FOOT-ROT DISEASES OF WHEAT IN AMERICA oS 
study the writer found that single-spore strains of H. sativum isolated 
from diseased barley and wheat plants readily reinfected these hosts 
when cross inoculations were made. Both strains produced the 
characteristic symptoms on the leaves and subterranean parts of 
both hosts, and when these strains were reisolated they produced 
the same symptoms on the reinoculated hosts. This procedure has 
been carried out repeatedly in sterilized and unsterilized soil to 
which no artificial medium of any kind was added, and there can be 
no doubt that the organism in question is parasitic on wheat and 
barley and that at least certain of the strains of the fungus attack 
one host as readily as the other. 
There can be little question that the organism studied by the 
writer is the same species described by Pammel, King, and* Bakke 
(53), occurring on barley leaves. Although several investigators 
(73, 19, 45, 67) have pointed out that this fungus manifests con- 
siderable variation in morphology, especially in regard to the 
co Wit 
qLY » agtiiim 
Fie. 4.—Conidia of Helminthosporium sativum. P., K., and B.: A, Grown on potato- 
glucose agar; B, produced on a wheat plant. Type B has also been found on frag- 
ments of straw "in the soil. This type conforms to the original description for H. 
sativum 
conidia (fig. 4, 4 and B) when grown on artificial media, the writer 
has found that conidia produced on leaf lesions of growing barley 
and wheat plants are more nearly like those of H elminthosporium 
sativum than of any other described species of Helminthosporium. 
HOST RANGE OF HELMINTHOSPORIUM SATIVUM 
From the work of Stakman (65) and Christensen (13) it is evi- 
dent that this parasite may attack many varieties of wheat, barley, 
rye, and a good many species of wild grasses. Out of the 113 species 
and varieties of wild grasses inoculated by Christensen, only 30 
gave negative results. None of the three species of Agrostis or the 
seven species of Poa inoculated was found susceptible to infection. 
The writer has not attempted studies dealing with host range, 
although several varieties of winter and spring wheats have been 
tested. The results, given in Table 3, were obtained in the green- 
house with sterilized soil which was inoculated just before sowing 
the wheat seed. Inoculation was accomplished by adding straw 
cultures of the organism to the soil, which was then thoroughly 
mixed to obtain uniformity. Three weeks after sowing, all seedlings 
