56 
Studies were made on the influence of temperature on the in- 
fection of oat varieties by a number of the different races. In 
1 of 
them at about 20° C. In most cases, no infection, or very little, 
occurs when the plants are germinated at a temperature of 30° C. 
One race of covered smut, however, gave comparatively high per- 
centages of infection when seeds were germinated at the latter 
temperature. Thus there is evidence that there are variations in 
the temperature relations for infection by the different oat smut 
races. 
general, the maximum percentage of infection occurs in a 
— 
— 
Additional experiments were carried out on the influence of 
environal factors on the appearance of smut in susceptible varieties. 
In all of these cases, seedlings were germinated under conditions 
most favorable for infection. After germination, the plants were 
then subjected to quite different conditions, which influenced pro- 
foundly the rate and amount of their growth. So far as our 
studies have gone, however, such differences in the subsequent 
development of the plants have not in any way appreciably in- 
fluenced the percentage of infected plants. 
Cultural Characteristics of the Oat Smuts 
Mr. L. Gordon Utter has continued his studies on the cultural 
characteristics of the different races of loose and covered smut. 
Most of the races have been grown in culture, and their behavior 
over variable periods of time has been determined. He is con- 
tinuing his studies in order to determine whether constant differ- 
ences exist in the characteristics of these races as grown in arti- 
ficial media in the laboratory. Inoculation experiments are also 
being carried out with the pure cultures obtained. 
Bunt of Wheat 
Some experiments were carried out with the different races of 
bunt of wheat which have been previously described. For the 
most part, the work has been concerned with the temperature 
relations for infection. So far as determined, the various races 
correspond quite closely in their response to different temperature 
conditions. There are, however, a number of lines for further 
experimentation. 
