(Von, H 
72 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
varies from 6.9 to 8.4. This well indicates the different reaction 
within the 2 types of media. 
The marked tolerance to slight alkalinity and the greater 
amount of growth in the peptone solution show that this medium 
is much the better of the two. In the Richards' solution there 
is no indication that this fungus will grow on an alkaline media, 
while the average weight of the mats is about one-fourth of the 
average for those obtained in the peptone solution. Although 
35? C. is the most favorable for growth of this fungus in the 
Richards’ medium, there is no sharp difference between the 3 
temperatures in the peptone medium. Here 35? C. is not as 
favorable as either 25? C. or 85° C., from the standpoint of Pg 
range, but it is a little better when considered from the amount 
of growth at the optimum Рн. With some individual variations, 
Pleurotus ostreatus shows, as indicated in both media, an optimum 
range between Pg 5.0 and 6.5. | 
Because of the wider range of growth at 25° C., this temperature 
is the optimum for growth of Polystictus versicolor in the Richards' 
solution (see table x and fig. 13). Тһе P, limits at this tempera- 
ture are 2.5 and 7.6, as compared with 3.5 and 7.3 for 15? C., 
and 2.9 and 6.8 for 85° C. Maximum growth at 25? C. is obtained 
at Pg 5.5 with a mat weighing 86 mgs. On either side of the 
optimum zone, Py 4.2-6.0, growth drops off rapidly. At the 
lowest temperature the optimum growth-zone is Pa 3.8-6.5 and, 
while there is no outstanding optimum Pg, growth is better at | 
5.0 with а mat of 59 mgs. than at any other point within the | 
optimum range. At 35° C. the fungus produces an optimum at | 
5.5 with 88 mgs. and an optimum zone between P, 4.2 and 6.6. 
_ This same fungus in the peptone solution (fig. 14) grows 8 
little better at 15° C. than at 25? C. and much better than at 35° 
C. At the 2 lower temperatures the Р, limits are practically | | 
identical, being 2.5 and 7.4 for 15° C. and 2.5 and 7.5 for 25°С. | 
At 35° C. there is a marked narrowing of the limits on the acid — 
side, the range being Py 3.0-7.5. At 25? C. and 15? C. marked 
optima are shown in the growth curves, the first being at Рн 3.5 | 5 
with 505 mgs. and the second at Pa 4.0 with 507 mgs. The | 
optimum is not so pronounced for 35? C., ranging from Py 4.0 to | 
4.9 with 316 and 304 mgs. 
