Cap. 5-8 cm, at first globose and violet-black, later violet or violet-brown, often very dark in the centre; occasionally with small patches of yellow or rusty colour; exceptionally the whole surface may be mottled with pale yellow and sordid violet. Cap, when expanded, fragile; margin finally striated. The surface beneath the cuticle is white or of a faint sulphur-yellow tint. Flesh white. Stem fragile; at first firm, finally soft; often long, and inclined to curve beneath the leaves on the ground; white, staining pale sulphur-yellow where rubbed, and easily becoming tinted with the colour from the caps of other species (chiefly those coloured red, purple, or violet) left in contact with it during collection. Gills free, white, finally cream faintly yellow-tinted. Taste mild. Inodorous. Restricted entirely to the vicinity of oak trees (see notes). June-Aug.
Neotypus: PC: Romagnesi 54-28,
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