Elementary Botany
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Cornell University Library BOUGHT WITH THB INCOME PROM THE ;SAGE ENDOWMENT FUND THE GIFT OF Z891 Mf/ iL 9092*^"""' """"™"y Library Elementary botany / ^^24 olfn,anxfn.an^ 031 266 525 ELEMENTARY BOTANY GEORGE ^ELL & SONS LONDON : YORK STREET, COVENT GARDEN NEW YORK : 66 FIFTH AVENUE, AND BOMBAY : 5^ ESPLANADE ROAD CAMBRIDGE : DEIGHTON BELL AND CO. ELEMENTARY BOTANY PERCY GROOM, M.A.(Cantab. et Oxon.), F.L.S. Examiner in Botany to the University of Oxford, and sometivte Professor of Botany at Whampoa iChina) WITH 275 ILLUSTRATIONS LONDON GEORGE BELL & SONS 1898 PREFACE In writing the present volume, I have endeavoured to place the subject before elementary students in such a way as to exercise to the full their powers of observation, and to enable them to make accurate deductions for themselves from the facts which they observe. To attempt the study of Botany without the practical examination of plants is futile. Students of plant-life must look at plants, and this book is specially designed for use during the process. Considerable experience as examiner in Botany as taught in schools has convinced me that comparatively few learners have the advantage of seeing specimens with the aid of a compound microscope, although the treatises usually employed should involve the frequent use of such an instrument. Under these circumstances, I have in the following pages assumed that a compound microscope is not employed, and for their proper understanding such an instrument is quite unnecessary. An ordinary inexpensive lens should be used to aid the naked eye ; but, on the other hand, in commencing the study of Botany a compound microscope is absolutely needless, and, in the case of young beginners, does more harm than good. The section on Physiology has been so written that no knowledge of the histology of plants is assumed—a feature which is, I believe, here introduced for the first time. Though by no means a "cram-book" for elementary examinations, a thorough know- ledge of the contents of this book will enable a candidate to pass with distinction. In order to lay more emphasis on the observation of facts, and with a view to simplify the >yhole matter, I have inserted no unnecessary technical terms, but, for the convenience of students who afterward use "Floras," I have added an appendix for use as a dictionary, but not for the purpose of elementary study. vi PREFACE Some words of explanation may be required in reference to the definitions of flowers and fruits. In more advanced works we are told that a flower is a collection of sporophylls inserted on a simple axis. This definition seems to me im- perfect. That the young carpels and stamens are homologous with leaves, and particularly with sporophylls, is proved beyond a doubt. But the mature carpel with the ripe ovules is no longer homologous with a sporophyll ; it is a sporophyll containing parasitic and symbiotic gametophytes. The sym- biosis of the gametophytes and the sporophylls before, during, and subsequent to fertilisation constitutes a phenomenon which is unique in the vegetable kingdom. Consequently, it appears that, when judged by the facts of the case and on historical grounds, it is at least incomplete and inexpedient to employ to the cone of Equisetum the same term as to the flower of a Buttercup. A single flower of a Buttercup is no more a mere collection of sporophylls than a frog is a fish because it passes through the tadpole stage. In reference to the definition of a fruit, I have followed that given in the "Lehrbuch der Botariik" written by Professors Strasburger, Noll, Schenck, and Schimper. The definition of a fruit is thus brought closer to the popular usage of the term, while we are extricated from any dilemma in reference to distinguishing between an inferior and a false fruit. .. In conclusion, it should be stated that for the most part the illustrations have, after careful consideration, been specially executed by my friend Mr A. H. Church of Jesus College, Oxford, to whose skill and care I am much indebted. To him, also, I owe a careful revision of the proofs of this book. Further assistance in the matter of illustrations has been rendered by Mr A. Robinson of the University Museum, Oxford. Students who desire a simple introduction to the study of Microscopical Botany are recommended to procure Dr D. H. Scott's "Structural Botany"; while those who wish for a comprehensive work, dealing with the science as a whole, will find all they require in " The Student's Text-book of Botany," by Professor S. H. Vines. Finally, such students as desire to identify wild British plants, and to do field-work, will find Hayward's "Botanist's Pocket Book" an excellent little work which contains all the necessary information. — . CONTENTS Part I. General Morphology CHAPTER PAGE I. INTRODUCTION . I II. ROOT AND SHOOT .... 3 ROOT • ... 5 Adventitious Roots, 6—Shapes of Roots, 8—Aerial Roots, 8. III. VEGETATIVE SHOOT . 9 Adventitious Shoots,; 1 1 ARRANGEMENT OF LEAVES . .II Whorled Leaves, 11 —Alternate Leaves, 12—^Diagrams, 13- FOLIAGE-LEAVES . -14 Sheath, 15—Stalk, 15 —Blade, 16—Form of Blade, 16 —Venation of Blade, 16—Division of Blade, 17. SIMPLIFIED LEAVES . .18 Scales, 18 —Cotyledons, 19—Prophylls, 21 —Bracts, 21. BUDS ..... 22 Estivation, 22—Vernation, 23. IV. STEM . ... .24 Definite and Indefinite Growth, 24—Axes of different Orders, 24—Sympodia, 25—Arrangement of Branches, 26^-Herbaceous and Woody Stems, 27—Increase in Thickness, 27. SUBTERRANEAN SHOOTS . .28 Rhizome, 29 — Tuber, 30 — Corm, Life-history of Crocus, 30—Bulb, 32. SUB-i«RIAL STEMS . -33 Direction of Growth, 33—Climbing Plants, 34—Root- Climbers, 34—Twining Plants, 34—Tendril-Climbers, 35, Scramblers, 36. ——— viii CONTENTS CHAPTER PAGE SUBSIDIARY OUTGROWTHS (hAIRS, ETC.) . 36 METAMORPHOSED SHOOTS . 3^ Spines, Thorns, and Prickles, 37 — Tendrils, 38 Cladodes, 38. V. LIFE-HISTORY OF FLOWERING PLANTS . 39 Frequency of Flowering and Duration of Life, 39 Methods of Resting, 40 — Methods of Vegetative Multiplication, 41 —Order of Succession of Events, 42. VI. FLOWER . -43 Flower of Buttercup, 43—Flowers of Scotch Pine, 44 Definition of a Flower, 45. : VII. GYMNOSPEKM^ —SCOTCH PINE . 47 VIII. INFLORESCENCE . -Si Racemose Inflorescences, 51 —Cymose Inflorescences, 54—Bracts, 55. IX. FLORAL LEAVES . -57 PERIANTH .... -57 Calyx, 57—Corolla, 58—Perianth, 60. ANDRCECIUM . ' . .60 GYN^ECIUM . -63 Apocarpous Gyneecium, 63—Syncarpous Gynjecium, 64 —Placentation, 64—Absence of Stamens or Carpels, 66. X. ARRANGEMENT OF THE FLORAL LEAVES . 67 CYCLIC FLOWERS . -67 Obdiplostemony, 67—Unequal Growth, 68—Atrophy and Suppression, 69—Fusion or Cohesion, 69 Branching or Doubling, 69—Symmetry, 70. HEMICYCLIC ACYCLIC AND FLOWERS . -72 FLORAL DIAGRAMS .... 72 ^Estivation, 73—Floral Formulse and Symbols, 74. SHAPE OF THE RECEPTACLE 74 Hypogynous Flowers, 74—Perigyrious Flowers, 75 Epigynous Flowers, 75—Other Modes of Insertion, 75—Disk, 76. NECTARIES XI. ..... 77 POLLINATION ..... 77 Gross-pollination, 78 — Arrangements for hindering Self-pollination, 78—Wind-pollinated Flowers, 79 Insect-pollinated Flowers, 80— Self-poUination, 82. — —— CONTENTS ix CHAP. PAGE XII. OVULE . 84 FERTILISATION AND CHANGES IN THE OVULE . 85 FRUIT . .... 87 Classification of Simple Fruits, Sg^Compound Fruits, 94—Complete Fruits, 94. XIII. DISPERSAL OF SEEDS . -95 Explosive P'ruits, 95—Dispersal by the Wind, 95 Dispersal by Clinging to Animals, 96 — Dispersal inside Animals, 96—Protection of the Embryo in the Seed, 97. FUNCTIONS OF THE PARTS OF FLOWERS, FRJJITS, AND SEEDS . .98 Part II. Classification of Angiosperms XIV. CHIEF CHARACTERS OF THE FAMILIES CONSIDERED I03 DICOTYLEDONS . I07 Apetal/e, 107 — CupulifeKE, 107—Salicacese, 114 Euphorbiacese, 116. PoLYPETAL/E, 118—Ranunculacepe, 118—Papaveracese, 123—CruciferEE, 124—^Violacete, 127—Caryophyllacese, 130—Malvaceae, 132—GeraniaceEe, 135—Oxalidaceas, 137—Papilionacese, 137—Rosaceie, 139— Umbelliferfe, 146. Gamopetal^, 148 —Primulacese, 148—ConvolvuIaceDS, 151 —Solanaceje, 151 —BoraginaceK, 153 — Labiatae, 153 — Scrophulariaceie, 156 — CaprifoliaceEc, 159 — Compositse, 161. MONOCOTYLEDONS. .169 Liliaceae, 169 —Amaryllidaceae, 170—Iridacea;, 171 OrchidaceiE, 175—Aracese, 178—Graminacess, 181. Part III.—Physiology XV. NUTRITION OF THE PLANT . .189 Chemical Composition of a Plant, 189—Composition of the Air and Soil, 190—Artificial Culture-solutions, 191 —Manufacture of Organic Compounds, 192. b — X CONTENTS CHAP. PAGE XVI. ABSORPTION OF CARBONIC ACID . -193 Influence ofTemperature, 194—Influence of Light, 194 —Chlorophyll, 194. XVII. ASSIMILATION OF CARBON . .196 Proteids, 196—Carbohydrates, 197—Fats, 197—Forma- tion of Starch, 198—Entrance of Carbonic Acid, 199 —Green Parts not producing Starch, 200—Why Light is Essential, 200—Transport of Carbohydrates, 200—Starch, Sugar, Fats, as Food-substances, 201 Nutrition of Plants devoid of Chlorophyll, 202. XVIII. ABSORPTION OF WATER AND INORGANIC SALTS . 203 Absorbing Functions of Roots, 203—Influence of Exter- nal Conditions, 204—Essential Chemical Elements and their Absorption, 205. ASCENT OF WATER AND SALTS . 2o6 XIX. TRANSPIRATION ..... 209 Measurement of Tianspiration, 209—Leaves as Tran- spiring Organs, 210—Conditions influencing Tran- spiration, 210—Function of Transpiration, 211. EXCRETION OF LIQUID WATER . .212 ROOT-PRESSURE . 213 CAUSE OF ASCENT OF WATER . .214 XX. RESPIRATION . -215 Oxygen essential to Flowering Plants, 217—Conditions affecting Respiration, 217—Liberation of Heat during Respiration, 218. XXI. GROWTH 219 Essential Conditions, 219—Growth