PART II.

AGRICULTURE CONSIDERED AS A SCIENCE.

285. All knowledge is founded on experience; in the infancy of any art, experience is confined and knowledge limited to a few particulars; but as arts are improved and extended, a great number of facts become known, and the generalisation of these, or the arrangement of them according to some leading principle, constitutes the theory, science, or law of an art.

1286. Agriculture, in common with other arts, may be practised without any knowledge of its theory; that is, established practices may be imitated: but in this case it must ever remain stationary. The mere routine practitioner cannot advance beyond the limits of his own particular experience, and can neither derive instruction from such accidents as are favourable to his object, nor guard against the recurrence of such as are unfavourable. He can have no resource for unforeseen events but ordinary expedients; while the man of science resorts to general principles, refers events to their true causes, and adapts his measures to meet every case.

1287. The object of the art of agriculture is to increase the quantity and improve the quality of such vegetable and animal productions of the earth as are used by civilised man; and the object of the agriculturist is to do this with the least expenditure of means, or, in other words, with profit. The result of the experience of mankind as to other objects may be conveyed to an enquiring mind in two ways: he may be instructed in the practical operations of the art, and their theory, or the reasons on which they are founded, laid down and explained to him as he goes along; or he may be first instructed in general principles, and then in the practices which flow from them. The former mode is the natural and actual mode in which every art is acquired (in so far as acquirement is made) by such as have no recourse to books, and may be compared to the natural mode of acquiring a language without the study of its grammar. The latter mode is by much the more correct and effectual, and is calculated to enable an instructed agriculturist to proceed with the same kind of confidence and satisfaction in his practice, that a grammarian does in the use of language.

1288. In adopting what we consider as the preferable mode of agricultural instruction, we shall, as its grammar or science, endeavour to convey a general idea of the nature of vegetables, animals, minerals, mixed bodies, and the atmosphere, as connected with agriculture; of agricultural implements and other mechanical agents; and of agricultural operations and processes.

1289. The study of the science of agriculture may be considered as implying a regular education in the student, who ought to be well acquainted with arithmetic and mensuration; and to have acquired the art of sketching objects, whether animals, vegetables, or general scenery, of taking off and laying down geometrical plans; but especially he ought to have studied chemistry, hydraulics, and something of carpentry, smithery, and the other building arts; and, as Professor Von Thaer observes, he ought to have some knowledge of all those manufactures to which his art furnishes the raw materials.

BOOK I.

OF THE STUDY OF THE VEGETABLE KINGDOM WITH A VIEW TO AGRICULTURE.

1290. The various objects with which we are surrounded are either organised, having several constituent parts which united form a whole capable of increase by nourishment; or they are unorganised, and only increased by additions to their external parts. To the first division belong the animal and vegetable kingdoms, and their study is founded chiefly on observation to the second belongs the mineral kingdom, the study of which in masses, or geology and mineralogy, is also founded chiefly on observation; and, with regard to composition and elements, on experiment or chemistry.

1291. Vegetables are distinguished from animals in not being endowed with sentiment, or a consciousness of existence. Their study has employed the attention of mankind from a very early period; and has been carried to a high degree of perfection within the last

century; more especially by the exertions of Linnæus, and those of Jussieu, Mirbel, and some other French philosophers. This study comprehends systematic botany, vegetable anatomy, vegetable chemistry, physiology, pathology, the distribution of vegetables, and vegetable culture. The study of these branches is of the utmost importance to the agriculturist, especially that of vegetable physiology; and though the limits of this work do not permit us to enter into the subject at great length; yet we shall direct his attention to the leading points, and refer him to the best books.

CHAP. I.

Of the Study of Systematic Botany.

1292. Glossology, or the study of the names of the parts of plants, is the first step in this department.

1203 All the arts and sciences require to express with brevity and perspicuity a crowd of ideas unused in common language, and unknown to the greater part of men: whence that multitude of terms, or technal turns, given to ordinary words, which the public often turn into ridicule, because they do not feel the use of them, but which all are obliged to make use of, who apply themselves to any study whatEver. Botany having to describe an immense number of beings, and each of these beings having a great variety of organs, requires a great variety of terms. Nearly all botanists are agreed as to these terms, and in order that they may be universally understood and remain unchanged in meaning, they are taken from a dead or fixed language.

1:54. A plant in flower, surveyed externally, may be perceived to be composed of a variety of obvious parts, such as the root, the stem, the branch, the leaf, the flower, the fruit, and perhaps the seed; and other parts less obvious, as buds, prickles, tendrils, hairs, glands, &c. These, with their modifications, and all the relative circumstances which enter into the botanical description of a plant, constitute the subject of glossology, or the study of the language of botany. The reader may consult Smith's Introduction to Botany, or almost any recent work on the elements of botanical science.

125. Phytography, or the naming and describing of plants, is the next part of the subject to be considered. Before botany became a regular science, plants were named as individual beings, without regard to any relation which they had to one another. But from the great number of names to be retained on the memory, and the obvious affinities existing among certain individuals or natural families, some method was soon found necessary, and it was then deemed requisite to give such composite names as might recall to mind something of the individuals to which they were applied. Thus we had Anagillis flore cæruleo, Méspilus aculita pyrifolia, &c. In the end, however, the length of these phrases became inconvenient, and Linnæus, struck with this inconvenience, proposed that the names of plants should henceforth consist of two words only, the one the generic or family name, and the other the specific or individual name.

126. The names of classes and orders were originally primitive or without meaning, as the Grasses of Tragus, Poppies of Bauhin, &c.; and afterwards so compounded as to be long and complex, as the Popisstemnopétale, Eleutheromacrostémones, &c., of Wachendorf. Linnæus decided that the names of classes and orders should consist of a single word, and that word not simple or primitive, but expressive of a certain character or characters found in all the plants which compose it.

1297. Is applying names to plants, three rules are laid down by botanists: 1st, That the languages chosen should be fixed and universal, as the Greek and Latin. 2d, That these languages should be used accord. ing to the general laws of grammar, and compound words always composed from the same language, and not of entire words, &c. Sd, That the first who discovers a being, and enregisters it in the catalogue of nature, has the right of giving it a name; and that that name ought to be received and admitted by naturalists, unless it belongs to a being already existing, or transgresses the rules of nomenclature. Every one who discovers a new plant may not be able to enregister it according to these laws, and in that case has no right to give it a name; but the botanist who enregisters it, and who is in truth the discoverer, may give it the name proposed by the finder, if he chooses.

195. The whole vegetable kingdom is divided into classes, orders, genera, species, and varieties. A class is distinguished by some character which is common to many plants; an order is distinguished by having some character limited to a few plants belonging to a class; a still more limited coincidence constitutes a genua; and each individual of a genus, which continues unchanged when raised from seed, is called a spe. A variety is formed by an accidental deviation from the specific character, and easily returns by send to the particular species from which it arose.

152. For the purposes of recording and communicating botanical knowledge plants are described; and this is done either by the use of language alone, or by language and figures, models, or dried plants, conjounol. The description of plants may be either abridged or complete. The shortest mode of abridgement is that employed in botanical catalogues, as in those of Donn or of Sweet. The most exact descriptions are deficient without figures or a herbarium. Hence the advantage of being able to see plants at pleasure, by forming dried collections of them. Most plants dry with facility between the leaves of books, or between sheets of paper, the smoother the better. If there is plenty of paper, they often dry best without shifting; but if the specimens are crowded, they must be taken out frequently, and the paper dried before they are replaced.

170 The language of botany may be acquired by two methods, analogous to those by which common languages are acquired. The first is the natural method, which begins with the great and obvious classes of vegetables, and distinguishes trees, grasses, &c., next individuals among these, and afterwards their parts or organs: this knowledge is acquired insensibly, as we acquire our native tongue. The second is the artificial method, and begins with the parts of plants, as the leaves, roots, &c., ascending to Domenclature and classification, and is acquired by particular study, aided by books or instructors, as one acquires a dead or foreign language. This method is the fittest for such as wish to attain a thorough knowledge of plants, so as to be able to describe them; the other mode is easier, and the best suited for cultivators, whose object does not go beyond that of understanding their descriptions, and studying their physiology, history, and application. A very good method, for a person at a distance from botanists, is to forin a collection of dried specimens of all the plants of which he wishes to know the names, and to send them to the curator of the nearest botanic garden, requesting him to write the name below each specimen, and to refer to some work easily procured, such as Lindley's Vasculares, or Withering or Gray's Arrangement of British Plants, in which are given its description, uses, history, &c. We know of no work in which an attempt has been made to comprehend so much, both of theoretical and practical botany, as is comprised in our Encyclopedia of Plants; and to those therefore who cannot afford to have many books, and especially to gardeners, for whose convenience it is more especially intended, it may be confidently recommended.

1301. Taxonomy, or the classification of plants, is the last part of the study of technological botany. It is very evident, that, without some arrangement, the mind of man would be unequal to the task of acquiring even an imperfect knowledge of the various objects of nature. Accordingly, in every science, attempts have been made to classify the different objects that it embraces, and these attempts have been founded on various principles: some have adopted artificial characters; others have endeavoured to detect the natural relations of the beings to be arranged, and thus to ascertain a connection by which the whole may be associated. In the progress of zoology and botany, the fundamental organs on which to found a systematic arrangement have been finally agreed on. In both, those which are essential, and which discover the greatest variety, form the basis of classification. Animals are found to differ most from each other in the organs of nutrition, plants in the organs of reproduction.

1802. Two methods of arranging vegetables have been distinguished by botanists, the natural and the artificial. A natural method is that which, in its distribution, retains all the natural classes; that is, groups into which no plants enter which are not connected by numerous relations, or which can be dis joined without doing a manifest violence to nature. An artificial method is that whose classes are not natural, because they collect together several genera of plants which are not connected by numerous relations, although they agree in the characteristic mark or marks assigned to that particular class or assemblage to which they belong. An artificial method is casier than the natural, as in the latter it is nature, in the former the writer, who prescribes to plants the rules and order to be observed in their distribution. Hence, likewise, as nature is ever uniform, there can be only one natural method; whereas artificial methods may be multiplied almost ad infinitum, according to the different relations under which bodies are viewed.

1303. The object of the natural method is to promote our knowledge of the vegetable kingdom by gene. ralising facts and ideas; the object of the artificial method is to facilitate the knowledge of plants as individual objects. The merits of the former method consist in the perfection with which plants are grouped together in natural families or orders, and these families grouped among themselves; the merits of the latter consist in the perfection with which they are arranged according to certain marks by which their names may be discovered. Plants arranged according to the natural method may be compared to words arranged according to their roots or derivations; arranged according to an artificial method they may be compared to words in a dictionary. The success attending attempts at botanical arrangement, both natural and artificial, has been singularly striking. Linnæus has given the most beautiful artificial system that has ever been bestowed by genius on mankind; and Jussieu has, with unrivalled ability, exhibited the natural affinities of the vegetable kingdom. For the study of this department we refer to the works of Smith, Lindley, Decandolle, and Gray, but especially to the Encyclopædia of Plants.

CHAP. II.

Vegetable Anatomy, or the Structure and Organisation of Plants.

1304. Vegetables may be classed for the study of their anatomy and physiology, accordingly as they are distinguished by a structure or organisation more complicated or more simple. The former will constitute what may be denominated perfect plants, and will form a class comprehending the principal mass of the vegetable kingdom; the latter will constitute what may be denominated imperfect plants, and will form a class comprehending all such vegetables as are not included in the foregoing class. We shall first consider their external, and next their internal, organisation.

SECT. I. Of the External Structure of Perfect Plants.

1305. The parts of perfect plants may be distributed into conservative and reproductive, as corresponding to their respective functions in the economy of vegetation.

1306. The conservative organs are such as are absolutely necessary to the growth and preservation of the plant, and include the root, trunk, branch, leaf, and frond.

1307. The root is that part of the plant by which it attaches itself to the soil in which it grows, or to the substance on which it feeds, and is the principal organ of nutrition.

1308. The trunk is that part of the plant which, springing immediately from the root, ascends in a vertical position above the surface of the soil, and constitutes the principal bulk of the individual.

1909. The branches are the divisions of the trunk, originating generally in the upper extremity, but often also along the sides.

1310. The leaf, which is a temporary part of the plant, is a thin and flat substance of a green colour, issuing generally from numerous points towards the extremities of the branches, but sometimes also imme diately from the stem or root, and distinguishable by the sight or touch into an upper and under surface, a base and apex, with a midrib and lateral veins or nerves.

1311. The frond, which is to be regarded as a compound of several of the parts already described, consists of a union or incorporation of the leaf, leaf-stalk, and branch or stem, forming, as it were, but one organ, of which the constituent parts do not separate spontaneously from one another by means of the fracture of any natural joint, as in the case of plants in general, but adhere together even in their decay. It is found in palms and ferns.

1312. The conservative appendages are such accessory or supernumerary parts as are found to accompany the conservative organs occasionally, but not invariably. They are permanent in whatever species they are found to exist, some being peculiar to one species, and some to another; but they are never found to be all united in the same species, and are not necessarily included in the general idea of the plant. They are denominated gems, glands, tendrils, stipula, ramenta, armature, pubescence, and anomalies.

1313. Gems or bulbs are organised substances issuing from the surface of the plant, and containing the rudiments of new and additional parts which they protrude; or the rudiments of new individuals, which they constitute by detaching themselves ultimately from the parent plant, and fixing themselves in the soil. 1314 Glands are small and minute substances of various forms, found chiefly on the surface of the leaf and petiole, but often also on the other parts of the plant, and supposed to be the organs of secretion. 1915. The tendril is a thread-shaped and generally spiral process issuing from the stem, branch, or peticle, and sometimes even from the expansion of the leaf itself, being an organ by which plants of weak and climbing stems attach themselves to other plants or other substances for support; for which purpose it seems to be well fitted by nature, the tendril being much stronger than a branch of the same

size

116 The stipule are small foliaceous appendages accompanying the real leaves, and assuming the appearance of leaves in miniature.

1517. Ramenta are thin, oblong, and strap-shaped appendages, of a brownish colour, issuing from the sur. face of the plant, and somewhat resembling the stipula, but not necessarily accompanying the leaves. 1318. The armature consists of such accessory and auxiliary parts as seem to have been intended by nature to defend the plant against the attacks of animals.

1319. The pubescence is a general term, including under it all sorts of vegetable down or hairiness, with which the surface of the plant may be covered, finer or less formidable than the armature.

1931. Anomalies. There

are several other appendages proper to conservative organs, which are so totally different from all the foregoing, that they cannot be classed with any of them; and so very circumscribed in their occurrence, that they do not yet seem to have been designated by any peculiar appellation. The first anomaly, affecting the conservative appendages, occurs in Diobea muscipula, Venus's fy-trap (g. 178. a) A second is that which occurs in Sarracenia pur

parea or purple side-sad

178

a

de-tower. A third, which is still more singular, occurs in Nepenthes distillatòria (c). The last anomaly is a small globular and membranaceous bag, attached as an appendage to the roots and leaves of some of the aquatics. It is confined to a few genera, but it is to be seen in great abundance on the roots or leaves of the several species of Utricularia inhabiting the ponds and ditches of this country; and on the leaves of Aldrovanda vesiculosa, an inhabitant of the marshes of Italy. In Utricularia vulgaris this appendage is pear-shaped, compressed, with an open border at the small end, furnished with several slender fibres originating in the margin, and containing a transparent and watery fluid and a small bubble of air, by means of which it seems to acquire a buoyancy that suspends it in the water.

1521. The reproductive organs are such parts of the plant as are essential to its propagation, whose object is the reproduction of the species, terminating the old individual, and beginning the new. It includes the flower, with its immediate accompaniments or peculiarities, the flower-stalk, receptacle, and inflorescence, together with the ovary or fruit.

1392 The flower, like the leaf, is a temporary part of the plant, issuing generally from the extremity of the branches, but sometimes also from the root, stem, and even leaf, being the apparatus destined by nature for the production of the fruit, and being also distinguishable, for the most part, by the brilliancy dits colouring or the sweetness of its smell.

1. The flower-stalk is a partial trunk or stem, supporting one or more flowers, if the flowers are not sessile, and issuing from the root, stem, branch, or petiole, and sometimes even from the leaf.

14 The receptacle is the seat of the flower, and point of union between the different parts of the flower, between the flower and the plant, whether immediate and sessile, or mediate and supported upon a Bower-stalk

135. The inflorescence, mode of flowering, is the peculiar mode of aggregation in which flowers are arranged or distributed upon the plant.

156. The fruit is the ripened ovary, or seed-vessel which succeeds the flower. In popular language the tern is confined chiefly to such fruits as are esculent, as the apple, the peach, and the cherry, but with the botanist the matured ovary of every flower, with the parts contained, constitutes the fruit,

1327. Appendages. The reproductive organs, like the conservative organs, are often found to be furnished with various additional and supernumerary parts, not at all essential to their constitution, because not always present, and hence denominated appendages. Many of them are precisely of the same character with that of the conservative appendages, except that they are of a finer and more delicate texture; such are the glands, down, pubescence, hairs, thorns, or prickles, with one or other of which the parts of the fructification are occasionally furnished: but others are altogether peculiar to the reproductive organs, and are to be regarded as constituting, in the strict acceptation of the term, true reproductive appendages. Some of them are found to be proper to the flower, as the involucre, spathe, bractea, &c. ; and others to the fruit, as the persisting calyx, exemplified in the pomegranate.

SECT. II. Of the External Structure of Imperfect Plants.

1328. Plants apparently defective in one or other of the more conspicuous parts or organs, whether conservative or reproductive, are denominated imperfect. The most

generally adopted division of imperfect plants is that by which they are distributed into Filices, Equisetaceæ, Lycopodíneæ, Músci, Hepática, Algæ, Lichènes, and Fúngi.

1329. The Filices, Equisetacea, and Lycopodineæ are for the most part herbaceous, and die down to the ground in the winter; but they are furnished with a perennial root, from which there annually issues a frond bearing the fructification. The favourite habitations of many of them are heaths and uncultivated grounds, where they are found intermixed with furze and brambles; but the habitations of such as are the most luxuriant in their growth are moist and fertile spots, in shady and retired situations, as on mossy dripping rocks, or by fountains and rills of water. Some of them will thrive even on the dry and barren rock, or in the chinks and fissures of walls; and others only in wet and marshy situations where they are half immersed in water.

1330. The Músci (fig. 179. a b) form a tribe of imperfect plants of a diminutive size, often consisting merely of a root, surmounted with a tuft of minute leaves, from the centre of which the fructification springs; but furnished for the most part with a stem and branches, on which the leaves are closely imbricated, and the fructification terminal or lateral. They are perennials and herbaceous, approaching to shrubby; or annuals, though rarely so, and wholly herbaceous, the perennials being also evergreens.

1331. The Hepática (fig. 179. c) form a tribe of small herbaceous plants resembling the mosses, but chiefly with frondose herbage, and producing their fruit in a capsule that splits into longitudinal valves. In their habitations, they affect for the most part the same sort of situations as the mosses, being found chiefly in wet and shady spots, by the sides of springs and ditches, on the shelving brinks of rivulets, or on the trunks of trees. Like the mosses, they thrive best also in cold and damp weather, and recover their verdure though dried, if moistened again with water.

1332. The A'lga, or sea-weeds, include not merely marine and many other submersed plants, but also a great variety of plants that are not even aquatics. All the A'lga agree in the common character of having their herbage frondose, or but rarely admitting of the distinction of root, stem, and leaf.

1333. The utility of the Algae is obviously very considerable, whether we regard them as furnishing an article of animal food, or as applicable to medicine and the arts. The Laminària saccharina (fig. 180 a), Halymènia palmàta (6) and edùlis (c), and several other Fùci, are eaten, and much relished by many people, whether raw or dressed; and it is likely that some of them are fed upon by various species of fish. The Fùcus lichenöìdes (Turner, c. 118.) is now believed to be the chief material of the edible nests of the East India swallows, which are so much esteemed for soups, that they sell in China for their weight in silver. (Far. Mag., vol. xx.) When disengaged from their place of growth and thrown upon the sea-shore, the European Algae are often collected by the farmer and used as manure. They are also often employed in the preparation of dyes, as well as in the lucrative manufacture of kelp, a commodity of the most indispensable utility in the important arts of making soap and glass.

1334. The utility of the Lichènes is also worthy of notice. The Lichen rangiferìnus forms the principal nourishment of the reindeer during the cold months of winter, when all other herbage fails. The Líchen islándicus is eaten by the Icelanders instead of bread, or used in the preparation of broths; and, like the Lichen pulmonàrius, has been lately found to be beneficial in consumptive affections. Many of them are also employed in the preration of some of our finest dyes or pigments; and it is from the Lecanora parélla that chemical analyst obtains his litmus. The lichens and the mosses seem instituted by nature to provide for the universal diffusion of vegetable life over the whole surface of the terrestrial globe. The powdery and tuberculous lichens attach themselves even to the bare and solid rock. Having reached the maturity of their species, they die and are converted into a fine earth, which forms a soil for the leathery lichens. These again decay and moulder into dust in their turn; and the depth of soil, which is thus augmented, is now capable of nourishing and supporting other tribes of vegetables. The seeds of the mosses lodge in it, and spring up into plants, augmenting also by their decay the quantity of soil, and preparing it for the support of plants of a more luxuriant growth,