244 



MILDEWS (ERYSIPHACE^) 



numerous small dark specks (Fig. 130, a), the ascus-fruits, on 

 the greyish-white mycelium. Under the microscope they are 

 seen to be almost spherical structures, provided with very diverse 

 hair-like appendages and without an aperture (Fig. 130, b.). 

 The hard black wall ruptures irregularly, exposing one or more 

 small asci (Fig. 130, e). 



In the Hop Mildew (Sphaerotheca castagnei) and one or two 



d 



FIG. 130. The Hop Mildew (Sphaerotheca castagnei). a, part of the leaf 

 of the Hop, with the ascus-fruits ; b, small part of the surface, greatly 

 magnified, showing the superficial hyphae (h.) and two ascus-fruits, 

 each with numerous long appendages (ap.) ', c, production of a chain 

 of gonidia (g.) ; d, sex organs in apposition ; e, ascus ; /, young fruit. 

 (a after Wettstein ; b, c, and e after Tulasne ; d and / after Harper.) 



other cases it has been established that the fruit arises from 

 club-shaped sexual organs of unequal size, the larger functioning 

 as the female (Fig. 130, d). Their tips become closely adpressed, 

 but, owing to the great difficulty of establishing such facts, there 

 exists a marked difference of opinion as to whether or not there 

 is a fusion analogous to that above described for the Phycomy- 

 cetes. The same doubt attaches to all cases of sexual fusion 



