May a6 ,1923 
Graminicolotis Species cf Helminthosporium 
727 
diately around the rather inconspicuous hilum visible within the contour 
of the base. Normal germination of mature spores proceeds by the 
proliferation of two polar germ tubes, one from each of the thin-walled 
regions (PI. 30, Cd, e); while less mature, subhyaline spores may produce 
germ tubes from intermediate segments as well (PI. 30, Ci, k). 
On tap-water agar the fungus grows sparsely, producing conidiophores 
and conidia (PI. 31, Aa, b; B) which, while somewhat narrower and more 
nearly colorless, are essentially similar to those found in nature. How¬ 
ever, on other substrata, as, for example, potato glucose agar, growth is 
very profuse, and owing to the blackish olivaceous color and velvety or 
felt-like texture of the mycelium, somewhat similar in general appearance 
to the growth of Helminthosporium sativum (PI. 31, D). The spores, 
although of a shape and size not entirely unlike those foimd in nature (PI. 
31, Cd, Da) in spite of many markedly irregular examples (PI. 31, Db, c) 
frequently exhibit such pronounced departures in respect to coloration as 
to suggest the suspicion that one might be dealing with a separate species. 
Instead of a uniform fuliginous, brownish or dark olivaceous color, they 
show in the same culture all gradations from subhyaline to deep oliva¬ 
ceous, and in some instances are so nearly black as to appear opaque 
even when a moderately bright illumination is used. Associated with 
the dark coloration is a peripheral wall conspicuously and uniformly thick 
except over the apical and basal regions involved in germination. (PI. 
31, Ca.) Frequently one or both end segments are altogether subhyaline 
(PI. 31, Cb, c, e, Db), in sharp contrast to the other segments, and occa¬ 
sionally one or more intermediate segments show similar differentiation 
(PI. 30, Cb, e). But whatever its position, the subhyaline segment is 
always set off from the dark segments by greatly accentuated heavy 
septa. Manifestly, coloration, and, in a smaller measure, structure are 
contingent here upon conditions not usually present wten the fungus 
grows on rice plants under natural conditions or on tap-water agar in 
artificial culture. 
In general morphological characteristics Helminthosporium oryzae sug¬ 
gests comparison with //. sativum^ H, monoceras, and H. turcicum. From 
H, sativum it may be distinguished by the greater length and the more 
pronounced tapering toward apex and base, characteristic of its conidia. 
On the other hand, the conidia of H, oryzae taper less markedly toward 
the basal end than the homologous structure of the parasites on barn¬ 
yard grass and on corn; and the hilum is contained within the contour 
of the base, not protruding as in the latter two species. Certainly Far- 
neti*s (jp) belief that H. oryzae and H, turcicum represent specifically 
identical fungi seems altogether incredible, in view of the well-defined 
morphological differences between the parasite affecting rice and the form 
causing leaf-blight of maize. 
During recent years methods for controlling the brown-spot disease 
have been investigated by Nishikado and Miyake (94) in Japan, where it 
constitutes one of the most serious troubles affecting rice culture. In 
the province of Okayama, for example, 90 per cent of the seedlings in the 
seed-bed were found affected to a greater or less extent, and sometimes 
practically all the seedlings bore lesions, making it difficult to find entirely 
healthy specimens. Controlled experiments brought to light the fact that 
this very general seedling infection was largely attributable to infected 
or contaminated seed. It was found that the spores of Helminthosporium 
oryzae are killed by immersion in water at a temperature of 51° C. for 10 
minutes, while air-dry rice seed is not injured by immersion for 10 to 15 
