CHAPTER I. THE ROOT. 



able to survive by means of their under-ground parts, because 

 they store away, year by year, in their tuberous roots, the 

 materials necessary for the succeeding year's growth. The 

 famous Banyan Tree of India sends downward, from its huge 

 horizontally spreading branches, roots which make their way to 

 the soil, and serve not only the ordinary uses but also that of 

 props or subsidiary stems to support the weight of the branches. 



But there are many instances of roots whose habits and func- 

 tions are quite different from the ordinary. The roots of air 

 plants or epiphytes, like those of many tropical orchids, for 

 example, never reach the soil at all, but cling to the bark of 

 trees and absorb nutriment from the air; the rootlets that spring 

 out laterally from the stems of the Poison Rhus, Trumpet Creeper 

 and Ivy, Fig. i, serve purely the use of climbing organs; those 

 of the Mistletoe and Dodder 

 penetrate the bark of the 

 plants on which they find 

 lodgment, and live at the 

 expense of the nutritious 

 juices absorbed from their 

 hosts ; a leafless epiphytic 

 orchid belonging to the 

 genus Aeranthus produces 

 roots which perform no 

 proper root-functions at all, 

 but develop in their interior 

 the green coloring-matter of 

 leaves, and do the duty 

 which ordinarily devolves 

 upon leaves. 



Roots differ from stems 

 in some important particu- 

 lars, notably the following : 

 They are much less regular 

 in their mode of branching, 

 they are simpler in their internal structure, they do not directly 

 bear leaves or leaf-rudiments, their growing-point is located just 

 back of the apex instead of at the apex, and in consequence of 

 this sub-apical growth, the tip, unlike that of the stem, becomes 



Fig. i. — Portion of stem of Ivy showing root- 

 lets. 



