204 AGRICULTURAL EXPERIMENT STATION. [Jan. 



has mentioned * an instance of the sort as having occurred 

 at Bethlehem, Penn. Soon after 1790, the very abundant 

 trees of what he calls " Amarellae," probably morello 

 cherries, were nearly all destroyed by the knot ; while a 

 second visitation, about 1830, swept off most of the plum 

 trees. Many farmers and fruit growers will recall similar 

 cases in their own experience. In spite of these facts, how- 

 ever, there is no evidence that there is more than a single 

 species of knot fungus, which attacks both plums and cher- 

 ries ; and we must probably seek other causes for its occa- 

 sional selection of particular hosts, to the exclusion of others 

 equally susceptible. 



As has been the case with many cultivated plants, cer- 

 tain varieties of plums have been claimed by originators or 

 dealers to be disease-proof. As early as 1843, Messrs. W. 

 R. Prince and Co., nurserymen of Flushing, N. Y., pub- 

 lished in the "New England Farmer" a list of varieties 

 claimed by them to be not subject to the black knot, with 

 the remark that they were all varieties of American origin. 

 A few months later, a brief editorial note in the same paper 

 stated, on the authority of prominent growers, that the list 

 was of no value for the vicinity of Boston. And similar 

 claims have usually met a similar fate. 



This fungus is strictly American in origin, and has not 

 yet, so far as has been reported, been introduced with its 

 host plants into Europe, as have so many other American 

 fungi. But in the United States it is very widely distrib- 

 uted, ranging from Maine to California, and from Wisconsin 

 to Texas, where it is said to be rare. In most parts of the 

 country it is abundant and destructive. 



As above stated, the fungus was first described and 

 named as Sp/urria morbosa Scnw. Various writers have 

 proposed various other generic names as better indicating 

 its relationships, but none of these was generally adopted 

 until Saccardo, regarding it as a member of the family 

 Dothidcaccce of the "Black Fungi" (Pyrcnomycetes), 

 called it Plozvrightia morbosa (Schw.) Sacc, by which 

 name it is now commonly known. 



* Synopsis Fungorum Amer. Bor. Proc. Amer. Phil. Soc, Vol. Ill, p. 269. 



