May 26,1923 
Graminicolous Species of Helminthosporium 
705 
to i.o mm. in width by i to 3 mm. in length, without any indication of a 
zone of etiolated tissue, as is present on leaves of Bromus inermis attacked 
by Helminthosporium bromi. The lower leaves were largely withered, 
apparently as a result of the same pathological conditions present in the 
younger foliage, and exhibited an abundance of similar elliptical spots, 
which here, however, were somewhat larger, often attaining a width of 1.5 
and a length of 5 mm. The older spots, moreover, showed less distinct 
outlines, having faded to a dull medium brown. On the leaf sheaths the 
discoloration was less intense than on the blades and extended over 
larger, less well-defined areas, especially near the base of the plant, the 
lower portions of the basal sheaths being often quite completely tinged 
with a diffused brown. In short, the symptoms were very similar to those 
previously observed on Poa pratensis attacked by H. uaganSy representing 
a combination of foliar lesions like those caused by H, sativum on barley, 
and a footrot condition such as is caused by the latter fungus on wheat; 
and a cursory examination of the material might readily have led one to 
attribute the injury to either one or the other of these two parasitic 
species. 
The microscope did, indeed, reveal an abundance of fructifications of 
Helminthosporium on the older withered leaf blades and dead basal 
sheaths of the host, which by their distribution left no doubt as to their 
relation to the foliar lesions observed. Somewhat to the writer's sur¬ 
prise the fungus, however, was markedly different in a number of details 
from both i/. sativum and*//, vagans. The dark brown sporophores 
(PI. 20, Ca-Cc), which usually emerge from the stomata singly or in 
groups of two or three, and are only slightly greater in diameter than 
those of //. sativum^ attain a height frequently more than twice as great 
as those of the latter species and in a corresponding measure are more 
remotely septate. The spores (Pi. 20, Da-n), the points of attachment 
of which are marked by geniculations occurring at moderately long inter¬ 
vals, are the most characteristic structures, however, being of a form 
so distinctive that they would readily be recognized in a mixture with 
spores of H, sativum or //. vagans, or indeed of any species discussed in 
the present paper. Usually widest near the middle, they taper gradually 
and quite uniformly toward the distal end until, at a point where the 
diameter scarcely exceeds one-third of the maximum diameter, they 
are abruptly rounded off to form the tip. The proximal portion of the 
spore tapers toward the base, usually somewhat more sharply, and the 
tapering is here prolonged uniformly until the diameter often represents 
less than one-sixth of the maximum diameter. A short distance above 
the hilum the contours usually exhibit a slight convexity. The hilum 
protrudes quite conspicuously, the fungus in this respect resembling 
H. turcicum and //. rostratum. 
The conidia on being mounted in water germinate readily by two polar 
germ tubes, one from each end cell. (Pi. 20, Ea-c.) As has been men¬ 
tioned in another connection, the spore wall is perceptibly thinner in the 
regions from which the germ tubes always are produced; that is, at the 
apex and in the narrow contracted zone adjacent to the hilum. Owing 
to the absence of olivaceous coloration from the modified regions, the 
portion of the spore near the hilum appears conspicuously subhyaline. 
On the types of artificial media ordinarily employed in laboratories 
the fungus grows luxuriantly, though without manifesting any cultural 
characters which would enable one to distinguish it readily from other 
dark, abundantly sporulating congeneric species, as for example, HeU 
39365—23-5 
