May 26,1923 
Graminicolous Species of Helminthosporium 
having been developed after the first two or three had perhaps commenced 
to proliferate spores. 
By far the most distinctive characteristics for taxonomic purposes 
are to be found in the spore. Within the genus these structures show 
an unusual range of difference with regard to size. Those of Helmin¬ 
thosporium giganteum, for example, which are among the largest repro¬ 
ductive bodies produced by any group of fungi, exceed those of the smaller 
species like H. dematioideum about twice in width and ten times in lengthy 
although the latter can not be regarded as especially small. The length 
of the spore, particularly in the case of those species in which this body 
is nearly colorless and straight cylindrical like //. tritici-repentis Died. 
H. hromi Died., H. teres, and H. giganteum, is subject to great variation, 
the length of the smaller ones often scarcely exceeding their width. 
For this reason the magnitudes approaching the maximum are to be 
regarded as the more characteristic of the species. The width of the 
spores of any particular species on the other hand is much more apt to be 
nearly uniform, regardless of considerable differences in length. 
With respect to coloration, the spores represented in the genus exhibit 
all gradations between the subhyaline condition present, for example, 
in Helminthosporium giganteum and H, tritici-repentis, to the dark 
olivaceous hue characteristic of H. sativum and a considerable number 
of closely related congeneric forms. Most of the species are interme¬ 
diate betvreen these extremes—^yellowish, yellowish brown, and brown. 
A few species have spores with subhyaline end cells, all the other cells 
being uniformly dark; or the middle cells may be dark, with the color 
becoming perceptibly fainter toward the ends. 
The spores of most forms of Helminthosporium are characterized by 
some peculiarity in shape by which they can be often recognized with a 
high degree of certainty. The general contour may be straight cylin¬ 
drical as in H. avenae Eidam, curved ellipsoidal as in H. sativum, or 
tapering toward the tip as in H. dictyoides. The basal end is usually 
most characteristic. In H, teres, the proximal cell is hemispherical; in 
H. bromi, hemi-ellipsoidal; in H, tritici-repentis, elongate conical* with 
rounded apex, thus crudely suggesting in outline the top or bottom 
aspect of a snake's head. In H, monoceras, the basal half tapers grad¬ 
ually toward the basal end, which is abruptly rounded off; in H, turcicum 
the tapering is more abrupt and continues to the insertion of the hilum. 
The same is true in H, micropus except that here the extreme basal end 
is drawn out somewhat, the contour being slightly concave near the 
hilum. In this connection, it may be stated that the hilum—^that is, 
the more or less calloused region at the base of the spore, marking the 
place of attachment to the sporophore—^may be represented by a con¬ 
spicuously protruding modification as in the two species last mentioned; 
or, as is much more frequently true, it is visible as a dark spot situated 
altogether within the contour of the spore wall. In a few species the 
hilum is not at all conspicuous, as in H. giganteum, where it appears 
as a small wedge-shaped basal prolongation, with a delicate single- 
contoured confining membrane. 
As a good deal of the taxonomic literature based on dead herbarium 
material gives a wrong impression of the structure of the spore, par¬ 
ticularly with reference to its walls and septa, a few remarks may be 
justified here. The developing spore remains nonseptate during the 
earlier stages of growth, usually until its definitive size has been largely 
