m MEMOI Richard M. RIAM Holman , OLOGY Richard *V, Holman A COMPENDIUM OF GENERAL BOTANY. BY DR. MAX WESTERMAIER, Professor in the Royal Lyceum, Freising, Germany. TRANSLATED BY DR ALBERT SCHNEIDER, Fellow in Botany, Columbia College, New York. 171 UUustratfons. FIRST EDITION. FIRST THOUSAND. NEW YORK : JOHN WILEY & SONS. LONDON: CHAPMAN & HALL, LIMITED. ST. LOUIS (17 S. Broadway): B, HERDER, 1896. BIOLOGY LIBRARf G Copyright, 1898, BY ALBERT SCHNEIDER ROBERT DRUMMOND, ELECTROTYPER AND PRINTER, NEW YORK. PREFACE. IN a compendium of botany intended for high schools it is permissible to introduce subject-matter which would be objec- tionable in a text-book of elementary instruction. Free use has been made of such privileges. It is assumed that the pupil has a general knowledge of chemistry, of physics, of the proper use of scientific terminology, and has the ability to estimate the value of hypotheses and undecided problems. From the con- sideration of the latter the disciple of our science will soon recognize the peculiar difference between layman and scientist. The layman looks upon many phenomena in plant-life as being quite clear and easy of explanation. The scientist, however, can demonstrate that we know but very little concerning these same phenomena. It must also be borne in mind that scientific progress depends upon the recognition of the present limits of our knowledge. Nearly every branch of science is more or less merged into general cosmology. It is therefore expected that every scientist should attempt to explain this relation. We find that the vari- ous authors have a tendency to call the reader's attention to the important (in the author's opinion) phases of cosmological rela- tionship. Even of this privilege I have made use. Incidentally I will make the following observation : The greater portion of physiology is intimately associated with anatomy. In accordance with this we find that the newer devel- opment of botanic rJ science considers the question, What for ? of prime importance when investigating plant-structures (ana- tomical-physiological tendency of Schwendener's school). In the special as well as in the general treatment of the subject-matter I have frequently made use of the works of NAGELI, SACHS, PFEFFEK, DE BARY, FRANK, GOBEL, and WARMING ; more especially those of SCHWENDENER and his pupils (Haber- landt among others). To this I have added the knowledge iii 921916 IV PREFACE. obtained through a long scientific association with my honored instructor, Professor Schwendener. The illustrations are added with the kind permission of various authors. For all this I express my sincerest gratitude. MAX WESTEBMAIEK. FREIPING, October 1893. TRANSLATOR'S PREFACE. IN presenting this translation it is perhaps well to offer a few explanatory statements. The book is just what the title implies, a compendium of gen- eral botany. Its great value as a text-book lies in the thoroughly logical and scientific treatment of the subject-matter. The neces- sarily condensed retrospect of the science of botany is well supplemented by the copious, well-chosen references to standard authorities. I have endeavored throughout to adhere as closely as possible to the author's form, style, and concept of the science of botany. The arrangement and treatment of the subject-matter are the same as in the original. In fact I have endeavored to make it a translation in the true sense of the word. I have, however, added some foot-notes. A few are explanatory ; others serve to indicate differences of opinion. Although it is difficult to make a good translation of the finer shades of meaning peculiar to a language, yet I sincerely hope I have met with fair success in such an attempt. Finally, I desire to express my grateful obligations to Dr. N. L. Britton, who made the final corrections of the proof for the first half of the translation. I am also greatly indebted to my wife, who has kindly aided me in correcting the manuscript and in reading the proof. ALBERT SCHNEIDER. COLUMBIA COLLEGE, July 1895. TABLE OF CONTENTS. PAGE PREFACE . . iii TRANSLATOR'S PREFACE v Divisions of Scientific Botany and General Considerations . . 1 PART I. The Cell. I. Introduction 4 II. Primordial Utricle and Cell wall in Their Mutual Relation- ship. Turgor. Plasmolysis .. . .. .... 7 III. Cell-contents . . . . . ... . . . 10 A. Living Inclusions of the Cytoplasm ... . . . 10 (a) Nucleus 10 (b) Chlorophyll-grains, Chromoplastids, Leucoplastids ... 13 B. Dead Inclusions of Cytoplasm . . . . ... 16 (a) Starch . . . . ... ' . . ... . 17 (b) Aleuron-grains . 21 (c) The Remaining Solid Dead Inclusions of the Cell . . .22 C. The Cell-sap and the Remaining Fluid Contents of the Cell . 24 IV. The Cell-wall .25 A. Internal Structure and Method of Growth of the Cell- wall . 26 B. Chemical Composition and Subsequent Changes in the Cell-wall 30 C. Products of the Growth in Thickness and Surface of the Cell- walls . . . . ... . , . . . 32 V. The Origin of Cells . ... . ... 42 PART II. Tissues and Simple Organs. A. Structure of Tissues and Simple Organs 45 B. Differentiation of Tissues according to Structure and Func- tion (Physiological Anatomy of Simple Organs) ... 49 Differences of Functions and Their Enumeration .... 49 SPECIAL FUNCTIONS : I. The Function of Formative Tissues (Meristem and Cambium) . 51 II. Structure and Function of the Epidermal Tissue-system . . 53 III. Function of Mechanical Tissues 63 vii Vlll TABLE OF CONTENTS, PAGE IV. The Function of the Conducting System 70 Consideration of the Conducting System in Itself and in Its Relation to the Mechanical System ...... 70 (a) The Various Cell-forms 70 (b) The Laticiferous Tissue 76 (c) The Stem-structure of Mosses and Vascular Cryptogams . 78 (d) The Stem of Monocotyledons, Dicotyledons, and Gymno- sperms .......... 80 (e) Growth in Thickness among Dicotyledons and Monocoty- ledons by Means of the Cambium 87 (/) Abnormal Structure of Stems 94 (g) The Structure of Roots 95 (h) Anatomy of the Transition-zone between the Stem and the Root 98 (0 The Special Physiology of the Movements of Food-sub- stances and Water in Plants ...... 99 a. Conduction of Albumen 99 P. Conduction of Carbohydrates 101 y. Conduction of Water 103 Protective Sheath or Endoderm. (Concluding Chapter to the Three Foregoing Ones on Special Functions.) .... 112 V. Protection of the Meristematic Areas of the Plant-body . . 115 (a) The Protection for the Terminal Meristematic Areas of the Plant-body 115 a. Protection of the Root-tip 115 ft. The Protection of the Stem-apex 118 y. Protection of the Leaf -tip 119 (b) Protection for Areas of Intercalary Growth .... 119 VI. Food-substances Derived from the Atmosphere. Assimilation of Carbon in Green Organs 122 (a) The Structural Principles of the Assimilating System . . 123 (b) Movements and Changes in Form of Chlorophyll-bodies . 128 (c) The Chemistry and Physiology of Chlorophyll . . . 128 VII. The Function of Aeration 132 (a) The Structure and Function of Breathing-pores (Stomata) 135 (ft) Lenticels 138 VIII. The Function of Roots . . . . . . . . 139 (a) Subterranean Roots . . 139 (b) Aerial Roots 140 IX. The Appropriation of Assimilated Food-substances . . . 141 (a) Condition of Seeds before the Beginning of Assimilation . 142 (b) Nutrition of Saprophytes and Parasites ..... 143 (c) Symbiosis .......... 145 (d) Insectivorous Plants . . 148 X. The Storing and Function of Reserve Material ... 150 (a) Storing of Water 150 (ft) The Storing of Starch and Other Food-substances, Espe- cially the Albuminous Substances ..... 151 XI. Secretion 152 TABLE OF CONTENTS. ix PART III. Organs and Systems of Organs. PAGE I. The Morphological and Physiological Relations of Organs . 155 A. The Principal Forms of Organs 155 B. Modification of Organs 157 (a) Modification of Stem and Root . . . . . . 157 (b) Modification of the Phyllome 159 Critical Observations on the Distinction of Organs . . . 163 C. The Complex Organ : Shoot 165 D. Metamorphosis and Correlation 167 II. Origin and Position of Lateral Organs and the Causes for Their Definitive Position 168 A. Spiral Arrangement of Leaves. Theories of Phyllotaxy . . 171 B. The Determination of a Divergence ...... 174 C. The Mechanical Theory of Phyllotaxy and the Idealistic Concep- tion of Nature ... 175 III. Difference in the Power of Development of the Members of Equal Morphological Value. Classification of Organ-systems 179 A. Inflorescence . ... 181 (a) Racemose Inflorescence . . 182 (b) Pauiculose Inflorescence . - > 182 (0) Cicinnose Inflorescence . 182 B. Rank and Succession of Shoots 183 PAKT IV. Reproduction. Introduction 185 I. Reproduction among Cryptogams . ... .... 188 A. Forms of Reproduction among Algae 192 B. Forms of Reproduction among Fungi 194 II. A Comparative Study of Reproduction and Alternation of Generation in Mosses, Vascular Cryptogams, and Phanero- gams 200 Gymnosperms and Angiosperms . . . . . . . 210 III. The Phanerogamic Flower . . . V .... 213 A. Calyx, Corolla, Nectaries. The Flower as a Whole ... . 214 B. The Stamens and Pollen-grains . . . . ... . 223 C. The Gyncecium. The Ovule with the Embryo-sac before and after Fertilization . 227 IY. The Morphology and Physiology of the Seed and Fruit of Phanerogams * 231 Germination . - . . . . 237 V. The General Physiology of Reproduction 238 A. Agents in Fertilization. Cross-pollination. Self-pollination . 238 X TABLE OF CONTENTS. PAGE B. Fertile Seeds. Hybridization. Apogaray . . . 241 C. Variability, Constancy, Heredity . 243 D. Special Creation and the So-called Theory of Natural Descent . 244 Appendix: The Life-period of Plants 250 PART Y. The General Chemistry and Physics of Plant-life. I. Chemical Physiology 252 Selection 257 The Cyclic Course of Food-substances 258 II. The Physiology of Growth 253 A. Active and Passive Growth 261 B. The Results of Unequal Growth 261 (a) Tissue-tension 262 (V) Curvatures 263 (c) Torsions 264 C. Molecular Organization of Plant-structures 266 III. Temperature, Light, Gravity, and Other Factors in Their Re- lation to Plant-life 268 A. Effects of Temperature 268 (a) Production of Warmth and Cold 268 (b) The Effect of Temperature upon Plant-life .... 269 B. Effect of Light 270 (a) Production of Light 270 (b) Influence of Light upon Plant-life 271 C. Influence of Gravity ......... 275 D. Electricity, Moisture, Water- currents, Radiating Heat . . 276 IT. The Physiology of Plant-movements 277 A. Classification of Movements according to Cause. The Outward Manifestation of Some Movements 277 B. Hygroscopic Movements ........ 278 C. Autonomous Movements 279 D. Irritable Movements 280 Mimosa 280 Behavior of Tendrils. Conduction of Stimuli. The Function of Irritable Movements 281 E. The Physiology of Twining 283 PART VI. Classification of Plants. Taxonomy . . 286 ALPHABETICAL INDEX 293 COMPENDIUM OF GENEEAL BOTANY, DIVISIONS OF SCIENTIFIC BOTANY AND GENEKAL CONSIDEEATIONS. THE two domains of plant study are MOEPHOLOGY and PHYSI- OLOGY. Morphology treats of the substance of the vegetable kingdom. Physiology treats of the forces or energies bound up with the plant-substance or which manifest themselves with it. Plant-func- tions, as we know them in the light of morphology and physiology, are not only proper adjustments to the environment, but above all fulfill the requirements of plant-life and are therefore life-func- tions. To define the term life, even only in its application to the plant kingdom, is impossible. Science can, however, proceed more and more into the order of things, to know more clearly the prop- erties of matter and the harmonious manifestations of force. In spite of this progress we cannot approach any nearer the solution of the " life-problem." Processes of a chemical and physical nature are the most that we are able to see in this order of things and this knowledge distinguishes the scientist from the layman who sees the order less clearly. The earnest investigator who has concluded to believe by faith finds the answer to the "why" of this order in the words " wonder of creation." To the one who is not so inclined this "why" becomes a darkness which grows denser in propor- tion as he sees more clearly the order in which chemical and physical processes are combined as they are in plant-life. Life manifests itself in certain chemical and physical processes, and in so far as physics and chemistry are concerned in life-processes there is a " physics and chemistry of plant-life." Plant-physiology may be designated by the expression " physics and chemistry of plant- 2 DIVISIONS OF SCIENTIFIC BOTANY life," but always in the sense that the exactness of the knowledge of life-manifestations adds nothing to the causal mechanical expla- nation of "life" itself. To morphology in the above sense belongs the description of the form, size, arrangement, and outer and inner numerical relations of the plant-body ; therefore anatomy is a part of morphology in the wider sense. Usually, however, anatomy (inner form-relations) is distinguished from morphology in a narrower sense (outer form- relations). Thus limited, morphology forms one of the fundamental principles underlying our present system of classification. Let us now return to the two main divisions of our science. A few examples will make clear to the novice how morphology may be distinguished from physiology, but that a complete and compre- hensive knowledge of the plant necessitates a combination of the two. "When an investigation has for its purpose the explanation of the cause of development of the woody cell-wall, then it concerns itself with a function, in this special case a function of nutrition ; this is therefore physiology. If one makes a microscopic compari- son of one wood with another and seeks to find the similarities or dissimilarities of the tissues, then no functions are involved and the study is morphology (anatomical morphology). If one seeks to find the relation of anatomical differences to the environment (as a rule this relation is considered from a teleological stand- point), then we must of necessity concern ourselves with phys- iological processes. If we seek after the conditions which cause plants to turn green, then the study is purely physiological : we are solely concerned with energies. If, with the aid of the highest magnifications, the finest structure of chromoplastids (chlorophyll bodies) is studied in order to describe them more correctly, we are concerned only with morphology. Development, for example, em- bryology, belongs to morphology. To study, describe, and repre- sent graphically, the successive stages of embryonic development lies wholly in the domain of morphology. If one, however, makes a study of the wall of the ovum in order to determine experimen- tally what forces eventually determine the position of the first septum, then we are again in the domain of physiology. If a minute description is given of the various cell-forms found in the stem, where, for example, the thick-walled cells occur, the form of the thickenings, etc., then we are concerned with morphology. If, however, one seeks for the significance of this or that cell- AND GENERAL CONSIDERATIONS. 3 form in the service of plant-life, then again we are concerned with a force effect which is bound to a specially constituted plant-sub- stance and is therefore physiology. Throughout the arrangement of this book a strong effort is made to adhere as strictly as possible to the combination of such methods of investigation as have just been indicated. How- ever, some attention must be given to the didactic uses of the book. Due regard shall be given to a proper summarizing. In its entirety we have adopted that disposition of subject-matter which SCHWEN- DENEK has so efficiently tested and found useful in the academic course of study. His arrangement is as follows : I. The cell. II. Tissues. A. Structure of tissues and simple organs. B. Differentiation of tissues (physiological anatomy of simple organs). III. Systems of organs. IV. Reproduction. V. General chemistry and physics of plant-life. VI. System of plant classification. PAET I. THE CELL I. INTEODUCTIOK The organisms which we designate as plants, though variable, have one thing in common : they are either single cells or cell- complexes. There is, so to speak, only one element in plants, and that is the cell. Every plant consists of at least one cell. Omitting for the present the embryonic conditions of the cell, it may be defined as, for the most part, a microscopic closed vesicle consisting of wall or covering and contents (large cells, as those of Gossypium species, 6 cm. long ; medium-sized cells, as those of elder- pith). We must distinguish between younger and older stages of the cell. At first an apparently homogeneous, mucous, tenacious substance plasm, protoplasm fills the entire cell-cavity (lumen] and is enclosed by the cell-wall (membrane]. The components of the cell-contents designated by the collective noun "plasm" are albumi- noid substances and hence contain besides carbon, hydrogen, oxygen, also nitrogen, sulphur, and sometimes phosphorus. Its mucous consist- ency is noticeable by its spontaneous escape from openings of the cell- wall (swarm-spore formation of algse, etc.). Gradually there appear differentiations in the apparently homogeneous plasm. Spherical particles filled with a watery substance vacuoles 1 are distinguish- able from the more dense contents ; the latter, the true plasm, are of different kinds, not homogeneous, as a superficial examination would indicate. Tlieplasmic utricle, which is of special importance, shall 1 According to more recent investigation (WENT) the "vacuoles" originate from pre-existing ones. (The conclusions of this investigator are generally con- ceded to be erroneous. Trans.) 4 THE CELL. first claim our attention. The water-bearing cavities (vacuoles) in- crease more and more in size and subsequently come in contact and become flattened by mutual pressure. Finally they are separated only by thin plasmic membranes and threads ; when these break the vacuoles flow together to form one. The plasm then lines the inner surface of the cell- wall as a membrane which is usually very thin, but which is never absent from the liv- ing cell. This membrane is called the primordial utricle or plasmic utricle. On account of its frequently immeasurable thinness it is invisible as long as it is in contact with the cell- wall. If by artificial means the plasmic utricle can be caused to separate from the wall by contraction, then this is looked upon as giv- ing evidence that it was a living cell. (Compare Fig. 10 The cell-wall and the plasmic utricle, the two coverings of the cell con- tents, differ (1) chemically, in that the primordial utri- cle being a part of the plasm is an albuminoid substance, while the cell-wall belongs to the group of carbohy- drates and contains there- fore C, H, and O, the latter in the proportion to form water (H 2 O) ; (2) physically, in that the cell-wall is highly elastic with but little extensibility, while the plasmic utricle is very ex- tensible and only slightly elastic. To this must be added a second physical difference, that of diosmosis. The physical differences are fl ' * oun parenchyma-cell of Zea Mays. A normal; 5, plasmolyced. m, membrane; p and h < protoplasmic utricle; n, nucleus; s, cell-lumen witb ^p. (After prank.) 6 COMPENDIUM OF GENERAL BOTANY. of such great importance that they will be more fully treated in Chapter II. The formation of the plasmic utricle is, as has been indicated, not the only differentiation product of the plasm. In the entire plasmic body one can distinguish a fundamental substance (" cyto- plasm" from ^uros", cavity, cell) and inclusions formed within this fundamental substance. These inclusions are of two kinds, (A) living and (B) dead. Tho plasmic utricle and threads constitute the cytoplasm. The living inclusions are the nucleus, the chromato- phores, and the fertilizing elements, made up chiefly of nuclear sub- stance and having a reproductive function. Of the dead substances formed from the plasmic body the most important are protein- grains, protein-crystals, starch-grains, crystals (of fat, salts, organic acids, etc.), oil-globules, and tannin. The term " chromatophores " includes three substances: chlorophyll bodies, color-granules, and colorless starch-builders. These bodies are considered collectively because they are either the bearers of color-substances or are formed out of such to be again converted into chromoplastids. (STRAS- BURGER, SCHIMPER.) The space not occupied by the above-mentioned solid constitu- ents is filled with a watery fluid, the cell-sap (sometimes having color-substances in solution). It is important to bear in mind that within the living cell gas accumulates only in very small quantities. No bubbles are ever rapidly formed. The reaction of cytoplasm is usually alkaline or neutral. In the living cell, cytoplasm has the property of reducing very dilute alka- line silver-nitrate solutions. (Low and BOKORNI.) In the cytoplasm an outer hyaline layer (hyaloplasm) and a more granular internal layer (polioplasm) may be noticed. According to REINKE the plasmodia of Aethelium septicum contain 73$ of water, and judging from the mucous nature of other forms of cytoplasm we may con- clude that they also contain a high percentage of water. To plasm in general, especially its important structures, as nucleus and chloro- plastids, one no longer ascribes homogeneity. 1 Careful microscopic examinations reveal a reticulated (spongy) structure of plasm. (SCHMITZ, BUTSCHLI, and others.) All life-processes of the cell take place within the plasm. A 1 I would especially recommend WIESNER'S Elementarstructur, 1892. Trans. THE CELL. 7 cell without plasm does not grow, does not take in food, does not live. There is no mechanics of plasm ; cell-life is still wrapt in obscurity. Direct observation shows that plasm gives rise to the cell-wall, as in the case of Stigeoclonium.. 1 The plasmic utricle contracts, escapes from the opening in the cell-wall, and in time surrounds itself with a new wall. To trace a phenomenon back to- plasm is as a rule the present limit of our ability. II. PRIMORDIAL UTRICLE AND CELL- WALL IN THEIR MUTUAL RELATIONSHIP. TURGOR. PLASMOLYSIS. The primordial utricle is usually of immeasurable thinness. In order to represent it in a figure such cells or portions of cells are selected in which it is of perceptible thickness as it lies in contact with the cell-wall. As a rule it can be made visible only by caus- ing it to separate from the cell-wall either through causes inherent in the cell itself or by artificial means. When this plasmic contraction is artificially induced it is recognized as "plasmoly- sis." The phenomenon of plasmolysis can be explained only from the inherently different properties of the cell- wall and primordial utricle. It is at once evident that the endosmotic properties of the bladder of an animal filled with a solution of some salt cannot be compared with a living cell. It can only be compared with a dead cell- wall. If a living cell with cell-sap (ex., hair-cell of petal of Tradescantia) of a given concentration is placed in distilled water, then the endos- motic flow of water through cell-wall and primordial utricle into the cell is greater than the outflow of cell-fluid. The endosmotic sub- stances within the cell attract the water, which therefore increases the cell volume. The limit of this increase is determined by the cell- wall because it is less extensible than the primordial utricle, although much more elastic. (Elasticity is that force which replaces dis- placed molecules. It is very great in the cell-wall and very small in the plasmic utricle.) The cell-wall is therefore a hindrance to the excessive expansion of the primordial utricle. Action induces reaction : the cell-sap which exerts a given pressure upon the cell- wall in turn receives an equal pressure. This mutual pressure of cell-sap upon cell- wall and cell-wall upon cell-sap is called 1 Studied by N AGE LI. 8 COMPENDIUM OF GENERAL BOTANY. " Turgor" l Sometimes the cell-wall cannot resist the expansive force of the continually expanding primordial utricle, and as a result the wall will rupture, which indeed sometimes happens in nature. If the utricle is not ruptured at the same time, then it may expand to the limit of resistance and finally rupture. Let us now suppose an inverse case. Let there be a more highly concentrated solution outside and a relatively more dilute cell-sap within the cell. In this case more fluid passes outward, and as a result the entire cell decreases somewhat in size. Here again be- comes manifest the difference in behavior of the two cell-coverings, the plasmic membrane and the dead membrane (cell-wall). The cell-wall contracts a given amount, corresponding to its previous expansion. If the wall is very delicate and the action of the solu- tion very sudden, it may be thrown into folds and may finally collapse. As a rule the action of the external solution is sufficiently slow and the cell-wall of sufficient thickness to escape such deform- ity, in which case the primordial utricle is removed from the inner cell-wall, corresponding to the decrease in volume of its interior. This continues and the space between cell-wall and utricle is filled by the solution from the outside and the inner cell solution. This behavior of the primordial utricle with certain concentrated salt solutions is also shown with certain dilute poisonous liquids, as for example iodine solution, and dilute acids. A longer or shorter ex- posure will kill the cell. The primordial utricle no longer permits all substances in aqueous solution to pass alike. In the case of plasmolysis this fact becomes known by the great contraction of the primordial utricle, so that it collects as a lump either in the centre or near one side of the cell. If, conversely, cells filled with cell-sap, as for example those of beet-root, are placed in pure water, for hours no sugar will pass into the surrounding liquid, although the membrane in itself certainly allows sugar to pass. Upon this impermeability of the living utricle to certain substances rests the possibility of producing within the cell a high hydrostatic pressure, amounting at times to ten or more atmospheres. 7 (PFEF- FER'S investigations.) The apparent elective choice which plants show in regard to the appropriation of food-substances does not 1 Owing to the lack of a corresponding English noun I have retained the original. Trans. * This subject will again be referred to under Water -movements and Tissue- tension. THE CELL. 9 depend upon this plasmic impermeability. This term should be used with caution. There certainly is no subjective choice. Whether a given substance is taken up by the plant depends upon whether it is of use or not. The unequal utilization of certain sub- stances by different plants depends upon inherent peculiarities of the plants. For example, of two plants growing in the same soil one will take up much and the other little silica (SiO 2 ), the one much and the other little calcium carbonate, and deposit it in the cell- walls. The above-mentioned behavior of plasm toward poison- ous solutions is quite different and might in a certain sense justify the term choice. It is, however, strictly speaking only the reaction of the living plasm to chemical stimuli. For the investigations concerning plasmolysis we are indebted to several authors, NAGELI, PRINGSHEIM, PFEFFER, and more recently HUGO DE YRIES. To the last-mentioned investigator we are indebted for a very important treatise entitled the <; Analysis of the Turgor Force." l This analysis was made by determining the so-called "iso- tonic coefficients." I will select only the following statements from the work of de Yries. The weakest solution (expressed in gram. molecules, not per cents) of potassium nitrate (JOsTO 3 ) which is just capable of inducing plasmolysis within a cell has the same attractive force for water as any other diosmotic combination, as for example oxalic acid, which is sufficiently diluted to just induce plasmolysis. Such concentrations of equal tension are said to be 4 'isotonic." Chemically related substances have the same coeffi- cient. If the isotonic coefficient of KNO 3 is 3, then it is also 3 for NaCl, KC1, in fact for all alkaline salts with one atom of the metal in a molecule. For organic compounds such as malic acid, citric acid, acetic acid, the coefficient is 2, as has been determined by actual experiment. For alkaline salts with two univalent acid radi- cles, as for example MgCl 3 , CaCl 2 , it is 4, etc. De Yries further determined chemically the various combinations in the cell-sap and then found the turgor force exerted by each (sum-total). The relation between turgor and growth will be referred to in the chapter on " Physiology of Growth." Before entering upon the discussion of the cell-contents it should be noted that the contracting primordial utricle carries with it all the solid constituents of the cell-contents ; also that the priraor- Analyse der Turgorkraft, Pringsheim's Jahrbiicher, XIV (1884). 10 COMPENDIUM OF GENERAL BOTANY. dial utricle sometimes ruptures during sudden artificially induced plasmolysis. III. CELL-CONTENTS. Tedious microscopic examinations of the cell-contents aided by staining methods have recently brought to light a series of facts and form-relations. But so far no conclusions of considerable importance have resulted therefrom. The partially compiled and partially original communications of A. ZIMMERMANN ' are especially suited to give a comprehensive view of the work done and our present knowledge of the subject. The most important results of the above-mentioned investigations were obtained by the study of the nucleus and the amyloplastids (starch-builders). STRASBURGEK, GUIGNAKD, HEUSEK, SCHMITZ, KLEBS, ZACHARIAS, HABERLANDT, and others have made special studies of the nucleus, while SCHIMPER. has devoted much attention to the amyloplastids. For the sake of clearness it is no doubt permissible to select from a subsequent chapter a few statements concerning cell-forma- tion before taking up the cell-inclusions. In general cells originate in two ways : by division and by free cell-formation. In the first case the form of the mother-cell and the position of the septum determines the form of the daughter- cells. In the second case the daughter-cells are approximately spherical and float freely within the contents of the mother-cell. In both cases the cells grow after they have formed. Deposits may be made in all parts of the cell-wall uniform surface growth or only at one portion apical growth of cell. In the latter case the cell will gradually become more and more elongated. A. LIVING INCLUSIONS OF THE CYTOPLASM. (a) Nucleus. 1. The nucleus is a more dense plasmic structure and is usually present in all cells, though it is difficult to prove its existence in the fungi. Some very large cells, as for example of Caulerpa (an alga) which are often a foot or more in length, contain many nuclei ; long bast-cells contain several nuclei. The majority of cells, hence those 1 Die Morphologic und Physiologic der Pflanzenzelle. Breslau, 1887. Beitrage zur Morphologic und Physiologic der Pflanzeiizelle, I, II, III. Tubingen, 1890, 1891, 1893. THE CELL. 11 of microscopic size, contain only one nucleus. A similarity in the form of the nucleus to that of the cell is not noticeable. In the younger cells it is approximately spherical ; after the period of cell- growth it becomes more ellipsoidal. It often lies near the cell-wall imbedded in the plasm, sometimes it is suspended in the cell-lumen by means of plasmic threads. To demonstrate the presence of the nucleus it is advisable to kill the cell with concentrated picric acid, which " fixes " the plasm, and subsequently to stain it red with hsematoxylin solution or green with methyl green. The nucleus, again, contains one or more nucleoli. 1 The nucleus (exclusiue of nucleoli) contains besides true albuminous substances- a characteristic compound or group of compounds also albuminoid in nature, namely, the phosphorus-bearing nuclein. It swells in a 10% solution of NaCl and is dissolved in a solution of potassium hydrate which distinguishes it from true albumen. As a rule the nucleus is located in that portion of the cell where- growth (growth in thickness or surface of cell-wall) is the most active or where it continues the longest. Usually the nucleus assumes- a definite position only in the undeveloped cell, later the position is indefinite. Rarely it may assume a definite position for a second time. From the foregoing statements it is to be supposed that the- nucleus is of special significance in the processes of cell-growth. What role it really does play and what functions it subsequently subserves is still a question. The observations made by KLEBS upon artificially-divided cells are of special interest. It was observed that only that portion of the cytoplasm which contained the nucleus is- capable of growing in length and surrounding itself with a mem- brane, while the function of the remainder is assimilation only. The difference between cell-division and free cell-formation is r according to our present knowledge of nuclear behavior, not so great as was formerly taught. During each cell-division and in general during each free cell-formation there is a nuclear division. The so-called indirect nuclear division occurs most frequently, and is connected with extensive changes in the nuclear substance. The details of this mode of nuclear division have been made known by STRASBTJRGER, FLEMMING, GUIGNARD, and HEUSER. I will not enter into a comprehensive description of indirect There are often denser portions noticeable within the nucleoli. Trans. 12 COMPENDIUM OF GENERAL BOTANY. nuclear division or " karyokinesis," but will limit myself to the explanation of the Lccompanying figures. One usually distinguishes a " chromatin " and an "achromatin" nuclear figure. The former is distinguished by the readiness with which the nuclein is colored by various stains, the latter is composed of the slightly staining portions of the nuclear substance. In the illustrations the chromatic figure is FIG. 3. Successive stages of nuclear division. 1 (After Strasburger.) In A an irregularly wound thread is formed from the nuclear network (spirem, Knauel). In B and Care seen the " chromatin-granules " resulting from the breaking up of the chromatin. At .Band Fa, certain arrangement and longitudinal division of chromatin-threads takes place. Somewhat previous to this the achromatin nuclear figure makes its appearance (delicate lines in E&nd F). The two halves of the chromatin-threads move along the fine achromatin lines in opposite directions to the poles (J)and form the " spirem" (Knauel) stage of the daughter-cells