Two new Quercus-associated Russulas from Costa Rica and their relation to some very rare North American species

Detailed descriptions are given for Russula cartaginis and R. quercophila associated with endemic Quercus in Costa Rica. Both species are compared with the closely resembling and very rare R. eccentrica from southeastern North America and R. imitatrix from northeastern North America. Microscopic features for all four species are here illustrated in more detail for the first time.