300 ANNALS OF THE 



[Vol. 10 



to the nitrogen determination, a precaution which was not ob 



served in the work of 



As many deter 



minations were made on control portions of the media as on 

 cultures of the various fungi. Under the several conditions of 

 the experiments the fixation of elementary N by Aspergillus 

 niger, Macrosporium commune, Penicillium digitatum, P. ex- 

 pansum, and Glomerella Gossypii could not be demonstrated: 

 whereas Phoma Betae, growing on mangel and sugar beet de- 

 coctions with sucrose, showed a definite fixation ranging approxi- 

 mately from 3 to 8 mgm. per culture. This latter fact lends 

 weight to the data of Ternetz ('04) indicating the marked ca- 

 pacity of Phoma radicis for assimilating free nitrogen. It, 

 moreover, "throws open the whole question for any and all 

 fungi," and suggests the sphaeropsidaceous and mycorhizal 

 forms as material for first investigation. 



The other important contributions to the subject of nitrogen 

 metabolism are here reviewed, the chronological order being ob- 

 served in so far as it was found compatible with clearness. 

 Critical evaluation of the cited articles is largely reserved for the 

 discussion at the end of this paper. The work with bacteria is 

 not considered. The recent developments of physiological tech- 

 nique, such as the determination of active acidity and the 

 improved methods for determining sugars and the various forms 

 of nitrogen, throw doubt on the validity of the interpretations of 

 many of the results of earlier investigators whose criterion for 

 the assimilability and nutritive value of a given compound was 

 generally based solely on the amount of growth. One now 

 avoids arbitrary cataloging of fungi as " ammonia organisms," 



<<»-^v^~«~ ~« : >> it 



organisms, "nitrate forms" and so on, as was done in 

 the older texts on plant physiology. 



That heterotrophic plants were early known to be capable of 

 utilizing inorganic nitrogen is evident from the challenge of 

 Pasteur to Liebig to grow any amount of ferment on a purely 

 synthetic medium which had ammonium N as the sole N source. 

 Duclaux ('64), speculating on the synthesis of proteins in the 

 course of fermentation, said that it was highly improbable that 

 it could follow by direct condensation of ammonia and sugar, 

 but rather that there must precede a breaking up of the sugar 



Ik 



