PLANTS. 165 



ROOTS AND LEAVES. 



Plants may be said to consist of two great pzdhs, 

 the root and the stem, with their various appenda- 

 ges. But since we are in this place merely to con- 

 sider one function of vegetable life, namely, the 

 function of absorption, or the manner in which plants 

 bring matter, external to themselves, within the 

 range of their vital actions, we may confine our re- 

 searches almost entirely to the roots and leaves ; 

 these being, beyond doubt, the parts by which ex- 

 traneous matter is first received into the plant ; and, 

 in the first place> let us examine the functions of the 

 root. 



The term root is generally considered to include 

 all that part of the plant which is beneath the sur- 

 face of the soil. This, however, "is not strictly cor- 

 rect ; for many plants possess what botanists call 

 a rhizoma, or underground stem. The true root is 

 that part of the plant which, from the instant of its 

 bursting the coverings of the seed, begins to direct 

 its course downward (or towards the earth's axis), 

 " with a tendency so powerful that no known -force 

 is sufficient to overcome it." Moreover, it differs 

 from the stem in many of its characters ; thus, it 

 does not divide itself into smaller fibres in the regu- 

 lar manner in which stems generally give off their 

 branches. Again, it never produces leaves or scales ; 

 and another important distinction is, "that it never 

 becomes green (at least in tissue) when exposed to 

 the action of air and light, while all the other parts 

 of vegetables, when thus exposed, assume that col- 

 our." The root is divided into the body and fibres, 

 the latter of which will alone claim our attention. 

 These fibres are furnished at their extremities with 

 a remarkable structure, which, from its resemblance 

 to a sponge, has been termed spongiole. It consists 

 of an extremely loose texture, and is most probably 

 merely " the nuwly-formed" internal " tissue" of the 



