Witson: NortTH AMERICAN PERONOSPORALES 413 
taken by Berlese, who formed for them a subgenus under the old 
genus P/asmopara, which he characterized as having the conidio- 
phores of Peronospora and the conidia of Plasmopara, 1. e. Rhyso- 
theca of the present treatment of the group. The final step was 
taken by Rostewzew who made an extensive study of P. cubensis, 
the results of which appeared in an elaborate paper which was 
published first in Russian and later in German. He concluded 
that this species represented a distinct genus intermediate between 
Peronospora and Plasmopara, sensu Schroter. He called the 
genus Pseudoperonospora, choosing this name, as he tells us, 
rather than Pseudoplasmopara as Peronospora antedates Plasmopara. 
Later Dr. Clinton made an extended study of the species in 
America, publishing an admirable paper upon his researches. 
Unfortunately, at least from a nomenclatural standpoint, he re- 
jected the earlier generic name in favor of Berlese’s subgeneric 
name, and still more unfortunately he has been followed in this by 
other American mycologists. The name proposed by Rostewzew 
has more than two years priority over the elevation of Berlese’s 
subgenus to generic rank, and is therefore the rightful name of the 
genus. 
Key to the species 
Conidiophores 3-4 times branched. 1. P. cubensis. 
Condiophores 4~5 times branched. 2. P. Celtidts. 
1. PSEUDOPERONOSPORA CUBENSIS (B. & C.) Rostew. 
Ann. Inst. Agron. Moscoug: 47. Ja 1903. — 
Flora 92: 422. O 1903 
Peronospora cubensis B. & C. Jour. Linn. Soc. Bot. 10: 363. 
1868. 
Plasmopara cubensis Humphrey, Rep. Mass. State Agr. Exp. Sta. 
> 212. 1891. 
Per onoplasmopara cubensis Clinton, Rep. Conn. Agr. Exp. Sta. 
1904: 335. 1905. 
pophyllous, or rarely amphigenous ; discoloration of the 
host yellowish, rather definite in outline, affected area apparently 
unoccupied or with a sparse marginal growth ; condiophores I—2, 
“led more, from a stoma, 180-400 X 5-9 #, 3-4, rarely 2-5, times 
ranched, the ultimate branchlets recurved, apically acute, 5-20 
long ; conidia gray, brownish or smoky, ovoid to ellipsoid, papil- 
