[Vor. 8 
74 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Py 8.2, and P, 9.2, respectively, were studied in the case of 
Fusarium sp.; for Colletotrichum Gossypii, solutions of P,, 4.5, 
Py 7.0, Py 8.2, and Py 9.2 were employed; and Penicillium 
italicum was grown in solutions of P, 3.0 and Pa 45. The 
flasks were placed in the dark at a constant temperature of 
28° C. for 2 weeks. At the end of this time, dry weight deter- 
minations were made and the final H-ion concentration of the 
culture media taken. Dry weight determinations were made 
of the fungous mats in 10 of the flasks. The material was 
poured upon a weighed filter-paper in a Gooch funnel, thor- 
oughly washed with doubly distilled water, and dried by means 
of suction. These mats were first allowed to dry in the air for 
24 hours and then over CaCl, in a desiccator for about one week. 
After this the final weighings were taken. The remaining cul- 
tures were filtered and dried in a similar manner. 
The H-ion concentration of the control culture solution and 
of the solution upon which the fungus had been grown was taken 
according to the method of Clark and Lubs (17). After 1 per 
cent, toluene was added to the culture solution, it was stored in 
a refrigerator for subsequent enzyme determinations, which 
were made within 1-3 days. 
ENZYME STUDIES 
Amyloclastic activity was studied with the fungous mycelium 
and with the culture solution. 
Preparation of materials——A series of buffer solutions of 
different H-ion concentrations in which enzyme activity could 
be tested were prepared by varying the amounts of N/5 NaOH 
added to a given volume of H,PO,, according to the orthophos- 
phoric acid titration curve given by Clark and Lubs (17). Solu- 
tions of P, 3, 4, 6, 7, 8, 9, and 11 and doubly distilled water 
were used in a series. With the exception of the P, 4 solution, 
the H-ion concentration coincided with that calculated from the 
curve. In the case of P, 4, the critical point as seen in the 
curve, is so sharply defined that the addition of a small fraction 
of a cubic centimeter of NaOH resulted in a decided change in 
the H-ion concentration. "Thus, this solution was usually about 
Py 5.2. 
