Upon’assimilation of atmospheric nitrogen by fungi 
L. H. PENNINGTON 
For several years the writer has been interested in the question 
of assimilation of atmospheric nitrogen by fungi. Experimental 
work was begun in 1907 upon Fusarium Zeae' at the suggestion 
of Professor J. B. Pollock, of the University of Michigan, to whom 
the writer is indebted for many timely suggestions and criticisms. 
The fungus was cultivated in several kinds of organic and 
synthetic media with dextrose, cane sugar, glycerine, or potassium 
tartrate as the source of carbon. In all cases the fungus made a 
good growth when nitrogen was supplied in the form of a nitrate; 
if very small amounts of nitrogen were supplied, the growth was 
proportional to the amount of nitrogen; if no nitrogen was supplied 
there was no growth beyond the mere germination of the spore. 
In no instance did the most careful chemical analysis of the fungus 
felt and the medium in which it grew, show any increase in the 
amount of fixed or combined nitrogen. 
These experiments led to similar experimental work with other 
species of fungi to determine whether any of them have the power to 
assimilate or fix atmospheric nitrogen, and to ascertain, if possible, 
why so many contradictory results have been obtained by different 
investigators. For example, Berthelot,? Puriewitsch,’ Saida,* 
Froehlich,> and Latham® have reported positive results with 
Aspergillus niger, while Czapek,’ Koch,’ and Winogradski® give 
negative results for the same fungus. 
Thus far, two species of Penicillium, Aspergillus niger, an 
Alternaria, and two species of Fusarium have been tried by the 
methods reported by Ternetz! and Froelich.’ After the appear- 
ance of Latham’s® work, in which she reported a very large 
increase in the amount of combined nitrogen in some cultures of 
Aspergillus niger, which had been supplied with large amounts of 
ammonium nitrate, a special series of experiments was tried with 
this fungus in a medium containing a large amount of ammonium 
nitrate. 
135 
