180 PLANT GROWTH 



energy. The first group of bacteria oxidizes the ammonia 

 to a nitrite form, after which another kind of bacteria oxi- 

 dizes the nitrite to nitrate. This nitrate is absorbed by the 

 plant just as effectively as that applied as fertilizer to supple- 

 ment the soil supply. 



REFERENCES 



Maximov, N. A., Plant Physiology, Edited by Harvey, R. B., and A. E. Murneek, 



McGraw-Hill Book Co., 1938. 

 Nightingale, G. T., "The Nitrogen Nutrition of Green Plants," The Botanical Review, 



vol. 3, pp. 85-174, 1937. 

 Wilson, P. W., "Symbiotic Nitrogen Fixation by the Leguminosae," The Botanical 



Review, vol. 3, pp. 365-399, 1937. 



