48 PLANTS AND MAN 



members of the plant world must be kept in check in order to 

 allow the more constructive ones to thrive, it is as vital to under- 

 stand how these plants live as to comprehend the activities of the 



Fig. 24. — ^The common mushroom consists of a subterranean vegetative body, 

 with the visible stalks and caps in reality only the reproductive organs. 



more familiar green plants. Once man has learned how these 

 parasites subsist, he can attempt to control them, furthering the 

 growth of useful species by restraining or eliminating the harmful 

 heterotrophic ones. 



