VARIETAL SUSCEPTIBILITY OF OATS TO SMUTS 29 
DISCUSSION OF RESULTS 
On examining Table 2 it is evident that there was a great deal of 
variation in the degree of infection of the different varieties at the 
different stations and during the different years. There is consider- 
able evidence that the results at Columbia in 1920 were somewhat 
lower than those for the previous years. There are indications also 
that the results at Ames and Aberdeen in 1919 were somewhat 
lower than those obtained in 1920. There are sufficient cases, how- 
ever, in which the results with certain varieties were higher in 1919 
than in 1920 to prevent definite conclusions. On the other hand, 
the results at Brooklyn in 1922 were notably lower than those ob- 
tained in 1921. This was particularly true with the varieties in- 
oculated with Ustilago avenae. A partial explanation of this fact 
is found in the results of germination studies on the spores of ■ U. 
avenae, in which very poor germination was obtained when compared 
with that of U. levis. 
RESULTS FROM AVENA BREVIS 
Six strains of Avena brevis Koth were grown in the course of the 
experiments, five of which, S. N. 1, 77, 134, 139, and 142, were en- 
tirely similar in their morphological features. Strain S. N. 289 
matured several days later than the other five. It also differed in 
other minor features, so that it could be readily distinguished. 
Of the first five strains, 4,390 plants 5 were grown in the experi- 
ments with Ustilago avenae and 3,734 plants in the experiments 
with U. levis. A single smutted head of S. N. 142 was recorded at 
Manhattan, but it may be doubted whether this head was actually 
that of A. brevis, as no special care was taken to preserve the plant 
on which it was observed. In every other case these strains of A. 
brevis proved entirely free from smut. 
The late-maturing strain, S. N. 289, was grown at all the stations. 
At Brooklyn in 1921 2 plants out of a total of 87 in the Ustilago 
levis plat were found infected, and in 1922 in the same plat 2 plants 
out of a total of 454 showed infection. There can be no doubt 
about the identity of these plants, for in practically every case they 
were only partially smutted, thus making their identification possible. 
At the other stations 475 plants were grown from the seed inocu- 
lated with Ustilago levis and 219 plants in the series inoculated with 
U. avenae, but none was found infected. 
It is evident from the results that Avena brevis is extremely resistant 
to both smuts. However, some strains occasionally may be infected. 
RESULTS FROM AVENA FATUA 
Three strains (S. N. 143, 290, and 375) of Avena fatua L., the 
wild species of Avena, were grown, and all proved highly susceptible 
to both smuts. Infections up to 40 per cent or more were common, 
varying with the year and the station. Examination of the results 
indicates a slightly greater susceptibility to Ustilago levis than to 
U. avenae, as higher percentages of infection were obtained from 
the covered smut. 
5 Since the data at Manhattan, Kans., are based on panicle counts and not on plant counts, the figures 
for that station are omitted from these and subsequent totals. 
