INTRODUCTORY CHAPTER. 



convey nourishment to one or more seed-buds {ovules), which eventually become 

 seeds, consisting of an embryo with its integuments, which is destined to produce a 

 plant similar to its parent. Though so dissimilar, the ovule or seed-bud presents a 

 remarkable analogy to an ordinary bud ; both spring from a node, and are protected 

 by a leaf; both are destined to reproduce the plant. Tbey only differ in the conditions 

 of their existence : the seed-hud needing for its development the fertilizing action of 

 the pollen ; the hranch-hud needing only the nourishment contributed by the node. 

 To this must be added, that the branch-bud multiplies the plant without separating 

 from it; whilst the seed-bud is destined to leave its parent, and reproduce at a 

 distance the plant which gave it birth. 



In some cases the branch-bud may be separated from its parent, and made 

 to germinate, which is due to the power which the stem possesses of emitting from 

 its surface supplementary or adventitious roots (r. adventitiae). Sometimes a young 

 branch, with its buds, inay be detached from the stem, and planted, when the 

 buried portion speedily sends forth roots, and the new individual becomes an 

 independent organism : this is called propagating by slips or cuttings (talea). Or the 

 branch, still attached to the trunk, may be surrounded with damp mould, into 

 which it emits roots, which soon become sufficiently strong to nourish the branch, 

 and to permit of its removal from its parent stem : this is termed propagation by 

 layers {malleoli). Or again, the branch, with its buds, may be separated from its 

 parent, and so attached to another plant, whose sap resembles its own, as to bring 

 into contact the parts in which the sap circulates ; the branch then grows as if on its 

 parent : this is called propagation by grafts, and the plant on which the branch is 

 grafted is called the stock. Lastly, the branch-bud may separate spontaneously 

 from the parent like a- seed-bud, and falling to the ground, may strike root and 

 become a separate individual, as in the Tiger-lily (fig. 22, b) : such branch-buds are 

 called bulbils {balbilli). 



The power of producing (naturally or artificially) buds and adventitious roots is 



not confined to the stem, the 

 /branches of many plants having 



also this power. The physiolo- 

 gist Duhamel, having planted a 



tree with its branches in the 



around, saw the roots become 



covered with buds, while the 



buried branches produced rools. 

 22. Biiibiferons Lily. In somo cases the divided root 

 s em. ^.^ j.gpj^.Q(j^(>e the plant, as in 

 the Japan Quince, the Osage Orange {Madura), and especially the Paulownia, the 

 roots of which may be cut into small sections, each of which, if planted, will 

 produce a perfect tree. 



In some plants the leaf itself possesses this reproductive power, as in the 

 Watercress, Cardamine pratensis, and Malaxis, &c., amongst native plants; and 

 amongst exotics, Bryophyllum calycinum (fig. 23), a succulent tropical plant, whose 



28. Bit/op?iylInni, 

 Leaf giving off embryos at each crenature. 



