Amongst the practical arts of life a knowledge of Botany is impor tant to many. Agriculture and Horticulture are the two arts with which its relation is the most obvious; for although a considerable pia of all the practices in each of them grew out of mere experience, or was discovered by chance, yet there is no possibility of improving them except by other fortunate accidents, or of advancing them at a more rapid rate, uuless by the application of vegetable physiology. The world, especially that part of it to which these arts belong, is little accustomed to trace to their source the common practices with which it has been familiar from its infancy ; and it is far from suspecting that many of the operations which are intrusted to the most ignorant rustics have one by one and piecemeal been hit upon during the careful study of nature by philosophers whose names it never beard. Gardening and Husbandry may be defined as the arts, firstly, of improving the quality of various useful plants, and secondly, of increasing the quantity which a given space of earth is capable of producing.
To improve the quality of any one plant, and to render it better adapted to the uses of mankind upon scientific principles, is a very complicated process, and is to be effected in many differeut ways, all of which require an intimate knowledge of the nature of the vital actions of plants, and of the degree in which they are affected by either external or internal causes. For example, a particular kind of flax produces fibres which are too coarse for the manufacturer ; it is impossible to know how those delicate elementary tubes are to be rendered fine without being aware of the manner in which vege table tissue is affected by light, air, and earth. The flavour of somo fruit is too acid ; it is the botanist only who could have discovered how to increase the quantity of saccharine matter. Potatoes are sometimes watery and unfit for food ; we learn from vegetable physiology that this is often caused by the leaves not being sufficiently exposed to solar light, the great agent in causing the production of vegetable secretions. The leaves of the tea plant are harmless and only slightly stimulating in certain latitudes; they become narcotic and unwholesome in others; this apparent puzzle is explained by the connection that .exists between climate and vegetation, a purely botanical question. Certain races of plants may exist, of which one is too vigorous, the other too debilitated for the purposes of the cultivator; the botanist shows how an intermediate race may be created, having the best qualites of both.
Certain vegetable productions are susceptible of being produced in particular latitudes, others are not, or not to any useful purpose : for instance, in England, on account of the want of the necessary heat at the period of ripening the grape, the vine will never yield grapes capable of making such wine as even that of champagne, nor will tobacco ever acquire that peculiar principle which gives it so great a value in tropical and subtropical climates when grown in other countries; and yet both these plants flourish in the soil of England.
The botanist can explain the cause of this, and thus prevent the commencement of speculations which can never end except in lose and disappointment.
The quantity of produce which may be procured from a given space of ground varies very much according to the skill of the cultivator, but that skill is in reality the mere application of the rules of vegetable physiology to each particular case; an application that is moat frequently made unconsciously, but which nevertheless is made. We are too apt to overlook causes in effects, and to ascribe the improvements we witness to a mere advance in art, without considering that that advance must have had a cause, and that the cause can only be the working of some master-hand which is after wards blindly followed by the community. The crops of orchard fruit are doubled and trebled in many places: old exhausted races are replaced by young, vigorous, and prolific ones ; the cider and Perry farmer will feel the benefit of this, but he will forget that he owes the change to the patient skill of a. vegetable physiologist. The produce of the potato is augmented in the same proportion ; twice at least the ordinary quantity of this important article of food may now be obtained from every field. The peasant will feel the additional comfort thus diffused around him, but he will never have heard of the name of Knight ; nor will he know, after a few years, that the produce of the land was ever smaller.
Nor is it alone to articles of food that this science is to be applied. Next in importance to food are fire and shelter, both of which are mainly furnished by timber. The laws of nature which regulate the production of this substance are among the most curious in science : we possess the most absolute control over them; we bold in our very hands the means of regulating their action; and if we neglect them, as is too often the ease, it is not science which is to blame, but those who undervalue and neglect her. Because trees will grow without assistance, and because in spite of neglect and ignorance timber is perpetually renewing itself upon the earth, we forget that either its rate of production may be accelerated or its quality improved. Instances are not wanting where plantations in this country made for particular purposes at a large expense have been totally ruiued, with reference to the objects of those who planted them, from ignorance of the simplest laws of vegetable physiology.