342 VEGETABLE PHYSIOLOGY 



plant, but they appear to utilise compounds of ammonia in 

 preference to nitrates. No doubt their protoplasm is ulti- 

 mately fed with the same substances as is that of the 

 higher plants, but they lack a great deal of the constructive 

 power of the latter. 



The degradation of the structure of such plants is 

 associated with the absence of the constructive processes 

 which depend on the presence of chlorophyll. Their body 

 is usually composed chiefly of delicate hyphse, which 



PIG. 147. Thesium alpinum, SHOWING THE SUCKERS ON THE BOOTS. 

 (After Kerner.) 



ramify in the nutrient either living or dead substratum, 

 and which absorb elaborated products of some complexity 

 freely by their whole surface. They have, therefore, no need 

 of differentiated absorbing or conducting tissues, which are 

 consequently not developed. A further consequence of the 

 ease with which they obtain their food is the readiness 

 with which vegetative and asexual reproduction is brought 

 about ; hence sexuality is in many cases non-existent among 

 them. 



Phanerogams which are completely parasitic show a 



