8 INTEODITCTOEY CHAPTEE. 



leaf produces buds furnislied with root, stem, and leaves, at the extremities of its 

 lateral nerves ; these buds, which spontaneously fall off, and root in the earth, may- 

 be likened to embryos that do not need to be fertilized before developing ; and 

 the leaf of Bryophyllum may be regarded as an open ca.rpel, on which the seeds 

 have been developed by nutritive action alone. This fecundity of Bryophyllum 

 completes the analogy between the true bud and the fertilized embryo. 



Amongst the examples of reproduction by leaves, the Begonias hold the first 

 rank; for if a Begonia leaf be placed on damp soil, and incisions made across its 

 nerves, roots and buds will spring from every incision, and as many fresh plants 

 will be obtained as the leaf has received wounds. The same vitality is observable 

 in some woody plants : thus, if a fresh-cut Orange leaf be placed under suitable 

 conditions of heat and moisture, a small swelling will be formed on the broken 

 petiole, from which will shortly spring roots and shoots, that will eventually form 

 a tree, capable of growing, flowering, and fruiting, like an Orange-tree raised 

 from seed. 



In this brief summary we have only spoken of the structure of the higher plants, 

 whose organs of fructification being obvious, and their seeds provided with mono- or 

 di-cotyledonous embryos, are called cotyledonous or phoBnogamous [p. eotyledonece v. 

 •phcenerogamcB). Other plants, which have no obvious stamens or pistils, and seeds 

 Jvithout embryos, are called cryptogamous or Acotyledonous {p. cryptogamem v. acoty- 

 ledonew), and are of much simpler organization. 



