1924] ; 
WOLPERT—FUNGI AND H-ION CONCENTRATION OF MEDIA 71 
but from the standpoint of range of Рн, 25? C. is a little better 
than 15? C. and considerably better than 35? C. Although at 
this medium temperature the growth curve fluctuates, making 
it difficult to determine the optimum range, the 2 high points 
lie at Pa 5.2 and 5.9. At 35? C., however, there is a very sharp 
optimum of 255 mgs. at Py 5.7, as compared with 237 mgs. at 
Ры 5.2, and 216 mgs. at Ру 5.9 for 25? C., and 217 mgs. at Pg 
i | ) T] | Т | рай 17, 
РН | 
Fig.13. Polystictus versicolor in Richards’ solution. 
6.0 for 15? C. Although the fungus may be a little more tolerant 
to acid at 25° C. than at 15? C., a comparison of the Py limits 
and of the optimum range show that there are no fundamental 
differences in the growth curves of these 2 temperatures. 
While the active acidity in the Richards' solution is slightly 
inereased in the majority of cases, in the peptone solution it is 
invariably decreased close to neutrality or to slight alkalinity. 
In the former solution, within the Ру range at which Pleurotus 
ostreatus grows, the final Pg at 25° C. varies from 3.3 to 6.2, 
while in the latter solution the final range at the same temperature 
