Parasitic Fungi of Illinois. 



397 



Fig. 8. 



Figure 7. Podosphxra 

 oxycanihx, (DC.) DBy. : o, 

 pericthecium with dichoto- 

 mously forked appendages 

 h, — magnified 90 times ; c, a 

 tip of an appendage more 

 magnified; ft, the single ascus 

 with eight spores, — magni- 

 fied 325 times. 



Figure 8. Micro?phxra 

 Ravenelii, Berk.: ct.perithecium 

 with its dichotomously forked 

 appendages h, — 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. . Sphjerotheca. 

 Perithecia containing several asci Erysiphb. 



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. 



Uncinula. 



Appendages needle-shaped, abruptly swollen at 



base, asci several Phyllaotinia. 



2. Perithecia containing only one ascus. 



PODOSPH^RA. 



Perithecia containing several asci . MiCROSPHiERA. 



