BULLETIN 1275, U. S. DEPARTMENT OF AGRICULTURE 
mutica (No. 45) and aurea (No. 7), gave low percentages of infection. 
Two strains of Black Mesdag (Nos. 70 and 117) consistently showed 
negative results. 
The varieties of Avena sterilis L. have proved to be only slightly 
susceptible to both smuts. Three strains of Burt (Nos. 67, 175, and 
253) have consistently showed very low percentages of infection with 
both loose and covered smuts. Two other strains (Nos. 74 and 75), 
the latter listed under the name of Early Ripe, proved to be some- 
what more susceptible, particularly to Ustilago avenae. The variety 
Fulghum proved to be exceptionally resistant, only 5 infected plants 
being obtained out of a total of 491 grown from seed inoculated with 
U. levis, while in the series inoculated with U. avenae 499 plants were 
grown, of which 2 were infected. The other varieties of A. sterilis — 
Italian Rustproof, ludoviciana, nigra, Selection, and Turkish Rust- 
proof — showed either negative results or low percentages of infection. 
It is noteworthy that the various strains and varieties used respond- 
ed similarly to inoculation with the two smuts. As a rule no impor- 
tant differences in the infective capacity of the two smuts were ob- 
served. In a given year one variety may have been infected slightly 
or not at all by one of the smuts and severely by the other, but in the 
following year the relations may have been reversed. It is especially 
noteworthy that the highly susceptible varieties, such as Avena nuda 
and A. sativa var. Canadian and var. Victor, were equally susceptible 
to both smuts, the highly resistant varieties, such as A. sativa 
var. Black Mesdag and A. sterilis var. Fulghum, were equally resist- 
ant to both smuts, and varieties that consistently showed negative 
results with one smut behaved similarly toward the other. 
Heald (4) recently reported his results with 19 varieties of oats 
inoculated with the spores of Ustilago levis. Three varieties of hull- 
less oats (Avena nuda) had more than 87 per cent of infection. Infec- 
tions ranging from 27.5 to 73.2 per cent were shown in 14 varieties, 
mainly A. sativa types. Two varieties showed negative results. 
One of these, Texas Red, belongs to the A. sterilis group, and the 
other, Kherson, belongs to the A. sativa group. 
Vavilov (20) has reported his observations on the behavior of a 
large number of varieties of oats with reference to Ustilago avenae. 
His results are briefly summarized in Table 1. 
Table 1. — Observations of Vavilov on the behavior of certain varieties of oats with 
reference to Ustilago avenae 
Oat varieties 
Num- 
ber of 
strains 
Remarks 
4 
1 
2 
2 
63 
8 
4 
2 
15 
1 
3 
4 
1 
1 susceptible, 1 immune, 2 in which the stamens 
brevis Roth. 
only were infected. 
Immune. 
byzantina C. Koch = A. algeriensis 
Trabut 
Do. 
Susceptible. 
diffusa Aschr. and Graeb. = A. sativa L. . 
f atua L 
56 susceptible, 6 resistant, 1 immune 
Susceptible. 
Do. 
nuda L_- 
1 susceptible, 1 resistant. 
oriental is Schrcb 
Susceptible. 
Do. 
Do. 
strinosa Schreb 
3 immune, 1 susceptible. 
wiestii Steud 
Susceptible. 
