Russula sororia (Fr.) Romell (R. amoenolens Romagn.) Scharfer Brattäubling, Russule soeur, Sepia Brittlegill.
Cap 3–6cm across, convex, later flattening and with a depression, sepia to greyish sepia, rarely white, thinnish-fleshed, slightly sticky when moist, half-peeling; margin furrowed, with small, low warts. Stem 30–60 x 10–20mm, whitish, fairly firm to soft and fragile. Flesh white. Taste unpleasant, oily, slowly very hot; smell rancid or suggesting Camembert cheese. Gills adnexed, creamy to dirty whitish, edge browning. Spore print pale cream (B–D). Spores broadly elliptic with warts up to 0.7µ high, a few joined by fine lines, no network, 7–9 x 5–7µ. Cap cystidia narrow, tapering, poorly reacting to SV. Habitat under oak. Season summer to autumn. Occasional. Not edible. Distribution, America and Europe.