PENNINGTON: ASSIMILATION OF NITROGEN BY FUNGI 137 
analyses of blanks and cultures in which dextrose was used gave 
amounts of nitrogen between 0.44 and 0.47 milligram. From 
these results it is evident that although the dextrose contained a 
very small quantity of combined nitrogen to begin with, no nitro- 
gen was assimilated or fixed in any of the cultures. 
In the next series of experiments, cultures of two species of 
Penicillium, Aspergillus niger, an Alternaria, and another species 
of Fusarium were tried with dextrose (a new stock). In all the 
. flasks there was a little growth. The analyses, again by the coloro- 
metric method, gave amounts of nitrogen between 0.53 and 0.60 
milligram, with but a single exception. One culture of one Peni- 
cillium gave 0.88 milligram of nitrogen. Since, however, the 
growth of mycelium was no greater in this culture than in the others 
it was thought that the excess of nitrogen may have come from 
something which might have dropped into the flask during the 
preparation of the cultures or in the analysis. 
In the experiments with Aspergillus (Sterigmatocystis) niger in 
which Latham’s method was followed, the following results were 
obtained: A thick felt of fungus hyphae was formed in each ex- 
perimental flask during the six-day growing period. Each fungus 
felt was carefully filtered, dried, weighed, and analyzed for its 
nitrogen content. The filtrate was also analyzed for its nitrogen. 
The total nitrogen content for three cultures was 155.8, 154.5, and 
153.1 milligrams, respectively (average 154.5 milligrams), and for 
three control flasks 156.1, 154.4, and 151.3 milligrams, respectively 
(average 153.6 milligrams). The individual differences were 
probably due in part to the fact that the culture medium was 
measured out in an ordinary graduated cylinder. To test the 
efficiency of the method of analysis, a sample of ammonium nitrate 
was carefully weighed and analyzed. The computed amount of 
nitrogen which it should have contained was 177.92 milligrams; 
the analysis gave 176.9 milligrams. This was considered very 
close in view of the fact that ammonium nitrate is deliquescent. 
Although these results are in harmony with the generally 
accepted notion that fungi do not have the ability to assimilate 
atmospheric nitrogen, the persistency with which reports of nitro- 
gen assimilation by fungi appear demands attention and explana- 
tion. There are at least two very probable reasons for the positive 
