196 
Journal of Agricultural Research 
Vol. XXVI, No. s 
Soon after the discovery of the rosette disease (zz) near Granite City, 
Ill., and in Indiana, it was found by the writer and others that Helmin- 
thosporium sativum P. K. and B. was associated with it in its later 
stages. While this association was rather consistent in many cases, 
it seemed somewhat doubtful to the writer and to certain other workers 
if Helminthosporium was to be looked upon as the primary cause of 
rosette, although it was recognized that rosette might possibly be an 
unusual manifestation of the Helminthosporium disease (9) brought 
about by some environmental condition, or due to some unfamiliar strain 
of the organism. Although Stevens ( 14 , 13) claims to have proved that 
the rosette disease (called footrot by him) (13, 14 , 13) is caused directly 
by Helminthosporium, it has been pointed out by the writer (9,zz) that 
positive proof of this causative relation is lacking. As to the ability of 
Helminthosporium to produce a definite, unmistakable disease in wheat, 
there is no doubt, as is shown in Plates 1, 2, 3, and 4, but as to its ability 
to produce the symptoms of wheat rosette, as the latter malady is now 
interpreted, there is a question. 
On a basis of field observations and isolations made from material 
collected by the writer and others, it is evident that the Helminthosporium 
disease of wheat occurs to a greater or less extent throughout the wheat¬ 
growing regions of this country (zo). 
In some cases the disease occurs in combination with other wheat 
diseases, as is the case in the district around Granite City, Ill., and in 
certain of the fields affected by take-all and footrot in Kansas. In other 
cases Helminthosporium sativum seems to be the chief or only parasite 
involved. 
In certain localities and under certain conditions the Helminthosporium 
disease causes considerable damage to the wheat crop. This is evidenced 
by the conclusions of Bolley (3) and Stakman ( 12) concerning Helmin- 
thosporium in North Dakota and Minnesota, respectively, and of 
Hungerford (3) concerning the situation in the vicinity of Rexburg, 
Idaho, in 1921* 
While more than one species of Helminthosporium may be involved 
in the disease, the bulk of evidence now in hand, as pointed out by the 
writer (zo), indicates that a single species (H. sativum) is the one chiefly 
involved. This organism apparently does not have as fixed a mor¬ 
phology as many fungi, and this is especially true in regard to conidia. 
Experiments which will be discussed fully in a later paper show that the 
same single-spore isolation, when submitted to different conditions as 
to substratum, temperature, etc., may produce spore forms which are so 
widely different as to suggest different species to persons not acquaint¬ 
ed with the situation. As to the possibility of different physiological 
strains within this species nothing definite can be said at this time. 
The studies on the symptoms of the Helminthosporium disease as 
published by Stakman ( 12) and by the writer (it) show that under 
favorable conditions H, sativum is capable of attacking all parts of the 
wheat plant from the roots to the head. It is evident, however, that 
under certain conditions infection does not take place, or takes place 
only in a mild form, even when the organism is present in the soil. 
Soon after the writer became interested in the Helminthosporium 
disease, it was realized that the disease does not attack the wheat 
plant with the same degree of severity in all localities or during the 
different periods of development of the plant in a given locality. As 
pointed out earlier in a brief note (zo), these observations led to the 
