196 



COMPARATIVE MORPHOLOGY OF FUNGI 



of the leaf, but later, in proportion as perithecia are formed on the upper 

 side of the leaf, they become limited to the lower side. According to the 

 manner of cutting off the spores, they are divided into two types; in the 

 first type, which includes the endo- and hemiendophytic forms, the 



r <^-... 



W- 



Fig. 123. — Sphacrotheca Humuli. Development of conidiophore. (X830; after Foex, 



1913.) 



conidia are cut off singly, in the ectoparasitic forms they arise in chains 

 (Foex, 1912, 1913; Bezsonov, 1913). 



In the first type, Leveillula taurica (Fig. 122), the hyphae collect in 

 the substomatal cavity to dense, almost pseudoparenchymatous knots, 

 whence radiate the mostly unbranched, aerial hyphae (conidiophores) 



