FIXATION OF NITROGEN BY FUNGI 177 



Berthelot- gives positive results on cultures of Aspergillus 

 niger, stating that in a month 5 to 10 mgms. was fixed by a 

 culture of 600 cc. or more exactly, 4 to 9 mgms. after allowing 

 2 mgms. for uninoculated controls. 



The first systematic study of definite fungi seems to have 

 been made by Puriewitsch^ whose work was chiefly on the 

 above mentioned organisms, though it seems that he was not 

 quite certain as to the purity of his cultures. The amount of 

 fixation reported bj^ him is scarcely beyond the limits of experi- 

 mental error, and for that reason are strongly criticized by 

 Czapek^ who was not able to detect the slightest particle of 

 fixation in any of his numerous cultures of Aspergillus niger. 

 Puriewitsch states that the amount of fixation found by him was 

 proportional to the amount of carbohydrate furnished in the 

 cultures but that it has no quantitative relation to the amount 

 of growth or drj' weight. Both of these statements seem a 

 little strange until we meet his statement that after some search 

 for stray nitrogen he found it in the sugar furnished to his 

 medium, in which case it would seem necessary that the nitrogen 

 would increase in a direct proportion with the amount of sugar 

 furnished. We should not, however, be too critical as to the 

 interpretation of this incident, as his analyses may have made 

 proper allowance for this item. At any rate, his work must be 

 looked upon as a very good beginning and a model for this 

 kind of investigation. 



The investigations of Saida' confirm the results of Puriewitsch, 

 but supply nothing new of importance except that he gives 



^ Berthelot, M., Recherches nouvelles sur les microorganismes fixateurs de 

 I'azote libre. Compt. Rend. 116: 847. 1893. 



' Puriewitsch, Ueber Stickstoffassimilation bei den Schimmelpilzen. Ber. d. 

 deut. Bot. Ges. 13: 342-345. 



* Czapek, F., Zur Kentniss der Stiekstoflfversorgung und Eiweiss-bildung bei 

 Aspergillus niger. Ber. d. deut. Bot. Ges. 19: 1.30-139. 1901. 



Czapek, F., Untersuchung iiber die Stickstoffgewinnung und Eiweiss-bildung 

 der Schimmelpilze. Beitrage f. Chem. Physiol, und Pathol. 1: 5.38^546 and 

 2: 557-590. 1902. 



Czapek, F., Biochem. der Pflanzen2: 12.5-144. 1905. 



= Saida, K., Uber die Assimilation des freien Stickstoffs durch Schimmelpilze. 

 Ber. d. deut. Bot. Ges. 19: 107-115. 1901. 



