540 TEXTBOOK OF BOTANY 



compounds of living cells are liberated; and ammonia and carbon dioxide 

 are formed. A few special groups of bacteria through these unique 

 respiratory processes oxidize the reduced nitrogen and sulfur of body 

 compounds to nitrates and sulfates, which may again be reduced by bac- 

 teria or by green plants. Thus by numerous activities of groups of bac- 

 teria following each other in definite succession the body compounds 

 indigestible by animals and green plants become converted into simpler 

 compounds that are usable by green plants. In the grand "passing show" 

 of nature, green plants and the larger animals play the easily visible 

 roles; but their action would soon cease were it not for the bacteria 

 and their associates, the fungi, most of whose activities are off-stage, un- 

 seen, and even unsuspected a century ago (Fig. 227). 



REFERENCES 



Waksman, S. A. Principles of Soil Biology. Williams & Wilkins Company. 1932. 

 Waksman, S. A., and R. L. Starkey. The Soil and the Microbe. John Wiley & 

 Sons. 1931. 



