1917] 
DUGGAR—FUNGI IN PLANT DECOCTIONS 173 
left the solution differing widely from the majority of the 
decoctions in hydrogen ion concentration. 
The changes which were induced in the hydrogen ion con- 
centration in the various solutions as a result of the growth 
of the different fungi is worthy of mention. In all solutions 
except the sugar beet and the corn meal decoctions, Asper- 
gillus caused, as might be expected, a shift toward the acid 
side, usually to about 103, while Macrosporium and Glom- 
erella generally induced a pronounced shift in the other direc- 
tion, these last, however, varying from a scarcely perceptible 
change in prune decoction to a maximum in the turnip, bean, 
and potato decoctions, where the test indicated from 10-9 to 
10-8. In the cultures of Penicillium acidity was evidently de- 
veloped in the bean, turnip, prune, and potato decoction when- 
ever sugar was added, but alkalinity was developed in the 
natural and standardized decoctions. 
Graduate Laboratory, Missouri Botanical Garden. 
