26 LIVING PLANTS 



The functions of the root are not so numer- 

 ous as those of the shoot, and while the effi- 

 cient performance of the necessary amount 

 of absorption, to keep pace with the increase 

 in mass and surface of the shoot, has de- 

 manded a repeated branching, yet no seg- 

 mentation Hke that of the shoot has occurred. 

 The less important function of the root, fixa- 

 tion, is purely mechanical, and the separation 

 of the two functions has not been effected by 

 a localization of the functions in different 

 organs, but is an incident to the stage or 

 degree of development of these organs . Phys- 

 iologically the basal portion of roots sustains 

 a relation to the absorptive system similar to 

 that of the basal portions of typical stems to 

 the chlorophyll-bearing and reproductive 

 organs. 



In the earlier stages of growth any given 

 portion of the root is purely directive, next 

 absorptive and in the later periods, is exclu- 

 sively fixative. Only in certain special classes 

 of aerial and other plants does a separation 

 or isolation occur. The stem, on the other 

 hand, is at first directive, and then fixative, 

 and does not in any stage of its existence as- 

 sume the relative importance which is to be 

 ascribed to ever^' portion of the root in one 

 period of its development. 



In explanation or this method of develop- 



