480 
Journal of Agricultural Research 
Vol. I f No. 6 
as in the wheat plants. This is shown in Plate LXII, figure 2. Barley 
plants from seed inoculated with Helminthosporium gramineum from 
barley were 5.82 inches high at the end of six weeks, those from seed 
inoculated with H . gramineum from wheat were 6.34 inches high, and 
those from clean seed, 6.46 inches high. The measurements are the 
averages of 50 plants in each case. There was no measurable difference 
in the height of oat plants grown from inoculated and from clean seed. 
H. gramineum was easily reisolated in every trial both from stunted 
wheat and stunted barley plants by external sterilization in mercuric- 
chlorid solution and incubation at room temperature. 
Fusarium culmorum was even more virulent than Helminthosporium 
gramineum , particularly on oats. Inoculated wheat seed produced only 
22.9 per cent of sound plants, barley seed 65.5 per cent, and oat seed 
only 1.7 per cent, while the controls produced 83.3, 88.5, and 85 per 
cent of sound plants, respectively. The results of the inoculations are 
further strikingly shown in PI. LXII, figures 3, 4, and 5. The 10-acre oat 
field where this fungus was secured had been practically destroyed by 
some disease, and these results show that F. culmorum undoubtedly was 
the causal organism. 
The two strains of Alternaria sp., one isolated from wheat culms from 
University Farm, St. Paul, Minn., the other from wilted wheat seedlings 
from Vermont, had no pathogenic effect on wheat, oats, or barley, the 
differences in percentage of germination from inoculated seed and control 
seed being so slight as to be negligible. Cladosporium gramineum also 
had very little if any effect on the seedlings, the percentage of germina¬ 
tion from inoculated seed being only slightly smaller than from control 
seed. 
To determine further how the Helminthosporium gramineum attacked 
the seed and seedlings, a large number of seeds and seedling plants grown 
from inoculated seed were dug and examined a few days after germina¬ 
tion. It was found that many of the seeds had been attacked by the 
fungus so rapidly that they had not had an opportunity to germinate. 
Many others had germinated, apparently became infected immediately, 
and were killed before they were an inch high. Plants which survived 
were severely affected, as shown by the brown discoloration at the base 
of the culms, a condition not noticed in any of the controls. This dis¬ 
coloration usually occurred in the basal leaf sheath. When the plants 
had grown for several weeks, it was also very noticeable in the root crown. 
The discoloration was not as marked in barley grown from inoculated 
seed as the discoloration in wheat and was entirely absent in oats. 
Numerous seeds and seedlings inoculated with Fusarium culmorum were 
also examined. Many seeds were found to have been killed before the 
process of germination had proceeded sufficiently far for any roots to 
form and before the plumule emerged from the ground. Eight days after 
