DECOMPOSITION OF PROTEINS 503 



readily, but seem to be unable to attack the /3-amino acids. Czapek 

 found that Asp. niger could not utilize all the various nitrogenous com- 

 pounds tested but grew very well on a large number of them. Amino 

 acids were used most economically, which led Czapek to suggest that 

 the fungi assimilate the nitrogen in that form and are spared the trouble 

 of synthesizing the amino acids needed for their protoplasm. Hagem 86 

 however, maintains that ammonia is the starting point in the synthesis 

 of protoplasm by microorganisms. Fungi can utilize urea, uric acid, 

 glycocoll, guanidine, guanine, nitrates, nitrites and ammonium salts as 

 sources of their nitrogen, while uric acid, gycocoll and hippuric 

 acid may serve as a source of carbon as well. 87 



The whole process of protein transformation and protein synthesis 

 in the soil is very complex and is constantly in a dynamic condition. 

 The net result is fertility or infertility, depending on which set of 

 factors predominates in the soil at any one time. A mere determina- 

 tion of the amount of ammonia formed after adding to the soil a definite 

 amount of a certain organic fertilizer, like dried blood or cottonseed 

 meal, cannot solve the question of the availability of the nitrogen in 

 the particular fertilizer; it does not indicate the amount of intermediate 

 compounds formed by the decomposition of the organic matter or 

 fertilizer in the soil and the character of the action of these compounds 

 on plant growth. 



niedere Pflanzen. Ber. deut. chem. Gesell., 36: 2289-2290. 1902; Butkewitsch, 

 1903 (p. 494); Brenner, W. Die Stickstoffnahrung der Schimmelpilze. Centrbl. 

 Bakt. II, 40: 555-640. 1914. 



" Hagem, 1910 (p. 237). 



« T Kossowicz. (Rev. Lathrop, 1917 (p. 474).) 



