152 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
this graph it will be seen that although the maximum growth was reached 
at the end of the third day, there was only a very slight decline up to the 
end of the seventh day. No appreciable loss is thus sustained by allowing 
the growth to proceed for seven days. 
Gus. 
Days 1 2 3 4 5 6 7 
Fig. I. Graph showing the rate of growth of Aspergillus niger in a three-salt medium. 
At the end of the growing period the fungus was placed upon a dried and 
weighed filter paper, washed with water, placed with filter paper into 
weighing bottles, dried to constant weight at a final temperature of 104° C, 
and weighed to the nearest milligram. 
Effect of Increasing Total Salt Concentration on the Growth 
OF Aspergillus niger 
Table 3 gives the absolute dry weights of the fungus from the cultures 
in each of the five series. By reading the yields across the columns in this 
table, it is seen that the dry weights increase as the total salt concentration 
increases. This increase is shown for all corresponding cultures, regardless 
of the salt proportions. Figure 2, in which yields are plotted in the form of 
graphs, shows the relation between total concentration and yield more 
clearly than does table 3. In these curves the dry-weight yields of series 
2 have been plotted in the descending order of their values and the yields 
from the other series are plotted with the same culture order as series 2. 
The light lines represent the yields from series 1,2, and 3, which differ from 
each other, with respect to the composition of the solutions used, only in 
