[Vor. 8 
288 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
growth. Best results were obtained from Py 2.5 to Pg 4.5, 
and only a few hyphae were produced at Py 8.0. During the 
growth of the organisms, certain shifts in the reaction of the 
medium were evidenced. In the initially acid cultures, Fusarium 
and Colletotrichum produced a shift towards alkalinity, while the 
reaction of the initially alkaline cultures remained more or less 
stable; in the case of Penicillium the initially acid cultures 
tended to shift towards neutrality. 
MATERIALS AND TECHNIQUE 
ORGANISMS 
Regarding the fungi and the media employed, the original 
plan of study was designed primarily to be one of a general 
nature. Fungi possessing widely divergent cultural relations 
with respect to the reaction of the medium, that is, fungi pro- 
ducing maximum growth at markedly different hydrogen-ion 
concentrations, would naturally furnish, it was realized, oppor- 
tunity for the most interesting data; hence these were given 
chief consideration. In addition, it prea desirable to select 
such economically important forms as might suitably serve to 
represent certain significant fungous groups. Accordingly, al- 
though only relatively few fungi were obtained which would 
germinate freely in water, the following were chosen and, from 
previous knowledge of their behavior, differentiated into pro- 
visional groups as follows: Acid forms—Botrytis cinerea, Asper- 
gillus niger, Penicillium cyclopium, P. italicum, Puccinia graminis, 
and Lenzites saepiaria; acid and alkaline forms—Fusarium sp.; 
alkaline forms—Colletotrichum Gossypii. The fungi mentioned 
were obtained from various sources: B. cinerea, isolated from 
lettuce plants growing in the greenhouse; A niger and P. cyclopium 
from a jar of beans which had become contaminated in the 
laboratory; P. italicum, from oranges grown in California; P. 
graminis, a strain ER was obtained from Berkeley, California: 
L. saepiaria, from sporophores collected at intervals from rail- 
road ties in the vicinity of St. Louis; Fusarium sp., isolated 
from a cotton boll; and C. Gossypit, furnished by the South 
Carolina Agricultural Experiment Station. 
