Wilson: Studies in North American Peronosporales 201 
unlike that figured by Desmazieres, having flexuose branches with 
the ultimate branchlets strongly recurved. That is to say, if we 
adopt the classification proposed by Berlese the material of 
Greville and Desmazieres would fall in the section intermediate 
while that described by Schlechtendal belongs to divaricatae. That 
Pcronospora effusa presented a wide range of variation was first 
pointed out by Caspary 7 who recognized two varieties, a major 
being the typical intermediate form of the older authors, while 
/? minor on A triplex patula from Bonn is the undulate form.. 
Recently Laubert 8 discussed the variations within the accepted 
limits of the species and figured portions of the conidiophores of 
the two forms. He does not refer to the synonymy of the species 
nor propose any new name for either form. In the course of the 
review of this article Detmann removes the typical portion of the 
species from Pcronospora effusa and calls it P. Spinaciae n. sp. 
The most recent pronouncement on the question comes as an 
echo from the Brussels congress where the assembled botanists 
of the world in their wisdom decreed that those fungi not other- 
wise provided for should begin their historical career with Fries’s 
Systema. As this work contains the reference noted above to 
Botrytis farinosa and its saphrophytic habits but does not mention 
the earleir better defined and strictly parasitic Botrytis effusa, 
Doctor Keissler concludes that it is necessary to take up Botrytis 
farinosa and drop P. effusa to the realm of prehistoric nomen- 
clature. He accordingly transfers the name to Pcronospora, cites 
the stock synonyms, and then issues in “ Kryptogamae exsiccatae ” 
i82p two specimens, “a) Austria inferior: ad folia Chcnopodii 
albi L . ... b) Hungaria : ad folio Chcnopodii hybridi L. . . . ” 
The first of these is P. farinosa as treated in the present paper, 
while the second belongs to the other side of the species. 
A careful study of these forms leads to the conclusion that as 
usually construed Pcronospora effusa consists of two quite dis- 
similar species. The complete synonymy as well as the list of 
hosts from which material was studied follows. 
r Rab. herb. Viv. Myc. II. cent. 2. IJ2. 1855. 
8 Gartenflora 55: 433-440. f. 45. 1906. 
