Mar., 1921] HAENSELER — GROWTH OF ASPERGILLUS NIGER 161 
weight yield was 2.283 gfams. It is thus clear that with 50 cc. of solution 
having a sugar concentration of 3 atmospheres, the maximum yield which 
can be produced is between 0.9 gram and i.o gram, the point at which 
the curve of series 3 (fig. 5) breaks abruptly. 
Effect upon Aspergillus niger of Substituting NaNOs for Ca(N03)2 
in the 3-salt solutions 
A microscopic examination of the fungus from the cultures containing 
Ca(N03)2 showed a slight precipitate of calcium oxalate crystals upon the 
hyphae. Not all of this deposit was removed by the washing process to 
which the fungus was subjected before drying. The amount of calcium 
oxalate crystals which remained after washing was not determined, so that 
it can not be stated definitely to what extent the dry weights were affected 
by it, but it is certain that increase in weight due to adhering crystals which 
remained after the washing process was small. However, since there is a 
possibility of the yield values of series 1,2, and 3 being slightly higher than 
they should be, and since the formulae of media used for the growth of fungi 
do not ordinaril}^ contain calcium nitrate, series 2 and 3 were repeated, 
substituting sodium nitrate in equivalent osmotic partial concentrations 
for the calcium nitrate in the various cultures of the corresponding series. 
These two series have already been referred to as series 4 and 5 of the NaNOs 
group, and the volume-molecular salt proportions of the solutions used are 
given in table 2. The yields from these two series are given in table 3 and 
plotted in the graphs of figure 5 in connection with those from the series of 
the Ca(N03)2 group. The yields are also shown on the triangular diagrams 
of figure 4 which have already been considered. 
A comparison of the graphs (fig. 2) shows at once that the yields from 
series 4 and 5 are uniformly much lower than are the corresponding yields 
from series 2 and 3 respectively. Thus, substituting in any culture NaNOs 
for Ca(N03)2 in equivalent osmotic concentrations had the effect of reducing 
the yield very considerably. This great reduction in yield is largely ac- 
counted for by the fact that the nitrate content of the cultures in series 4 
and 5 is only 68.3 percent of the NO3 content in the corresponding cultures 
of series 2 and 3 respectivel}^ this difference in the NO3 content of the cul- 
tures being due, of course, to the difference in the composition and osmotic 
value of the nitrate salts employed. That this large difference in yields, 
however, is not entirely due to the difference in the NO3 content of the 
cultures is clearly brought out by the graphs of figure 5. It will be ob- 
served that the graphs representing series 1,2, and 3 lie throughout above 
the graphs of series 4 and 5, thus indicating that with equivalent amounts 
of NO3 per culture (grams per liter of nutrient solution) the cultures con- 
taining Ca(N03)2 gave uniformly higher yields than did the cultures con- 
taining NaNOs. 
The exact cause of these observed dift'erences in yield is not clear. They 
