668 
Journal of Agricultural Research 
Vol. XXIV, No. 8 
acteristic of the foliage of barley infected with H. gramineum. The 
conidial fructifications of H. tritici-repentiSy moreover, make their appear¬ 
ance scattered sparsely here and there over the surface of the dead leaves, 
not crowded on the affected parts like those of the stripe fungus. It is 
evident, therefore, that at least in some respects, the development of 
H. tritici-repentis on the host presents closer analogies to types like 
H. dematioideum and //. siccans than to //. gramineum. 
The dark olivaceous usually 3 to 6 septate sporophores of Helminthospo- 
rium tritici-repentis (PI. 5, Da-f) emerge from the stomata, or, more 
frequently, from between epidermal cells. Above the somewhat swollen 
basal segment, they vary in width from 7 to 9 /i, being thus perceptibly 
inferior in this dimension to the homologous structures of H. hromi. In 
length they vary from 80 to 220 /i. The conidia (PI. 5, Ba-m) are typi¬ 
cally subhyaline, straight-cylindrical, from i to 9 times septate, from 
12 to 21 ju in diameter, and 45 to 175 ju in length. As in H. teres^ the septa 
usually are associated with slight but perceptible constrictions in the 
contour of the thin peripheral spore wall. 
The most distinctive peculiarity in the spores of this species is found 
in the shape of the basal segment, the proximal portion of which usually 
tapers abruptly in the manner of a cone to be rounded off or flattened 
near the hilum. In profile the basal segment thus is remotely suggestive 
of the horizontal aspects of the head of a snake, while the distal end 
usually is rounded off in a hemispherical form (PI. 5, Ba, e, j, k). It 
may not be superfluous to add that departures from this type are not' 
infrequent. The 2 or 3 terminal segments may taper appreciably 
toward the distal end (PI. 5, Bb, c, d, m) or the width of the different 
segments may vary considerably (PI. 5, Bg, m) or the axis of the spore 
may be somewhat curved (PI. 5, Be). Germination begins within an 
hour after the spores are mounted in water. Each segment is capable of 
producing a germ tube, the larger spores (PI. 5, C) thus producing from 
6 to 8 or more germ tubes, although usually one or several cells may 
remain seemingly inert. 
The*ascigerous stage of this species of Helminthosporium, as mentioned 
before, occurs in great abundance on the dead culms of Agropyron repens 
and to a small extent also on the leaves, particularly on the sheaths. 
(PI. 6, Ba-b.) Although the black perithecia are readily discernible in 
autumn, their subsequent maturation appears to be rather slow. In 
the vicinity of Madison, Wis., mature perithecia have been collected 
from early in April until well toward the end of May. When developing 
in the looser tissue of the leaf, especially after some decay has taken place, 
the imbedded portion usually is distinctly subspherical, from 0.2 to 0.35 
mm. in diameter, and tapers into a short, well-defined beak as shown in 
Plate 6, A. However, when developing in the harder tissue of the culm, 
the perithecium usually is much more irregular in shape and the beak 
less readily recognizable as a special modification. In any case, the beak 
usually bears near the ostiole a number of dark-brown sterile setae which 
may be straight or flexuous, continuous or several times septate, occasion¬ 
ally branched, and varying in number from several to over a score. As 
Diedicke pointed out, under certain conditions a large number of coni- 
diophor^ and conidia may be produced from the upper side of the 
perithecium, the further development of the ascospores, if not complete, 
then often being checked altogether. This tendency toward conidial 
production usually is well expressed in the case of those perithecia found 
on the upright culms; on the other hand, when the host material is loosely 
