654 
Journal of Agricultural Research 
Vd. XXIV, No. 8 
distal portion, measuring usually approximately 6 n as compared with 
7 to 9 // for those of H, teres and H, avenae. 
The spores vary from subhyaline when newly proliferated to yellowish 
brown when fully mature, never, however, becoming dark olivaceous, 
like those of H, sativum. They are (PL i, Ba-h) typically straight or 
very slightly curved; subcylindiical, but quite frequently widest in the 
basal portion and tapering more or less toward the apex. Both apical 
and basal ends are rounded off, abruptly presenting a hemispherical 
contour. The peripheral wall is relatively thin as in other species having 
subhyaline or light-colored spores. The septa vary from i to 7 in all 
the material the writer has had occasion to examine, and are only infre¬ 
quently associated with perceptible constrictions (PI. i, Bf, h), while in 
the spores of H, teres (PI. 2, Ca) constrictions are more common and often 
moderately pronounced. Germination takes place promptly when the 
spores are mounted in water, usually within 30 minutes. Germ tubes 
are proliferated usually from both end segments and from several inter¬ 
mediate segments, the numbers produced from the basal segment varying 
from I to 3, while the other segments rarely give rise to more than one 
(PI. I, Ca-d). 
A phenomenon undoubtedly related to germination is the production 
in nature of secondary spores or short secondary fructifications from 
primary spores, that in this species occurs to a greater extent than in the 
other congeneric forms parasitic on cereals, and which suggests com¬ 
parison, for example, to H, catenarium. The secondary spores are not 
generally produced directly on the apex, but on a sporophoric process 
arising from the apex (PI. i, Dc, e) or obliquely from the apical cell 
(PL I, Da, d) or less frequently laterally from the basal segment (PL i, 
De). Not infrequently the process remains short and gives rise to only 
a single spore (PL i, De), while again it grows out into a sporophore bear¬ 
ing half a dozen spores (PL i, Dc). Evidently such secondary develop¬ 
ment may take place after the primary spore has become detiied from 
the sporophore on which it was borne, as it usually is associated with a 
collapse of some or all segments of the primary spore involved (PL i. Da). 
The secondary spores (PL i, Dca-cc, Dda) may be nonseptate or show 
I to 3 cross walls; they are, in general, decidedly smaller than the pri¬ 
mary ones, the minimum dimensions approximating ii by 20 (PL i, 
Dca-cc, Dda). As the smaller individuals of the one order can not be 
readily distinguished from the larger individual of the other, all grada¬ 
tions may be found between these magnitudes and the maximum dimen¬ 
sions of the primary spores, 20 for width, 105 /z for length. The maxi¬ 
mum measurement for spore length of H. gramineum is thus barely two- 
thirds as large as that of H, teres —a fact of great importance in identi¬ 
fying the species by microscopical examination. 
Diedicke (29), in 1903, reported from Germany the discovery of an 
ascigerous stage of Helminthosporium gramineum in a species of Pleo- 
spora, which he found to correspond fairly well to P, trichostoma (Fr.) 
Winter. However, as the latter appeared to include a number of forms 
parasitic on different hosts but not interchangeable in their host rela¬ 
tions, he regarded it as a collective species, and separated it first into a 
number of biologic races {28) which later he recognized as individual 
species (^9). The perithecial form collected on old barley straw in a 
field that had been affected severely with the stripe disease was accord¬ 
ingly referred to a newly derived species, P, graminea. On inoculating 
barley leaves with sclerotia of the fungus, typical symptoms of stripe 
