(Vor. 11 
78 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
The mycelial growth of Schizophyllum commune tends to 
increase the active acidity of the Richards’ solution throughout 
the entire Ри range and at all temperatures. The degree of 
increase is not pronounced in any case, the highest being 1.6 
Рн units and the lowest 0.1 unit, while the majority of changes 
are less than 1 unit. In the peptone solution, on the other hand, 
there is a tendency to decrease the acidity of all solutions with 
an initial acidity greater than P, 6.0 and to increase it when the 
initial acidity is less than this figure. The initial reaction, P 6.0, 
at the 2 lower temperatures is slightly increased, while at the 
highest temperature it is slightly decreased. Within the initial 
range used in these experiments, growth between Рн 4.0 and 8.0 
tends to produce a final range from Py 3.7-6.5. In the Richards’ 
solution, on the other hand, this tendency to change the acidity 
to approximately Pg 6.0 is not evident, as the final Ру range is 
more acid than the initial. 3 
The most outstanding feature in comparing Schizophyllum 
commune in the 2 solutions is that in the peptone medium the 
fungus grows from 15 to 20 times better than in the Richards’ 
solution. It shows optimum growth in both cases at 15° C. and 
poorest at 35° C. The differences are not so marked, however, 
in the Richards’ solution as in the peptone solution where the 
inferiority of 35° C. for growth is quite noticeable. The optimum 
Рн range for both solutions lies between 4.0 and 6.0, with little or 
no evidence that the fungus tends to grow better at any one Pa 
than at any other within this zone. 
The results, from cultures at 25? C. in a 0.5 per cent peptone- —— 
nutrient solution at initial acidity of Py 3.0, 4.0, 5.0, 6.0, and 7.0 
(table хп, figs. 17 and 18), indicate that in every case except 
for Pholiota adiposa the fungi grow best when the initial Pg is 
4.1. This one fungus grows better at Py 5.0. Pleurotus ostreatus 
(fig. 17) and Daedalea confragosa (fig. 18) grow more actively 
than the other 6 species, reaching 139 mgs. at Py 4.0 and 135 
mgs. at Рн 5.0 in the first case, and 127 mgs. at Py 4.0 and 118 | 
mgs. at Рн 5.0 in the second. These same 2 fungi fail to grow 
at Ри 3.0, while all of the other species produce some felt at this 
acidity. These other 6 species are closely grouped with respect 
to the amount of growth, all being able to utilize peptone аз 8 
source of carbon. | 
