Cap 3-7 mm across, parabolical, campanulate, broadly conical, with a small papilla or somewhat truncate, shallowly sulcate, translucent-striate, glabrous, pale brown to whitish, often with a dark brown centre and pallid to white margin. Gills 14-17 reaching the stem, broadly adnate to somewhat decurrent, white, the edge concave to horizontal, concolorous. Stem 20- 50 x 0.5-1 mm, equal or somewhat broader at the apex, straight to curved, glabrous, cartilaginous, pale yellow-brown, whitish apex and darker below, the base covered with long, coarse fibrils. Odour none. Basidia 16-27 x 7-9 µm, clavate, 4-spored. Spores 7.5 - 9.8 x 4.5 -5.7 µm, Q = 1.3-1.8, Qav ˜ 1.5, pip-shaped, amyloid. Cheilocystidia 16-33 x 10-17 µm, forming a sterile band, clavate to obpyriform, apically covered with cylindrical excrescences 1 - 7 x 0.5 µm. Pleurocystidia absent. Lamellar trama dextrinoid. Hyphae of the pileipellis 3-12 µm wide, densely covered with cylindrical excrescences up to 3 x 0.5 µm. Hyphae of the cortical layer of the stem 1 - 5 µm wide, smooth to sparsely covered with minute warts to cylindrical excrescences 0.5-1 x 0.5 µm, terminal cells clavate, diverticulate. Clamps present but not always easy to detect.
Ecology and distribution
Densely cespitose on fern rhizomes, mainly of Athyrium filix-femina. Autumn. Rare in Norway, mostly found in northern parts of the country.