1916] 
DUGGAR AND DAVIS—NITROGEN FIXATION 421 
2.45-3.06 mg. He considers these quantities as possibly within 
the limit о” experimental error. Unfortunately, various de- 
tails regarding the handling of cultures and the methods of 
analysis are omitted. 
Lipman (711-7112) made an extended study of the relation 
of certain yeasts and fungi to nitrogen fixation, employing 
7 species of yeast, 5 pseudo yeasts, and Mycoderma, also 
Aspergillus niger, Penicillium glaucum, and Botrytis cinerea. 
In the first extensive series, omitting the moulds, there was 
a slight gain of nitrogen in practically all cases, but only in 
a single case, a pseudo yeast, was this more than 1.0 mg. In 
a second series 9 out of 15 forms gave a gain of 1.05-2.28 mg., 
while 6 forms yielded less than 1 mg. increase of nitrogen. In 
the final series, which includes the fungi, the yeasts exhibited 
gains of .07-3.78 mg., while the fungi ranged from .05 to 2.38 
mg. 
Preliminary to her studies in nitrogen fixation Stahel (211) 
made an extensive trial of fungi on media low in nitrogen. 
She isolated 54 species, largely from decaying vegetation, and 
then grew these on various media, including silica jelly with- 
out combined nitrogen. Five species were found to grow well 
on the last-named medium, while 22 made some growth. In 
the studies regarding N-fixation it is determined that the 5 
species which grew on nitrogen-free media are capable of fixa- 
tion, likewise 4 of the organisms from the group growing in- 
differently also possess this capacity. The method of hand- 
ling the flasks is not given in detail, but it appears that the 
mycelium was filtered off from the solution and separate 
analyses made. The fungi were grown on 200 ce. of nutrient 
solution, and, in general, the amount of fixation was related 
to the initial nitrogen content. While the method suggests 
some possibilities for error, yet in some cases the amount of 
fixation is certainly well above the usual experimental errors. 
It is to be noted, however, that the following amounts repre- 
sent questionable fixation: Aspergillus .41 mg., Penicillium 
.50 mg., Botrytis 46 mg., Melanoma Ap mg., Epicoccum .41 
mg., Bispora .61-1.44 mg.; while the following give higher re- 
