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 
Tre. Orin 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, ete. In general, however, the nutrition of hystero- 
phytes differs but little from that of holophytes (i.e. 
plants containing chlorophyll) except in their inability 
to manufacture their own carbohydrates. 
133. The means by which hysterophytic plants 
M 
