CHAPTER XLI. 



THE ROOT 

 I. Function of Roots. 



784. The most obvious function of the roots of ordinary plants 

 are two: ist, To furnish anchorage and partial support, and 



^2d, absorption of liquid nutriment from the soil. The environ- 

 mental relation of such roots, then, in broad terms, is with the 

 soil. It is very clear that in some plants the root serves both 

 functions, while in other plants the root may fulfil only one of 

 these requirements. 



The problems which the plant has to solve in working out 

 these relations are: 



(1) Permeation of the soil or substratum. 



(2) Grappling the substratum. 



(3) A congenial moisture or water relation. 



(4) Distribution of roots for the purpose of reaching food- 

 laden soil. 



(5) Exposure of surface for absorption. 



(6) The renewal of the delicate structures for absorption. 



(7) Aid in preparation of food from raw material. 



(8) The maintenance of the required balance between the 

 environment as a whole and the increasing or changing require- 

 ments of the plant. 



785. (i) Permeation of the soil or substratum. The funda- 

 mental divergence of character in the environmental relations of 

 root and stem are manifest as soon as they emerge from the 

 germinating seed. Under the influence of the same stimulus 

 (gravity) the root shows its geotropic character by growing down- 



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