PREFACE. 



In the present state of mycological knowledge, the classification 

 and description of the species of North American Pyrenomycetes is 

 attended with many difficulties; chief among which is the fact that 

 many of the published diagnoses are too imperfect to enable one to 

 recognize the species, of which many of the types are either lost or 

 practically inaccessible. An examination of the Schweinitzian Herba- 

 rium, at the Academy of Natural Sciences at Philadelphia, reveals the 

 i;ict that about two hundred of the most valuable species described in 

 Schweinitz' Synopsis of North American Fungi are not represented in 

 the Herbarium at all, and that many of the specimens still remaining 

 are too meager or too imperfect to be of much service. Coming to the 

 species described by Berkeley & Curtis, the case is no better, but, as 

 far as specimens are concerned, even worse, the types being entirely 

 beyond the reach of the ordinary student. Our knowledge of the 

 species is derived from the brief descriptions in Grevillea and the 

 supplementary notes by Dr. M. C. Cooke, who has also examined and 

 determined, by comparison with the original types, many of the species 

 included in the present work. We are also indebted to Drs. Rehm, 

 Winter, and Saccardo for the identification of many doubtful species; 

 but above all to the many collectors who have furnished abundant 

 material from all parts of the country, thus making it possible to give 

 an approximately complete synopsis of the North American species of 

 this extensive Order. The names of these contributors appear in con- 

 nection with the species they have furnished. The name of Ravenel 

 is attached to most of the species collected by him and described by 

 Berkeley A: Curtis in Grevillea; and Schweinitz or -'Schw.'' to his 

 species published in the Synopsis of North American Fungi. 



