192 VEGETABLE PHYSIOLOGY 



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 hyphse 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 

 construction. 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. 



The Dtricularias, which are members of this group, are 

 plants which live floating in water (fig. 91) ; they have a 



