M 
IOWA ACADEMY OF SCIENCE 
Experiment Station has found the disease existing in his state. Recently 
(August 10, 1911) H, T. Gussow of Ottawa, Canada, wrote the following to 
L. H. Pammel of the Iowa State College Experiment Station: 
“This Helminthosporium has been quite serious on our barley plots here 
this year.” 
More recently BeckwTth^=‘, in his work on root and culm infections, has 
shown that Helminthosporium species play an important part in such in- 
fections. * * 
CAUSE OF THE DISEASE. 
After noticing the physical effect imparted to the barley plants by the 
disease, the next step was to ascertain the cause. Upon a microscopic ex- 
amination, conidia or spores of a species of Helminthosporium were found in 
great numbers. In the first publication of this fungus form, the cause was 
attributed to Helminthosporium sativum n. sp.-*', but since that time cultural 
experiments have determined that the disease is due to Helminthosporium teres 
Sacc.^® The description** given to H. teres is as follows: 
“Oblong spots on either side of the leaves, becoming dark green; hyphae in 
clusters, lOOu — 130u x 12u, cylindrical, acrogenous, erect, rounded on both 
sides, lOOu — 115uxl8u: 4-5 divided, not constricted, rather dark green.” 
This description would hardly be diagnostic for the Iowa species. The 
characters are as follows*’: “Spots oblong, irregular, dark greenish, penetrating 
the entire leaf, hyphae fascicled, 150 — 180u=60 — 80u, smoky, reddish brown to 
dark, somewhat flexed tip, blunt septate, conidia straight or curved, slender, 
widest at middle, 150 — 130u=15 — 20u, pale, greenish gray, 7-14 divided. 
A great deal of variation is apparent from the two descriptions. Specimens 
of the diseased leaves were sent to Saccardo of Italy. He expressed the opinion 
that the disease was due to Helminthosporium teres. Since the time of the 
last publication, the organism has been grown upon artiflcial media. Great 
variations in form and structure are found in all cases. During the summer 
of 1910, it was the writer’s privilege to meet Dr. K, Ravn of Denmark. He had 
been working upon the Helminthosporiums in that country. He further sub- 
stantiated my opinion that the disease was due to H. teres and similar to what 
had been so prevalent in Denmark during the years 1898 and 1899. 
ARTIFICIAL INFECTION. 
Even before active experimentation had been commenced, it appeared in all 
probability that the infection was transmitted through the seed, as was shown 
by Pammelio for Helminthosporium gramineum (Yellow Leaf Disease of Barley). 
Barley grains inoculated with the spores of the fungus were planted in flower 
pots and covered with bell jars. A short time after the appearance of the 
first leaves, they became yellow in color, indicating a pathological condition. 
Microscopic examinations revealed the presence of the mycelium of a Helmin- 
thosporium species. Spores or conidia were inoculated into the leaves of the 
corn plant, but in no case was there a resulting infection. 
Twenty varieties of barley, furnished by Mr. Burnett, were used in the 
experiment to ascertain definitely whether the fungus is transmitted by the 
*Bull. Iowa Agr. Exp. Sta. 116. 
*Bull. Iowa Agr. Exp. Sta. 116: In a recent letter to L. H. Pammel, A. G. Johnson 
of Madison, Wis., considers H. sativum and H. teres distinct forms. 
Saccardo, P. A. Sylloge Fungorum. 
