead Tecate 321-323, Position of the chlorophyll granules in the cells of the frond of Lemna trisulea in darkness, in diffused light, and in sunlight (after Stahl) 324-327. Potamogeton natans: palisade cell of leaf i in diffused light and in sunshine, with sections of same (after Stahl) 328. Diagrammatic section of Orchid flower (after Darwin) 329. Orchis mascula (after Bentham) 330. Orchis mascula: side view of flower, with sepals anil petals cut off except the lip, of which the near half is cut away, showing relation of pollinia and nectary (after Darwin) 331, Orchis mascula: front view of flower, with sepals and petals removed except the lip (after Darwin) PAGE 373 374 374 375 875 376 376 377 377 377 379 381 384 384 385 385 387 387 387 390 392 393 395 400 401 402 402 FIG. 332, 333, 334,” 335 337. 338. 339. 340. 341, 342, : 344, 345. 346. 347. 348, 349. 350. 351. 352. LIST OF ILLUSTRATIONS Orchis mascula : the two pollinia (after Darwin) Ophrys apifera (after Bentham) Cephalanthera grandiflora (after Bentham) ; 336. Cypripedium Calceolus: front and side views of flower . Iris Pseud-acorus, showing relation of petal, stamen, and stigma . Allium ee (after Bente) Seed of Narthecium Pistil of Colchicum autuwmnale (after Grenier and Godron) Flower of Juncus articulatus (after Grenier and Godron) 343. Male and female flowers of Sedge (Carex acuta) Carex paludosa: vertical section through part of a leaf, showing protection of stomata from moisture by papilla-like outgrowths of the surface (after Kerner) . Diagram of a spikelet of Wheat dissected (from Ward after Oliver) Diagram of a spikelet of atest teat Seeded (from Ward after Oliver) Leaf of Poa trivialis Poa annua: transverse section of half of leaf, including the median keel, and showing the motor cells (after Ward) Nardus stricta: transverse section of leaf showing support- ing tissue and motor cells (after Ward) Awned fruit of Stipa pennata Margin of leaf of Festuca set with barbs Arrhenatherum avenaceum: spikelets and anthers in various stages illustrating pollination (from Ward after Kerner) xvii PAGE 402 408 410 413 415 421 422 425 426 430 430 431 432 432 433 433 434 436 440 GLOSSARY Accumbent (p. 77), of the radicle when lying parallel with the edges of the cotyledons. Achene (p. 47), a one-seeded fruit with a thin dry wall, which does not split open when ripe. Albumen, see Endosperm. Alien, a plant which has presumably been introduced by human agency. Anatropous (p. 365), of the ovule, turned through 180°, so that the micropyle points towards the placenta. Androdiecious, having hermaphrodite and male flowers on different plants. Andromonecious, having hermaphrodite and male flowers on the same plant. Anemophilous (p. 5), of plants in which the pollen is carried to the stigma by the wind. Anther, that portion of the stamen which contains the pollen. Arillus, arilloid, or aril, a growth on the outside of the seed-coat. Berry, a fruit which, except for the outer skin, is succulent or juicy, as in Grape or Gooseberry. Bipinnate (p. 49), twice pinnate (q.v.), the pinne again pinnately divided. Biternate (p. 49), with three parts, each of which again divides into three. Bract, a leaf from the axil of which springs a flower or flower-bearing shoot. Bracteole (p. 371), a small bract, situated on the flower-stalk. Caducous, falling early, as the sepals of Poppy. Calyx (p. 3), the outer whorl of the flower. Capsule, a dry many-seeded fruit, opening when ripe to allow the seeds to escape. Carpels, the leaves which make up the gynecium or pistil. xix XX BRITISH FLOWERING PLANTS Carpophore (p. 17), fruit-bearer, applied to the axis of the fruit in Umbellifers which splits lengthwise and bears the two mericarps. Chlorophyll (p. 32) the pigment to which leaves owe their green colour. Cleistogamous (p. 8), of plants which, besides the usual conspicuous flowers, have others which are smaller, generally uncoloured, and do not open. Corolla (p. 3), the second whorl of the flower. In most cases this is tle coloured part. Corymb, an inflorescence in which, owing to the inequality of their stalks, the flowers stand on one level. Cyme, a definite inflorescence, one in which the main axis ends at once in a flower, Deciduous, lasting for a time, but ultimately falling, as opposed to persistent. Decussate, crossing at right angles, like the pairs of leaves in Dead- nettle, Dehiscent, opening when mature, as an anther or many fruits. Dichogamous (p. 4), of flowers in which the anthers and stigmas do not mature simultaneously. Diclinous, having all the flowers on any one plant either male or female ; that is to say, either with stamens but no pistil, or pistil but no stamens. Dicotyledon, having an embryo with a pair of seed-leaves or cotyledons. Dimorphous, of species in which there are two forms of flowers, differing in the relative position of the anthers and stigma. Diccious (p. 4), having the stamens and pistil situated not only in distinct flowers, but also on separate plants, Disk, an outgrowth of the floral axis, often secreting honey. Drupe, a fruit the inner wall-layers of which are hard, forming a “stone,” as in plum. Endosperm, the food-store present in many seeds along with the embryo. Entomophilous (p. 5), of plants in which the pollen is carried to the stigma by insects. Epidermis, the outermost layer of cells of a leaf or young stem. Epigynous, situated upon the ovary. Equitant (p. 378), when leaves are folded one over the other in the bud. Exalbuminous, without albumen (endosperm), when the embryo occupies the whole seed. GLOSSARY xxi Filament, the stalk of the anther. Follicle, a several-seeded pod-like fruit, which splits when ripe down one side only, as in Larkspur or Columbine. Geotropic (p. 45), affected by the stimulus of gravity. Glabrous, not hairy. Glume (p. 431), the bract of a grass flower. Gynodiccious, having hermaphrodite and female flowers on different plants. Gynomonecious, having hermaphrodite and female flowers on the same plant. Heterogamous, having male, female, and hermaphrodite flowers, or any two of them united in one head, as in Composite. Heteromorphous, having more than one form of flower. Heterostyly, when two or more forms of flowers are characterised by styles of different lengths. Homogamous, of flowers in which stigmas and anthers are functional at the same time. Hypogynous, arising below the ovary on the floral axis. Incumbent (p. 76), of the radicle when lying parallel with the faces of the cotyledons. Indehiscent, not opening when mature. Involucre, an association of bracts round the base of a flower or in- florescence. Lanceolate, shaped like the head of a lance. Lenticel (p. 219), a small area of loosely arranged cork cells allowing the passage of air. Linear, narrow, with parallel sides, like a grass leaf. Loculicidal dehiscence, of a capsule, splitting down the middle line of each carpel. Mericarps (p. 17), one-seeded portions of a compound fruit which separate when ripe. Micropyle, the aperture between the ovule-integuments through which the pollen tube reaches the embryo-sac. Monecious, having stamens and pistil in separate flowers, but on the same plant. Monocotyledon, having an embryo with a single seed-leaf or coty- ledon. xxil BRITISH FLOWERING PLANTS Monomorphous, of species in which all the flowers resemble one another in the relative position of the anthers and stigmas. p, one-thousandth part of a millimetre. Nectary, that part of the flower which secretes honey. Obovate, of a leaf which is egg-shaped (ovate) in outline, but attached at the narrower end. Orthotropous (p. 364), of the ovule, standing erect, the micropyle being at the opposite end to the stalk. Palmate, of a leaf, with divisions spreading from a common point. Panicle, a branched inflorescence with stalked flowers. Pappus (p. 231), the hairy development which replaces the calyx in Composite. Parenchyma, thin-walled cellular tissue, with cells not much longer than broad. Pentamerous, with parts in fives. Pericarp, the wall of the fruit. Perigynous, situated around the ovary. Petals, the leaves of the corolla. Pinnate, of a leaf, with divisions arranged in a series right and left of an axis, as the barbs of a feather. Pinnatifid, of a leaf, when pinnately cut about half way to the mid-rib. Pistil, the central organ of the flower. It generally consists of one or more ovaries and stigmas ; the stigma is often raised on a stalk, called the style. Placenta, the part of the ovary on which the ovules are borne. Plumule, the bud in the embryo which will develop into the stem and leaves of the plant. Polygamous, having male, female, and hermaphrodite flowers on the same or on distinct plants. Pome, a fruit in which the succulent floral receptacle surrounds and is completely merged with the pistil, asin Apple and Pear. Protandrous, of flowers in which the stamens come to maturity before the stigmas. Protogynous, of flowers in which the stigmas come to maturity before the stamens. Raceme, an inflorescence consisting of an elongated axis bearing stalked flowers, the youngest at the top. % Radical, of leaves springing from a shortened stem, thus appearing to come from the root. GLOSSARY xxiii Radicle, the root of the embryo. Receptacle, the axis of the flower, generally more or less thickened. Rhizome, an underground stem, generally more or less thickened. Rostellum (p. 401), the non-receptive third stigma of an Orchid flower. Samara, a winged fruit. Scape, a leafless stem bearing flowers. Sclerenchyma, hard tissue, for support (mechanical tissue). Sepals (p. 3), the leaves of the calyx. Septicidal dehiscence, of a capsule splitting along the septum which separates the constituent chambers. Silicula or silicule (p. 85), w siliqua which is not longer than broad. Siliqua, the fruit characteristic of Crucifere, opening longitudinally by two valves which separate from a central septum. Spike, like a raceme (q.v.), but with sessile flowers. Stamens (p. 4), the parts of a flower which generally stand next the corolla, on the inner side. They usually consist of a stalk or filament, and an anther, containing the pollen. Staminode, a barren stamen, generally much reduced in size. Stigma (p. 4), that portion of the pistil on which the pollen must be deposited in order to fertilise the flower. Stipule, an appendage of the base of the leaf, generally borne in pairs. Stoma, the month or aperture between two adjacent epidermal cells. Style, the stalk of the stigma. Testa, the secd-coat. Tetramerous, with parts in fours. Transpiration, the giving off of water-vapour by green leaves. Trimorphous, of species in which there are three forms of flowers, differing in the relative position of the anthers and stigma. Tricecious (p. 110), having hermaphrodite, male, and female flowers on distinct plants. Tripinnate (p. 50), thrice pinnate (y.v.). Umbel, an inflorescence in which several stalked flowers spring from one point ; the youngest flowers are nearest the centre. Viviparous (p. 442) when the seed is replaced by a green shoot, as in several Arctic and Alpine grasses. Fic. 1.—Geranium sylvaticum. CHAPTER I INTRODUCTION Our knowledge of the origin and past history of our British Flora is still very incomplete. The researches of geologists, however, and especially of Mr. Clement Reid, have made it probable that before the glacial period the flora of the British Isles did not materially differ from the present. Some, at any rate, of our northern forms were already here, as well as other more southern species, such as the Hawthorn (Crategus) and some, such as the Spruce Fir, which were driven away, or rather killed out, by the cold, and have never returned. Some of our plants have been introduced by man intentionally, and others, the so-called weeds of cul- tivation, unintentionally. Some which might be thought to be thoroughly established—the Lime, for instance,— though they produce abundance of fruit, never or scarcely ever reproduce themselves by self-sown seed. Even the Common Elm is said to produce perfect seed two or three times only in a century. The northern limit of plants is not determined merely by the average temperature ; it depends on the respective gL B 2 BRITISH FLOWERING PLANTS CHAP. summer and winter temperatures, on the amount of sunshine, of moisture, and various other factors. For instance, some plants can stand a severe winter, pro- vided the summers are sufficiently hot; others are satisfied with moderate warmth in summer, but cannot stand a severe wmter. Hence some plants will thrive at Paris, but cannot maintain themselves in Kent; while others flourish near London, but are killed by the colder winters of Paris. Apart from their systematic distribution in natural orders, plants fall into certain great biological groups, differing according to the poitit of view from which we consider them. Thus they are annual, biennial, or perennial, according as they run through their life- history in one or two seasons, as do many of our herbs, or persist for several or many years, as in the case of some herbaceous plants like the Nettle, and all the larger plants which become shrubs or trees. They may be evergreen, retaining their leaves for more than one season, so that the tree is never bare, as in Holly, Pines, or Yew; or deciduous, shedding at the end of each grow- ing season the leaves which expanded earlier in the same year. Again, while most live on land, many are aquatic. In some the pollen is carried by the wind, in others by animals, especially insects. ANNUALS AND PERENNIALS In very dry localities we find an unusual proportion of annual species, which come up during the wet season, if there be one, or after the rains which occasionally occur. According to Boissier, annual species rise to their maximum on the hot coast region of Granada, where, out of 1070 species, 542 are annual, 46 biennial, and 482 perennial. Alpine and Arctic conditions, on the other hand, favour perennial species. These generally have strong roots which go deep into the ground, and are thus pro- tected from cold, while on the return of more genial conditions they throw out aerial shoots. In the moister I INTRODUCTION 3 regions of the tropics, also, there is a great preponder- ance of perennial species, but with this difference, that while in cold regions the persistent parts are under- ground, in the form of woody stems, or bulbs, tubers, ete. protected by the soil against extreme cold, in hot regions they require no such protection, and are to a great extent aerial. Uniform climates also appear to favour perennial species. In the Sandwich Islands, for instance, species of Violet and Geranium, of Composites and Caryo- phyllaceze, become shrubby. We owe to Messrs. Bonnier and Flahault a very interesting memoir on the flora of Dauphiné from this point of view. They found— Annual, Perennial. In the region below the Pine forests . 60 per cent. 40 per cent. » Pine and Grass region oS ee 67 Cy, » Upper Alpine , . 6. os, 94 —C« As regards the character of the soil, etc., they give the following table :— Annual and , - Perennial. Biennial. Stony and sandy places 32 per cent. 68 per cent. Dry meadows j ‘ 97 4, 90°3 ,, Damp ,, 5 ‘ : ISS. sy 857s, Woods and bushy places 4 55 96 Aquatic é é 26, 974 Arable fields : . 888 ,, 112 ., Many plants, as, for instance, Mignonette (Reseda odorata), which are habitually annual, become biennial if the flower-buds are pinched off.’ Tur FLOWER If we examine a common flower, such, for instance, as a Geranium (Fig. 1), we shall find that it consists of, first, an outer envelope or calyx, sometimes tubular, sometimes consisting of separate leaves called sepals ; secondly, an inner envelope or corolla, which is gener- ally more or less coloured, and which, like the calyx, is 1 Hildebrand, in Engler’s Bot. Juhro, ii. (1881). 4 BRITISH FLOWERING PLANTS CHAP. sometimes tubular, sometimes composed of separate leaves called petals; thirdly, of one or more stamens, consisting of a stalk or filament, and a head or anther, in which the pollen is produced; and fourthly, a pistil, which is situated in the centre of the flower, and consists generally of three principal parts—the ovary comprising one or more compartments at the base, each containing one or more ovules; the style; and the stigma, which in many familiar instances forms a small head at the top of the style or of the ovary, and to which the pollen must find its way in order to fertilise the ovule. But though the pistil is thus surrounded by one or more rows of stamens, and though most flowers are capable of fertilisa- tion by their own pollen, still it is a great advantage to a species that the flower should be fertilised by pollen from a different stock. How, then, is self-fertilisation prevented ? There are three principal modes. Firstly, in many species the stamens and pistil are in separate flowers, sometimes borne on different plants. Secondly, even when the stamens and pistil are in the same flower, they are in many species not mature at the same time. This was first observed by Sprengel in Hpz/obium angusteifolium as long ago as 1790. In some cases the stigma has matured before the anthers are ripe, while in other and more numerous cases the anthers have ripened and shed all their pollen before the stigma has come to maturity. Thirdly, there are many species in which, though the anthers and stigma are contained in the same flower and are mature at the same time, they are so situated that the pollen can hardly reach the stigma of the same flower. Another circumstance which makes for cross-fertilisa- tion is the prepotence of pollen from another plant of the same species. If plants of several varieties are grown together, the seeds cannot be reckoned on to come true. lJiven after twenty-four hours Darwin found that pollen from another plant exercised a pre- dominant influence. He placed on several stigmas of a long-styled Cowslip (Primula veris) plenty of pollen I INTRODUCTION 5 from the same plant, and after twenty-four hours added some from a short-styled dark-red Polyanthus, which is a variety of the Cowslip. From the flower thus treated thirty seedlings were raised, and all these without ex- ception bore reddish flowers; so that the effect of the plant’s own pollen, though placed on the stigmas twenty- four hours previously, was quite destroyed by that of the red variety. In rare cases the pollen, if placed on the stigma of its own flower, acts like a poison ! In most of our trees—Oaks, Beeches, Spanish Chest- nuts, Conifers, and many herbaceous plants—the pollen is carried by wind, and the plants are therefore said to be anemophilous. In such cases there is a tremendous waste of pollen. We all know the clouds produced by a Scotch Pine. Wind-fertilised flowers, as a rule, are small, green, and regular; the pollen is dry and dusty, often round and generally smooth. The stigmas are covered with long hairs or papille, thus offering a larger surface to the pollen and increasing the chances of fertilisation. On the other hand, in the great majority of flower- ing plants the pollen is carried from one flower to another by insects. Such flowers are called entomo- philous. They are generally large, and coloured— yellow, white, red, or blue. They often emit scent and produce honey, both of which serve to attract insects. They also present great diversities of form and struc- ture, often being irregular. The pollen is often angular, with teeth, spines, or furrows, and more or less sticky. Bees and humble bees play a most important part in carrying pollen from flower to flower. Every one knows how important flowers are to insects; every one knows that bees, butterflies, etc., derive the main part of their nourishment from the honey or pollen of flowers; but it is, on the other hand, only recently that we have realised how much the flowers themselves are dependent on insects. Yet it has, I think, been clearly shown that if insects have been in some respects modified and adapted with a view to the acquirement of honey and pollen, flowers, on the other 6 BRITISH FLOWERING PLANTS CHAP. hand, owe their scent and honey, their form and colour, to the agency of insects. Thus the lines and bands by which so many flowers are ornamented have reference to the position of the honey; and it may be observed that these honey-guides are absent in night flowers, where they, of course, would not show, and would there- fore be useless, as, for instance, in Lychnis vespertina or Silene nutans. Night flowers, moreover, are generally pale; for instance, Lychnis vespertina is white, while Lychnis diurna, which flowers by day, is red. It must be borne in mind that, as a rule, each work- ing bee keeps during each journey to a single species of plant. It is interesting that this fact: was mentioned by Aristotle. It has been questioned, probably because male bees have been watched, and they are not so con- stant as the females. For them it is not so important. Male bees take no share in the provision of food, and their time is of no value. Hence neither of the two reasons which influence female bees apply to them. One advantage to the bees is the economy of time resulting from doing the same thing over and over again; but another, no doubt, is thatthe pollen of different species is kept separate and not mixed together. Working bees waste no time, and fly quickly. Darwin timed humble bees at 10 miles an hour, and I believe hive bees are considerably more rapid. I have often watched them, and seen them visit some twenty flowers in a minute; and though one would suppose that when flowers are numerous many must be missed, this does not appear to be the case. Darwin, for in- stance, near Bournemouth, in the course of a long walk examined several hundred flowers of Heath (Hrica Tetralix), and every one had been visited. Nay, each flower is visited several times a day. In the case of Dictamnus Fraxinella he found the visits amounted to thirty in a day. Of course, however, in the case of many species the visits are comparatively few and far between. 1 Avebury (Lubbock), Flowers, Fruits, and Leaves. I INTRODUCTION 7 Flowers may be divided into groups according to the manner in which the anthers and stigma are pro- tected against wet and cold. 1. Pendent or hanging flowers: as, for instance, some Campanulas, Heaths, Rhododendrons, Rosacez (Geum), Solanaceze (Atropa), Boragineee (Pulmonaria), Ranunculacez (Aquilegia), Liliaceze (Convallaria), Ama- ryllidaceze (Snowdrop, Leucojum), ete. 2. Others are more or less horizontal: as, for instance, Viola, Aconitum, most Labiates, as Lamium (Dead- nettle), Nepeta (Ground Ivy), Stachys, Prunella, ete. ; Leguminose, Scrophulariacese, as Antirrhinum (Snap- dragon), Linaria, Mimulus, ete. 3. Others are upright, but the anthers and stigmas are arched over by the sepals or petals, or both: as, for instance, among Ranunculacez, Trollius and Eranthis. 4, Others are protected by the leaves: as, for instance, Tilia (Lime) and Impatiens (Balsam). 5. Another group stand upright, but («) the passage is so narrow that rain and dew cannot enter, or (0) it is partly closed by projections or (c) by hairs: as, for in- stance, some Primulas and Geraniums. 6. Some flowers are upright by day or in sun- shine, but hang down at night or in rain: as, for instance, some Campanulas (C. patil), Scabiosas, Geraniums (G. Robertianum), Epilobiums, Anemones, Saxifrages, ete. Sometimes it is the flower-stalk which bends, some- times, as in Epilobium, the ovary. 7. In some cases the flowers or flower-heads close : as, for instance, many Composites, Crocus, Gentians, Campanulas, Peonies, Flaxes, Water-lilies, Anemones, Erythrea. Sometimes the anthers themselves open or close: according to the weather : as, for instance, in Alchemilla (Lady’s Mantle), Laurus, Plantago, Thesium, etc. Those of Thesium alpinum are said to close in 30 seconds if moistened. In addition to the ordinary coloured flowers, some 8 BRITISH FLOWERING PLANTS CHAP. plants have a second kind in which the petals are absent, or at any rate minute, and which do not open. For instance, in some of the Violets—V. odorata, canina (p. 98), ete.,—besides the blue flowers with which we are all so familiar, there are others almost without petals and stamens, which indeed have scarcely the appearance of true flowers, but in which numerous seeds are produced. “Cleisto- gamous” flowe1s, as these have been called, occur in Lamiwm am- plexicaule (Fig. 2), Oxalis Acetosella, Tri- folium — subterraneum, and other plants be- oe Fra. ae of longing to very different togamous flower. groups. The flowers of water plants also fall into certain well-marked groups. In the first we may place those which have a con- spicuous coloured flower and are adapted for fertilisation by insects: as, for instance, the Water-lilies, Water Ranunculi, Limnanthemum, MHottonia, Utricularia, Lobelia Dortmanna, Alisma, Hydrocharis, Stratiotes. These project singly, or in terminal bunches, above the water. They have undergone no special modifica- tion, though the flower-stalk is more or less strengthened so as to maintaim them in an upright position, and the leaves are often arranged so as to serve the same purpose. Hair-like outgrowths are sometimes found in the flower (eg. Limnanthemum) which will prevent the nectar from being flooded by water which may be splashed in. They are generally white or yellow, which makes them more conspicuous against the bluish water. Lobelia Dortmanna is the only blue flower in the group, but, as Schenck says,’ we must remember that blue is in any 1 Die Biologie der Wassergewiichse, I INTRODUCTION 9 case by no means a common colour. Such flowers if kept under water, by flood or otherwise, sometimes become cleistogamous (see above): as, for instance, in Ranunculus aquatilis, Alisma natans, Subularia aquatica, and Lllecebrum verticillatum. To a second group belong certain species in which the flowers raise themselves into the air, but which are not large or conspicuous, and which are presumably wind-fertilised : as, for instance, Myriophyllum, Potamo- geton (Pondweed), and some Sparganiums. In a third group the flowers as well as the leaves are submerged. Callitriche is an intermediate form ; some species have aerial, others submerged flowers. The flowers are very simple, arranged in the axils of the leaves—the males reduced to a single stamen, the females to a pistil. As typical of this group I may mention Cerato- phyllum demersum. The flowers are surrounded by a whorl of minute bracts: the female consists of a small ovary with a single style; the male of from 12 to 20 oblong sessile anthers. The pollen, as in all submerged flowers, has no extine. Zostera, the Grass-wrack of our shallow seas, has the small flowers enclosed in a sheath at the base of certain leaves, which do not materially differ from the rest, but are somewhat smaller. They are arranged in two rows, with alternately male and female flowers. They are protogynous, and the pollen is peculiar, being thread- like, but without motion. Lastly, there is a small group, of which Vallisneria is the best-known form, and which in our flora is repre- sented by Ruppia. The flowers are very simple, and consist of two bilocular anthers and an ovary with four carpels. The spadix or stalk on which they grow is at first short. The anthers open first, and eject the pollen, which, being lighter than water, at once rises to the surface. Immediately afterwards the spadix lengthens rapidly, carrying the female flower to the surface, where it meets the floating pollen. In Vallisneria the male 10 BRITISH FLOWERING PLANTS CHAP. flowers are on a separate part of the plant, but are set free and rise to the surface, on which they float in some numbers around the female flowers, one or more of the dehiscing anthers coming in contact with the stigmas. While some water plants (Utricularia, Hottonia, and Lobelia, for instance) ripen their seeds in the air, by far the larger number after flowering draw the ovary down under water. In many cases the shell of the fruit develops air cavities, which, when the seeds are ripe, carry them up again to the surface, and thus promote dispersal. No doubt in many cases birds carry them from one river or lake to another. It is easy to understand that the seeds and fruits of water plants do not develop wings or parachutes, which in so many land plants serve this purpose; nor do we find cases in which they are thrown or jerked. It would appear that the chances of the ovule being fertilised and the seed coming to maturity are, on the whole, fewer in water plants than in land plants. On the other hand, the constant supply of water renders the vegetative orowth more luxuriant. Hence we find that aquatic plants are generally perennial. In our own flora Subularia aquatica and Najas marina are the only annual species. Freshwater plants, for obvious reasons, do not reach high latitudes or great altitudes. In temperate regions, however, the species have, as a rule, very wide ranges, not only in many cases round the world, but even reappearing in islands far from the mainland, mainly, we can hardly doubt, through the agency of water birds. Najas marina is a very good instance. Widely spread in the north temperate zone, it occurs also in Australia, the Sandwich Islands, Chndinies. Venezuela, Brazil, etc.’ Another remarkable peculiarity of flowers which I think, as I suggested in a lecture to the British Asso- ciation at Belfast in 1874, has reference to their 1 Rendle, Trans. Linn. Soc. (Bot.) ser. 2, vol. v. I INTRODUCTION 11 relations with insects, is the habit of “sleeping,” which characterises certain species. Many flowers close their petals during rain, which is obviously an advantage, since it prevents the honey and pollen from being spoilt or washed away. Every- body, however, has observed that even in fine weather certain flowers close at particular hours. This habit of going to sleep is surely very curious. Why should flowers do so? Tn animals we can understand it; they are tired and require rest. But why should flowers sleep? More- over, some flowers sleep and not others, and those which do sleep keep different hours. The Daisy opens at sun- rise and closes at sunset, whence its name “ day’s-eye.” The Dandelion (Taraxacum officinale) is said to open about seven and close about five; Arenaria rubra, to be open from nine to three; NMymphea alba, from about seven to four; the common Mouse-ear Hawkweed (Meracium Pilosella), from eight to three; the Scarlet Pimpernel (Anagallis arvensis), to waken at seven and close soon after two; Tragopogon pratensis, to open at four in the morning and close just before twelve, whence its English name, ‘“‘ John-go-to-bed-at-noon.” Farmers’ boys in some parts are said to regulate their dinner- time by it. Other flowers, on the contrary, open in the evening.' Now, it is obvious that flowers which are fertilised by night-flying insects would derive no advantage from being open by day; and, on the other hand, that those which are fertilised by bees would gain nothing by being open at night. Nay, it would be a distinct disadvan- tage, because it would render them liable to be robbed of their honey and pollen by insects which are not capable of fertilising them. It may be observed also that wind-fertilised flowers do not sleep; and that some of those flowers which attract insects by smell emit 1 In my own observations the opening and closing were more gradual and more dependent on the weather than I should have expected from the state- ments quoted above. 12 BRITISH FLOWERING PLANTS CHAP. their scent at particular hours; thus, Hesperis matron- alis and Lychnis vespertana smell in the evening, and Habenaria bifolia is particularly sweet at night. Besides the means of attracting welcome guests, many plants have adopted various devices for barring access to their stores of honey of insects whose visits would be of no use in transferring pollen. For instance, in aie case of bee flowers, small flying insects are kept from the nectar by barriers of stiff hairs which they are not strong enough to pass—e.g. Tro- peolum. Creeping insects, as ants, are frequently kept back by sticky hairs on the stem or flower-stalk —as in many Saxifrages. A large proportion of dicotyledonous flowers have five sepals and five petals. Why is this? It is probably to be ex- plained by the phyllo- taxy, or arrangement of the leaves on the stalk. The petals, as Goethe seems first to have sug- gested, are modified leaves. Now if we ex- amine a Rose shoot (Fie. 4) we shall find that the leaves are arranged in a spiral round the stem in such a manner that with whatever leaf we start the sixth comes directly over it, the seventh over the second, and so on. In fact, the leaves form whorls of five, one over the other. This is still more evident in those species which have a five- Fic. 4.—Shoot of Rose. I INTRODUCTION 13 angled stem. If we hold it so that the youngest leaf (1) of the piece of shoot figured sits on the uppermost ridge in Fig. 5, the leaf immediately above (2) rises not from the next ridge, but the next but one, that on the lower left-hand side. The next (3) sits on the ridge on the upper right-hand side. No. 4 is on the left. Finally, leaf No. 5 is on the ridge forming the lower right-hand edge of the stem. I say finally, because this completes the series. Leaf No. 6 is on the same ridge Fic. 5.—Whorl of Bramble leaves. as, and corresponds to No. 1, leaf No. 7 to leaf No. 2, No. 8 to No. 8, and so on. The leaves, in fact, are not on the ridge next to the ones immediately above and below, but on the next but one. Thus, then, each whorl consists of five leaves arranged in a double spiral round the stem. This is known as the 2/5 arrangement. Incidentally it throws light on the pentagonal form of the stem. The arrangement is, however, not quite so obvious as would otherwise be the case—firstly, because the stem is often somewhat twisted, and, secondly, because the petiole of the leaf is itself sometimes bent, so that the leaf may 14 BRITISH FLOWERING PLANTS CHAP. take the position to secure the fullest amount of light. In Fig. 5 this arrangement is clearly shown. Now if we imagine the intervals between the leaves suppressed, we shall see that they would lie in whorls of five. In fact, the five sepals form one such whorl and the five petals another. We may test this suggestion by taking the case of the Lilac and Privet, which have 4 sepals and 4 petals. Here the leaves are opposite, each pair at right angles to those above and below. Here, therefore, the whorl of leaves would consist, not of five, but of four. There are indeed some excep- tions which must be otherwise accounted for. For instance, in genera which contain species of different sizes the number of sepals and petals is. often less in the smaller than in the larger ones. Flowers with parts in fours are also frequently met with in orders where the pentamerous arrangement is the more common. Caryophyllacez is a good example. Taking our British genera, we find in the smaller flowered ones—such as Cerastium, Stellaria, and Sagina—the number of parts sometimes 4 instead of 5. Assuming, as we may, that all had a common penta- merous ancestor, we regard the tetramerous forms as resulting from the dropping out of one member from each whorl. In other cases, however, the tetramery is due, not to a loss, but to a fusion of parts. Thus most species of Veronica have 4 sepals and a 4-lobed corolla. There is no doubt, however, that the upper petal represents two which have become united. It is very often larger than the others, and sometimes its double origin is indicated by a notch. In some cases, more- over, both petals are developed, and we have a penta- merous corolla, bringing Veronica into line with the other members of its family, Scrophulariness, where the corolla is formed on a pentamerous plan. The tetra- merous calyx is explained by the loss of the upper- most sepal; in pentamerous species this, however, is developed. In one of our commonest British orders, Cruciferee, the flower is built on a 4-plan, but we I INTRODUCTION 15 cannot correlate this with the leaf-arrangement or derive it in any simple way from a pentamerous flower —it is a remarkably constant type of flower, and the story of its development is lost. Last come such cases as the Lilac and Privet, where the leaves are in pairs, and opposite, so that the whorl would consist of four leaves. FRUITS AND SEEDS As regards fruits and seeds, one main point to be considered is the mode in which they are dispersed. From this point of view they may be divided into various classes :— Seeds or fruits with wings, which are carried by wind. Seeds or fruits with feathery appendages, carried by wind, and sometimes, as in Willow, floated by water. Seeds in capsules which open at the top, the seeds being jerked out by wind. Seeds or fruits with hooks, which are carried by animals, Fruits which are eaten and the seeds thus carried by animals. Seeds which are thrown by the plants. To the first category, viz., those with wings, belong mainly trees: as, for instance, Pines and Firs, Syca- mores and Maples, Elms and Birch; while though the fruit of the Lime is not itself winged it is attached to a leafy bract which serves the same purpose. The same is the case with the Hornbeam. The next class, those with hairy appendages, is very extensive. To it belong the Willows and Tamarisks, many Grasses, Bulrushes, Cotton-grass, Willow-herbs, Dandelion, Thistles, and many other Composites, etc., ete. Examples of plants in which the fruits or seeds are provided with hooks are found in Agrimony, Bur- parsley, Burdock, Carrot, Cleavers (Galium), Enchanter’s 16 BRITISH FLOWERING PLANTS CHAP, Nightshade (Circea), some Forget-me-nots, etc. That these hooks really serve to attach the seeds to passing animals is shown by the interesting fact that they are characteristic of low plants. In our flora they do not occur on any plant which exceeds 2 or 3 feet in height, nor do they occur on water plants. On the other hand, this argument does not apply to seeds which are eaten and thus carried by animals, especially by quadrupeds and birds. To this class belong all those popularly known as fruits and nuts, viz., Apple, Pear, Plum, Hazel, Beech, Oak, etc., ete. It is interesting that while more or less green and inconspicuous when immature, in many cases as they become ripe they assume bright colours, especially orange, red, purple, and dark blue. It seems probable that it is an advantage for fruits which ripen when the leaves are still green to be red, as this gives the greatest contrast. On the other hand, red would not be con- spicuous against faded leaves which are brown, or even sometimes themselves reddish. For such fruits, blue or black would be more advantageous, and, as a matter of fact, many heath and moor species have bluish or black fruit, as, for instance, the Bilberry, the allied Vacciniwm uliginosum, or the Black Bearberry. In some cases the juicy pulp only is assimilated, and the hard seeds pass through uninjured; but even digestible seeds often pass undigested; moreover, we know that small birds continually fall victims to hawks, etc., and perish from accidents, so that the cases are numerous where undigested seeds have a chance of growing. The northern birds, as Mr. Reid points out,’ generally come to us in autumn when the seeds are ripe, and must bring many southwards with them. Many plants develop their seeds in capsules, which open at the upper end, so that while the seeds lie quiet while it is calm, they are jerked out by a high wind. This is the case, for instance, in Poppies, in 1 Origin of the British Flora. I INTRODUCTION 17 which the tiny seeds are jerked out through small holes round the upper edge of the capsule. In many Campanulas the capsule opens by pores at the base of the capsule, which, however, becomes inverted when mature. One of the most interesting groups of seeds are those which are thrown by the plants themselves, as, for instance, in the Geraniums, Oxalis, some Violets, Car- damines, Euphorbias, ete. It is remarkable how much in these cases the mechanism differs. Some seeds mimic small insects, and are no doubt picked up, and carried some distance before the mistake is discovered, by birds (see, for instance, the Mallows), or even by insects, as in the case of Melam- pyrum. A large number of species have very minute seeds. These, of course, have a larger surface in proportion to their weight, and are readily carried by wind without any special provision for the purpose. Arctic and Alpine species very generally belong to this class. Many seeds and fruits develop air cavities, which renders them lighter, and thus facilitates dispersal. This is specially the case in water plants, and the seeds are thus enabled to float. In the great family of Umbellifers, as a rule, the ‘“‘carpophore” splits lengthwise, and the two mericarps, each containing a seed, hang loosely by their upper ends to the two whip-like filaments. The dry plants are very elastic, and sway backwards and forwards in the wind, until at last some strong gust tears the mericarps off and carries them away. Even when there is no special provision for dispersal, seeds must be often carried about on the feet of animals and the flanks of wallowing quadrupeds. Another point to be considered with reference to seeds is the character of the surface. Some are smooth and shining, some reticulate, some pitted. Those with hooks or hairs have already been mentioned. Reticula- tions often, as, for instance, in Geraniums, fit into c 18 BRITISH FLOWERING PLANTS CHAP, TREES, SHRUBS, AND CLIMBING SHRUBS NATIVE OR NATURALISED IN BRITAIN Clematis Vitalba Berbers vulgaris Lime (Tilia ewropea) Maple (Acer campestris) Sycamore (Acer Pseudo- _platans) Spindle Tree (Euonymus) . Buckthorn (Rhamnus catharticus) Rhamnus Frangula . Sloe (Prunus) . Rose (Rosa). Apple (Pyrus Malus) Pear (Pyrus communis) Hawthorn (Crataegus) Medlar (Mespilus) Ivy (Hedera) Cornel (Cornus) Elder (Sambucus) Guelder Rose (Viburnum) Honeysuckle (Lonicera) Arbutus (Arbutus) Holly (Ilex) Ash (Fraxinus) Privet (Ligustrum) Elm ‘Ulmus) Hop (Humulus) Alder (Alnus) 1 Birch (Betula) . Hornbeam (Carpinus) Nut (Oorylus) . Beech (Fagus) . Oak (Quercus) . Willow (Salix) Poplar (Populus) Pine (Pinus) Fir (A bies) Yew (Taxus) = Edible. | x XXX xX xX XXX XxX xX xXXXX x x Seed or Fruit. Hairy. Winged. Hooked. 1 Some species of Alder have winged fruit. i INTRODUCTION 19 depressions in the carpels. In other cases, perhaps, they serve to promote dispersal by diminishing the specific gravity of the seeds. It has been suggested that the smooth surface of many seeds is perhaps an advantage by enabling them to pass through the body of an animal without being digested. Another explanation may be that seeds which are thrown by the plant, or jerked by the wind, would no doubt go further if the surface was smooth, because it would offer less resistance to the air. It may be convenient to say a few words as to the fruits of trees with reference to the dispersal of the seeds. Nature, as we have already seen, has devised several plans for the dispersal of fruits and seeds. For instance, some are edible, and are carried by animals ; some are hairy or winged, and are carried by currents of air; some have hooks, and become entangled in fur and hair. That these differences of structure are really adapta- tions comes out clearly if we take some definite group, such as our common forest trees, shrubs, and tall climbing plants; not, of course, a natural or botanical group, for they belong to a number of different orders, but a group characterised by attaining to a height of, say, over eight feet. We will in some cases only count genera; that is to say, we will count all the Willows, for instance, as one. These trees and shrubs are plants with which we are all familiar, and are about thirty-six in number. Now of these thirty-six no less than twenty-two have edible fruits or seeds, such as the Plum, Apple, Arbutus, Holly, Hazel, Beech, and Rose; three have seeds which are provided with feathery hairs; and all the rest, namely, the Lime, Maple, Ash, Sycamore, Elm, Hop, Birch, Hornbeam, Pine, and Fir, are provided with a wing. Moreover, as will be seen by the following table, the lower trees and shrubs, such as Cornel, Guelder Rose, Rose, Thorn, Privet, Elder, Yew, and Holly, have generally edible fruits, much eaten by birds. The winged seeds or fruits characterise the great forest trees. 20 BRITISH FLOWERING PLANTS cHAP. In considering the importance of these provisions we have not only to bear in mind the desirability of the seeds being scattered beyond the shadow of the parent plants, and the soil which has been more or less exhausted by them, but must also remember the vicissitudes of climate through which our islands have passed. Before the glacial period our flora seems to have been, on the whole, very much what it is now. During the glacial period our plants were driven south, a few of the Arctic and Alpine species only remaining in the extreme south and west. During this period there seems to have been certainly one, and possibly several comparatively mild periods, so that the whole, or nearly the whole, of our plants have been compelled at least twice, probably several times, to migrate long distances.’ Perhaps for this reason our flora is highly specialised for dispersal, or rather the species best organised in this respect are those which have been able to re-establish themselves here. The methods of packing the embryo in the seed-coat, the germination of the seed, and the characters of the seedling afford interesting subjects for study. Some account of these will be found in my books on Seedlings. LEAVES The leaf originates as a slight protuberance of the bud. Fig. 6 represents a longitudinal section through the growing point of a winter bud of Abies pectinata (Silver Fir), and shows the commencement of two leaves (b, 6). It also illustrates the cellular structure of young tissue. The nourishment absorbed by the roots from the soil passes as crude sap into the leaves and is there elaborated. Carbonic acid gas is absorbed from the air by means of the stomata,—minute slit-like apertures between two epidermal cells which guard the entrance (guard-cells), and, by contraction, close it at night and in dull weather. The stomata allow communication 1 Reid, Origin of the British Flora. I INTRODUCTION 21 between the outside air and the intercellular spaces in the leaf-tissue, which are specially developed on the lower face of the leaf (see Fig. 11 below). Through the stomata also escapes the surplus water in which the nitrogenous and other mineral food has been carried up from the roots to the leaves. Some of the water is required for nutrition and as cell-sap to maintain the turgescence of the tissues, but a large proportion serves only as a carrier, and is ultimately given off, or trans- pired, through the stomata. They are very numerous. Fie. 6.—Longitudinal section through the growing point of a winter bud of Abies pectinata, x about 200. WS, apex of growing point; b, 6, youngest leaves 5 7, cortex ; m, pith. It is estimated, for instance, that on such a leaf as that of the Oak there are not less than 2,000,000. The carbon is assimilated and the oxygen released, at least in part. It is remarkable that plants do not take up carbonic acid from the soil. It might have been expected that the roots, ramifying as they do in earth more or less saturated with water containing carbonic acid in solution, would absorb what is so important an element in their food. This function is, however, mainly performed by the leaves, and especially under the influence of daylight. It is carried on by protoplasm containing “chlorophyll granules.” These are roundish green corpuscles, which give their peculiar 22 BRITISH FLOWERING PLANTS CHAP. colour to leaves. On them depends the life of plants, and ultimately, therefore, of land animals also. Every one knows that plants grown in the dark are unable to produce Fia, 7.—Twig of Beech, chlorophyll. But though light is necessary for its production, and though the leaves of our plants are, as a rule, arranged so as to secure the greatest amount of light, still it becomes injurious if too intense. In our own country leaves are generally arranged so as to secure the maximum of light and air, as, for instance, those of the Beech (Fig. 7), the Spanish Chestnut (Fig. 8), and the Maple (Fig. 9). We have, however, some shade- loving species, and in hotter regions the tendency becomes greater to avoid the too brilliant sunshine. As familiar examples may be men- tioned the leaves of the Black Poplar (Fig. 10) and Eucalyptus, which Fic, 8.—Twig of Chestnut (Castanea). are vertical, and those of several Fig. 9.—Twig of Norway Maple. New Zealand Veronicas, which are placed in four rows, one under the other. The summer shoots sometimes produced on our forest trees are often pale, the bright I INTRODUCTION 23 light having checked the formation of chlorophyll. Young shoots, especially, require protection from the action of light, which would otherwise check the forma- tion of chlorophyll. This is afforded in several ways, of which the principal are—by the thick and often glossy epidermis; by the position of the leaf; by the struc- ture of the leaf; by the arrange- ment of the chlorophyll granules ; by change in their form; by hairs, which often fall off when the leaf is fully developed ; by stipules—either those of the same leaf, as in the Hop (Humulus), or of an older leaf, as in the Pea. The latter safeguards are useful also in other ways; for instance, as a protection against cold, against insects, etc. : Again, the presence of red colour Fis. 10.—Shoot of Black : ‘ Poplar (Populus nigra). is very common in young shoots, when it perhaps serves to protect the chlorophyll in the delicate tissues from too much light; and this seems to have been taken advantage of and developed in the corolla and other parts of the flower, as an attraction to insects. In ordinary parlance, when we speak of a leaf we think only of the leaf blade. The leaf blade is only one part of the leaf, which, if complete, may be regarded as consisting of four parts—the blade, the stalk, the stipules, and the base. One or more of these parts, however, may be wanting. In some cases, for instance, the leaf is sessile ; in others the blade is absent. Stipules are the two small leaflets which often occur just above the base of the leaf, as, for instance, in the Violet, Pea, Rose, ete. Linnzus gave them the name from stipula, a little straw. This term happily expresses their appearance in the case of the Beech. In this species they drop early, and in spring make the ground under Beeches almost brown. In this case, 24 BRITISH FLOWERING PLANTS CHAP. as in many others, they serve to protect the young leaves. Every one who loves a garden knows to his cost how delicate young leaves are; how susceptible to cold, so that often—too often—the bright promise of spring is ruined by a single cold night. Moreover, young leaves require protection not merely from cold but from too great heat, from dryness, moisture, and light, as well as against the attacks of animals. The principal modes by which they are protected are :— 1. By the preceding leaves, as in Hypericum. 2. By the base of the preceding leaf, which persists through the winter, as in Spartium, sometimes forming a cup, covering the bud as in Philadelphus, the Mock Orange or Syringa of gardens. 3. By scales which represent modified outer leaves, as in Willows. 4. By scales which represent leaf-stalks, as in Maples and Ash. 5. By scales which represent stipules, as in Beech and Oak. If an Oak bud be carefully opened, more than forty scales will be counted before coming to a true leaf. 6. By the two connate stipules of a leaf, as in Elm and Spanish Chestnut. 7. By two connate stipules belonging to different leaves, as in the Hop. 8. By spines. 9. By furry hair. 10. By gum, resin, or mucus. Leaves may be arranged in various classes: ever- green or deciduous, broad or narrow, opposite or alternate, entire or divided, hairy or smooth, ete. ete. Deciduous plants keep their leaves on longer as the summers lengthen. The Cherry (Prunus Cerasus) keeps its leaves longer in Southern Europe, and in Ceylon is evergreen. Broad leaves are generally horizontal, narrow leaves more or less upright. Thus many trees and herbs, such I INTRODUCTION 25 as the Daisy, have broad horizontal leaves ; while grasses have more or less upright and narrow ones. The Plantain and Drosera give good illustrations. Plantago media and Drosera votiundifolia have broad flat leaves; while in Plantago lanceolata and Drosera anglica they are narrow and upright. Hairs on plants fulfil numerous functions: they prevent undue transpiration, hence the hairiness of so many species of hot dry countries, as the Riviera; they also protect the plant from too brilliant sunshine ; again, they keep moisture from clogging the stomata, or breathing pores, and are thus useful in cold foge districts, as, for instance, our northern heaths and moors. Such hairs are dry and contain air; but another sort are juicy and conduct or even themselves absorb moisture, as, for instance, is said to be the case with those on the Chickweed. In some cases hairs protect plants from being eaten by browsing quadrupeds, and in many they prevent ants and other creeping insects from obtaining access to the flowers and robbing them of their honey. Hairs intended to perform this function are often rendered more effective by pointing downwards. Water plants and those living in damp _ localities have no need of hairs and are glabrous. Some species, such as Stlene inflata and Polygonum amphibiim, are glabrous in damp, and hairy in dry places. Their leaves are also much cut up, often into long linear segments. I have suggested' that the object of this is to expose as large a surface as possible to the action of the water. We know that the gills of fish consist of a number of thin plates, which while in water float apart, but have not sufficient consistence to support even their own weight, much less any external force, and consequently collapse in air. The same thing happens with these thin, finely-cut leaves. In still water they afford the greatest possible extent of surface with the least expenditure of effort in the formation of skeleton. This is, I believe, the explanation of the prevalence of this form in sub- \ Flowers, Fruits, and Leaves. 26 BRITISH FLOWERING PLANTS CHAP. aqueous leaves. Again, in still air the conditions, except so far as they are modified by the weight, would approximate to those of water, but the more the plant is exposed to wind the more would it require strengthening. Hence perhaps the fact that herbs, which, of course, are less exposed to wind, so much oftener have finely-cut leaves than is the case with trees. We may instance those of many Geraniums, Umbellifers, Delphiniums, Buttercups. There are, moreover, many groups of plants which, while habitually herbaceous, contain some shrubby species, or vice versa. Let us take some groups of this description in which the herbaceous species have their leaves much cut up, and see what is the character of the foliage in the shrubby species. The vast majority of Umbellifers are herbaceous, and with leaves much divided, the common carrot being a typical example. One European species, however, Bupleurum fruticosum, is a shrub attaining a height of more than 6 feet, and has the leaves coriaceous and entire. Common Groundsel (Senecio vulgaris) again is a low herb with much cut leaves. Some species of Senecio, however, are shrubby, and their leaves assume a totally different character, Senecio laurifolius and S. populifolius having, as their specific names denote, leaves respectively resembling the Laurel and Poplar. In the genus Oxalis, again, there is a shrubby species, O. Laureola, with leaves like those of a Laurel. One common type of leaf is that of which the Laurel may be taken as an example. Such leaves are more or less oval, somewhat tough, caducous or evergreen, and with the stomata, as a rule, on the lower surface. They are adapted to resist wind, and are charac- teristic of trees and shrubs. To this type belong, besides those of Laurel, the Laurustinus, the Way- faring tree, Evergreen Oak, Holly, Beech, Hornbeam, Elm, Pear, ete. In others the leaves are larger, but, perhaps as a protection from the wind, are pinnate, with more or I INTRODUCTION OF less oval leaflets, as in Ash, Mountain Ash, Robinia (Acacia of gardeners), ete. Palmate leaves form another type: as, for instance, those of Sycamore, Maple, Plane, Guelder Rose. Jungner regards the palmate form also as an adaptation to resist wind. He observes that species with palmate leaves are particularly abundant in windy countries and districts. The elastic stalks enable them to arrange themselves so as it were to turn their back to, and fly like flags in, the wind. As we have seen, the leaves of aquatic plants are in many cases divided into filiform segments, thus exposing a large surface to the action of the water. On the other hand, floating leaves have a tendency to be circular. Some plants have both these forms of leaf,—rounded ones on the surface ; others finely divided, below. This is the case, for instance, with some species of Ranunculus. Leaves growing in damp and shady places—shade leaves as they may be called—are large, flat, smooth, and delicate. Those of Petasites, Lactuca Scariola, Dentaria, Orobus, Paris, Lunaria, Mercurialis perennis (Dog's Mercury), Impatiens (Balsam), etc., belong to this type. In dry, arid regions, such as the Riviera, they would not survive a day. Another type of leaf may be called ericoid, as the Heaths afford typical and familiar examples. That of Empetrum (Fig. 11) is a striking example. They are evergreen, rolled at the edges, leathery, small, and crowded. They suit cold and damp, and hot and dry localities. To the former they are adapted, as they present a smaller surface to the cold air, and especially because, as the stomata open into the space which is more or less completely enclosed by the rolled edges, and are, moreover, also as a rule protected hy hairs, they are not liable to be clogged by moisture, but are in a position to fulfil their important function as soon as the sun comes out, and even to some extent during rain. But though it is important that the power of evaporation should be protected, it is, on the other 28 BRITISH FLOWERING PLANTS cuar. hand, equally necessary that it should not be too rapid, for in severe weather the frost often checks the supply of water by the roots, even though they go to a con- siderable depth. The same safeguards against too rapid evaporation render them suitable to hot dry regions. The leatheri- ness of the leaves is also, no doubt, a protection against browsing quadrupeds, as also are the aromatic properties of many such species. Besides the Heaths, Azalea, Empetrum (Fig. 11), Silene acaulis, and some Saxi- frages belong to this type. Another northern type is that represented by arm © £3 Gd» 4 Fig. 125. Fig. 126, Fig, 127, Fig. 128. Fig. 129. Fig. 130. Fics. 125-130.—Scales of bud of Rose. Showing successively the Ist, 3rd, 4th, 5th, 6th, and 9th scale. dispersal by birds. If they fell to the ground they would be liable to be eaten by mice, etc. On the branches, however, they are sufficiently protected by the thorns and prickles. If we examine a leaf-bud, say in December (Figs. 125-130), we shall find that it consists of a number of scales with three more or less well-marked projections at the apex. In this case the scale itself represents the leaf-base, while the stipules and upper part of the leaf are indicated by the three points. The outermost scale is the shortest, and they gradually increase in length. After about ten of such scales the little leaf- blade becomes much larger, and the leaf-base smaller in Fic. 131.—Expanding bud of Rose. proportion. The expanding Stem bearing expanding lateral bud is shown in Fig. 131. ee . ~ revealing its axillary bud (d) ; five One specles ot Rose, R. scales are shown, and two of the berberidifolia, has leaves con- —‘"s* leaves, Li’, Li". — Sketched sisting of a single leaflet only. It is a native of the dry regions of Central Asia, and probably would lose too much moisture if it had the 1 Buds and Stipules. 184 BRITISH FLOWERING PLANTS CHAP. leaf surface of an ordinary Rose. The stipules also have disappeared. The single leaf appears to represent the terminal leaflet of an ordinary Rose-leaf.’ Pyrus Protogynous plants, with half-concealed honey, secreted by the base of the flower. P. Malus (Apple).—The scent is especially strong at night, and the flower is much visited by moths. According to Waite,” self-fertilisation gives little fruit. When the flower opens the stigmas are ripe. On the second day the anthers begin to open, commencing from the outer rows. The flower lasts five to six days. P. communis (Pear).—The life-history of the Pear flower is similar to that of the Apple, but the female condition lasts two to four days, and the whole tower life seven to eight days. It is also nearly sterile to its own pollen. P. Aria (White Beam).—The under side of the leaves is covered with a soft white cotton, and is often turned upwards, so that the tree looks quite white. The cottony down protects the stomata. The buds stand upright, thus exposing a small surface to the sky, and minimising the effect of cold. I have described them at length in my Buds and Stipules, p. 140. CraTEGUS C. Oxyacantha (Hawthorn).—The flowers are proto- gynous, with half-concealed honey secreted by a ring at the base of the flower. The scent is one of the few which we consider pleasant, and which is also very attractive to flies. The anthers do not begin to open until the flower is one or two days old. The plant is protected by modified branches which assume the form of spines. On the lower part of long shoots a long spine and a bud develop together, on the upper part a bud only. 1 See Gardeners’ Chronicle, July 6, 1889. *" Waite, Pollination of Pear Flowers. Washington, 1894. u ROSACEE 185 The stipules on the leaves of the short lateral spurs and those at the very base of the elongating shoots are minute and tooth-like, or subulate, soon becoming brown and falling early. Those on the upper part of the elongating shoots vary from unilateral, falcate, serrated, small but foliaceous organs, to large, half - cordate, simply or doubly serrate, shortly stalked, foliaceous, much - reticulated organs, with the principal nerves radiating from the base of the lamina and passing into the principal teeth. Thus there are at least three dis- tinct types of stipules. These differences are probably connected with the differences in the shoots. The latter may be described as of two kinds, namely, those which develop into more or less lengthy, leafy shoots, which go to increase the height and breadth of the tree, and those which form short lateral spurs. The latter are very numerous, forming dense rosettes of leaves, and produce clusters of flowers in profusion in adult bushes and trees. Owing to the crowded state of their leaves the bases of their petioles occupy the whole, or very nearly the whole, of the surface of the short axis, thus leaving little or no space for stipules. The lower or euter leaves are very small, and entire or tridentate, or trifid, with short petioles. Very often these have no trace of stipules. The inner or upper leaves of these rosettes are better developed, with elongated petioles, so as to enable them to extend beyond and occupy the space between the short ones. This is obviously a pro- vision to expose every leaf to light. The stipules of these longer-stalked leaves vary from mere points to subulate or linear small brown organs, which, being relatively functionless after the expansion of the leaves, goon shrivel up and fall away. At or near the base of the elongated leafy shoots fairly well-developed leaves occasionally occur which have no stipules, but as a rule the stipules in this position are also well developed. As these shoots elongate and become vigorous the internodes become 1 Avebury (Lubbock), On Buds and Stipules. 186 BRITISH FLOWERING PLANTS CHAP. longer and the leaves and stipules larger. The latter, indeed, become quite leafy, and supplement the area of foliage. This is doubtless an advantage, as the leaves themselves do not by any means utilise the area at their disposal, as do those of the Lime, Beech, or Elm. CoToNEASTER C. vulgaris is a native of Kurope and temperate Asia, found wild in Britain only on the Great Orme. The tiny pink flowers are homogamous or protogynous, with concealed honey. This species ascends to the Arctic Circle, and high up in mountain ranges. The leaves are typical of a cold wet district: small, ovate or orbicular, entire, and glabrous on the upper surface, so that wet runs off easily, while below they are covered with a short dense cottony down, which protects the stomata from wet during rain, and renders transpiration possible as soon as the sun comes out again. MESsPILuUS M. germanica (the Medlar), a native of the East Mediterranean area, has become naturalised in hedges and thickets in Central and South England. The flowers are homogamous, with half-concealed nectar. They are remarkable for the great development of the sepals, which are broad and leafy. ONAGRACEA The flowers are, with a few exceptions, regular, with the parts in twos or fours, and an inferior ovary. Epriosium (Willow Herb) We have ten species of this genus. One of them, E. angustifolium, has the flowers irregular, the others ul ONAGRAUE 187 regular. Three have the stigma deeply four-lobed, one, LE. hirsutum, with clasping leaves, while the other two may be distinguished by the form of the leaves, which in one, L. montanwm, are ovate or ovate-lanceolate, in the other, E. parviflorum, are lanceolate. The flowers also are small. Of the five species with a club-shaped stigma, two have the stem marked with two or four raised lines; FE. tetragonwm has sessile leaves, while in E. roseum they are shortly stalked. Of the three species with a cylindrical stem, one, E. alpinum, is a small Alpine species, not six inches high; &. alsinifoliwm has ovate, EL. palustre lanceolate leaves. The flowers secrete honey from the summit of the ovary. In wet weather the long ovary bends so that the flowers turn downwards, thus protecting the pollen from rain. The fruit is a long narrow capsule, which splits open from above down- wards both between the valves and also along the centre of each, leaving the central axis with the seeds attached to it. The seeds are very numerous, small, oblong, brown, and with a tuft of long white silky hairs at the upper end. ‘The hairs act as a parachute, and facilitate the dispersal of the seeds by wind. E. angustifolium (Rose-bay) has large purplish flowers in conspicuous heads (Fig. 132), and is much frequented by insects. The flowers, as Sprengel pointed out, are so strongly protandrous that self- fertilisation is almost out of the question. They open soon after sunrise. The lower parts of the filaments are flattened, and form a hollow cone protecting the honey, which lies between them and the ovary. The space between the aS two is arched over by hairs, which Fre. 182. —Zpilobinm angusti- exclude rain while permitting the eee essere passage of the probosces of insects. When they have shed their pollen the stamens turn outwards, while the pistil grows up and the stigmas take their place. 188 BRITISH FLOWERING PLANTS OHAP. Warming, however, as stated by Knuth, found the specimens examined by him to be weakly protogynous, and Schulz found the flowers in mountainous regions less protandrous than those of the lowlands. Kerner also found those examined by him less protandrous than those of Sprengel, and capable of self-fertilisation in the absence of insect visits. E. parviflorum.—The stigmas are ripe when the flower opens. Gradually the stamens elongate, and the anthers open, so that self-fertilisation becomes possible. The petals close up during the night, but open again the following morning. Some of the anthers now project beyond the stigma, and the pollen is readily transported to other flowers. While E£. angustefolium has conspicu- ous purplish-red flowers in long ter- minal bunches or racemes, and is much frequented by insects, this species (Fig. 133), on the contrary, has small soli- tary flowers, and is seldom visited. Now, to the former species the visits Fic. 133. —Epilobium Of insects are necessary, since the parviforun. Flower stamens ripen before the pistil, and : the flower has consequently lost the power of self-fertilisation. In E. parviflorum, on the contrary, the stamens and pistil come to maturity at the same time, and the flower can therefore fertilise itself, It is, however, no doubt sometimes crossed by the agency of insects; and, indeed, I am disposed to believe that this is true of all the flowers which are either coloured or sweet-scented. The plant is covered with soft hairs. E. montanum.—