7o6 
Journal of Agricultural Research 
Vo). XXIV, No. 8 
minthosporium sativumy H. halodes, or even H. turcicum. On media 
containing much organic food material, like potato glucose agar, a 
black velvety mat of sporophores results; on less concentrated media, 
like tap-water agar or commeal agar, growth is much less profuse and 
the individual fructifications are scattered sparsely over the surface, 
A comparison of Plate 21 with Plates 19, 23, and 25 reveals the similarity 
of the fungus to the other species mentioned in respect to general habit, 
mode of development, and relationship of conidiophore and imbedded 
mycelium. The conidia, which are produced in abundance (PI. 21), 
although in general smaller than those developed in nature, are other¬ 
wise quite similar to the latter in shape and septation, and show very 
clearly the characteristic tapering of the acuminate basal portion toward 
the protruding hilum (PI. 21, F). 
Although observed thus far only at one station, perhaps largely be¬ 
cause the host is not especially abundant in the region in which the 
writer carried on his studies, the fungus appears to be a parasite of 
more than moderate virulence. It would not be surprising to find it 
fairly common in agricultural regions where barnyard grass occurs to 
some extent.^^ In this connection it may be mentioned that Schwein- 
furth and de Thuemen (131) reported Helminthosporium flexuosum 
Corda ( = Brachysporium flexuosum [Cda] Sacc.) on the culm and inflores¬ 
cence of Echinochloa crus-galli in Egypt. While there is some reason 
to doubt that the fungi from various sources that have been referred by 
different writers to Corda’s species are all identical with each other, 
such identification may safely be interpreted to indicate spores of a 
relatively small size, measuring approximately 8 to 16 /z in length, and 
divided by 2 or 3 septa. Manifestly the fungus in question is altogether 
different from the Egyptian form. It is apparently new to science and, 
owing to. the characteristic shape of the proximal portion of its spores 
crudely suggesting that of a horn, is designated here as Helmintho¬ 
sporium monoceras. 
DIAGNOSIS 
Helminthosporium monoceras, n. sp. 
Producing dark brown or chocolate-colored spots on leaf blades of Echinochloa 
crusgalli (D.) Beauv., at first measuring 0.3 by i mm., later increasing in size and 
eventually attaining linear dimensions five times as large. On the sheaths the spots 
are larger, less intensely colored, and tending to become confluent, especially toward 
the base of the plant, where they frequently merge into a generally diffused light 
brown discoloration; tiie foliar structures attacked dying prematurely, the withering 
proceeding from the tip toward the base. 
Conidiophores appearing after the death of the affected tissues, thick-walled, emerg¬ 
ing usually from stomata, singly or in groups of 2 or 3; meastuing 6 to 9 /u in diameter 
and 120 to 325 ju in length; dark brown or olivaceous except at the extreme tip which is 
nearly hyaline; usually 3- to 7-septate, the septa occurring at intervals of 30 to 60 ju; 
producing the first spore 120 to 200 from the base, its position, as well as that of sub- 
quent spores, indicated by scars at moderate geniculations separated at intervals 
varying from 5 to 50 /*. 
Spores yellowish when young, becoming dark olivaceous when fully matured, 
exactly similar in color to Helminthosporium sativum, H. vagans, and H. rostratum; 
measuring usually 15 to 22 in diameter and 40 to 150 /* in length; typically straight or 
showing a slight crescentic or sigmoid cxuve, yet not infrequently exhibiting more 
pronounced irre^lar or geniculate bends; widest at the middle segment except where 
modified by an irregular median constriction, typically tapering gradually toward the 
tip to one-tiiird or one-half of its maximum width, then bluntly rounded off; tapering 
toward the base to approximately one-sixth of the median diameter, the contours then 
Since this text was written the fungus has been collected on barnyard grass at Bladensburg, Md., 
and Takoma Park, Md., both of these stations being located in the immediate vicinity of Washington, D. C. 
