CHAP. II. ROOT. 85 



its deviation from the ordinary characters of Endogenous 

 structure is mucli less considerable than it seems to be at first 

 sight. 



According to Mohl, the structure of an Exogenous and an 

 Endogenous stem, during the first year of their growth, is al- 

 together the same ; but in the second year the wood and the 

 liber of the former separate, and new matter is then inter- 

 posed ; while, on the contrary, in Endogens no such separa- 

 tion occurs, and consequently the newly-formed matter of the 

 stem is forced towards the centre, through which it passes, 

 with a constant tendency, however, to reach the outside. This 

 statement must, however, be received with distrust ; because 

 any one may satisfy himself that the new shoot of an Aspara- 

 gus and of an Elder-bush are totally dissimilar. 



Sect. III. Of the Root, or descending Axis. 



At or about the same time that the ascending axis seeks 

 the light and becomes a stem, does the opposite extremity of 

 the seed or bud bury itself in the earth and become a root, 

 with a tendency downwards so powerful, that no known force 

 is sufficient to overcome it. Correctly speaking, nothing 

 can be considered a root except what has such an origin ; for 

 those roots which are emitted by the stems of plants, are in 

 reality the roots of the buds above them, as will be hereafter 

 explained. Nevertheless, nothing is more common than even 

 for botanists to confound subterranean stems or buds with 

 roots, as has been already seen. (See Bulb, Tuber, Soboles, 

 &c. &c.) 



Independently of its origin, the root is to be distinguished 

 from the stem by many absolute characters. In the first 

 place, its ramifications occur irregularly, and not with a sym- 

 metrical arrangement: they do not, like branches, proceed 

 from certain fixed points (buds), but are produced from all 

 and any points of the root. Secondly, a root has no leaf-buds, 

 unless indeed, as is sometimes the case, it has the power of 

 forming adventitious ones ; but, in such a case, the irregular 

 manner in which they are produced is sufficient evidence of 

 their nature. Thirdly, roots have no scales, leaves, or other 



G 3 



