Growing singly or in small groups on (usually moss-covered) bark of various deciduous trees, but even on Abies and Picea (Aronsen & Læssøe 2016). Autumn to early winter. Widespread but rare to absent in Northern parts of Scandinavia. Very rare in Norway. Listed as NT in the Norwegian red list.

Pileus 2-7 mm across, viscid when moist, covered with a separable gelatinous pellicle, hemispherical, parabolical to convex, shallowly sulcate, translucent-striate, puberulous to finely pubescent, glabrescent, grey, mostly dark grey centrally, turning dingy white with a greyish shade. Lamellae 7-12 reaching the stipe, ascending, fairly broad, the edge convex, adnate, soon receding stellately from the stipe, grey to dingy whitish, the edge white. Stipe 5-10 x 0.2-0.5 mm long, somewhat elastic, terete, equal or somewhat widened towards the base, straight to curved, shiny, puberulous, glabrescent except for the lower part, grey to watery grey to whitish, usually darker below, springing from a very small, pubescent, whitish basal disc which is 1-2 mm across. Odour nitrous, sometimes experienced as indistinctive. Taste not recorded.

Basidia 22.5-30 x 13.5-18 µm, broadly clavate to obpyriform, 4-spored, with sterigmata up to 9 µm long. Spores 8-11.5 x 6.5-11 µm, Q 1.0-1.2, Qav ~ 1.1, globose or subglobose, sometimes almost triangular, smooth, amyloid. Cheilocystidia 10-22 x 5-13 µm, partly forming a sterile band, clavate, with fairly few, curved to flexuous excrescences 10-22(-33) x 0.5-1.5 µm, sometimes apparently absent or hard to find, very fugacious. Pleurocystidia absent. Lamellar trama dextrinoid, brownish vinescent in Melzer's reagent. Hyphae of the pileipellis 1-4 µm wide, embedded in gelatinous matter, smooth, branched and interwined. Hyphae of the cortical layer of the stipe 1.5-4.5 µm wide, smooth, caulocystidia up to 125 x 2-5 µm wide, more or less inflated at the base 6-9 µm wide, thin- to fairly thick-walled, septate, occasionally branched. Clamps absent.

Microphotos of cheilocystidia and pileipellis

Microphotos of cheilocystidia 2

The basal disc and occurence on bark of mostly deciduous trees should be sufficient to identify this species. In addition the (sub-)globose spores, the 4-spored basidia, absence of clamps, and the smooth, interwined hyphae of the pileipellis are reliable characters. The separable pellicle is hardly demonstrable in these tiny specimens, and this feature is easily overlooked. It is interesting to notice that the cheilocystidia seem to be an unreliable character. They are very fugacious, and now and then apparently absent. This feature was also mentioned by Maas Geesteranus & Winterhoff (1985: 248). Mycena clavularis can be found together with other bark growing 'Mycenas', as e. g. M. pseudocorticola, M. meliigena, Phloeomana hiemalis, and P. alba. The latter has equally globose spores, but is a clompletely different species, lacking a basal disc and with smooth cheilocystidia. M. tenerrima, which also can be found on moss-covered trunks of deciduous trees, has a small basal disc, but the spores are pip-shaped, the cheilocystidia are different, and clamps are present.

M. corynephora (which not yet has been recorded in Norway) has globose spores, but lacks the basal disc. Besides, it possesses clamp connections, the cheilocystidia are apically covered with warts, and the terminal cells of the hyphae of the pileipellis are conspicuously shaped, obpyriform to globose, with spiny excrescences.

M. pachyderma, a species known from southern Europe, but also recorded in Norway, is very similar, but it lacks the basal disc, it possesses clamps, the cheilocystidia are somewhat different, the spores are somewhat smaller, and it possesses pileocystidia.