8o 
The Ohio Naturalist. 
[Vol. VII, No. 4, 
which recently befell Buchtel College. In the preparation of 
this paper I have written to all the prominent herbaria and the 
laboratory of Vegetable Pathology, Washington. Michigan 
specimens are equally rare in Michigan, as are Illinois specimens 
in Illinois, so we are informed by those who know. 
I may further state that from the writer’s first connection 
with the Experiment Station in September, 1894, he was dili¬ 
gently striving to secure specimens of Phytophthora upon potato 
in Ohio, but did not succeed until August 1904, when it was 
collected in several counties. The fungus has reappeared and 
been collected in Northern Ohio each season since 1903, including 
that of 1906. The maximum injury to the potato crop was in¬ 
flicted in 1905. 
By the kindness of Mr. E. C. Green, of Medina, Ohio, I have 
been able to fix definitely the occurrence of Phytophthora in 
Granger township, Medina County, in 1883, thus confirming 
the Akron specimens destroyed by fire. 
We are now prepared to ask, “What conditions determine 
the occurrence of outbreaks of Phytophthora injestans in Ohio?” 
—a questian which all will admit is more easily asked than 
answered. 
Before undertaking to reply to such a question we may con¬ 
sider what conditions favor the propagation and development 
of this fungus, which so far as is known, is propagated by short¬ 
lived conidia or by the mycelium, the vegetable portion of the 
fungus; no oospores are known. Herein, we find some diversity 
of opinion among mycologists. Dr. W. G. Farlow * records 
that the potato rot due to Phytophthora injestans always occurs 
or begins about the first of August, that mositure is absolutely 
essential and that damp “muggy” weather is quite as favorable 
to its development as heavy rains. This applies more specifi¬ 
cally to New England. 
In this statement moisture is especially emphasized and pro¬ 
perly so. Dr. B. D. Halsted f in his Mycological Notes of 1898 
points out “A Close Relation between Rainfall and Potato 
Rot,” in which he emphasizes the rainfall of 1889 (10.19) inches) 
and 1897 (11.42 inches); in both these years there were marked 
outbreaks of rot in New Jersey with none, or next to none, in in¬ 
tervening years, and states further: “It seems to me that Phy¬ 
tophthora or late blight is quite dependent upon an abundance of 
moisture in midsummer, and if this relation is noted sufficiently 
the time may come wehn it may be predicted with reasonably 
certainty, that a wet July will mean a decaying potato crop un¬ 
less some successful method of checking tills rapidly developing 
* Bulletin of the Bussey Institution; 1:320 (187o). 
t Bull, 'l'orr Bot. Club XXV:160 (1898). 
