Parasitic Fungi of Illinois. 



397 





Fig. 8. 



Figure 7. Podosphaera 

 oxycanthx, (DC.) DBy. : a, 

 pericthecium with dichoto- 

 mously forked appendages 

 b, — magnified 90 times ; c, a 

 tip of an appendage more 

 magnified ; b, the single ascus 

 with eight spores, — magni- 

 fied 325 times. 



Figure 8. Microsphsera 

 Ravenelii, Berk.: a, perithecium 

 with its dichotomously forked 

 appendages b, — magnified 75 

 times ; c, a tip of an appendage 

 more magnified ; d, one of the 

 several asci containing eight 

 spores, — magnified 375 times; 

 e, a group of asci from one 

 perithecium, — magnified 150 

 times. 



Key to the Genera of Erysiphe^. 



I. Appendages consisting of simple threads similar to the 



. mycelium, and often interwoven with it A. 



II. Appendages dissimilar to, and free from the mycelium. B. 



A. Perithecia containing only one ascus . . Sph^erotheca. 

 Perithecia containing several asci Erysiphe. 



B. Appendages simple, not usually forked at the tip . . .1. 

 . Appendages dichotomously forked at the tip 2. 



1. Appendages coiled at the tip, asci several. 



Uncentjla. 



Appendages needle-shaped, abruptly swollen at 



base, asci several . Phyll actinia. 



2. Perithecia containing only one ascus. 



PODOSPH^RA. 



Perithecia containing several asci . Microsph^ra* 



