=Formation of buds on leaves.=--The formation of little bulbs upon the surfaces or edges of leaves, forming what are called viviparous leaves, has long been familiar to botanists amongst Alliums. Professor Alexander Braun,[160] who has paid much attention to this subject, divides cases of this kind according to the position of the buds; thus, for instance, they are sometimes formed upon the upper portion of the leaf or petiole, as in many ferns, in _Nymphaea guineensis_, some _Arads_, &c. The same condition has been met with as a teratological occurrence in the leaves of _Cardamine pratensis_, _Hyacinthus Pouzolzii_, _Drosera intermedia_,[161] _Arabis pumila_, _Chelidonium majus_, _Chirita sinensis_,[162] _Episcia bicolor_,[163] _Zamia_, &c.[164] Many species of _Begonia_ possess the power of emitting buds from the petioles and veins of the leaf; the little ramenta or scales which so plentifully beset the surface of some of these plants likewise, in some instances, pass gradually into leaves. _B. phyllomaniaca_, Mart., is the species best known as manifesting this tendency, but others have it also.[165] 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. [Illustration: 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. [Illustration: FIG. 83.--Adventitious buds in sea kale.] [Illustration: FIG. 84.--Hyacinth bulb cut across to induce the formation of new bulbs.] [Illustration: FIG. 85.--Showing the formation of new bulbs on the cut edges of an old hyacinth bulb.]