in _Polygonum viviparum_,
and in _Juncaceae_, _Cyperaceae_, &c.

In the genus _Allium_ an analogous formation of little buds or bulbils
takes place in lieu of flowers; this is specially the case with _A.
vineale_, the flowers of which are rarely seen.

Other illustrations of a similar character, where the adventitious
leaf-buds are mixed in amongst the flower-buds, are cited under the head
of Prolification of the Inflorescence.

=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
instanc