The study of <i>Russula</i> in the Western United States

A short history to the study of Russula in the Western United States is provided and for the first time an exhaustive list of all 49 taxa described from this part of the country has been compiled. As a start to a revision of these species, a first series of four holotypes (one from California and three from the Pacific Northwest) have here been studied microscopically, resulting in some very substantial changes concerning species concept and consequent systematic placement. Russula flava var. pacifica appears unrelated to the type variety. It is therefore excluded as member of Integroidinae, subgen. Polychromidia, and deserves probably to be upgraded to species level within subgen. Russula. The Californian R. paxilloides is lectotypified and is a good member of subgen. Russula, but is closer to sect. Persicinae than to the white-spored Vinaceae as previously suggested. Russula maxima, widely accepted as a species of subsect. Subcompactinae (subgen. Heterophyllidia), certainly does not belong there and has to be moved to subgen. Polychromidia. Finally, R. inconstans is here maintained as member of subg. Polychromidia.