IOWA ACADEMY OF SCIENCES. 
127 
Rice tytarch.—ki the end of three days color gathered 
around the edge. Starch was not liquefied but seemed to 
dry up. Color remained about constant. 
When grown in milk a curd was first produced. The 
color gathered on the top and later a greenish-blue 
color was disseminated through the liquid. In one week’s 
time the curd was dissolved and a pellicle of heavy growth 
was in the bottom of the tube. 
j 
In ordinary bouillion a growth could be seen, the bouil- 
lon was cloudy but no color came. However when one- 
tenth of one per cent solution of potassium nitrate was 
added to agar slant and stab cultures, which being duly 
inoculated, produced growth in about the same time as did 
the nitrogen-free agar. But at the end of one day color, 
which spread rapidly over the entire surface, could be seen. 
From these observations it may be noted that the organ- 
ism grows on top of nitrogen-free agar but without color; 
and that oxygen is necessary for its growth. Also that 
the organism produces color and grows on top of agar that 
contains nitrogen . Therefore nitrogen seems necessary 
for the development of pigment. 
As a result of these observations the conclusion is that 
the production of color is dependent on environment; and 
that this chromogenic organism grows rapidly in the proper 
medium. 
Although i?. violaceus var. does not produce color in nitro- 
gen-free bouillon nor agar without nitrogen, one should 
not draw the conclusion that all chromogenic organisms 
require nitrogen . For the large amount of color in arrow- 
root starch and in sugar bouillon after standing five 
months should receive attention. 
To further determine the conditions in which it would 
grow in non-proteid medium of known composition the 
following media were made: 
