561. Bulbs arc, properly, underground stems which send upwards their leaves and flower-scapes, and downwards their true roots, as may be seen in hyacinths and tulips, when grown in glasses. What are commonly called bulbs are of three kinds: namely, the tunicated, which consist of a number of coats or tunica, which may be peeled off one after another, as in the onion and the hyacinth; the scaly, which consist of large fleshy scales, adhering together only at the root, as in the lily; and the solid, which consist of a homogeneous, white, nut-like mass, as in the crocus, and which, indeed, are not bulbs, hut corms.

562. The culture of bulbs is a matter of much difficulty. It was formerly supposed to he necessary to take up all the kinds as soon as they had done flowering; as it was found that if left in the ground, comparatively few survived the winter, being destroyed not so much by cold as by damp. Most bulbous plants are natives of hot dry countries, where they have alternate seasons of excessive rain, and excessive drought; and where the extraordinary provision of feculent or starchy matter laid up in the bulb, is necessary to supply nourishment to the leaves and flowers during their rapid growth in the rainy season; as at that season they want food faster than it could possibly be taken up by the roots and leaves. When the plant has done flowering, all this matter is exhausted, and only the membranous part is left. The plant, when left in the earth, then begins, through its leaves and roots, to take up sufficient nourishment from the soil and air to form a new bulb; and this process of alternate exhaustion and replenishing goes on every year, if the bulb is kept dry while it is in a state of repose.

If, however, the bulb is exposed to moisture during the winter, the starchy matter laid up in it is dissolved too soon, as in winter there is not light and heat enough fur it to develope its leaves and flowers; and consequently the bulb rots instead of germinating. It is on this account that bulbs are generally taken up as soon as they have done flowering, and their leaves have begun to decay, and replanted in spring. If, however, they can be kept dry, it is much better to leave most of the kinds in the ground all the year, as then they form masses of bulbs, which, from their roots never being disturbed, grow with extraordinary vigour, and flower splendidly. All the kinds which are called conns, such as the gladioli, the different kinds of crocus, and nearly all the Cape bulbs, succeed best when treated in this manner; but choice hyacinths and tulips are still generally taken up as soon as the leaves begin to decay, as the flowers are said to degenerate if the bulbs are left all the year in the ground.

563. List of hardy ornamental flowering bulbs and corns, to be planted in beds or borders.

564. Tubers closely resemble in their nature what are called solid bulbs or corms, and appear to be reservoirs of nourishment which have been laid up by nature for the support of the infant plant. Some tubers have numerous buds in different parts of their substance, like the potato, and others have only buds in the upper part, like the Dahlia and the Ranunculus.

565. The culture of tubers depends in a great measure upon their nature; and the principal tubers grown in the open ground being the Ranunculus, the Anemone, and the Dahlia, we shall say a few words on each separately.