724 
Journal of Agricultural Research 
Vol. XXXI, No. 8 
Perithecia developing on disintegrating host tissues, usually early erumpent, 
black, often bearing a variable number of conidiophores, but no differentiated 
sterile setae; ascigerous portion subglobose or more frequently somewhat ellip¬ 
soidal, measuring usually 0.4 to 0.6 mm. in transverse diameter and approxi¬ 
mately 0.4 mm. in vertical diameter; ostiolate beak well defined, subconical or 
paraboloid, approximately 0.15 mm. at base and 0.15 mm. in length; interior 
composed of colorless pseudoparenchymatous tissues consisting of vertically 
oriented appressed filaments, diminishing usually with the development of the 
asci. 
# Asci numerous, short-stipitate, with rounded apex, subcylindrical but some¬ 
times becoming more inflated before discharge; 160 to 180 n in length by 24 to 
28 fi in diameter; containing 1 to 4, typically 4, spores. Ascospores filamentous, 
fuliginous, thin-walled; in somewhat immature condition, of uniform diameter of 
6 to 7 ju, except at extremities which are somewhat attenuated; later becoming 
five to nine times septate, the septa usually associated with perceptible constric¬ 
tions, the delimited segments becoming somewhat swollen so as to attain in 
places a diameter up to 9 n) thrusting firmly against apex and into base of stipe 
in multiple heterostrophic helicoid arrangement with approximately four turns 
to each spore; measuring 130 to 340 n in length; discharged simultaneously, often 
with mucous envelope; germinating promptly by producing indiscriminately 
from any or all segments, either laterally or terminally, germ tubes up to eight 
in number, from 3.5 to 5.0 m in diameter. 
Conidiophores arising singly or in groups of two or three from stomata in center 
of killed foliar parts; olivaceous, septate at intervals of 15 to 60 m; bearing the 
first conidium after attaining a length of 50 ju or more; points of attachment of 
successive spores marked by scars occurring at intervals from 10 to 40 m at genicu- 
lations not always pronounced; in nature measuring usually 120 to 170 m in 
length, but under moist condition occurring as irregularly branching sporophoric 
filaments, often exceeding 1 mm. in length. Conidia developed at 25° C. on 
diseased maize leaves in damp chambers or in pure culture on artificial media, 
fuliginous to light olivaceous, measuring 30 to 115 m in length by 10 to 17 n in 
diameter; often strongly curved, usually widest near the middle and tapering 
perceptibly toward the rounded ends; peripheral wall thin, especially in the apical 
and basal regions; basal scar broad, not conspicuous, contained within rounded 
contour; germinating promptly by the production of two polar germ tubes. 
Found on diseased leaves of Zea mays L. collected at Sanford, Fla., September 
22, 1923 (type), Brooksville, Fla., June, 1917 (fig. 3, Aa to Ae), and at Los Bafios, 
P. I., in 1918, 1919, 1920, and 1921. Perhaps identical with the more luxuriant 
Helminthosporium form widely occurring on the inflorescence of maize in tropical 
and subtropical regions. Found also on leaves of Euchlaena mexicana Schrad. 
near Los Banos, P. I., September and November, 1918; and possibly to be 
identified with H . euchlaenae Zimm. 
TAXONOMIC CONSIDERATIONS 
The pleomorphism of the maize parasite casts light on the affinities 
of a large proportion of the fungi referred to Helminthosporium. In 
their excellent account of Pleospora polytricha {15, v. 2, p. 269-271, 
pi. 29) , the Tulasne brothers set forth an association with one repre¬ 
sentative of the genus which has since been paralleled by the discovery 
of analogous relationships in other graminicolous forms —Pyrenophora 
teres (Diedicke), P. tritici-repentis (Diedicke), andP. bromi (Diedicke) 
found in Europe and America, as well as Pleospora graminea Diedicke, 
the ascigerous stage of the parasite causing the widely distributed 
stripe disease of barley, which stage, however, has hitherto been re¬ 
ported only from Europe. A significant fact concerning all the species 
of Helminthosporium achieving their perfect form as members of the 
genera Prenophora or Pleospora is that their conidia are of the straight 
cylindrical type, germinating by the production of germ tubes later¬ 
ally or obliquely from intermediate as well as end segments. In 
pure culture, on many artificial media, under ordinary laboratory 
conditions, these species are characterized usually by abundant 
anastomoses in the submerged portion of the mycelium, resulting 
in the production of complexes of inflated elements plausibly inter- 
