PREFACE vii 



biotic, fungus-alga relationship are of much more importance 

 than the morphology of reproductive parts. If it is borne in 

 mind that this specialized thallus makes possible specialized func- 

 tional relationships, it is appreciated that the lichen thallus is 

 neither an als^a nor a fune^us, but is a lichen. Moreover one can 

 best appreciate the possible complexities that may arise in this 

 speciaHzed dual relationship by consideration of such a species 

 as Strigula coviplanata. Its algal component, Cephaleiiros vires- 

 cens, widely parasitizes the foliage of broad-leaved evergreens 

 in tropical and subtropical regions and may be found living 

 happily apart from the pyrenomycetous component. On the 

 other hand, the two may form a lichen, and each component may 

 reproduce itself in its own characteristic fashion. 



Most of the illustrations are adapted from those of others. If 

 the author of the original drawing has not been mentioned, the 

 omission is unintentional. The degree of magnification is not 

 stated for the reason that the drawings are intended only to con- 

 vey some idea of appearance and relationship of parts. 



It is intended that the illustrations and explanatory legends will 

 serve to help define terms and thus to provide an understanding 

 of the general morphology of representative genera or species. 

 References to illustrations are omitted from the text. In this 

 way all explanations occur as legends and remain concise. 



Nearly all the drawings and graphs are the result of our own 

 efforts, ably supplemented by those of Mary H. Wolf. Certain 

 cuts, drawings, and photographs were, however, provided by 

 others; and, even though their sources are mentioned in the 

 legends, we herewith acknowledge again, with grateful appre- 

 ciation, these kindnesses. We are indebted also to Dr. L. E. Weh- 

 meyer, who carefully read the entire manuscript, for his criti- 

 cisms and suggestions and to Mrs. Fred T. Wolf for assistance 

 in proofreading and indexing. 



These volumes are dedicated to Lewis David de Schweinitz 

 (1780-1834), a distinguished pioneer in American mycology, 

 whose achievements were the results of a labor of love during 

 the spare moments of an otherwise all-too-busy life that was 

 consecrated to official duties in the Moravian church. His best- 

 known contribution. Synopsis Fiingomvi in America Boreali 

 Media Degentium, lists 3098 species of North American fungi. 



