1924 
WOLPERT—FUNGI AND H-ION CONCENTRATION OF MEDIA 59 
25? C. and 35? C. and at 3.3 at 15? C., and that the optimum 
range at 15° C. is Py 4.5-4.9 and 3.6—4.0 at 35° C. indicate less 
tolerance to acid at the lowest temperature. The growth curve 
at 25° C. is the only one to show а secondary maximum toward 
the neutral point. 
In the Richards' solution, in general, the active acidity is in- 
creased by growth. The final Ру range from 3.5 to 6.5 at 35° C. 
with a mean of 5.0, and from 3.6 to 6.3 at 25? C. with а mean 
Fig.5. Armillaria mellea in Richards' solution. 
of 4.9. On the other hand, in the peptone solution the active 
acidity is markedly decreased toward neutrality, the final values 
at 15? C. being Ру 4.7 to 6.9 with a mean of 5.9; at 25? C., 6.2- 
6.9 with а mean of 6.5; and at 35? C., 5.6 to 7.1, with a mean of 
6.3. Only in the initial P, range, 6.0-7.0 at 15° C., and Pg 7.0 
at 25° C. and 6.5 at 35? C. is the acidity of this solution increased. 
While this fungus grows a little better at 35? C. than at 25° C. 
in the Richards’ solution, it grows much better at the lower 
temperature in the peptone solution. In fact, 35? C. is the least 
favorable of the 3 temperatures in this latter solution, while 15° 
C. is evidently the poorest in the former. In the peptone, although 
