140 



THE LEAVES. 



the primary root imbibes. They are likewise apt to send forth 

 secondary roots of their own, to establish a di- 

 rect communication with the soil (as in Fig. 

 168, b). This they uniformly do when in con- 

 tact with the soil (130), and not rarely when 

 raised to some distance above it (131) : or they 

 may be made to strike root and live independ- 

 ently, when taken off as cuttings (227). When 

 the dicotyledonous embryo goes on to develope 

 double phytons, like itself, each node bears a 

 pair of leaves (as in Fig. 101 104), or, in 

 botanical description, the leaves are said to be 

 opposite ; as they are in the Maple, in the Mint 

 Family, &c. But quite as frequently the phy- 

 tons become disjoined or simple after the first 

 or second, each bearing a single leaf only ; so 

 that the leaves become alternate, just as in those from the mono- 

 cotyledonous embryo, except that they are there alternate from the 

 very first. This occurs in the Apple, Cherry (Fig. 169), and num- 

 berless other instances. 



232. The same analysis applies to axillary buds and branches. 

 In most of our trees and shrubs these buds acquire considerable 

 complexity before they begin to unfold (144), and then grow 

 almost simultaneously : but in some of them, as in most annual 

 herbs, the axillary phytons begin to develope one by one. 



CHAPTER V. 



OF THE LEAVES. 



SECT. I. THEIR ARRANGEMENT. (PHYLLOTAXIS, ETC.) 



233. THE fundamental organs of the vegetable, namely, the 

 root, stem, and leaves, are so intimately associated and mutually 

 dependent, that the structure and office of no one of them can be 

 separately treated of. The stem, in particular, cannot be under- 

 stood apart from the leaves. It has accordingly been necessary to 



FIG. 169, Germination of the Cherry ; the leaves alternate after the first pair, or cotyledons. 



