88 PLANT PHYSIOLOGY 



pounds. These bacteria form galls on the roots of the 

 host plants. As they grow old the host plant digests 

 them and is thus able to thrive in a soil free from nitrog- 

 enous compounds. Thus if the bacteria are present, 

 crops of beans, clover, alfalfa, etc. will actu- 

 ally increase the amount of nitrogenous 

 compounds in the soil instead of decreas- 

 ing it. 



131. The proteins formed may be stored 

 up as such for future use by the plant (e.g. 

 aleuron in seeds) or may be transported to 

 those parts of the plant where new cell 

 ■^SdulermcL') * production and growth are taking place. 

 Here it is built up into protoplasm. How 

 this is accomplished we do not know. The path of 

 transportation seems to be in the sieve and possibly 

 laticiferous tissues. The form in which protein matters 

 are transported may be either as simple proteins or as 

 amids. 



132. Hysterophytic plants, i.e. plants that lack chloro- 

 phyll, must obtain their organized food (carbohydrates, 

 proteins, fats, etc.) from sources outside of themselves. 

 We find all degrees of ability to make use of various 

 food sources. Some hysterophytes simply require 

 carbohydrates and mineral salts and can produce their 

 own proteins, others must have special, and in the case 

 of parasites, living forms of proteins. Some even are 

 able to use simpler carbon compounds than carbohy- 

 drates such as some of the simpler organic acids, glycer- 

 ine, etc. In general, however, the nutrition of hystero- 

 phytes differs but little from that of holophytes (i.e. 

 plants containing chlorophyll) except in their inabihty 

 to manufacture their own carbohydrates. 



133. The means by which hysterophytic plants 



