THE FUNGI WHICH CAUSE PLANT DISEASE 237 



Conidia, 2. (=Coryneum beyerinckii) conidiophores short, 

 crowded, from a minute subepidermal stroma; conidia single, 

 elliptic-oblong, 1 to 5-septate, brown, about 36 x 15 /i- On 

 drupaceous hosts. 



In spots on the bark the mycelium is often sterile, but when 

 it becomes old distinct pustules usually show in a well developed 

 subepidermal stromatic tissue and from these pustules, as they 

 rupture the epidermis, the conidiophores are produced. Conidia 

 usually abound on the surface of twigs which have borne affected 

 leaves. They germinate readily and produce either a sooty super- 



Fio. 172. — Section through a Coryneum pustule on peach. 

 After Smith. 



ficial mold or if on new bark enter the host tissue and induce 

 spotting. 



The conidial stage (Coryneum) of the fungus was grown in arti- 

 ficial culture by Smith i" but no ascigerous stage corresponding 

 with that of Vuillemin was found. 



A. geographicum (D. C.) Desm. is common on leaves of pome 

 fruits and A. padi Grev. defoliates cherries in Europe. 



Guignardia Viala & Ravaz (p. 236) 



Perithecia sunken, globoid or flattened, black, leathery; ostiole 

 flattened or papillate; asci clavate, 8-spored; spores ellipsoid or 

 fusiform, hyaline, somewhat arched, 1 or 2-celled; paraphyses 

 none. 



