186 VEGETABLE PHYSIOLOGY 



ground, on which are only a few rudimentary leaves. At 

 the base of the stem there is found a cluster of fairly stout 

 root-like structures which intertwine with each other to form 

 a mass sometimes as large as a man's fist. These are 

 developed only in masses of humus, from which they absorb 

 the products of decay. These plants differ thus from 

 normal phanerogams by their method of absorbing food. 

 Their subterranean members are not provided with the 

 system of short-lived root-hairs which are so characteristic 

 of the ordinary roots. They are not in need of such close 

 contact with continually fresh particles of soil as are the 

 latter, lying as they do embedded in a mass of humus. In 

 some cases all their external cells absorb material from 

 this ; in others special absorptive cells are present, but 

 these are not localised like the ordinary root-hairs, and they 

 are not being continually renewed, but remain active for 

 long periods. Frequently they are only found at the points 

 where contact with the humus is effected. Many of these 

 saprophytes have the cells of their cortex infested with the 

 hyphae of a fungus. 



The food which is thus absorbed from the decaying 

 organic matter is not necessarily in a fit condition for 

 immediate assimilation by the protoplasts. It may, and 

 frequently does, require alteration before being available 

 for nutrition. 



The plants of the next group which we must consider 

 differ from the saprophytes in an important particular. Like 

 them they are provided with a chlorophyll apparatus, and 

 are consequently capable of carrying on carbohydrate con- 

 struction. Indeed they are generally more active in this 

 respect than the members of the last group. As in the case 

 of the greater number of the latter, it is chiefly their nitro- 

 genous material that they obtain nearly or quite ready for 

 assimilation. They appear to need this nitrogenous food 

 in the form of proteins, and they obtain it by capturing 

 and killing various animal organisms whose putrefying 

 bodies yield them what they want. 



