80 
species or strains of Helminthosporium. These are throughout referred to 
by number rather than by name, partly for brevity and partly because 
the species of many of the races had not been determined, while in some 
cases the names were of more or less doubtful reliability. That the reader 
may formulate his own judgment of these forms, introduced for comparison, 
a complete list of them is given in the appendix (pages 181-184) together 
with certain notes regarding them. 
VARIOUS AGARS AS MEDIA 
Corn-meal agar in Petri dishes.—This medium, prepared after the di- 
rections given by Shear and Stevens (104), was found to be admirably 
suited to Helminthosporium and was the medium chiefly used. 
The fungus grew rapidly, the colony being at first nearly hyaline 
both in the submerged and aerial parts, but when a diameter of about 2-3 
cm. was attained the whole colony became much darker. Profusion of 
conidia was the chief factor in giving the dark hue to a colony, the slight 
darkening of the mycelium having little to do with it. The aerial mycelium 
varied largely with change of conditions, sometimes being very scant 
and at other times 5-6 mm. high, with windrow effects corresponding 
with the zones. After the colony was about 3 cm. in diameter zonation 
became quite pronounced, the zones corresponding approximately with 
the growth of each day. At room-temperature the colony attained a 
diameter of about 4.5 cm. in six days. Conidia-production was quite 
uniform over the surface of the colony unless checked by some growth- 
inhibiting cause, as drying, cold, or the antagonism of another colony 
near by, when it was much increased, as evidenced to the eye by black 
bands in such regions. By transmitted light the mycelium, and to some 
extent the conidia at certain ages, had a distinctly greenish tinge. H. No. 1 
could be distinguished from H. Nos. 5-8, which were paler and produced 
fewer conidia. H. No. 6 approached nearer to H. No. 1 in these regards 
than did the others. H. Nos. 3, 4 (see Pl. IX), 6, 15-17, and 18 typically 
developed more.aerial white mycelium than did H. Nos. 1 and 14. H. No. 
36 was of very distinct character owing to large development of aerial 
mycelium (see Pl. X). 
Corn-meal agar in Freudenreich flasks.—Vhe flasks, of about 100 c.c. 
capacity, each received 50 c.c. of agar and were slanted. The large amount 
of nutriment available and the sustained moisture gave noteworthy 
characters. At 7 days, with H. No. 1, the surface of the slant was com- 
