May 26 ,1923 
Graminicolous Species of Helminthosporium 
661 
When the spores are mounted in water, they germinate promptly, germ 
tubes being produced laterally or obliquely from intermediate as well as 
end segments, the protoplasm changing from a uniform to a regularly 
vacuolate structure. (PI. 2, Da-d.) Like those of related species they 
are relatively short lived, a considerable proportion of the segments dying 
during the first 10 to 15 days of exposure, and probably few surviving 
after two months. It appears very probable that Bakke's account (7) 
of the longevity of Helminthosporium teres was based on material not of 
this species, but of H. sativum. 
On media containing little organic food material, like tap-water agar (tap 
water 1,000 cc. agar-agar 20 gm.), or Beyerinck's agar (distilled water 
1,000 cc., ammonium nitrate 0.5 gm., dipotassium phosphate 0.2 gm., 
magnesium sulphate 0.2 gm., calcium chloride o.i gm., ferrous sulphate 
trace, agar-agar 15 gm.), aerial growth, although sparse, often consists 
almost entirely of conidial fructifications bearing spores similar in struc¬ 
ture and color to those developed in nature, but usually much shorter and 
containing only 2 to 3 septa. A strong tendency toward production of 
secondary spores is apparent also in artificial cultures, giving rise to con¬ 
ditions like those illustrated by Ravn (jj5). 
On media containing a large amount of organic food material, a profuse 
white aerial growth results, consisting partly of fluffy mycelium, and 
partly of more or less compact erect columnar masses. The submerged 
mycelium shows abundant anastomosis with the formation of numerous 
complexes composed of dark brown inflated or lobulate segments. (PI. 9, 
Fa-b.) The latter apparently represent incipient stages of sclerotia which 
on sterilized barley straw may become readliy visible to the naked eye, 
often exceeding 0.5 mm. in diameter. Ravn, although failing to observe 
any indication of ascus formation in these cultivated bodies, nevertheless 
interpreted them as immature perithecia of a Pyrenomycete, probably 
related to Pleospora polytricha (Wall.). This interpretation was justified 
by Johnson's (69) discovery in Wisconsin of the ascigerous stage of the 
netblotch parasite in a fungus he refeired to the genus Pleospora, the 
specific identity of the stages in the pleomorphic forms being supported by 
apparently conclusive inoculation and cultural studies. The same ascig¬ 
erous form was collected by the writer on barley straw and stubble from 
fields near Madison, Wis., late in March, 1919, as well as in March and 
April of the following year. As Diedicke (^9) and Noack (95) recognized 
a similar ascigerous form as the perfect stage of H. gramineum in Germany, 
it may not be superfluous to mention that the P)n:enophora fructifications 
found on barley stubble in Wisconsin do not seem to be confined to weak 
culms such as might conceivably represent the remains of plants affected 
with stripe, but are found very abundantly on culms which, because of 
their manifest normal size and attachment to a perfectly developed head, 
can not easily be supposed to be derived from “striped" plants. (PI. 3, 
A.) Previous to the publication of Noack's paper, Diedicke (29) had 
suggested the binomial Pleospora teres for the ascigerous stage of H, teres, 
at that time unknown, and consequently somewhat hypothetical. 
The perithecia on barley straw (PI. 3, B) are of the same type as those 
of Helminthosporium hromi and H. tritici-repentis. In general, however, 
they are perceptibly larger, measuring usually about 0.5 mm. in diameter. 
Although the lateral wall may sometimes taper toward the top, a distinct 
ostiolar beak usually is not present, and in most instances the ostiole is 
represented by a mere opening in the apical portion of the fruiting body. 
Se^e may be altogether absent, or present in moderate number not 
