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, 1S94, 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 H)()o, including 

 that of 190(1 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 18S3, 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 189(S 

 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 tihs ra])i(lly (le\el()])ing 



* Bulletin of the Bussey Institution; I;.320 (1875). 

 t Bull. Ti.rr. Bot. Club XXV:U10 (1,S9S). 



