May a6 ,1923 
Graminicolous Species of Helminthosporium 
643 
WHITE BLAST 
Helminthosporium turcicum Pass, produces on maize (Zea mays L.) a 
type of injury that is probably more common than might be supposed, 
as it is likely to escape detection. The green color of the affected tissue 
disappears completely, leaving a chlorotic area that increases in size 
until it may be several inches long and perhaps one inch in width. 
Owing to the large size of the com leaf blade, the desiccated areas, which 
may be surrounded, moreover, by a narrow, brownish, marginal zone, 
contrast sharply with the surrounding green tissue and are quite Teadily 
recognizable as due to the agency of a parasite. However, with the 
larger number of graminaceous hosts, having much smaller leaves, 
proportionately large segments of the blade are involved at once; wither¬ 
ing usually starts at the tip and proceeds downward, thus simulating the 
appearance of withering due to drought. It may be mentioned that 
the parasitic nature of species of Helminthosporium not associated with 
dark discoloration or conspicuous pathological changes in the mechanical 
properties of the plant tissues involved manifestly can not be ascertained 
definitely by observation alone. Helminthosporium dematioideum Bub. 
and Wrob. on the leaves of sweet vernal grass (Anthoxanthum odoratum 
L.) may be cited as an example of a considerable number of fungi, the 
relation of which to their host or substratum is certainly not as obvious 
as might be desired. 
other types op injury 
Differing quite markedly from all of these forms of injury is that 
caused by a species of Helminthosporium attacking young plants of a 
species of Paspalum, provisionally identified as Paspalum hoscianum 
Fluegge, which will be further discussed as H, micropus. The first evi¬ 
dence of infection appears as a water-soaked area, the tissue of which 
has lost all its rigidity. The condition suggests an injury such as might 
have been brought about by the application of a few drops of boiling 
water. The affected area frequently dries and shrivels, often leaving 
the surrounding tissue quite normal; or if the affected spot is large 
enough to interrupt the vascular communications the more distal portion 
of the leaf blade may gradually wilt without any further advance of the 
fungus. 
In the attack of Helminthosporium ravenelii Curtis on Sporoholus 
indicus (D.) R. Br. it is quite impossible to notice either wilting or dis¬ 
coloration. The fructifications of the fungus grow directly out of the 
inflorescence in a dense, dark, brownish green, velvety layer, the latter 
being so conspicuous and abundant as to have suggested the term 
“smut grass“ as common name for the host. The infection undoubtedly 
is altogether local, for even when the larger portion of the panicle has 
been overgrown with the fungus, the exposed parts present an appear¬ 
ance not greatly different from that of an entirely healthy inflorescence. 
The fungus discussed in this paper as H. oryzae, when developing on the 
inflorescence of rice, shows an approach to H. revenelii in the crowded 
habit of its sporophores. 
TAXONOMIC CHARACTERISTICS 
The definition of the genus Helminthosporium Link as recognized 
in the large works of Saccardo {izSy v. 4, p. 402) and Lindau (< 5 *^) has 
been very generally adopted by mycologists. The genera Brachysporium 
