Wilson : North American Peronosporales 363 









Phytophthora Thalictri Wilson & Davis 



Material of this species collected by Dr. Davis later in the 

 season than the type collection indicated that the species is rather 

 well distributed over southeastern Wisconsin. Although a careful 

 search was made in New York in the early summer and in Indiana 

 in the late summer, the species was not found in either locality. 

 Dr. Davis observed the germination of the conidia, which behave 

 in the typical manner for the genus. 



Peronospora Cyparissiae de Bary 



This species is reported by T. A. Williams from South Dakota 

 on Euphorbia glyptospcrma Engelm. and E. metadata L.* An ex- 

 amination of this material shows the species in question to be 

 Peronospora Euphorbiae Fuckel, the only species so far detected on 

 North American Euphorbiaceae. The two fungi in question infest 

 widely separated sections of the old genus Euphorbia. 



Peronospora Rumicis Corda 



The species has been recorded from North America on Poly- 

 gonum aviculare L., P. dumetorum L., and P. scandens L. European 

 mycologists recognize two species of Peronospora on Polygonaceae, 

 "• Rumicis Corda on Rumex spp. and P. Polygoni Thumen on 

 Polygonum spp. The two fungi are separated by differences of 

 both conidia and conidiophores. P. Rumicis has conidiophores 3 

 -6 times branched, with very short ultimate branchlets(2~4 ft long) 



and broadly ellipsoid conidia (26-33 P X l6 ~ 2 3 !")» while R Pol >'~ 

 #"«has conidiophores more lax, 5-7 times branched, the ultimate 

 branchlets long (6-12 /1) and often curved, and elongate conidia (30 

 ~40 11 x 1 5-20 /x). The latter species is rather widely distributed in 

 the nor thern United States, while the former, so far as my own 

 observations go, has not been substantiated by authentic material 

 r °m our region, nor do any of the recorded hosts indicate its 

 Presence in North America. 



Peronospora arborescens (Berk.) de Bary 

 »n his report upon a collection of western Fungi Humef 



vonospora Corydalis de Bary on Argemone platyceras 



Bull Torrey Club i 9 : 82. 1891. 

 Tlroc. Davenport Acad. Sci. 7 : 254. 1899. 



