Introduction

Cornell IDlntversit^ Xibrari? OF THE IRewl^orR State College of Hgriculture .a^,.fA^.-^.. lJuJix. Cornell University Library SB 107.P42 1910 Agricultural botany, theoretical and pra 3 1924 000 603 971 Cornell University Library The original of tliis book is in tlie Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924000603971 AGRICULTURAL BOTANY Agricultural Botany THEORETICAL AND PRACTICAL JOHN PERCIVAL, M.A., F.L.S. PROFESSOR OF AGRICULTURAL BOTANY UNIVERSITY COLLEGE, READING FOURTH EDITION NEW YORK HENRY HOLT AND COMPANY I 9 lo Alt Rights Beservid PREFACE Practical men and the agricultural press have from time to time complained of the absence of text-books of botany suited to the wants of the student of agriculture, those in existence being works which treat the subject from a purely scientific standpoint and contain a large amount of matter which, though important to the botanist, is nevertheless of little interest or value to the agriculturist whose time for training in such matters is necessarily limited. The recent growth of interest in technical instruction, which has resulted in a^large increase in the number of colleges and schools for agricultural education, has rendered it imperative that so serious a defect should be remedied, and this I have endeavoured to do by writing the present volume. The contents are based upon many years' experience in teaching and lecturing to students, practical farmers and gardeners, and embrace all those botanical matters which such experience has led me to consider essential to a sound working knowledge of the general principles of the science and its more immediate application to the crops of the farm. Although the book has been primarily written for the benefit of students of agriculture, the greater portion of it is equally well adapted to meet the requirements of gardeners and all who desire to obtain an insight into the general structure and lifeprocesses of plants, a knowledge of which must undoubtedly conduce to a more satisfactory and economical management of all cultivated plants. Until quite recently botanical knowledge has apparently been deemed of little importance in examinations in the science and practice of agriculture, the science of botany being usually treated as an ' optional subject.' It is, however, gratifying to note that in the new regulations for the examination for the National Diploma in the science and practice of Agriculture, issued by the National Agricultural Examination Board, Botany takes its proper place as an obligatory subject beside its sister science Chemistry. VI PREFACE All the drawings in the work are original, and with the excep- tion of the diagrammatic figures have be-en made by the author from living or natural examples. The panicles or ' ears ' of the grasses are all drawn the natural size of average specimens, in order that the figures may be of use in the identification of these important plants. The farm seeds are also drawn to a uniform scale ; their relative sizes may therefore be seen at a glance. In this as in all scientific study, practical work is absolutely essential to a proper understanding of the subject ; in recognition of the importance of such work I have introduced into the text of the volume a series of exercises and experiments, illustrative of the principles and facts to be studied. These and others, which will suggest themselves to intelligent students, should be attacked and carried out in the spirit of research, so that students may learn to observe, record and discover things themselves. In conclusion, I tender my sincere thanks to my colleague Mr Cousins, and also to Mr W. H. Hammond, Milton Chapel, Canterbury, and Dr A. B. Rendle, of the British Museum (Natural History Department), for valuable criticism and assist- ance in reading through the proofs. JOHN PERCIVAL. South-Eastern Agricultural College, Wye, Kent. March, 1900. PREFACE TO THE SECOND EDITION The very appreciative reception and rapid sale of the first edition have proved that a real want has been met by the book. The present edition has been emended and revised throughout in accordance with recent work and the criticisms of botanical friends. , I shall be grateful for any further suggestions which may be deemed necessary to render the work more complete for educational purposes or more useful to the student of this and allied branches of applied botany. JOHN PERCIVAL. Nov. 1 90 1. 1 PREFACE VI PREFACE TO THE FOURTH EDITION To this edition a new chapter has been added and very considerable additions made throughout the work, with a view of improving its usefulness and keeping the matter up to date. It is gratifying to find that the volume is highly appreciated by teachers and students in all countries wherever English is spoken. JOHN PERCIVAL. Jem. 1910. ;; X CONTENTS PART II. INTERNAL MORPHOLOGY (ANATOMY). CHAPTER IX. The plant cell : Cell-division : Tissues . . The cell, 105; Cell-division; Continuity of protoplasm, no; Tissues, III. ""^ 104 X. The anatomy of the stem, root and leaf . 113 The herbaceous stems of dicotyledons, 113 ; The perennial woody stems of dicotyledons, 122 ; Stems of monocotyledons, 136 ; The root, 140; The green foliage-leaf, 144; The growing-points of stems and roots, 148. PART III. PHYSIOLOGY OF PLANTS. XI. The chemical composition of plants . .152 Carbohydrates, 155 ; Fats and fixed oils, 163 ; Volatile or essential oils, 164 ; Organic acids, 164 ; Proteins or Albuminoids, 165 Amides, 166 ; Alkaloids, 167. XII. The composition of plants {continued) . .168 The elementary constituents of plants, 168; Water-culture, 169; Essential elementary constituents of plants, 171 ; Non-essential elementary constituents, 175. XIII. Osmosis; absorption of water . 177 Osmosis, 177 ; Absorption of water, 182 ; Exudation pressure Root pressure ; ' bleeding ' of plants, 186. XIV. Transpiration : The transpiration-current . 191 Transpiration, 191 ; Transpiration-current, 198. XV. The absorption of food materials . . 201 Food and food-materials, 201 ; Food-materials and their ab- sorption, 202. XVI. ' Carbon-fixation,' 'Assimilation' or 'Photo- synthesis' . . , . . .208 ; CONTENTS XI CHAPTER PAGE XVII. Formation of proteins. Translocation and STORAGE OF FOODS . . . .217 Formation of proteins, 217 ; Utilisation, translocation and storage of plant-foods, 219 ; Nutrition of semi-parasites and semi-sapro- ........... phytes, 225. XVIII. Enzymes and the digestion of reservematerials XIX. Respiration 227 233 Ordinary respiration in the presence of free oxygen of the atmo- ...... sphere : aerobic respiration, 233 ; Anaerobic or Intramolecular respiration, 238. XX. Growth 240 Growth, 240 ; Conditions which influence growth, 243 ; spontaneous movements of growth ; nutation and tissue-tension, 247 ; induced movements of growth, 250. XXI. Reproduction . . . . .258 .... Vegetative reproduction, 258; Cuttings, 259; Layers, 261; Budding and grafting, 262. XXII. Reproduction {continued) 269 Sexual reproduction, 269 ; Structure and germination of the pollen-grain, 269 ; The ovule and its structure, 271 ; Fertilisation and its effects, 273 ; Pollination ; Self-fertilisation and Cross- fertilisation, 279 ; Transference of pollen, 281 ; Sexual affinity hybridisation and hybrids, 285 ; Mendelian laws of inheritance, aSg ; ...... Artificial pollination ; methods of crossing plants, 299. . XXIII. Cultivated plants and their origin ; Plant BREEDING 303 Bud-varieties or ' sports,' 304 ; Variation among seedling plants, 305 ; Variations, how induced, 312 ; Correlated variability, 316 ; Reversion, ' throwing back ' or atavism ; Degeneration of varieties, 317- PART IV. CLASSIFICATION AND SPECIAL BOTANY OF FARM CROPS. XXIV. The classification of plants . . . Individual and species ; variety and race, 321 ; Genus ; plant- names, 321 ; Divisions of the Vegetable Kingdom, 323. 320 1 ;; XI CONTENTS CHAPTER XXV. Cannabace^ ..... PAGE 332 ... The Japanese Hop, 332 ; The common Hop, 332 ; Hemp, 348. XXVI. ChenopodiacEjE . 350 ...... Sea Beet, 351 ; Common Beet, 351 ; Mangel Wurzel, 352 ; Sugar- Beet, 361. XXVII. Crucifer* 365 Wild Cabbage, 366 ; Cultivated cabbage and its varieties, 367 ; Turnip, 371 ; Swede, 376 ; Rape, cole or coleseed, 379 ; Black mustard, 381 ; White mustard, 383; Charlock, 385 ; Wild Radish, 386. XXVIII. Linages 389 General characters of the Order, 389 ; Flax or Linseed, 389. XXIX. Rosacea . . . . . -397 Plums and Cherries, 397 ; Sloe, BuUace, Wild Plum and Apricot, 399; Dwarf Cherry, Gean, Bird Cherry, Almond, Peach, 400; Strawberries, 401 ; Raspberry and Blackberry, 403 ; Dog Rose, 404 ..... Pear, 405 ; Apple, 406 ; Medlar, Whitethorn and Quince, 407 ; Lesser Burnet, 408. XXX. Leguminos^e 410 Peas, 412; Bean, 416; Vetch, 418; Vetchling, 420; Red clover, 421 ; Zig-zag clover, 424 ; Alsike, 425 ; White clover, 425 ; Crimson clover, 426 ; Yellow suckling, 428 ; Hop clover, 428 ; Black medick, 429 ; Lucerne, 429 ; Melilot, 432 ; Sainfoin, 432 ; Serradella, 434 ..... Kidney Vetch, 434 ; Bird's-foot trefoil, 435 ; Harrow, 437 ; Lupins, 437. XXXI. UmbellifeR/E Gorse, 436 ; Rest- 441 Wild carrot, 444 ; Cultivated carrot, 444 ; Parsnip, 452 ; Hemlock, ...... 454 ; Water Hemlock or Cowbane, 454 ; Water Dropwort, 455 ; Fool's Parsley, 455. XXXII. SOLANACE/E 456 ...... Potato, 456 ; Bitter-Sweet, 468 ; Black nightshade, 468 ; Deadly nightshade, 468 ; Henbane, 469. XXXIII. COMPOSITiE 470 General characters of the Order, 470 ; Yarrow ; Millefoil or Thousand-leaf, 473. XXXIV. Gramine^. True Grasses . . . 475 XXXV. Gramine^ {continued). Cereals . . . 483 CONTENTS ;; Xlll XXXVI. Cultivated and Wild Oats (Genus Avena) . 493 Wild Oat, 493 ; Bristle-pointed Oat, 494 ; Animated or Fly Oat, 494 ; Short Oat, 494 ; Common Cultivated Oats, 494. XXXVII. Cultivated Barleys (Genus //or^/faiw) . Cultivated Barleys, 501 ; Distinguishing features of Barley-grains, 506 ; Characters of a good malting barley, 508. 500 XXXVIII. Cultivated Rye (Genus 5^ra/�) . . 512 XXXIX. Cultivated Wheats (Genus Triticum) . 515 XL. Common Grasses of the Farm . . 530 XLI. Grasses and Clovers for temporary and permanent pastures . . -556 Grasses and clovers for leys of one, two or three years' duration, 558 ; Grasses and clovers for temporary pastures lasting from three to six years ; Grasses and clovers for permanent pasture, 561 Weight of seed to be used, 569. PART V. WEEDS OF THE FARM. XLII. Weeds: General. . . . .571 Their injurious effects, 571 ; Mistletoe, 575 ; Duration of weeds, 577 ; Habit of growth of weeds, 579 ; How weeds are spread, 580 Extermination of weeds, 582. XLI 1 1. Weeds: Special . . . . Weeds of arable ground, 589 ; Weeds of pastures, 604. ..589 PART VI. .... FARM SEEDS. XLIV. Farm Seeds: General 614 Purity, 616 ; Germination Capacity, 620 ; Speed of germination or germination energy, 626 ; Weight, 629 ; Form, colour, bright- .... ness and smell, 635. XLV. Farm Seeds: Special 639 XIV CONTENTS PART VII. FUNGI, OONSIDEKED CHIEFLY IN RELATION TO SOME COMMON DISEASES OF PLANTS. CHAPTER PAGE XLVI. Fungi: General . . � ' \ . Hypha and mycelium, 677; Reproduction, 679; Germination of spores, 682; Mode of Life; saprophytesand parasites, 683 ; General advice to be followed when dealing with plant diseases, 686. XLVI I. Fungi {continued) Phycomycetes . . .688 Eumycetes, 688 ; Phycomycetes (sub-class i. Zygomycetes), 689. XLVIII. Fungi (continued) Phycomycetes . . .692 Phycomycetes (sub-class ii. Oomycetes), 692 ; Damping-off, 693 ; Potato diseases, 698. XLIX. Fungi (^o�A��^^ Basidiomycetes . . 715 ' Smut ' of Oats, 716 ; ' Smuts ' of wheat, barley and rye, 718 ; Bunt of wheat, 723 ; Rust and mildew of wheat, 726 ; Other species of Rusts, 735 ; The common mushroom, 740. L. Fungi {continued) AscOMYCETES . . . 745 Yeasts, 746 ; Mildews, 748 ; Ergot, 758. LI. 'Clue-root' Disease . . . .763 PART VIII. BACTERIA. ...... LII. Bacteria: their morphology and reproduc- tion 769 Forms of Bacteria, 769 ; Vegetative reproduction, 770 ; Reproduc- tion by means of spores, 771 ; Conditions affecting development, 774 ; Sterilisation and pasteurisation, 776. LIII. Bacteria: their work . . . Lactic fermentations, 780 ; Butyric fermentations, 782 ; Acetic fermentations, 784 ; Fermentation of cellulose, 785 ; Fermentation of urea, 786; Putrefaction, 7B7 ; Nitrification, 789 ; Denitrification, 792 ; Fixation of free nitrogen, 793 ; Bacteria and diseases of animals, 803 ; Diseases of plants caused by bacteria, 805 ; Black rot of cabbages, 806. 779 PART I. GENERAL EXTERNAL MORPHOLOGY. CHAPTER I. INTRODUCTORY. I. The things met with every day can be separated into two dis- tinct classes or groups, namely, those which are alive, such as birds, insects, cattle, trees, flowers, and grasses, and those which are never possessed of life, such as air, water, glass, and iron. Although it is impossible to give a complete and satisfactory account of what life is, for all practical purposes the difference between the two classes of objects is easily recognised, and a more extended study of them leads to the conclusion that between the living and the inanimate world there is a hard and fast line of separation. The chief and most obvious peculiarity of living things is their -- power of giving rise to new individuals that is, their power of reproduction. They are ordinarily separated into two classes, namely animals and plants. The term Biology in its widest sense is used to denote the study of all forms of living things, that branch of it dealing with animals being known as Zoology, while the science of Botany is concerned with the study of plants. The most familiar animals have the power of moving about in a way which is not possessed by plants. Moreover, the former require as food, substances which have been derived from other living things, such as flesh of all kinds, milk, bread, potatoes, and similar materials ; while most common plants are capable of utilising substances which belong entirely to the inanimate world, 2 INTRODUCTORY such as carbon dioxide, water, and various minerals. Although these points of difference between plants and animals are suificient to separate the two classes from each other, so far as the purposes of everyday life are concerned, it must be mentioned that a further examination of living things shows that there are some which in structure and power of utilising inorganic sub- stances as food-materials resemble plants, but which are never- theless able to move about as freely as animals, and that other structures usually considered as animals move very little. Then, again, there are living things always classed as plants, which produce flowers and seeds, although they cannot live when supplied with carbon dioxide, water and minerals, but must be fed upon the same or similar substances to those needed by animals. Indeed, all attempts to draw a hard line of separation between plants and animals are found to end in failure. The living substance within them appears to be the same, and between the socalled animal and vegetable kingdoms there is no distinct point of difference. The living world is essentially one, and not two, and it is very necessary to constantly bear in mind that plants are just as much living structures as animals are, since by far the larger number of mistakes in the management and cultivation of plants are due to want of proper appreciation of this fact. 2. For the present our attention will be confined to the common plants of the farm and garden. In form and structure these are altogether different from animals, and as the difficulty of defining the two classes of living things is only met with in studying minute and practically unseen organisms it may be dismissed for the present. It will be readily understood that plants may be studied from a great many different points of view, and consequently special branches or divisions of the science arise. Attention may be confined to an investigation of the uses of the various parts of a plant's body--to the work which the leaves, roots, and flowers perform in the life of the plant ; this part of the subject is known ;; --; INTRODUCTORY 3 as physiology. Another branch is concerned with the form, origin, development, and relationship of the various parts to each other, without any reference to the work they do : the term morphology is used to denote this division of the science. Then, again, the structure and arrangement of the various parts of plants may be studied in order to determine their points of similarity and of difference with a view of placing together in groups all those possessing certain degrees of resemblance : this is usually termed Systematic Botany. For purposes of convenience and methodical extension of knowledge of the subject many other divisions of the Science are made, and in each of them the study of plants is made from a somewhat different standpoint. Although other classes of the vegetable kingdom need attention it is advisable to confine our study at first to the seed-bearing plants, as this division includes all those which are everywhere most familiar. It is essential that farmers and all who are interested in the management of plants for pleasure or profit should examine and investigate them from as many different aspects as possible, as only by so doing can real progress be made in their cultivation. 3. Most plants of the farm belong to the class known as Sperma- phytes or seed-bearing plants ; the latter are sometimes called Flowering plants or Phanerogams, but their chief characteristic is the production of seeds. The life-history of a spermaphyte is a continuous process of development or unfolding of parts in which we may recognise four fairly distinct periods, namely : (i) Germination of the seed and the escape of a young plant from it (2) The development and growth of roots, stems, and green leaves (3) The flowering period or formation and opening of flowers and (4) The production and ripening of fruits with their contained seeds. 4 INTRODUCTORY The succession of events is generally in this order, and usually the formation and unfolding of roots, stems, and leaves occupies by far the greatest portion of the plant's life. There is, however, great variation in the time taken to reach the several stages of development, and the periods are not always of the same duration in the same species of plant, 4. So far as their total duration of life is concerned, plants may be usefully divided into annuals, biennials, and peren- nials. By an annual is meant a plant which completes its life-history in one growing season. Starting as a seed in spring or early summer, it develops root, stem, and leaves, and then produces flowers and seeds, after which it dies, leaving behind it offspring in the form of seeds. The time taken by annuals to reach the stage of seed-production is not always the same ; usually the whole of the season, from spring to autumn, is necessary, and only one generation is produced in that time. Some of them, however, termed ephemerals, such as chickweed and groundsel, produce seeds in a few weeks, and these may germinate and produce a second and third crop of plants before frost cuts them down in autumn and winter. Biennials, beginning life as seedlings in spring or summer, occupy the first growing season in the production of root, stem, and leaves only. They then rest during winter, and in the following year start growth again, and produce a stem bearing flowers and seeds, after the ripening of which the plant dies. Wild carrot, parsnip, and some varieties of thistles behave in this manner. Perennials are plants which live more than two years, and often several seasons elapse before flowers and seeds are produced. They are frequently divided into two classes, namely, (i) herbaceous perennials and (2) woody perennials. In the former the leaves and stems above ground are of a soft nature and die down at the INTRODUCTORY 5 end of the growing season, the parts of the plant which still remain to carry on growth in subsequent years being underground : the stinging nettle, hop, and potato are representatives of this class. In woody perennials, of which all trees and shrubs are examples, the stems above ground are hard and woody. This method of dividing plants according to their length of life, although useful, is by no means a strict one, as the duration is dependent to some extent upon season, time of sowing, and the treatment which they receive. Wheat, for example, if sown in early spring behaves as an annual, but if sown in late summer or autumn does not perfect its seed and die until the following year. If kept continually cut or cropped down by animals it may even remain two years or more without dying, especially when thinly sown on good soils and allowed plenty of room for branching. Annual mignonette of gardens is often made to last several years in pots by pinching off the flowering stems as soon as they begin to form. Turnips and other plants, usually biennials in ordinary farm practice, are invariably annuals if sown early in the year, say in February. Climate and soil also influence the duration of plants, annuals in some districts becoming biennial or even perennial in others. -- -- Ex. 1. Sow short rows ol the cereals and ' roots ' mangels, turnips, -- swedes and carrots on the first day of each month during a whole year, and make careful observations and notes on their subsequent growth up to the time of seed production. Interesting and useful results are obtained. 5. As the duration of flowering plants is subject to such variation and their classification into annuals, biennials, and perennials, consequently somewhat arbitrary, they are sometimes placed in groups according to the number of times they are able to produce seeds. Those which yield only one crop and then die are termed 6 INTRODUCTORY fnonocarpic plants : annuals and biennials are of this nature, and some perennials also. Such plants as most trees and shrubs, thistles, bind-weed, coltsfoot, and many grasses which are able to produce flowers and seeds during an indefinite number of seasons are described zs polycarpic CHAPTER II. SEEDS : THEIR STRUCTURE AND GERMINATION. I. It is well known that one of the most ordinary methods of raising plants is to sow what are called seeds, yet how few there are among the many who use them who fully appreciate their real nature and capabilities. This want of knowledge is not due perhaps so much to want of interest in them, as to the fact that for their proper management they are usually buried away in the ground, and are therefore unseen ; moreover, many of them are so small that their structure is difficult to observe with the naked eye. In order to understand the true nature of a seed it is necessary to examine its origin and construction, and watch its development as far as possible from the earliest stages to the time when it gives rise to a completely formed young plant. -- The Common Bean. A broad bean is one of the largest seeds met with in ordinary farm or garden practice, and as its parts are all sufficiently large to be observed without the special aid of anything more than an ordinary pocket lens, it is especially fitted for study. When a nearly ripe pod of a broad bean plant is opened, each seed within it is found attached to -- means ^ the inside byJ of E^l.G^. I. ,,. Piece of, b, ean podj slhowi� ng tvhe ,funi�cl, e , (/) a short stalk ox funicle and its attached seed ^ig. i), and it is through this stalk that all the nourishment 7 8 SEEDS : STRUCTURE AND GERMINATION passes from the parent to enable the young seed to develop. At first the pod