May 26,1923 
Graminicolous Species of Helminthosporium 
715 
{i28)y 5 to 8; Ducomet (54), 3 to 8; Butler (19), 3 to 7; although the 
range 3 to 5 given by Cooke and Ellis (24), while perhaps expressing an 
average condition, would not seem to be large enough. It may be noted 
that the septa are somewhat tardy in making their appearance and, as a' 
result, many of the spores when newly proliferated show segments of a 
length not usual in species of similar dimensions. (PI. 24, Ba, g, h.) 
The peripheral spore wall always is relatively thin, the accounts of 
Saccardo {128) and Schwarze (150), for example, as well as figures like 
those of Massee (90) and of Smith (155), describing or illustrating a thick 
membrane, being apparently based upon dead material. As usual in 
species of Helminthosporium, the thin peripheral wall is associated with 
a relatively light color of the conidia. This color varies from a subhyaline 
light fuliginous tint when the spores are newly proliferated to a moderate 
fuliginous, greenish yellow, yellowish brown, or pale olive when they are 
fully mature. The dark olivaceous color, characteristic of the conidia 
of Helminthosporium sativum, H, monoceras, or H, vagans, is never 
approached, descriptive phrases like that given, for example, by Saccardo 
(i2i^), “olivaceofuscis,'' indicating such approximation, being evidently 
quite erroneous and misleading. 
A morphological feature that the writer feels inclined to emphasize, 
particularly as a diagnostic character useful in separating Helminiho- 
sporium turcicum from most of the congeneric forms wi& which the 
student of economic botany has to deal, is the protruding hilum. (PI. 25, 
C.) This apiculate basal protuberance, while rather minute, is uniformly 
present, regardless of whether the proximal portion of the spore is dis¬ 
tinctly tapering or more nearly rounded. It must, therefore, be consid¬ 
ered apart from the basal contour of the conidium. That it has not been 
mentioned in the writings of previous workers is somewhat surprising. 
Ideta (65), it is true, figured the proximal cell as being conspicuously 
constricted at the base. If this attenuated portion was intended to 
represent the part of the conidium by which the latter is inserted on 
the conidiophore, its proportions would seem, in view of the condition 
obtaining in American material, greatly exaggerated. 
As has been pointed out or figured in the publications of Ducomet (54), 
Smith (JJ3), Butler (19), Reinking (117), and Zhavoronkov {162), 
the spores of Helminthosporium turcicum germinate regularly by the 
production of two polar germ tubes, one from each end. (PI. 15, Db, c.) 
Occasionally an intermediate segment may proliferate one or several 
lateral germ tubes. Such atypical germination apparently is more 
likely to occur with newly proliferated subhyaline conidia (pi. 25, 
Da, d), or with abnormally curved spores than with fully mature spores 
of typical shape; and sometimes occurs as the result of injury and 
death to one of the end cells. 
The fungus develops well on the media usually employed in laboratories. 
On substrata rich in organic food materials, as for example, potato glucose 
agar, a luxuriant growth of grayish black aerial mycelium is produced. 
On substrata poorer in organic substances, like tap-water agar, growth 
is less luxuriant, but may be studied to better advantage. The embedded 
mycelium anastomoses abundantly with the resultant production of 
numerous complexes consisting of dark brown lobulate segments. The 
sporophores arise from the prostrate fuliginous hyphae that compose a 
large portion of the aerial growth. They are somewhat inferior in 
diameter to those developing in nature, measuring approximately 6 in 
width, but, at the same time, are considerably longer. As the first spore 
