1921] 
KARRER—H-ION CONCENTRATION AND AMYLASE ACTION 71 
and thus would embody acid, neutral, and alkaline conditions. 
Under these conditions, he found that potassium salts inhibited 
digestion more than sodium salts, that potassium and calcium 
did not seem to be connected with amylase formation, and that 
there appeared to be an intimate relation between nitrogen and 
amylase formation. In the nutrient solutions, where salt substi- 
tutions were made, the H-ion concentrations, when determined 
by the method outlined in this paper, were found to vary from 
Py 3.3 to 5.4. After the growth of the fungus, the H-ion con- 
centration undoubtedly was shifted, a fact which might have 
been significant in explaining the results. It is worthy of note 
that a marked difference was observed by Robbins between the 
speed with which Aspergillus Oryzae and Penicillium Camem- 
bertiz, on the one hand, and Fusarium sp. and Mucor Rouzii, 
on the other, digest soluble starch in the absence of all nutrients. 
The former had a very slow rate while the latter showed fairly 
rapid digestion. 
That invertase formation in yeasts is dependent upon acidity 
has been shown by Euler and Svanberg (19). Optimum ac- 
cumulation was effected at an H-ion concentration of Py 5-6 and 
a concentration of Py 2 was found to be destructive. 
Further, Euler and Emberg (19) attempted to determine the 
influence of acidity and alkalinity upon enzyme formation by a 
bottom yeast and the adaptation of these living cells to nutrient 
solutions. They showed that the maximum H- and OH-ion 
concentrations at which the cells reproduce themselves or ex- 
hibit enzymic relations could be modified by adaptation. 
METHODS AND MATERIALS 
ORGANISMS 
The fungi used in this investigation were selected with a view 
to obtaining a group of parasitic organisms which differ in 
optimum growth with reference to the H-ion concentration of the 
medium. One organism producing maximum growth in acid 
media, one growing well in alkaline media, and one requiring 
either acid or alkaline media were thus chosen. Colletotrichum 
Gossypii (Southworth), Penicillium italicum, and Fusarium sp. 
1 Determined by Dr. Chas. Thom. 
