JOIML OF AfflCtlTim 6ESEARCB 
VoL. XXIV Washington, D. C., May 26, 1923 No. 8 
SOME GRAMINICOEOUS SPECIES OP HELMIN- 
THOSPORIUM: I‘ 
By Chari^ss DrECHSLRR * 
Assistant Pathologist^ formerly Office of Cereal Investigations, Bureau of Plant Industry, 
United States Department of Agriculture, now Offiice of Cotton, Truck, and Forage 
Crop Disease Investigations 
INTRODUCTION 
Although the genus Helminthosporium includes a large number of 
forms thnving saprophytically on the bark, leaves, and stems of both 
woody and herbaceous plants, it has become familiar to plant pathologists 
and perhaps, in a large measure, to students of fungi generally, through a 
relatively moderate number of p^asitic species. Undoubtedly the most 
widely Imown of tiiese parasitic forms are those affecting graminaceous 
hosts, as considerable losses to important cereal crops, incluc&ig especially 
barley, com, rice, oats, wheat, and sorghum, in various parts of the 
world, have continued for several decades to encourage a desire for 
knowledge leading to some sort of effective control. Besides these 
economically important forms, many parasitic species of Helminthosporium 
have been recorded as thriving on various members of the grass family, but 
have remained more or less obscure because either the hosts affected were 
of little economic valilfe, or, being important, the parasitism occasioned 
little or no observable damage. 
However, as is not uncommon in the case of large genera, publication of 
an increasing number of descriptions of presumably new species, thriving 
on related or even identical hosts, has injected a large degree of uncer¬ 
tainty into the specific taxonomy. In many instances, writers have failed 
to compare their organisms with congeneric forms, or have used for such 
comparison herbarium material which had already undergone the degen¬ 
erative changes in structure incident to the death of the spores. It was 
in an effort to define the more distinctive differences between the forms 
parasitic on barley and oats, and those found on a few of the more common 
uncultivated or wild grasses that the present study was undertaken. 
This paper, which it is hoped may be followed by others dealing wiUi the 
very considerable variety of species of Helminthosporium growing on 
grasses in the United States, is offered as a comparative mycological 
account of some of the more readily available species. No attempt is 
made here to deal with the intimate pathological aspects, as these have 
been for som^ years the subject of intensive study by other workers, both 
in this country and abroad. 
1 Accepted for publicaUon Aug. 23, 1922. 
*Iii the work reported in the present paper, the writer received help from a number of investigators not 
mentioned in the text. Acknowledgments are due especially to Mrs. Agnes Chase and Dr. A. S. Hitdhco^ 
for the identification of various grasses; to Dr. Theodor Holm for help in the preparation of the manuscript; 
to Dr. C. S. Gager for permission to use the facilities <rf the Brooklyn Botanic Garden, where the studies 
were in large part carried out; and to Dr. A. G. Johnson of the Office of Cereal Investigations for helpful 
suggestions and criticisms. 
Journal of Agricultural Research, Vol. XXIV, No. 8 
Washington, D. C. May 26,1923 
aeh Key No. G-306 
39385—23-1 
(641) 
