[Vor. 8 
70 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
From the preceding discussion, it is evident that in recent 
years the effect of the H-ion concentration upon amyloclastic 
activity has been carefully studied by several investigators. 
Although the results are not voluminous, they have shown that 
the reaction of the solution has a marked effect upon enzymic 
activity. They have shown, further, that amylases from differ- 
ent sources may react differently in this respect. 
Scarcely any investigations have been undertaken with a 
view to determining the influence of H- and OH-ion concen- 
tration upon the formation of amylase in the organism. In 
most of the work on the effect of various conditions upon the 
secretion of amylase, no mention has been made of the concen- 
tration of the H ions coincident with the varying conditions. 
It is not pertinent to the present discussion to review such works 
as those by Katz, Dox, Hasselbring, Saito, and others who have 
studied the relation of organic substances to the production and 
secretion of amylase. However, it is worthy of note that in 
many cases neutral, alkaline, and acid substrates were used and 
that no attempt was made to control the H-ion concentration 
during the experiment. 
The results obtained on the influence of inorganic substances 
on amyloclastic activity are likewise often difficult to interpret. 
Robbins (716), in an extended study of the secretion of amylase 
by Penicillium Camembertii, determined the effect of single 
salts and the absence of salts in a nutrient solution. The fungus 
was grown for two weeks at 25? C. in various solutions contain- 
ing an approximately constant amount of starch. At the end 
of this time, in the single salt cultures, the mycelium was filtered 
off, the acidity or alkalinity determined by means of methyl 
orange and phenolphthalein, and the starch and dextrins undi- 
gested in the solution measured by a new method which was 
based on their insolubility in an acidified aqueous alcoholic 
solution. The salts in the single salt series, with the exception 
of the acid phosphates, were all neutral salts, so it was very 
likely that the H-ion concentration at the beginning of growth 
was the same, since the highest purity chemicals were employed. 
The reaction of the solution after the growth of the fungus was 
found to be alkaline to methyl orange and acid to phenol- 
phthalein, which might indicate a variation from about Py 4-8 
