Type studies in Russula subgenus Heterophyllidia from the eastern United States

Microscopical characters of type specimens for five species in Russula subgenus Heterophyllidia: R. albiduliformis Murrill, R. flocculosa Burl., R. maculosa Murrill, R. heterosporoides Murrill and R. subgraminicolor Murrill are described in detail. Taxonomy, systematic placement and nomenclatural aspects are discussed. Both R. heterosporoides Murrill and R. subgraminicolor Murrill are likely good species of subsection Virescentinae, whereas the other three species are more difficult to place with precision, but show affinities with both Virescentinae and Heterophyllinae.