STUDIES IN NORTH AMERICAN PERONO- 

 SPORALES— VII. NEW AND NOTE- 

 WORTHY SPECIES 



Guy West Wilson 



Peronospora grisea Unger 



This is one of the rarer members of the genus, at least in Amer- 

 ica. It is confined to various species of Veronica in the northern 

 portion of the United States and Canada, as well as in Europe. 

 It was with considerable interest that this species was found in 

 the field last spring near Carmel, Indiana, where in April it was 

 very abundant on the young plants of V . arvensis L., causing a 

 pronounced and conspicuous yellowing of the infected leaves. It 

 persisted through May, and during the latter month it was found 

 sparingly in the same locality on V. peregrina L. On this host, 

 the surface discoloration was red, very similar to that caused by 

 the work of aphids. In this connection it might be of interest to 

 note that in the case of other species of Peronospora which nor- 

 mally cause a yellowish discoloration of the host, especially P. 

 Polygoni Thiim., this was of a decided reddish cast during the 

 cold, wet weeks of spring. In early June, the normal color was 

 the prevalent one. 



Peronospora Seymourii Burrill 



This species was abundant on Houstonia minor (Michx.) 

 Britton at Iowa City, Iowa, in April, 191 5. So far as the writer 

 knows, but two previous collections have been recorded. The 

 type was collected in Union county, Illinois, by Prof. Seymour, 

 the other collection being made in Alabama by Dr. Underwood. 1 

 In the Iowa material, the oospores are produced abundantly in 

 the fruits of the host, causing a slight hypertrophy and a decided 

 purplish color. 



1 Underwood, Bull. Torrey Club 24: 83. 1897. 



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