May 36, X933 
Graminicolous Species of Helminthosporium 
665 
That the correspondence is not especially close is indicated by Harvey's 
statement that the spores of his fungus were somewhat shorter, measuring 
40 to 80 by 15 fi, and sometimes less frequently septate, namely, i to 5 
times. And his figure of the spore, showing this body as an ellipsoidal, 
comparatively closely septate structure does not suggest any close 
resemblance either to H, inconspicuum C. & E. or to H. teres^ between 
which Grove's variety was reported as occupying a median position. 
Nor is it any more suggestive of H, avenae. On the assumption 'that 
only one parasitic species of Helminthosporium occurs on cultivated 
oats, Harvey's fungus might perhaps nevertheless be supposed to be 
identical with the one distributed by Briosi and Cavara. An examina¬ 
tion of specimens of diseased oats collected near Bloomington, Ill., in 
June, 1920, bearing conidiophores and conidia of a type somewhat 
different from that generally found characteristic of the oat leaf-spot 
fungus, has, however, made the writer inclined to believe that such an 
assumption might probably prove to be incorrect. 
The disease caused by Helrninthosporium avenae is widely distributed. 
It was reported early from Germany (55), Austria (56), Denmark (rJ5), 
Bel^um {88), Holland {121), and Italy. Fraser (45), in 1913, found the 
“stripe disease of barley" severely affecting oats in Quebec. Anderson 
(j, p, 103) reported H, avenae from Alaska. According to records of the 
Plant Disease Survey the Helminthosporium leaf spot of oats appears to 
have been observed in New York, Pennsylvania, Indiana, Wisconsin, 
Louisiana, Iowa, Minnesota, Nebraska, Montana, Idaho, and Washing¬ 
ton. Undoubtedly, it occurs at least in all the northern States to a 
greater or less extent; the writer, for example, has found it quite abun¬ 
dant in Connecticut and Maine during the season of 1921, apparently 
wherever the host was cultivated. Yoshino {161) reported H, avenae 
as occurring in Japan, and Butler (79) records le^ spot as being very 
common in India, especially on young plants. 
Ravn's investigations have shown that, in general development, the 
disease follows the same course as netblotch of barley. The infection of 
the seedling during the germination period results in the production of 
primary lesions on the first leaf; from the primary lesions the fungus 
spreads to the foliage, is disseminated later by successive generations of 
spores, and finally the maturing fruit is infected or contaminated to 
propagate the trouble the next season. The local symptoms of infection, 
on the other hand, however, are quite different. Instead of numerous 
spots exhibiting an irregular reticulate pattern of short accentuated 
lines or streaks, the affected oat leaves rarely show more than 3 or 4 
brown spots. (PI. 4, A.) It is true that the colored figure in Butler's 
manual shows a large number of lesions on a single leaf. Such a heavily 
spotted condition certainly has never been observed by the writer, and, 
perhaps, may be associated with a more severe manifestation of the 
disease in India. 
The spots may be broad and irregular, or long and narrow; in any case, 
the margins are frequently poorly defined, merging gradually into yellow, 
reddish, or orange shades which eventually spread over a large portion 
of the leaf blade. The gradual extension of diffused yellow and reddish 
discoloration appears to be coincident with the progress of the fungus in 
the affected tissue. In the absence, usually, of extensive brown conspicu¬ 
ously abnormal spots, the morbid decline of the leaf, due to the develop¬ 
ment of the parasite, simulates ^yithering occasioned by weather conditions 
or maturation much more closely than in any of the three Helminthospo- 
