Terrestrial, among mosses, wooden chips or humus, possibly connected to buried wood. Summer to autumn. Very rare. Known from France, Switzerland, Spain, (Germany?), and Norway.
Pileus 10-15 mm across, at first conical, becoming convex to plano-convex with a prominent, acute papilla, hygrophanous, dark grey-brown to blackish when moist, sometimes paler at the margin, then cinereous to sepia-grey when drying, with black papilla, glabrous, translucent-striate, somewhat shiny and cartilaginous, margin sometimes crenulate with age. Lamellae (15-) 18-25 (-28) reaching the stipe, ascending, broadly adnate, never decurrent, whitish to pale grey, the edge covex, concolorous. Stipe 20-50 x 1-3 mm, cartilaginous, terete to compressed, equal or slightly enlarged at the base, glabrous, shiny, whitish to grey-ochraceous, sometimes dark grey or pale brownish towards the base, more or less rooting (up to 2.5 cm under the ground), the base covered with numerous, long, white fibrils. Odour absent.
Basidia (20-) 25-40 x 5.5-9 µm, clavate, generally 4-spored, sometimes 2-spored or 1.spored at the same lamella, rarely 2-spored, with sterigmata up to 6 µm long. Spores 8-11(-13) x 6-8(-9) µm, Q=1.5-1.9, Qav=1.7, broadly pip-shaped, smooth, non-amyloid. Cheilocystidia 21-49 x 2.5-7.5 µm, occuring mixed with basidia, but on part forming a sterile band, variable in shape, cylindrical to clavate, never ventricose, often flexuous, smooth, apically obtuse, sometimes furcate or covered with a few short excrescences. Pleurocystidia absent. Lamellar trama non-dextrinoid. Hyphae of the pileipellis 2-4.5 µm wide, irregularly covered with sparse, obtuse, single or rarely furcate or branched, sometimes curved excrescences 1-10 x 0.5-2.5 µm. Hyphae of the cortical layer of the stipe 1-4 µm wide, smooth, terminal cells 1-4 µm wide, often in clusters, irregularly clavate, flexuous, sometimes branched apically. Clamp connections present in 4-spored form, but not numerous, hard to find.
Additional microscopic drawings.
The description has been taken from Kühner's account and Esteve-Raventós (1995), complemented by observations on two Norwegian collections.
Mycena atropapillata is a member of section Hiemales Konrad & Maubl. subsection Hiemales on account of its ascendent, broadly adnate lamellae and non-amyloid spores. According to Esteve-Raventós (1995), the diagnostic characters of M. atropapillata are: 1) the prominent and black papilla, 2) the typical rooting stipe, which sometimes may be quite reduced, 3) the presence of a diverticulate pileipellis, 4) heterogeneous lamellar edge, 5) more or less cylindrical cheilocystidia, which are never ventricose, and 6) terrestrial habitat.
It seems to be rare all over Europe, and there are not many references to this species in the literature. Esteve-Raventós (1995) provided a comprehensive description, based on material from France, Switzerland and Spain. Contrary to Maas Geesteranus (1991), who never saw any material, he showed that the pileipellis of M. atropapillata is diverticulate, and in that aspect it comes close to M. hiemalis. The latter may also sometimes have a little umbo on the pileus and similar attachment of the lamellae. However, M. hiemalis is paler coloured, it grows directly on wood, and, above all, the cheilocystidia and caulocystidia are broader, typically ventricose. Kühner measured narrower spores. Esteve-Raventós too described the spores somewhat narrower than in the two Norwegian collections.
Mycena radicifer Favre is possibly the same species. It was described by Favre in 1957, and was supposed to differ from M. atropapillata by 1) gills narrowly adnate to adnate, decurrent with a very short tooth, 2) hyphae of the pileipellis sparsely covered with simple to furcate or branched excrescences up to 35 µm long, 3) hyphae of the cortical layer of the stipe smooth, and 4) terminal cells coarsely diverticulate. Maas Geesteranus (1991) accepted both as separate species (although he did not see material of M. atropapillata) because M. atropapillata was considered as a species with smooth hyphae in the pileipellis and M. radicifer as a species with the hyphae diverticulate. Esteve-Raventòs (1995), however, showed that the pileipellis in M. atropapillata is diverticulate too.
Further images on the web:
Matthias Dondl (as Mycena radicifer)
Pilze München (as Mycena radicifer) 1 2 3 4