39 
Physiologic Races of Oat Smuts 
The results described in the above paragraph were obtained 
by using collections of loose and covered smut originally made in 
Missouri. One of the most important discoveries in our study 
has been the fact of host specialization of both species of smut, 
and further investigations along these lines have been continued. 
Collections of spores from various regions have been secured and 
have been tested out on a number of different varieties of oats. 
It has been clearly demonstrated that there are many distinct 
races of both loose and covered smut, characterized by their 
different behavior on certain oat varieties, and they can be sharply 
distinguished from each other by differences in their capacity for 
infection. 
While a number of new races have been more or less delimited 
during the past year, the new races of loose smut on Fulg 
and Red Rustproof oats are probably most interesting. These 
varieties are derived from the species A. sterilis, being grown 
quite extensively in the southern United States. While paz- 
ticularly adapted to the winter oat section, some strains of these 
varieties are proving well suited to the more southern spring oat 
gO. 
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section. They are quite distinct from the A. sativa type, which 
includes most of the varieties grown in the main oat belt in the 
United States and Canada. Outside of the southern oat sec- 
tion these varieties have a reputation for being remarkably free 
from smut. In our previous studies, the races of smuts used 
have failed to produce any marked infection of either Fulghum 
or Red Rustproof. Three collections of smut, however, were 
obtained from the south, one each from Tennessee, Texas and 
Oklahoma, which have shown a marked capacity for infecting 
Fulghum. In our experiments six different strains of Fulghum 
were grown, and the percentage of infection varied from 53.6 
per cent. to 97.8 per cent. The Fulghum race of smut is further 
characterized by its ability to infect Hulless, Black Diamond, 
Canadian, Early Champion, and, to some extent, Early Gothland 
and Monarch. It did not, however, pass over onto Red Rust- 
proof. 
A single collection of smut was obtained from Texas on Red 
Rustproof. This collection proved capable of infecting five dif- 
