Type studies in Russula subsection Nigricantes from the Eastern United States

After a short historical summary of the species in Russula subgenus Compacta subsection Nigricantes in the United States, the microscopic features of the type specimens of four taxa from North America are described and discussed: Russula decora, R. densifolia var. paxilloides, R. sordida and R. subsordida. Previous suggestions of possible synonymies with European taxa are rejected.