38 
and enclose the spores, thus giving the common name to the smut. 
These spores remain enclosed until the harvesting and the thresh- 
ing operations, at which time they are more or less broken apart 
and scattered upon the sound grain. When the contaminated 
seed is planted, infection takes place in the young seedling by 
means of these spores adhering to the grain, 
For several years extensive studies on the resistance of oat 
varieties to these two smuts have been carried on. A very com- 
plete collection of oat varieties from all over the world, belong- 
ing to all the main groups of cultivated oats, has been used in 
these experiments. It has been found that most of the varieties 
of the common, or Sativa, type are susceptible to both species. 
As a tule, if a variety is susceptible to one species it is also sus- 
ceptible to the other, and if it is resistant to one it is resistant to 
the other. Several varieties of oats, however, have been found 
which appear to be more susceptible to the loose smut than to 
the covered, and a very few varieties have proved to be more sus- 
ceptible to the covered smut than to the loose. During the past 
year the behavior of these has been further studied, and additionai 
data on their resistance or susceptibility to the two smuts have 
been obtained. The varieties Black Diamond, Black Norway, 
Danish, Danish Island, Early. Gothland, Green Russian, Irish 
Victor, Japan, Monarch Selection, Scottish Chief, Trisperma and 
White Queen have proved to be highly susceptible to the loose 
smut, usually giving 100 per cent. infection, but they have give 
either negative results or low percentages of infection with the 
covered smut. On the other hand, Monarch has proved to be 
very susceptible to the covered smut, while showing a high degree 
of resistance to the loose. The cultivated oats derived from 
Avena sterilis have shown a high degree of resistance to both 
smuts. Some cultivated varieties of A. strigosa are equally sus- 
ceptible to both, while other strains possess a high degree ot Te 
sistance. A. brevis is highly resistant to the loose smut, but has 
eiven some infected plants with the covered, and A. barbata and 
A. fatua have proved to be very susceptible to both smuts. 
