174 
IOWA ACADEMY OF SCIENCES. 
noticed. Cultures growing under seemingly identical con- 
ditions in some cases produced very little, if any, color, in 
other cases producing a large amount. An effort was 
made to determine the cause, or some of the causes of this 
variation. 
Effect of the Acidity and Alkalinity of the Culture Medium, 
— ^To test tubes containing 10c. c. of bouillon, varying 
amounts of normal hydrochloric acid, and sodium hydrate 
were added, i.e.,^V c.c., ^^c.c., c.c.,iu c.c., A c.c., and by tenths 
of C.C., up to nine-tenths c.c. These together with 
neutral bouillion were inoculated with this organism. The 
limits of growTh were found to lie between 0.1c. c. sodium 
hydrate, and a little less thanO.lc.c. of normal hodrochloric 
acid, the maximum at about #o c.c. hydrochloric acid. The 
organism is quite sensitive in the variations of the reac- 
tions of the medium in which it is grown, but reaches its 
maximum development in a medium which is very slightly 
acid. The amount of growth in all cases and the amount 
of color produced were similar. In no case was there 
growth without color production. 
Effect of Sunlight. — Agar slants of the organism, freshly 
inoculated, were exposed to the direct rays of the sun for 
periods ranging from five minutes to four hours. In no 
case could any difference be detected between the growth of 
cultures so exposed, and those which were kept in a dark 
chamber. The organism seems to be unusually resistant to 
the antiseptic properties of light. 
The Relation of Free Oxygen to Growth and Color Pro- 
duction. — The absence of oxygen practically prevents the 
growth of the organism, and no color, therefore, is pro- 
duced. 
Effect of Variations in the Composition of Medium on the 
Groivth and Color P^'oduction. — Various solutions and media 
were tested to determine, if possible, what were the sources 
of carbon and nitrogen that would produce the maximum 
growth and production of color. 
As a basis for these solutions the Stickstoffreie Mineral- 
ische Nahrlosung (M. nahrlosung) of Meyer"^ was used. 
♦Arthur Meyer. Mikrokopisches Practicum . II. 15. 
