41 
ceptible to loose smut but resistant to covered, was also studied 
in the second generation. All the plants inoculated with loose 
smut were infected, while of the plants inoculated with covered 
smut, 18.1 per cent. were smutted. 
Varietal Resistance and Physiologic Specialization in Bunt of 
Wheat 
For a number of years studies on the bunt of wheat caused 
by Tilletia tritici and T. laevis, with particular reference to 
varietal resistance, have been carried on. Dr. James A. Faris, 
formerly Resident Investigator at the Brooklyn Botanic Garden, 
published his studies on these two species, his experiments being 
concerned primarily with ¢ 
— 
ary 
etermining the influence of certain en- 
vironal factors on infection, such as temperature, moisture, soil re- 
action, etc. In the course of his studies, however, he found some 
evidence of a host specialization of these smuts. These clues 
have been followed up and a large amount of additional data has 
been obtained. The evidence is now clear that both species of 
bunt of wheat contain highly specialized races which are dis- 
tinguished by their capacity for infecting certain varieties ot 
wheat. The variety Martin, which has shown a high degree of 
resistance to the usual collections of bunt, has proved to be quite 
susceptible to some coilections of spores. Additional experiments 
are in progress to determine more completely the limits of some 
of these races. 
Experiments with the Covered Kernel Smut of Sorghum 
The main studies during the past year have been concerned 
with a continuation of the investigations on the inheritance of 
resistance of certain crosses between sorghum varieties to the 
covered kernel smut. A large amount of additional data has 
been secured on the second, third and fourth generations. A 
cross between the very resistant Feterita and the susceptible 
Sumac Sorgo seems to indicate that susceptibility is dominant and 
resistance recessive, since a large proportion of the second gen- 
eration plants are infected. During the past year, in one cross 
69.6 per cent. and in another 67.1 per cent. of the plants were 
smutted, as compared with 86.1 per cent. of the plants of the 
