Densely gregarious to fasciculate on decayed wood of deciduous trees, typically Fagus. Often in great numbers. Late autumn to early winter. Known from Austria, Belgium (red listed), Denmark, Estonia, Finland, Germany, Norway, Poland, Sweden, and Switzerland. Not recoded in the UK (Aronsen & Læssøe 2016). Fairly common in one old Fagus forest in south east Norway. No other confirmed records, except for two collections on Betula from Troms in north Norway (confirmed by microscopy and sequences). Listed as Near threatened (NT) in the Norwegian Red List (2021).

Pileus 5-26 mm across, at first hemispherical, then conical, parabolical, convex to almost plane, sometimes with recurved margin, often with a small umbo but also at times slightly depressed at the centre, pruinose, glabrescent, not or very shallowly sulcate, not striate or only striate at the margin, lubricous to somewhat viscid, hygrophanous, dark brown with black-brown centre to pale brown, darker at the centre and paler at the margin, which often is whitish, drying to beige-brown to greyish beige with whitish margin. Lamellae 23-30 reaching the stipe, ascending-arcuate, broadly adnate, decurrent with a tooth, with age subhorizontal, elastic-tough, somewhat veined and forked with age, whitish, pale grey to pale brown, sometimes with brown spots, and in some collections with a pink flush. Stipe 15-45 x 1-3 mm, hollow in the upper part, terete, equal, straight, curved or somewhat flexuous, tenacious, pruinose at the apex, glabrous farther down, whitish to greyish when young, mostly with whitish apex and darker below, then becoming more yellow brown to dark brown with whitish apex, the base densely covered with whitish fibrils. Flesh tenacious, greyish to whitish. Odour indistinctive or experienced as spermatic, sourish, somewhat raphanoid-aromatic or as camembert cheese. Taste astringent-bitter. (Aronsen & Læssøe 2016)

Basidia 15-28 x 4.1-5, 4-spored, with sterigmata 2.5-4.5 µm long. Spores 4.5-6.5 x 2-3 µm, Q 1.8-2.4, Qav ≈ 2.2, narrowly pip-shaped, smooth, amyloid. Cheilocystidia 15-35 x 8-14, clavate to somewhat irregularly shaped, covered with fairly few, unevenly spaced, coarse, simple to branched, more or less curved excrescences 1.5-11 x 1-2 µm. Pleurocystidia absent. Hyphae of the pileipellis 1-3 µm wide, embedded in gelatinous matter, more or less smooth or with scattered excrescences, often undulate. Hyphae of the cortical layer of the stipe 1.5-4 µm wide, embedded in gelatinous matter, smooth to covered with excrescences 2-10 x 1-1.5 µm, terminal cells widened to 7 µm, variously shaped, coarsely divericulate. Clamp connections present at all tissues.

Microphotos of cheilocystidia 1

Microphotos of cheilocystidia 2

Microphotos of hyphae of the cortical layer of the stipe and terminal cells.

Mycena tintinnabulum is a member of sect. Mycena, where it can be identified by the more or less fasciculate growth, generally on Fagus stumps, and often in great numbers, late in the autumn and also during mild winters. The thick gelatinous pellicle, which gives it a viscid, lubricous or shiny appearance is a typical feature. Microscpoically it is first of all characterized by the very small spores, that separate it from all the other species in the section.

The spelling variant M. tintinabulum also occurs in the literature.

Further images on the Internet:

Galerie vorpommerscher Pilze

Nahuby.sk

http://www.gobice.com/html/myegallery.php?&do=showpic&pid=101&orderby=titleA

Fungi of Poland