30 
20° or 25° C., depending, however, uport the variety and upon the 
soil moisture. In general much higher percentages of infection 
were obtained in the lower soil moistures than in the high mois- 
tures. However, these two interacting factors must be considered 
together. It was further found that the soil reaction influenced 
the amount of infection. In general slightly acid soils were more 
favorable for the high infections. 
Inheritance of Disease Resistance-—Important progress was 
also made in studying the inheritance of resistance to Ustilago 
Avenae in the F, (second filial) and F, (third filial) generations 
of a cross between a resistant and a susceptible variety of oats. 
Relation of Soil Temperature and Moisture to Infection— 
Investigations with the covered kernel-smut and loose kernel- 
smut of sorghums were continued. The most important experi- 
ments dealt with the relation of temperature and moisture to 
infection. Four varieties of sorghums (Blackhull Kafir, Valley 
Kaoliang, Red Amber Sorgo, and Darso) were used in the ex- 
periments. All these varieties were previously found to be sus- 
ceptible to the loose kernel smut. Darso, however, appeared to 
be highly resistant to the covered kernel smut. 
The experiments demonstrated quite clearly the very great im- 
portance of temperature and moisture in infection. In general 
the highest percentages of ees were obtained at tempera- 
tures ranging from 20° C. to 25° C. Infections occurred, how- 
ever, over a wider range (15° to 35° C.). The infections were 
much higher in the lower soil moistures. Soil reaction was also 
an important factor. 
During the past year, a paper on a comparison of the suscep- 
tibility of sorghums to the loose and covered smuts has been 
published. An extensive paper embodying the results on the 
varietal resistance of oats to loose and covered smuts and another 
on the varietal resistance of sorghums to covered smut have been 
submitted to the Office of Cereal Investigations, U. S. Depart- 
ment of Agriculture, for publication as bulletins of the Depart- 
ment, since a considerable portion of these investigations were 
carried on while Dr. Reed was pathologist in that Office. 
Mr. James A. Faris, Research Fellow, has continued his studies 
on the influence of environmental factors on the infection of 
