350 
LON A. HAWKINS AND NEIL E. STEVENS 
Early in this work it became apparent that all the members of the 
genus studied elaborated pigments which were bright yellow when 
acidified and red when alkaline. This suggested the possibility that 
if E. parasitica could be grown on a sufficiently alkaline medium it 
might produce the purple color considered characteristic of E. fluens. 
The writers were able to suppress the production of the purple color 
in cultures of E. fluens by the addition of lo cc. n/io sulphuric acid to 
each ICQ cc. culture flask. Cultures of E. parasitica were made to 
produce a wine color in the culture media by the addition of 2 grams of 
calcium carbonate to each icq cc. flask before sterilizing. 
While not particularly significant, these tests furnish another 
example of the necessity of carefully standardizing culture media 
used in critical comparative study of fungi. This is especially true 
since no character is more commonly used to distinguish species of 
fungi in pure culture than the production or nonproduction of color 
changes in the mycelium or culture media. Under carefully controlled 
cultural conditions the ability to produce color on certain media may 
be a distinguishing character of great value, as in the work of Appel 
and Wollenweber^^, Grossenbacher and Duggar,^^ Thorn, and others. 
In studying the growth of species of Endothia on liquid media it 
was noticed that E. parasitica produced a red coloration in old cultures 
when the medium contained peptone. This was found to be due to 
the ammonia liberated by the growth of the fungus acting on the 
yellow pigment. Anderson (loc. cit., p. 14) mentions the fact that 
old cultures of E. parasitica often become purple or wine colored and 
attributes this change to the fact that the fungus in its growth on the 
agar gradually causes it to become alkaline, thus changing the pigment 
from yellow to purple. The writer's investigations indicate that these 
conclusions were probably correct and that the change to an alkaline 
reaction may have been due to the formation of ammonia in the 
cultures., 
In the experimental work described it has been shown that three 
1^ Appel, O., and Wollenweber, H. W. Grundlagen einer Monographie der 
Gattung Fusarium (Links). Arbeiten aus der Kaiserlichen Biologischen Anstalt 
fiir Land- und Forstwirtschaft. 8: 1-207. 1910. 
Grossenbacher, J. G., and Duggar, B. M,, A contribution to the Life-history, 
Parasitism, and Biology of Botryosphaeria ribis. N. Y. Geneva Agr. Exp. Sta. 
Tech. Bull. 18. 1911. 
Thorn, Charles. The Pencillium luteum-purpurogenum group. Mycologia 7: 
134-142. 1915. 
