New YorkK AGRICULTURAL EXPERIMENT STATION. 153 
The cause of this red color and the conditions under which it is 
formed are not thoroughly understood. Apparently, the requisite 
conditions vary with different fungi. In the case of the carnation 
stem-rot Fusarium the writer has found that in order to secure 
bright colors it is necessary to grow the fungus at a rather high tem- 
perature. Erwin Smith has studied this problem in its relation to 
the melon-wilt fungus, Neocosmospora vasinfecta (Atk.) Erw. Sm. 
After recording the color of the mycelium of this fungus when 
grown on various culture media he says :*%" “ My conclusions rela- 
tive to the formation of color by the melon fungus are as follows: 
“(a) On neutral or acid media in the presence of free oxygen 
and of starchy foods—e. g., potato, bread, rice, tapioca, wheat, 
hominy, cucumber agar, etc.—this fungus develops in the sub- 
stratum a series of the most brilliant colors, which are then absorbed 
by the hyphz. These hues include many shades of pink, red, pur- 
ple and violet, and in some of the substrata — e. ¢., bread or boiled 
rice — are particularly brilliant, changing gradually from shades of 
purple and rose color into the deepest crimson (rose carthamine). 
This color is much brighter and purer than any I have been able to 
obtain with Went’s Monascus purpureus. During the development 
of this pigment the substratum becomes intensely acid (mostly CO: 
but some lactic acid according to Mr. K. P. McElroy). If, however, 
alkaline substances (caustic lime, carbonate of soda, etc.) be added 
to the substratum in advance, so as to neutralize the acid or acids 
as fast as formed, no color is developed, the fungus remaining snow 
white, as in the vessels of the melon plant. If less alkali be added, 
the colors appear gradually after a time, which is longer or shorter 
according to the amount added. 
“(b) The yellow and brown colors are formed in the presence of 
an alkali, but apparently not unless sugar is also present.” 
Later, Smith and Swingle®® found that also incultures of the 
potato dry-rot fungus, Fusarium oxysporum Schlecht., there exists 
a somewhat similar relation between the acidity of the medium and 
the production of red color. Light, also, seemed to be a factor when 
the fungus was grown on certain media, while on other media it 
7 Smith, Erwin F. Wilt disease of cotton, watermelon and cowpea. 
U. S. Dept. Agr. Div. Veg.. Phys. and Path. Bul. 17: 23. 18900. 
* Smith, Erwin F. and Swingle, Deane B. The dry rot of potatoes due 
to Fusarium oxysporum, U.S. Dept. Agr. Bureau Plant Ind. Bul. 55: 34- 
49. 1904. 
