[Vor. 3 
432 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
From our results it is clear that under the conditions of 
the experiments no fixation can be claimed for Aspergillus 
niger, Macrosporium commune, Penicillium digitatum, P. 
expansum, and Glomerella Gossypu. For the most part, with 
these fungi, the differences between the various members of 
any series, including the controls, represent variations which 
might be expected, and the fact that the averages of the con- 
trols are slightly above or below those of the flasks contain- 
ing the fungi is of little significance. 
With Phoma Betae the case is different. Here the assimila- 
tion of free nitrogen seems definite. The quantities obtained 
vary from practically 0.0 to 7.75 mg. рег 50 се. of culture 
medium. All cultures on sugar beet and mangel decoction 
exhibit a nitrogen increase which points definitely to free 
nitrogen assimilation. It should be noted that these cultures 
represent series maintained for a shorter and a longer period 
of time; those maintained for the longer interval yielding 
higher fixation quantities than those cultured for the shorter 
interval. In one series, 19B, where the source of nitrogen is 
Л gram (NH4)2804, the nitrogen difference is perhaps suffi- 
cient to indicate nitrogen fixation. At any rate, if we regard 
fixation as occurring in this solution, it is fair to explain the 
absence of fixation in series 20B, in which only .014 
(ХН.) 804 was employed, as due to the small amount of 
growth occurring in the last-mentioned series. As would be 
expected, fixation is somewhat related to the length of the 
period of growth and to the extent of growth. The results 
with Phoma Betae were so unexpected, in view of the long 
series of negative values obtained with other fungi, that a 
further check upon the work was introduced in the following 
way: A known amount of KNOs was added to a series of 
flasks containing 50 ce. of the sugar beet medium, and analyses 
were then made to ascertain with what accuracy this nitrogen 
could be determined. No difficulty was experienced in recov- 
ering this nitrate nitrogen, as shown by the data in table rr. 
Furthermore, it seemed well, as a result of the experiments 
with Phoma Betae, to employ by comparison certain organ- 
isms known to have nitrogen-fixing power. Accordingly, the 
