May 36,1923 
Graminicolous Species of Helminthosporium 
711 
inclined to make irregular turns and unusual angles than those of most 
congeneric forms. (PI. 23, Ka-c.) 
The specific name leucostylum, descriptive of the conidiophores of 
the fungus, is suggested. 
DIAGNOSIS 
Helminthosporitun leucostylum, n. sp. 
Occurring on withering or withered leaves of Eleusine indica (L.) Gaertn. 
Conidiophores subhyaline to light fuliginous, emerging from stomata singly or in 
groups of 2 to 6: measuring usually 5 to 6 /x in diameter by 35 to 100 ju in length; 2 to 
8 septate, the cross walls usually inserted at intervals of 10 to 30 //; producing the 
first spore 20 to 50 /* from base, and successive spores at intervals of 5 to 25 /x, the 
points of attachment being marked by circular scars at the apices of usually very 
pronounced geniculations or more rarely at the tips of short lateral branches. 
Spores dark olivaceous; measuring ii to 17 by 15 to 67 ju, typically approximately 
15 by 50 I to 6 septate, typically 3 to 5 septate, the septa never associated with 
constrictions; usually narrowly ovoid, widest well below middle, near a point approxi¬ 
mately one-third of distance from base to apex, the proximal portion exhibiting a 
paraboloid contour, the distal portion tapering uniformly to the narrow apex, then 
abruptly rounded off; more rarely and atypically subcylindrical, and, when short, 
ellipsoidal, ovoid or obovoid; exospore thick except at a small subhyaline spot at 
apex and in narrow subhyaline zone immediately surrounding the hilum which is 
contained within basal contour. Spore germinating by production of 2 polar germ 
tubes, one from each of the small hyaline regions. 
Habitat. —Collected near Washington, D. C., October 9, 1921. 
During August and September, 1922, after this paper had been sub¬ 
mitted for publication, the fungus was collected repeatedly on Era- 
grostis major in several localities in Virginia and Maryland near Wash¬ 
ington, D. C., generally occurring together with Helminthosporium 
rostratum and, more rarely, also with H, giganteum. It was found to be 
present in abundance on ^e same host near Seaford, Delaware, where 
collections were made August 29, 1922. The relation of H. leucostylum 
to Eragrostis major is an obviously parasitic one, as on green and other¬ 
wise healthy leaves the fungus gives rise to dead regions that appear on 
the upper (adaxial) side, typically as sharply delimited medium-gray 
linear streaks measuring 0.3 to 0.5 mm. in width and 5 to 20 mm. or more 
in length. The sporophores ajise on the killed areas usually in dense 
clusters which often are found in longitudinal alignment. Apparently 
they develop earlier and often in greater abundance on the upper side 
than on the lower side of the le^, probably emerging from between 
epidermal cells as well as from the stomata. On being dried, the diseased 
leaves, like those of similarly affected goose grass, split readily into 
longitudinal shreds along the streaks representing the lesions. 
The occurrence of the fungus on Eragrostis major suggests its com¬ 
parison with Helminthosporium hadotrichoidesy described on the same 
host from Delaware by Ellis and Everhart {36) in 1888. According to 
the diagnosis given by these authors, H, hadotrichoides would appear to 
produce conidiophores not greatly unlike those of the fungus under con¬ 
sideration in size and septation, but differing from them in being of a 
smoky brown'' color, and in having “the apex swollen so as to form a 
knob like the head of a pestle, 8 to 12 ju in diameter." A modification so 
striking and unusual could scarcely fail to arrest attention, yet was 
certainly never observed in any material examined by the writer. The 
conidia, which are rather inadequately described as “ clavate-obovate, 
or clavate cylindrical or yellowish brown" without any mention being 
made either of their dimensions or septation, would seem to differ some¬ 
what, at least in coloration, from the corresponding dark brown or dark 
olivaceous structures of the parasite discussed in the present account. 
