338 Notes on Parasitic Ascomycetes. [Sess. 



asci, and each ascus usually contains two, or more rarely three 

 or four, spores. One species — P. corylea (Pers.) Karst. ( = P. 

 suffulta Sacc.) — is sometimes common on leaves of hazel, and 

 is also said to occur on various other trees and shrubs, such 

 as hawthorn, elm, ash, beech, birch, alder, willow, oak, horn- 

 beam, honeysuckle, spindle-tree, cornel, and sea-buckthorn. 



In Uncinula the perithecia bear appendages which are 

 usually simple, or more rarely forked, and are curled or hooked 

 at the tip. Two species may be noted. V. aceris (DC.) Sacc. 

 occurs on leaves of the plane-tree or great maple (Acer Pseuclo- 

 platanus), where, in its conidial state (known as Oidium aceris 

 Eabh.), it is often very abundant in autumn. Each peri- 

 thecium contains 8 asci, and each ascus 8 spores. Another 

 species — U. salicis (DC.) Wint. (= U, adunca Lev.) — attacks 

 the leaves of willows, and sometimes also those of poplar and 

 birch. The individual perithecia are surrounded by a rather 

 dense circle of unbranched appendages which are hooked at 

 the apex. Each perithecium contains from 8 to 12 asci, and 

 each ascus 4 spores. 



In the genus Microsphcera, as the name indicates, the peri- 

 thecia are of a comparatively minute size. They bear append- 

 ages which are repeatedly forked at the tip. Each perithecium 

 contains several asci, and each ascus from 3 to 6 spores. 

 One species — M. grossularice (Wallr.) L^v. — affects the leaves 

 of the common gooseberry, which it coats on both surfaces 

 with a delicate covering of whitish mycelium. The perithecia 

 usually occur in small scattered groups, and are furnished 

 with appendages which are from 4 to 6 times forked at the 

 tip. Each perithecium contains from 8 to 10 asci, and each 

 ascus from 3 to 6 spores of somewhat variable size. Another 

 species — M. herheridis (DC.) Lev. — forms similar patches of 

 mycelium on leaves of barberry. The perithecia bear append- 

 ages which are 4 times forked at the tip. Each perithecium 

 contains from 4 to 9 asci, and each ascus from 4 to 6 

 spores. 



In the genus JErysiphe the perithecia bear simple or irregu- 

 larly branched appendages, closely resembling the threads of 

 the mycelium with which they are intermixed. Each peri- 

 thecium contains several asci, and each ascus from 2 to 8 

 spores. The most common species are — 



