A new Genus of Powdery Mildews— Erysiphopsis 



Bv BvRON D. Hai,stkd. 



While at a meeting of tlie A. A. A. S., held in Aladison, Wis., 

 in August, 1893, and upon one of the delightful botanical excur- 

 sions of the week the writer, in compan>' with Prof. S. M. Tracy, 

 found a mildew upon a Par/iassia in considerable abundance. It 

 has characteristics that do not admit it to any of the existing 

 genera and as it approaches the Erysiphc more than any other, the 

 next nearest being Phyllaciima the name of Eiysiphopus, that is, 

 like or similar to Erysiplic is offered. 



X 



Erysiphopsis gen. nov. 



• _ Appendages rigid, brittle, usually nearly straight and frequently 

 slightly swollen at the tip. 



Erysiphopsis Parnassiae 



Amphigenous, but most abundant upon the upper surface ; 

 hyphae inconspicuous. Perithecia widely scattered, almost black' 

 60-110/^ in diameter with reticulations coar.se and distinct: ap- 

 pendages 8-15, about 10 n in diameter at base and varying greatly 

 in length— the shorter, 25-50 //, being straight and brown through- 

 out with the tips rounded and often distinctly swollen while the 



longer are 2-5 -septate, somewhat bent, the upper cell being pale 

 brown and without distinctly swollen tips : asci 4-5, oval, pcdi- 

 cillate, 25-30 by 40-45 n ■ sporidia oval, usually 4 (4-5) 6-?, by 

 12-16 It. 



On leaves of Parnas^in rm-nliiiinun MiVJi^' 



Madis 



The key of the genera given below modified from that ar- 

 ranged by Dr. l^urrill in his " Erysipheae " * will help to show the 

 position taken by the new genus. 



I. Appendages consisting of simple threads similar to the mycelium and often inter- 

 woven with it. 



1. IVrithecia containing only one ascus. Sphaerotheca. 



2. Perithecia containing several asci. • Etysiphe. 

 II. Appendages dissimilar to and free from the mycelium. 



A. Appendages simple— not usually forked at the tip. 



3. Appendages coiled at the tip. Uncimila. 



* Parasitic Fungi of Illinois, Bull. Nat. Hist., 1SS7. 



(594) 



