Hay 26,1923 
Graminicolotis Species of Helminthosporium 
687 
at Bloomin^on, III; Annapolis, Md.; Washington, D. C.; Hyde Park, 
Mass.; Meriden, Conn.; and Lisbon Falls, Me. It thus appears to be 
quite widely distributed through the northeastern and middle western 
sections of the country. Indeed, the possibility of a distribution nearly, 
if not quite, approaching in extent the range of the host, is not to be 
excluded; for although Poa pratensis is one of the most common and 
valuable of the grasses, both in this country and in Europe, and might 
thus be expected to be kept under observation by pathologists, the fungus 
is nevertheless very apt to escape detection. Not only are the foliar 
lesions caused by the parasite usually small and infrequent, but to a 
casual observer they may readily be mistaken, in spite of the unbroken 
epidermis and more intense dark discoloration, for old sori of Puccinia 
poarum Niels., almost always present in some abundance. It need hardly 
be mentioned that the economic loss caused by a disease ordinarily so 
lacking in severity is relatively insignificant; yet under certain conditions 
of moisture and of temperature such as would favor a multiplication of 
foliar lesions and accentuate the footrot symptoms, the damage may 
not be altogether unappreciable. 
On microscopic examination, the fungus shows considerable similarity 
to Helminthosporium sativumy not only in its effect on the host, but to 
some extent also in regard to morphological features. The sporophores 
(PI. 15, Da-g) found on leaves of Poa pratensisy to be sure, are appreciably 
greater in diameter and frequently greater in length (PI. 15, Da) than 
the corresponding structure of the parasite causing spotblotch; and the 
tendency toward branching exhibited by them (PI. 15, Db, e) is rarely 
to be found in H. sativum. On the other hand, complete agreement 
prevails with reference to coloration of the spores, the latter (PI. 15, 
Ba-q) when fully mature, being uniformly dark olivaceous. In both 
species, too, the peripheral spore wall is relatively thick and the num¬ 
ber of septa rarely exceeds the usual maximum of 10. With respect 
to spore shape, the form on Kentucky bluegrass, however, is notice¬ 
ably different, its conidia being typically straight, never, as a rule, be¬ 
coming distinctly curved. 
The most distinctive character, however, is to be found in the germi¬ 
nation of the spore, the germ tubes being proliferated not alone from the 
end segments, but indiscriminately from both intermediate and end 
segments regardless of position; and not infrequently every segment 
participates in the process. (PI. 15, Ca, b.) This behavior would seem 
to suggest a measure of affinity with species having straight cylindrical 
spores like H. teres and H. gramineumy a suggestion borne out in a mea¬ 
sure by the cultural characters of the fungus on ordinary media. Sporu- 
lation very rarely occurs on potato dextrose agar, although an abundance 
of dark aerial mycelium usually is produced. The imbedded mycelium 
presents an unusually distinctive aspect, for instead of consisting like 
that of most species of Helminthosporium, of a miscellaneous growth of 
hyphae, it is composed largely of a relatively small number of ramifying 
systems, all of an intense bluish black color, and bearing hundreds of 
branching elements. 
The literature, beyond a brief abstract published by the writer {31) 
appears to contain no reference to any species of Helminthosporium 
parasitic on Poa pratensis. Karsten (74), in 1884, cited H. flexuosum 
Corda { = Brachysporium flexuosum [Corda] Sacc.) as occurring on the 
leaves of a congeneric host, Poa stricta. However, the obvious disparity 
in size and septation between the spores of the species figured by Corda 
