A systematic study of the euagaric genus Pluteus emphasizing section Celluloderma in the U.S.A

An investigation of the agaric genus Pluteus (Pluteaceae, Agaricomycetes), a circumglobal saprotroph commonly found on lignicolous substrates, was undertaken. Twenty species and varieties total of Pluteus section Celluloderma were recognized as occurring in the U.S.A. Two species and one variety are reported as new to science. Additionally, one variety resulted from a new combination and, one new name is proposed for a species incorrectly classified outside of Pluteus. Synonyms are proposed for several taxa. Two species have been excluded from Section Celluloderma.;Detailed descriptions of each of these taxa, as well as two other species known from Europe, are offered. These were constructed with morphological data from approximately 150 collections including both herbarium and fresh materials. Type studies of all known Section Celluloderma taxa described from the U.S.A. were performed, and separate descriptions are included for each type specimen. Type specimens, when necessary, were designated. Descriptions are supplemented with line drawings of microscopic characters, and also, whenever possible, photographs of fresh basidiocarps. Keys for examined taxa from the U.S.A. and those found in the Midwestern U.S.A. are presented. The known distributions of several taxa were expanded, especially in the Midwestern U.S.A.;Phylogenetic analyses on the genus Pluteus were performed in order to address sectional and subsectional classifications and relationships. Primarily morphology-based analyses were employed using exemplar taxa. No changes were proposed to the current widely accepted infrageneric classification of Pluteus. Inquiry utilizing DNA sequences was abandoned due to a lack of data resulting from technical problems.;Pluteus aurantipes, a Section Hispidoderma species from the U.S.A., was circumscribed and presented as new to science.;The agaric genus Chamaeota (Pluteaceae, Agaricomycetes) in the U.S.A. was also studied. Based on the morphological and molecular data obtained and the results of subsequent analyses, one species, Pluteus mammillatus, was recognized as occurring in the U.S.A. This study marks the first time that an annulate Chamaeota species was transferred to Pluteus, thus altering its generic concept.