Light is most essential to the perfect and healthy developement of vegetable organization, the performance of the functions essential to the health of plants being dependent on its agency. It cannot indeed be assumed that plants will not continue to grow, unless they are supplied with an intense degree of light; but it is certain that the successful nature of their growth, their maturation, and their fructification, are dependent in no ordinary degree upon the nature and force of its action; for without it, the vital energies of animated beings are unable to maintain and perform the processes of elaboration, and assimilation, upon which their nutrition depends. The mere extension of vegetable tissue, may indeed go on, though less satisfactorily, under the almost total privation of light, but with the exception of cryptogamic vegetation, the organs of fructification are not under those circumstances, produced at all: the stem may be formed, but does not become solid: the leaves may expand, but their condition is imperfect; and it is only by means of the full and complete action of these organs in the nutrition of plants, that the developement of the floral parts is brought about: the roots may take up fluids, and these may be conveyed in the natural upward channels, and then dispersed among the stems and the leaves; but it is the action of solar light, aided indeed by the natural condition of the elements supplying heat and moisture, which alone, by a process of elaboration, can convert this fluid, once crude and undigested, into the compound organic substances, such as lignin, gum, starch, gluten, &c. which in their turn, are destined to minister to the support of the organs of reproduction. Growth, that is mere extension, may go on in proportion as heat and moisture are supplied to plants, but light is the agent to whose especial influence we owe the production of their active properties and secretions, and the perfection of their fruit.