Paxillus Fr.
Cap depressed, velvety or tomentose, later smooth, cap margin inrolled and remaining so for a long time. Gills forking. Spore print rusty, brownish or vinaceous.
At least eight species are described in Europe. With exception of Paxillus rubicundulus, that is relatively easy to recognize, the rest of the species gravitate closely around Paxillus involutus.
The colour of the spore print is thought to be important for the species recognition, so it should be thoroughly noted when freshly deposited. The crystals that occur in the rhizomorphs are also considered important so any Paxillus collection must contain fruitbodies with preserved basal mycelium.
Reaction with ammonia solution is used to separate some of the species. It has been proven in other bolete genera that the ammonia reaction has little (if any) taxonomic value. However, it has not been evaluated in Paxillus and it should be tested systematically.