and others, finding tliat these conceptacles were borne on the same 

 mycelium as the conidia and perithecia, naturally concluded that they 

 were organs of the same plant, and, from their analogy to certain 

 asexual reproductive bodies in allied groups of the Ascomycetes, called 

 them pycnidia, and the minute bodies they contain, stylospores or 

 pycnidiospores. This is still the accepted belief of many botanists. 

 De Bary (Morph. und Phys. der Pilze, III, pp. 53-75, Tafeln VI, VII), 

 shows that the pycnidia instead of being reproductive organs of the 

 Erysiphe, are, in Teality, the fructification of a fungus that is parasitic 

 on the Erysiphe. He calls it Cicinoholus Cesatii, and gives numerous 

 figures showing its delicate, septate mycelium, developing within the 

 mycelial threads of the Erysiphe, and sending up branches which, by 

 repeated division, form the cellular wall of the pycnidium. 



There is much confusion in regard to the nomenclature of this 

 group. The earlier authors, with poor magnifiers or none at all, made 

 meager descriptions of their supposed species, for which reason it is 

 often impossible to determine from their writings what they had in 

 hand. Host plants are not so much of a guide here as in most cases 

 for pai-asites, though many specific names have been proposed, it seems 

 solely upon the observed habitat of the fungus. In what follows, an 

 earnest endeavor has been made to identify and describe true species 

 wherever they grow. The Bulletin of the Illinois State Laboratory 

 of Natural History, Volume II, Article VI, Parasitic Fungi of 

 Illinois, part II, by T. J. Burrill and P. S. Barle. has been made the 

 basis of this work. This bulletin was founded upon collections made 

 in Illinois, mostly by A. B. Seymour who also made studies upon the 

 species. 



KEY TO THE GENERA. 



1. Appendages to the perithecia simple, and similar 



to the threads of the mycelium. - . 2. 

 Appendages various, readily distinguished from the 



mycelium. - - ... 3_ 



2. Only one ascus in a perithecium. Sphcerotheca. 

 Several asci in each perithecium. Erysiphe, 



3. Appendages branched at their tips. 4, 

 Appendages not branched. - - - 5. 



4. Only one ascus in a perithecium. Podosphoera. 

 Several asci in each perithecium. MicrosphcBra. 



5. Appendages swollen at base, tips straight. Phyllactinia. 



