674 
Journal of Agricultural Research 
Vot. XXIV. No. 8 
very promptly, producing lateral or oblique germ tubes indiscriminately 
from middle and end cells, the number of tubes originating from any par¬ 
ticular segment not usually exceeding two. Anastomoses of newly 
proliferated germ tubes are not infrequent, the germination of spores 
lying in juxtaposition, thus often yielding scalariform figures united by 
several hyphal connections. (PI. 8, Db-c.) As has been pointed out 
previously, when the fungus is cultivated on potato agar media, anas¬ 
tomosis of hyphae is associated often with the production, below the 
surface of the substratum, of numerous groups of inflated segments. 
Of the latter, a small proportion develop into subspherical sclerotia, 
usually from 0.2 to 0.5 mm. in diameter, the presence of which in agar 
cultures (PI. 9, C) is characteristic of the fungus, and which, judging 
from their size and structure, doubtless represent immature perithecia. 
In Germany, Diedicke (28) noted the appearance on Bromus asper of 
the sclerotia or young perithecia as early as July 26. This date corre¬ 
sponds quite closely with their appearance in southern Wisconsin. When 
fully matured, they consist of a subglobose portion imbedded within the 
somewhat distended leaf tissue, usually from 0.3 to 0.4 mm. in diameter 
and tapering into an irregular ostiolar beak protruding approximately 
o.i mm. above the broken epidermis. A variable number of septate, 
tapering, sterile bristles usually are to be found near the tip of the ostiolar 
modification; and although it is not improbable that in some seasons 
conidiophores may be produced abundantly from the perithecium as in 
Pyrenophora tritici-repentis and P. ieres, oiily a sparse production was 
observed during the season of 1920. 
The development of the asci appears to be delayed until spring, 
beginning evidently with the warmer weather usually experienced in 
our northern latitudes late in February or early in March, and proceeds 
slowly, until toward the middle of April they readily discharge their 
spores when mounted in water. In all morphological details the asci 
closely resemble those of Pyrenophora tritici-repentis, although they 
usually seem to be somewhat larger. The difference, which is not pro¬ 
nounced, becomes, perhaps, most evident during the process incident to 
to spore discharge, as the asci of the parasite on brome grass appear to 
undergo perceptibly greater distention before the outer membrane is 
burst than the asci of the congeneric parasite on quack grass. Plate 9, 
D, representing an ascus partly distended, measuring 300 /i in length and 
65 iJL in diameter, shows the 8 spores in distichous arrangement immersed 
in granular epiplasm, the thickened ringlike modification at the apex, 
and the short well-defined stipe common to both species. 
The ascospores, light brown in color and measuring 20 to 30 n by 45 
to 72 /A, are uniformly divided by 3 transverse septa. Longitudinal 
septa may be absent, or one or both of the middle segments may be 
further divided by a longitudinal wall. Germination takes place by 
the production of a germ tube from several or all of the segments. Cul¬ 
tures of the fungus derived from ascospores differ in no particular from 
those derived from conidia. 
Because of the distinctive and extraordinarily large conidia character¬ 
istic of the parasite and its production of sclerotia on various kinds of 
agar media, the writer agrees with Diedicke in regarding the fungus as 
an independent species. In this connection it may be mentioned that 
Diedicke (28) first reported it as a biological species of the stripe fungus, 
a disposition which Noack (95), who recognized Pleospora trichostoma as 
the ascigerous stage of Helminthosporium gramineumy later sought to 
