658 
Journal of Agricultural Research 
Vol. XXIV, No. 8 
Kirchner called attention to the fact that up to eight septa were present 
in the spores. This fact, together with the relatively mild nature of the 
disease, indicates that he was most probably dealing with net blotch. 
In 1898 Rostrup (125) had discussed a disease of barley which he desig¬ 
nated as a “leaf-spot disease'' {Bladpletsyge), characterized by the 
presence, largely on the lower, less vigorous leaves, of elongated dark 
brown spots, surrounded by a narrow yellow margin. This malady, 
which was not observed to be very destructive, Rostrup attributed to JT. 
gramineum Rab. Apparently the same trouble had been investigated 
later also in Silesia by Eidam (55), who attributed it to a new species of 
Helminthosporium, H, hordeiy which he found was not transmissible to 
oats and consequently different from the congeneric parasite causing 
leaf spot of the latter host. 
The disease is evidently widely distributed in the United States, the 
records of the Plant Disease Survey containing reports of its occurrence 
in 21 States, including all the barley-growing districts of any importance. 
In this connection it may be mentioned, however, that although often 
responsible for appreciable loss, net blotch is of relatively minor economic 
importance compared to stripe or spot blotch. It is true that in Bakke's 
paper (d), which contains the first published record of the disease in this 
country, Helminthosporium teres is represented as probably the most 
serious parasite of barley. As Bakke failed to distinguish between the 
disease under consideration and the much more serious trouble attrib¬ 
utable to H, sativum, the exaggerated account of the destructiveness, 
as well ^ the somewhat inaccurate morphological treatment of H. teres, 
both of which unfortunately appear to have been incorporated in Butler's 
handbook (j9), are readily explained. 
The course of development of netblotch has been described in detail 
by Ravn (j/5). In the vicinity of Madison, Wis., where in 1919 the 
writer had occasion to observe the progress of the disease, the regular 
crops exhibited the characteristic symptoms in small measure during 
the earlier part of the season. Later the lesions sparingly present on 
scattered leaves were completely obliterated by the blotches due to 
Helminthosporium sativum, that began to appear in great profusion at 
the heading stage about June 20, A much more favorable opportunity 
to study the disease presented itself with its development on volunteer 
plants from the latter part of August until the beginning of November, 
when netblotch was present in considerable abundance, to the practical 
exclusion of both stripe and spotblotch. The writer is informed that a 
somewhat suppressed manifestation of the trouble on the regular crop, 
and its extensive distribution on the volunteer crop, is, in general, not 
altogether uncharacteristic of its seasonal occurrence in our nor&em 
latitudes. 
According to experiments reported by Ravn {115), the disease is 
propagated by seed infected or contaminated by the fungus. When 
such seed germinates at a relatively low temperature, as, for example, 
10° to 15^ C. or less, there results a local infection of the first seedling 
leaf which he designated as primary Helminthosporiosis. This is in 
contradistinction to secondary Helminthosporiosis resulting from infec¬ 
tion by conidia developed on the dead tissues involved in the primary 
or in subsequently developed secondary lesions. On the other hand, 
when germination took place at a temperature of 20° C. or above, pri¬ 
mary Helminthosporiosis failed to develop even though the seed was 
infected or contaminated. That such thermal relations are effective 
