ArTICLE V.—The Helminthosporium Foot-rot of Wheat, with Observations 
on the Morphology of Helminthosporium and on the Occurrence of Saltation in 
the Genus. By F. L. Stevens. 
INTRODUCTORY 
The present study of wheat disease is based upon a foot-rot, or rot of 
the basal portion of the stems, of wheat plants, as it occurred in Madison 
county, Illinois, in 1919 and subsequently. This disease was first reported 
in United States Government publications as “‘take-all’’ (Ophiobolus gram- 
inis) ; later, merely as ‘“‘take-all,’’ no cause being assigned; and for some time 
past, in Government publications it has usually been designated as ‘‘so- 
called take-all... An annotated bibliography of nearly one hundred 
titles concerning foot-rot disease of wheat, prepared by the writer, was 
presented before the Cereal Pathologists of America at St. Louis in June, 
1919, and this, expanded to one hundred and eighty-eight titles, was 
published in October, 1919 (116). As early as May, 1919, cultural studies 
quite clearly pointed to Helminthosporium as the true cause of the disease, 
and at the December meeting of the American Phytopathological Society 
I announced this fungus as the probable cause. In May, 1920, in a note in 
Science (117), I published the statement that it had been conclusively 
established that this foot-rot of wheat is caused by Helminthosporium. 
One purpose of the present paper is to present the evidence on which 
the foregoing conclusion is based and certain facts concerning the mor- 
phology and parasitism of the fungus; but far transcending in interest the 
disease itself—which now appears to be one of much less alarming nature 
than was at first feared—is the fact that very striking phenomena of 
variability are found in this and related fungi. In the following pages, 
therefore, appear (I) an account of the Illinois foot-rot of wheat and its 
causal fungus; and (II) evidence and discussion of the occurrence of salta- 
tion within the genus Helminthosporium. 
ACKNOWLEDGMENTS 
In this study I have been assisted financially by grants from the 
Illinois Natural History Survey and from the University of Illinois. I 
am indebted for specimens to persons mentioned in the list of species 
used for comparison (pages 181-184), and to W. P. Snyder for compu- 
tation of data embodied in several of the graphs. I wish also to express 
my thanks to Prof. J. A. Detlefsen, who kindly read the manuscript and 
offered valuable suggestions regarding genetic questions. 
