62 JOURNAL OF THE 



Perhaps the chief point of (departure from that work i.s iu 

 regarding Microspluertxi Van Bruntunia Ger. as a (Hstinct spe- 

 cies and not one of the many synonyms of M. Alai (D C.) 

 Winter. The appendages are totally different fron) the descrip- 

 tion there given or from those of the other species placed as 

 svnonvms. On the other hand, an examination of a large series 

 of specimens of lllcrosjyhcera on diiferent species of oak only 

 confirms the correctness of the judgment displayed in uniting 

 Peck's extensa et abhrevi'da into one variable species. It is 

 doubtful, however, if M'lcrosphcei^a Quercina (Schw.) Burrill can 

 be morphologically distinct from M. Alni (D C.) Winter, since 

 many of the intermediate forms between Peck's extensa et ahbre- 

 viata agree perfectly with the description of M. Alni (D C.) 

 Winter, and have constantly been referred by various authors 

 and to 31. Hedwigia et penicillata wdiich are now regarded by 

 many as synonyms of M. Alai (D C.) Winter. I prefer, how- 

 ever, to suspend a final judgment on this subject, considering the 

 local character of this contribution. 



There seems to be no necessity for a full presentation of the 

 synonomy of all the species, and where synonyms are'given it is 

 only because of the peculiar value of these expressions in inter- 

 preting a few of the forms. 



It is hoped that to members of the Society, and other readers 

 in the South who are interested in microscopic study, this contri- 

 bution will prove a stimidus and aid in the study, collection and 

 determination of this common, easily recognized and interesting 

 group of plants. For this reason the notes are S() arranged as 

 to enable one to determine the species presented here. 



The Erysiphece, or, as they are commonly called, the powdery 

 mildews, are parasites growing generally upon the surface of the 

 leaves, often on the stems, occasionally upon the fruits and 

 deformities of plants. The vegelive condition from wliicii they 

 obtain the name of mildew consists of a loose wefi of white fmi- 

 gous threads distributed over the affected parts, sometimes cover- 

 ing a large part or all of the leaf surface, or again confined to 

 definite spots. The fungus derives its nourishment through the 

 medium of short suckers, or haustoria, which here and there 



