66 o 
Journal of Agricultural Research 
Vol. XXIV, No. 8 
leaf tissue. As long as weather conditions are suitable, each successive 
leaf to be unfolded sooner or later becomes infected and in time may be 
killed. Plate 2, A, showing a volunteer seedling with five leaves, the 
first (PI. 2, Ae) entirely withered, the next three (PL 2, Aa-b) exhibiting 
increasingly earlier stages, and the fifth (PI. 2, Aa) apparently healthy, 
drawn from material collected September 2, 1920, represents a rather 
severely affected specimen. It may be mentioned that after September 
15 the production of new lesions was much slower, with the result that, 
on November 3, the upper leaves of the plants, then about 24 inches tall, 
were entirely free from the disease, although fresh lesions could be 
found on the leaves lower down, while the lowermost withered foliage 
was covered with an abundance of profusely sporulating conidial 
fructifications. 
The brown or olivaceous conidiophores (PI. 2, Ea-d), emerging from 
the stomata or between epidermal cells, singly or in groups of 2 or 3, 
vary usually from 120 to 200 ju in length, and above the swollen basal 
cell, from 7 to 9 /i in diameter. They are thus somewhat stouter than 
those of Helminthosporium gramifieum and H, sativum, besides being less 
closely septate, the septa occurring at intervals varying usually from 
15 to 60 ii, and averaging approximately 35 m- The writer has not 
observed them in fascicles of 5 and 6, indicating that their occurrence in 
groups of such number is at least less common than in the case of the 
stripe fungus. On the other hand, the conidiophores of H, teres appear 
to he quite indistinguishable from those of H, avenae in all respects. 
Although Helminthosporium teres has been confused with both H, 
gramineum and H, sativum, the spores of the netblotch fungus are cer¬ 
tainly not readily mistaken for those of the latter species. The writer's 
material, collected near Madison, Wis., October 28, 1919 (after a pro¬ 
tracted period of damp, cloudy weather under conditions apparently 
nearly optimum for sporulation) showed these structures (PI. 2, Ca-f) to 
vary from 30 to 175 pt in length and from 15 to 22 /u in width. In respect 
to spore length, therefore, the species is altogether superior to the two 
congeneric forms occurring on barley and inferior to H. bromi in approxi¬ 
mately the same degree as the latter is inferior to H, giganteum. From 
I to 10 septa were found present, the septa, after the delimited segments 
have partly rounded up, being associated usually with perceptible con¬ 
strictions in the contour of the spore. As the constriction at the proximal 
septum is especially pronounced and constant, and the basal, as well as 
the apical end, is rounded off in a hemispherical form, the basal segment 
is given a subglobose shape as characteristic for the species as are the 
basal segments of H. tritici-repentis and H. bromi. 
The spores are subhyaline in color, like those of the latter two species, 
when newly proliferated, but become greenish fuliginous or yellowish 
when older, usually, however, not assuming a tinge quite as dark as the 
brownish yellow of fully matured spores of the stripe fungus, and con¬ 
sequently never approximating the dark olivaceous color of those of H. 
sativum. Associated with this light color is a thin peripheral wall, the 
drawings of Saccardo {126) and some other authors showing the outer 
wall as a thick structure being apparently based on dead material. While 
the spores of H. gramineum usually are entirely straight, those of the net- 
blotch fungus not infrequently exhibit slight irregular crooks (PI. 2, Cf), 
in which respect as well as in the general subcylindrical shape and location 
of the hilum within the contour of the basal end, a similarity to H. bromi 
and H. tritici-repentis again is evident. 
