84 STORRS AGRICULTURAL EXPERIMENT STATION. 
area was changed first to blue and then to red. As the acid 
diffused outward from the center the wave of blue travelled 
outward, being replaced constantly by red until all trace of the 
phenolphthalein reaction was gone. The other species used did 
not give this reaction. There are forms including some species 
of Penicillium, Aspergillus niger, Monilia fructigena, and others, 
which produce the acid reaction in litmus media without any 
change to blue. Several species of Penicillium rapidly produce 
the purplish color which is characteristic of the turning point 
of litmus at which their further development occurs, apparently 
these bring acid or alkaline media to that point without further 
change. It would appear then that the relations of these molds 
to acidity as indicated by the litmus reaction is reasonably uni- 
form. To determine whether the litmus reaction would be 
reliable upon a medium closely allied to cheese, test tubes of 
separated milk were prepared, blue litmus added, and the tubes 
sterilized. Eleven species of Penicillium were inoculated into 
these tubes and observations were made every day. Of these, 
four species including the Camembert Penicillium produced a 
layer of red milk for a few millimeters below the colonies which 
later was changed back to blue. ‘The other species either in- 
tensified the blue or produced no change. 
The suggestion has been made that neutralization of acid is 
due to the production of ammonia. A series of cultures were 
made in cooperation with Mr. A. W. Bosworth to test the pro- 
duction of ammonia compounds by mold action. The species 
used were the Roquefort Penicillium, the Camembert Penicil- 
lium, Penicillium sp (Record No. 310), Oidium lactis, Oidium 
sp (Record B), and Aspergillus niger. These were grown upon 
potato agar to which litmus and lactic acid were added. ‘The 
Aspergillus culture remained bright red, all. the others became 
deep blue. Upon analysis the Aspergillus niger was found to 
have produced the largest amount of ammonia. Study of the 
figures showed that the ammonia alone was not sufficient to 
neutralize the acid used in any case. It is clear then that the 
lactic acid must have been neutralized by some other.basic pro- 
ducts of digestion rather than neutralized by ammonia. If the 
acid were absorbed and dissociated after absorption the area 
of blue would be restricted to the neighborhood of the hyphae 
or the diffusion of the acid for considerable distances would 
