MYCOSPHAERELLACEAE 



209 



laria, Cercospora, Cercosporella, Ovularia, and Marssonia. Mani- 

 festly the type of imperfect stage could be employed as a 

 criterion for separating this large group into sections, as was 

 suggested by Klebahn (1918). On this basis he proposed such 

 names as Septoriosphaerella, Cercosphaerella, and Ramularisphae- 

 rella. Some species do not possess conidial stages, for example, 







Fig. 78. Formation of spermatia by Mycosphaerella bolleana. A. Uni- 

 nucleate spermatiferous cell just before first nuclear division. B. Binucleate 

 spermatiferous cell. C. Quadrinucleate cell, only three of the cells shown. 

 D. Sterigma being formed and protoplast from one quadrant migrating into 

 the sterigma and forming a spermatium. E. Spermatium formation nearly 

 completed. F. Spermatium with relatively large nucleus. (After Higgins.) 



Mycosphaerella fraxhiicola [Wolf (1939)] and M. nyssaecola 

 [Wolf (1940, 1940a)]. Mycosphaerella jraxinicola is associated 

 with Phyllosticta viridis and M. nyssaecola with P. nyssae; both 

 of these species of Phyllosticta proyed to be not conidial stages 

 but spermogonial stages. 



The conidial stage of species of xAIycosphaerella generally ap- 

 pears during the pathogenic portion of their deyelopmental cycle, 

 and the perithecial stage is initiated during late summer or fall 

 and becomes mature during the follo^^'ing spring. Two distinct 

 stromatic structures are concerned in perithecial formation, and 

 both are initiated concurrently. One of these is the spermo- 

 gonium, containing spermatia; the other is the perithecial primor- 

 dium, containing within it one or more coiled ascogonia. Each 



