1921] 
KARRER—H-ION CONCENTRATION AND AMYLASE ACTION 91 
ever, this variation was considered within the limits of experi- 
mental error, the weights produced being small. It has been 
shown in these results and also in the investigations of others 
that alkalinity produces 
inhibition of enzyme ac- 
tivity. Thiswould explain 
the small curve obtained 
for the extracellular amy- 
lase. However, a similar 
reduction occurred for the 
intracellular enzyme 
which may mean that 
either the cell sap had al- 
kaline properties similar 
to the culture solution 
and inhibited the enzyme 
as it was produced, that 
the culture solutions in- 
creased the permeability 
of the cells to the enzyme, 
or that the effect was 
upon the secretion itself. 
The results obtained 
for Colletotrichum (fig. 13 
and table vr) were quite 
different from the above. 
Accumulation seemed to 
increase as the cultures 
became less acid, which 
was evident in both the 
intra- and extracellular 
amylase determinations. 
Maximum accumulation 
occurred in the Py 7 
series but there was only 
F3 $ 7 
Fig. 12. "Total action of extra- and intra- 
cellular amylase produced by Fusarium sp. 
grown in Czapek’s solution of Px3.0 (---), 
Pa4.5 (—-), Pa7.0 (- . -), Px8.2 (444.), Pa9.2 
(x—x). 
slightly less in the Py 8.2 series. At Pa 9.2 there was more 
activity than in any one of the series with Penicillium or with 
Fusarium. In a comparison of these organisms, it must be 
remembered that the reaction of the medium after the growth 
