332 



AUGUSTO BONAZZI 



The most important feature of the recalculated data, and one 

 that the author apparently overlooked, is the one presented in 

 the last column of table 1. A very appreciable "loss" of nitro- 

 gen takes place from the cultures, either as free nitrogen or as a 

 volatile nitrogenous compound. It is assumed that the cultures 

 used by Hills were pure. 



Greaves (1918) in his recent review of this work seems not to 

 consider this important phase of the metabohsm of Azotobacter. 



TABLE 1 

 Nitrogen balances in the cultures of Hills 



After this very brief sm-vey of the data in question it may be 

 well to recall a statement which appeared in a previous communi- 

 cation from this laboratory (1915) to the efTect that A. chro- 

 ococcum may be a fixer of atmospheric nitrogen only under such 

 conditions as we call ''normal," i.e., in absence of fixed nitrogen 

 and a denitrifier when such conditions are changed, i.e., when 

 there is a possibihty for it to consume nitrate under naturally 

 normal conditions. In our present study of the Hterature we 

 have excluded purely agronomic investigations and have con- 

 sidered only studies which have been made under conditions of 

 control such as to give results of fundamental importance. 



Historical 



A simple study of the relation of the carbon consumed to the 

 nitrogen fixed has only a hmited value, and this is especially 

 true when we consider the great variations in the nitrogen fixing 

 power of the same organism under different conditions. The 

 quaUty of the carbohydrate utihzed in the experiment and its 



