Cystinarius crassus

A species characterized by its robust stature, with a pileus reaching up to 12 cm, brown, and adorned with appressed fibrils that impart a slightly felty texture. Recently transferred to the genus Cystinarius, it possesses an exceptional microscopic character: its cystidia (both pleurocystidia and cheilocystidia) contain very striking, bright yellowish intracellular contents.

Found from summer to autumn, predominantly in broadleaved forests (Fagus, Quercus, etc.).

Collected in two localities: an acidophilous beech forest in Orozko (Bizkaia) in June-July, and a Quercus rubra plantation in Aramaio (Álava) in October. Microscopy corresponds to specimens gathered in the Biscayan locality.