July is, 1914 
Fusarium on Sweet Potato 
281 
The color range indicates that related species have similar colors of 
corresponding organs. The relations of color and reaction of organisms, 
studied also by Milbum (1904) and Bessey (1904), are constant under 
constant conditions. On substrata rich in carbohydrates many fungi 
and bacteria produce alkaline substances; on those rich in peptone, acid 
substances. Each reaction is accompanied by special colors, which 
change with the change of reactions of the substratum. Many fungi, 
however, forced to grow on very alkaline or acid media refuse to develop 
characteristic colors. 
Table II, therefore, does not refer to artificially made acid or alkaline 
media, but to reactions developed by the fungi on potatoes, rice, and 
stems sterilized after the addition of water, but otherwise unchanged. 
The reaction of these media differs but slightly from neutral. 
Blue perithecia of Gibberella turn red to brown, and carmine mycelium 
turns yellow with acids, but their original color redevelops by addition 
of sufficient alkali. This alternative change of color can be produced 
repeatedly. The yellow color on rice turns violet with alkali and rede¬ 
velops yellow with acids. These relations between reaction and color 
are so constant that they facilitate the determination of many species 
and are also of value for the characterization of sections. 
