252 BOTANICAL GAZETTE [OCTOBER 
in quantities all the way from 1.6 to 205.1 mg. The author 
believes that the critical point of the fungus with regard to the 
nitrogen supply is slightly below 160.3 mg. of nitrogen in 50 cc. 
of the solution, and when a greater quantity of nitrogen is supplied 
to the fungus, it ceases to fix nitrogen and begins to consume it. 
All this weight of evidence would seem to establish fully the 
fact of nitrogen-fixation by fungi, were there not also a large and 
increasing amount of negative evidence by well recognized investi- 
gators. WunoGrRapsky (21) has reported that he failed to confirm 
the results of BerTHELOT on Aspergillus niger, while Kocu (8) 
states that he was unable to confirm the work of either PuRIE- 
WITSCH or SaipA, giving as his opinion that they worked with 
impure cultures or were in some other way mistaken in their results. 
Again, CzAPEK (22) reports negative results for Aspergillus niger. 
Also HEINZE (9) has recorded a repetition of the work of PuURIE- 
WitscH and Sama, using similar solutions as well as numerous 
modifications, including variation of the sugar content and also 
of the fixed nitrogen content. In no case was he able to confirm 
the earlier work. He fails, however, to give his analytical data. 
Further, it may be noted that TERNETZ disagrees quite widely with 
PURIEWITSCH regarding the amount of nitrogen gain in the case 
of Penicillium and Aspergillus in nitrogen-free solutions. It 
may be added further that BREFELD (23) and HEINzE (9) have 
reported negative results with reference to the nitrogen-fixing 
power of certain species of Ustilago and with Dematium-like fungi 
and yeasts. 
More recently, further weight has been added to the negative 
side by the work of PENNINGTON and Ducear, as well as by the . 
work of this investigation. PENNINGTON (24) first reported no 
nitrogen-assimilating power for a species of Fusarium isolated 
from the soil. Later (25) he reports absolutely no nitrogen-fixing 
bower for Aspergillus niger, Penicillium glaucum, and Alternaria 
(sp.), either in nitrogen-free or in nitrogen-containing media, using 
methods similar to those of FROELICH and TERNETZ. DUuGGAR 
(26) has very recently reported negative results for the following 
at Coprinus comatus, Daedalea quercina, Polyporus sulphureus , 
richoderma lignicola, and Aspergillus niger. With these he carried 
