Buds are also very often formed upon the margins of the leaf, the best known instance of which occurs in Bryophyllum calycinum; Weinmann[166] figures an instance of this kind in Alchemilla minima, or they may occur upon the lower surface of the leaf, as in Ornithogalum scilloides and longe-bracteatum. M. Duchartre[167] mentions a case in the tomato in which the leaves gave origin to small leaf-bearing branches, which, of course, must have originated from buds, just in the same way as in the Drosera before mentioned.
Fig. 82.—Formation of shoot on leaf of Episcia bicolor.
Gardeners occasionally avail themselves of this formation of buds from leaves to propagate plants, e.g. Hoya, Gesnera, Gloxinia, &c.
Formation of buds in the pith.—This is said to be a normal condition in the curious Stangeria paradoxa,[168] and Mr. Berkeley records an instance of this in sea-kale[169] (fig. 83) where the crown had been injured, and buds were seen sprouting from its centre.
Fig. 83.—Adventitious buds in sea kale.