Part 1
A TEXTBOOK OF BOTANY FOR COLLEGES eine Oc«e THE MACMILLAN COMPANY WEW YORK - BOSTON - CHICAGO - DALLAS ATLANTA * SAN FRANCISCO ‘MACMILLAN & CO., Limrrep LONDON - BOMBAY «+ CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Lro, TORONTO A TEXTBOOK OF .BOTANY FOR COLLEGES BY WILLIAM F. GANONG, Pu.D. PROFESSOR OF BOTANY IN SMITH COLLEGB Neto Bork THE MACMILLAN COMPANY 1918 Al rights reserved Corrarient, 1916 amp 1917, By THE MACMILLAN OOMPANY. Set up and electrotyped. Published August, rozg. Reprinted October, 1917. Nortsyosd Press J. 8. Cushing Co. — Berwick & Smith Co. Norwood, Mass., U.8.A. PREFACE Tus book is written in recognition of the fact that to nearly all college students an introductory course in Botany is part of a general education, and not a preparation for a professional botanical career. The distinction is important because our existent courses are largely adapted, even though unconsciously on our part, to the latter end. The needs in the two cases are not the same, though the difference is less in matter and method than in proportion and emphasis. All students alike need that personal contact with specific realities, and that exercise in verifiable reasoning, which laboratory courses render possible. Knowledge, however, is valuable to the specialist in proportion to its objective importance, but is useful to the general student in accordance with its bearing on the actions and thoughts of mankind. In the one case the demands of the science are paramount and in the other the interests of the student. This aim to provide for the general rather than the special student will explain certain characteristics of the book, — notably its emphasis upon the larger and more evident phenomena, its attention to the interpretation or “prin- ciple’”’ of things, and its full consideration of man’s rela- tions to plants. Indeed, the book may be described as an attempt to present and interpret the humanly important aspects of plant nature in the light of our modern scientific knowledge. For the same reason the book is deliberately conservative, and adopts only such statements and views as have passed the test of wide criticism, and attained to the impersonal, and non-institutional, validity of science. The book is intended to be used in conjunction with sys- tematic laboratory work, around which is thus to be welded v V1 ~ PREFACE the general content of the science. Its use is not dependent, however, upon any particular sequence of topics, for the material is presented in the form of semi-independent essays intended to be separately understandable. Obviously there is far more in the book than can be touched in a year in the laboratory, but every topic thus studied should form a leaven of objective understanding for many contiguous subjects. From the abounding wealth of material it has been difficult to select, and it is not supposable that the choice will please everybody, any more than will all the particulars of the treatment. Perhaps, however, the various objections will to some extent counterbalance one another. At all events, I have tried to present systematically and in good proportion the salient and essential matters in our scientific knowledge of plants. The illustrations are taken from many sources, which are acknowledged with the cuts in all cases except where they are new. It is surely as legitimate to use a good published picture as a good published idea, of course with due credit, and, moreover, its use seems a deserved tribute to its ex- cellence such as its author would desire. Many are taken from the well-known works of Sachs, Goebel, Kerner, Gray, and Strasburger, and are so good that better can hardly be made; and we should not deprive the student of their use, or waste labor in providing inferior new ones, only because the frequency of their appearance has made them wearisome to us. Messrs. Henry Holt and Company have given me full permission to use pictures from Kerner’s work, as well as two from Sargent’s Plants and their Uses, and several from my own book The Living Plant, published by them. Also I have used many, by permission, from publications of The Macmillan Company, and especially from one of the greatest of botanical publications, the Cyclopedia of American Horticulture, edited by Professor L. H. Bailey, who has graciously granted me the privilege of drawing at will from that work. The Bausch & Lomb Optical Company have PREFACE Vil kindly loaned me several cuts from their catalogues illus- trating apparatus of my own invention made by them. The new illustrations, comprising about a third of those in the book, have mostly been contributed by my colleagues in the department of Botany at Smith College. Several of the more notable of the figures, especially those in groups, viz., 62, 210, 213, 215, 298, 304, 311, 312, 318, 319, 321, 355, were drawn from nature by Professor Julia W. Snow, while the more elaborate of the anatomical drawings, viz., 85, 162, 163, 164, were drawn, also from nature, by Professor F. Grace Smith. The best of the diagrammatic figures, viz., 81, 169, 182, 191, 222, 225, 226, 227, and 228, are the work of Miss Helen Choate, though the other diagrams are my own. Most of the remainder of the new figures, including several from nature, many from photographs, and a large number adapted from standard sources, are the work of my assist- ant, Miss Marion T. Pleasants. In many other ways also, these friendly co-workers, with another, Professor Grace Clapp, have rendered invaluable aid, which I, hereby grate- fully acknowledge. This work was at first issued in two separate parts, and I have taken advantage of their combination into one volume to remedy some slight defects in the first impression, of which the only ones of importance are corrections of minor errors on pages 100, 108, and 254. A good many teachers have asked me whether laboratory outlines are planned to accompany this text. It happens that they exist already, for Part II of my book The Teaching Botanist (second edition, also published by the Macmillan Company), is devoted to outlines and full practical directions for teaching the topics of a general laboratory course. While not prepared especially to accompany this book, they accord with it so closely as to render needless an additional work. W. F. GANONG. NORTHAMPTON, Mass., June 26, 1917. -_ em, CONTENTS INTRODUCTION CuarTrer I. Tue Score anp VALUE oF BoTanicat Stupr. CHarprern IL Tue DistincTivE CHARACTERISTICS OF PLANTS THE STRUCTURES AND FUNCTIONS OF PLANTS CHapTzsr III. Toe Morrro.iocy anp Paysiotocy or LEAVES § 1. § 2. § 3. . The cellular anatomy of leaves. . The characteristics of protoplasm ‘ . The water-loss, or transpiration, from plants . . The adjustments of green tissues to light . . The various forms of foliage leaves . . The forms and functions of leaves other than foliage . The nutrition of plants which lack chlorophyll . The autumnal and other coloration of leaves . The economics, and treatment in cultivation, of leaves . The uses of the photosynthetic food . PART I The distinctive characteristics of leaves. . . The structure of leaves. The synthesis of food by light in leaves Carrer IV. Tre Morruowocy anv Paysio.ocr or STEMS § 1. § 2. § 4. § 5. § 6. eee The distinctive characteristics of stems . . The structure of stems and support of the foliage . The cellular anatomy of stems . The development of stems and leaves from buds The arrangements of leaves on stems The transfer of water and food through plants The growth of stems and other plant parts. F ix PAGE 15 15 17 19 52 72 82 88 97 113 1138 116 128 185 189 144 153 § 8. § 9. § 10. § 11. § 12. § 18. CHAPTER CONTENTS The respiration of plants . . . : . . . The geotropism of stems . . ; . . The various forms of foliage-bearing stems . The forms and functions of stems not connected with support of foliage . The monstrosities of stems and leaves . The economics, and treatment in cultivation, of stems V. Tre MorpHo.tocy anv PayrsIoLocy or Roors . The distinctive features of roots . The structure of roots . . The cejlujar anatomy of roots . . The absorption of water, and other functions of roots . Osmotic processes in plants . . The composition and structure of soils . The self-adjustments of roots to prevailing conditions . The additional, and substitute, functions of roots . The economics, and treatment in cultivation, of roots . Summary of the functions and tissues of plants VI. Tue Morpso.ocr ano PayYsio_tocy or FLOWERS. . The distinctive features of flowers . The structure of flowers . . The accomplishment of fertilization by flowers . The nature and consequences of fertilization . The methods and meaning of cross-pollination . Methods of asexual reproduction . The origin and significance of sex . Heredity, variation, and evolution . The methods used by man in breeding better plants . The morphology of flowers . . The morphology and ecology of flower clusters . Special forms, abnormalities, and monstrosities of flowers . The economics, and treatment in cultivation, of flowers . VIL Tue Morpso.ocy anv ParsIoLocr or FRvITSs . The distinctive characteristics of fruits . The structure and morphology of fruits . . The dissemination and dispersal of plants . Special forms and monstrosities of fruits . . The nature and cure of plant diseases . The economics and cultivation of fruits . . PAGE 162 174 179 191 196 212 212 215 224 232 287 247 250 257 261 267 267 269 276 279 288 298 302 317 822 340 343 345 845 347 366 867 870 CONTENTS CuHaprer VIII. Tae Morpro.iocy anp Puysio.ocr or SEEDS . § 1. The distinctive characteristics of seeds § 2. The structure, morphology, and functions of seeds . § 8. The suspension of viaey, resting Periods and duration _ of life in seeds . § 4. The germination of seeds . . § 5. The economics and cultivation of seeds § 6. The cycle of development from seed to seed PART II. THE KINDS AND RELATIONSHIPS OF PLANTS Cuaprer IX. Tse PHYLOGENETIC CLASSIFICATION OF PLANTS Cuarrer X. Division 1. THactitopprta: THe THALLUS PLANTS Class 1. Cyanophycesx : the Blue-Green Alg@w . Class 2. Schizomycetes : the Bacteria Class 8. Flagellata: the Flagellates . Class 4. Myxomycetes: the Slime Molds . Class 5. Chlorophycesz : the Green Algz . . Order 1. Protococcales : the Unicellular Green Alge Order 2. Confervales: the Confervoid Algze Order 3. Conjugales: the Conjugating Algz Order 4. Siphonales: the Tubular Algz2 Order 5. Charales: the Stoneworts . Class 6. Phycomycetes: the Algal Fungi . . Order 1. Saprolegniales : the Water Molds Order 2. Peronosporales : the Blights Order 8. Mucorales: the True Molds. Class 7. Pheophyces: the Brown Alge Order 1. Phsosporales: the Kelps Order 2. Fucales: the Rockweeds Class 8. Rhodophycex: the Red Algw Class 9. Ascomycetes: the Sac Fungi . Order 1. Discomycetes: the Cup Fungi Order 2. Pyrenomycetes: the Black Fungi Order 8. Erysiphes : the Powdery Mildews Order 4. Plectascales: the Blue and Green Molds Order 5. Exoasci: the Naked-ascus Fungi Order 6. Saccharomycetes: the Yeasts Order 7. Lichenes: the Lichens . xi PAGE 872 372 378 377 381 885 386 PAGE 891 396 899 402 410 412 415 416 420 424 429 432 485 436 437 439 440 442 443 447 450 452 455 456 458 458 459 xl CONTENTS Class 10. Basidiomycetes: the Basidia Fungi . : . Order 1. Ustilaginales: the Smuts... . : : Order 2. Uredinales : the Rusts . . . Order 8. Hymenomycetes: the Toadstool Fungi Order 4. Gasteromycetes: the Puffballs Fungi Imperfecti . . . . . CHaprer XI. Division 2. Brrorpsyta: tHe Moss PLants . Class 1. Hepatice: the Liverworts . . . : . Order 1. Ricciales . . . . . . : Order 2. Marchantiales . . : : . Order 8. Jungermanniales . . . : : Order 4. Anthocerotales Class 2. Musci: the Mosses. . . . Order 1. Sphagnales: the Peat Mosses . . ; Order 2. Bryales: the True Mosses . . . : CHarprer XII. Division 8. PTERIDOPHYTA: THE FERN PLANTS. Class 1. Filicines : the Ferns : Order 1. Ophioglossales : the Adder’s ‘Tongue Ferns . Order 2. Filicales: the Ferns Proper . Order 8. Hydropteridales: the Water Ferns Class 2. Equisetinexw: the Horsetails Class 8. Lycopodines: the Lycopods . Order 1. Lycopodiales : the Club Mosses Order 2. Selaginellales : the Selaginellas Cuaprer XIII. Division 4. SPERMATOPHYTA: THE SEED PLANTS Class 1. Gymnosperms : the Gymnosperms . . Order 1. Cycadales: the Cycads . . . . : Order 2. Coniferales: the Conifers Order 8. Gnetales: the Gnetums Class 2. Angiospermz: the Angiosperms Sub-class 1. Monocotyledones : the Monocotyledons Series A. The Primitive Monocotyledons Orders 1-5. Pandanales to Arales . . Series B. The Differentiated Monocotyledons Orders 6-7. Bromeliales to Liliales - Series C. The Specialized Monocotyledons Orders 8-9. Scitaminales and Orchidales Sub-class 2. Dicotyledonez : the Dicotyledons Series A. The Primitive Dicotyledons . . Orders 1-12. Verticillales to Caryophyllales . : CONTENTS xii PAGE Series B. The Differentiated Dicotyledons F - 646 Orders 13-24. Ranalesto Umbellales . . . 646 Series C. The Specialized Dicotyledons . . . . 658 Orders 26-32. Ericales to Campanulales . . . 658 CHarrer XIV. Tse Ecorogicat CLassiFICaTION OF PLrants . 6658 1. The Ecological Groups . . . . . . . 658 2. Plant Habitats and Vegetation Forms . ‘ . . . 659 (1) The Water Habitats and the Hydrophytes. . . 561 (2) The Aérial Habitats and the Aérophytes . . . 664 A. The Optimum Habitats and the Mesophytes . . 566 B. The Humid-Dry Habitats and the Tropophytes . 567 C. The Dry Habitats and the Xerophytes . : . 869 \ D. The Undrained Habitats and the Helophytes . . 571 E. The Saline Habitats and the Halophytes . . 578 F. The Acid Soil Habitats and the Oxalophytes . . 678 (8) The Organic Habitats and the Hysterophytes . . 674 A. Habitats of Climbers . . 515 B. Habitats of Epiphytes . . . . . . 576 C. Habitats of Half-parasites . . . . 87 D. Habitats of Parasites and Saprophytes . . . 877 E. Habit of Insectivorous Plants . . : . . 578 8. Plant Formations and Associations . . : : . 579 List of the Principal Formations . ‘ . . 584