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with a high soil moisture, and while infections occur over a rather 
wide range of soil reactions, the severest infection occurs in the 
slightly acid soil. It has also been found that infection with the 
covered smut of barley will take place over a wide temperature 
range from 5° to 30° C. The highest percentages of infection 
were obtained at 15°. In general, higher percentages of infection 
were obtained in a soil moisture of 50 per cent. than in one of 4o 
per cent., provided the soil was acid in reaction. It must be em- 
phasized, however, that in all these cases these various factors in- 
fluence each other. They are interdependent factors and their 
interaction determines whether the infection will take place and 
also the severity of the attack. 
Another line of investigation has been the determination of the 
varietal resistance of hosts. The best and ultimate solution of the 
control of various plant diseases is the utilization of resistant va- 
rieties. Consequently, the determination of varieties which will 
produce a full crop and withstand particular diseases becomes a. 
matter of very great importance. In the investigations at the 
Garden a large series of varieties of sorghums, oats, and barley 
have been tested for the resistance to their respective species of 
smuts. Various sorghums, as the Milos and Feterita, have shown 
a marked resistance to both the covered kernel smut and the loose 
kernel smut. On the other hand, the Kafirs and Sorgos have been 
more or less susceptible. The varieties in general have responded 
in a similar fashion to the loose kernel smut. Darso, however, has 
proved to be highly resistant to the covered kernel smut and mod- 
erately susceptible to the loose kernel smut, A lar ge number of 
varieties of oats also have been tested for their behavior to both 
loose and covered smut. While the great majority of the varieties 
are susceptible, a few have been found to be notabl y resistant. In 
general the oats belonging to the Sterilis group, including such 
varieties as Fulghum and Red Rustproof, have shown a marked 
degree of resistance. Again, it is an interesting fact. that the ma- 
jority of the varieties have responded somewhat similarly to the 
two smuts. A few varieties, however, have behaved differently 
with reference to them. 
