On fallen leaves of Salix. Autumn. So far Mycena terena has been reported from two localities in South East Norway, and in western Jutland, Denmark. Listed as DD in the Norwegian Red List (2021).

Pileus 1-3 mm across, conical, parabolical, campanulate, hemispherical, young occasionally with a small papilla, later mostly umbonate, flattening with age, rarely plano-convex and with the centre somewhat depressed, generally shallowly sulcate, translucent-striate or not, minutely pruinose, glabrescent, dry, at first very pale grey or pale beige, often with the centre darker grey, fading to white, often with the centre yellowish or ochraceous brown when drying. Flesh thin, pallid. Lamellae 0-8 reaching the stipe, usually well developed (although less than 0.5 mm broad) but occasionally only showing as faint ridges, tender, ascending, becoming subhorizontal, adnate to broadly adnate, smooth, white, the edge more or less concave, white. Stipe 5-10(-23) x <0.2 mm, equal, terete, flexuous, smooth, minutely pruinose, glabrescent, entirely black in very young specimens except for the base which is whitish, retaining the black colour only at the very apex when growing older, watery grey to dark grey farther below, finally fading to greyish white or watery white throughout, the base attached to the substratum by shorter or longer, fine, white, shiny fibrils, but often seemingly inistituous. Odour none, taste not recorded.

Basidia 17-27 x 7-10 μm, clavate, 4-spored, with plump sterigmata 4.5-6.5 μm long. Spores 7.2-9.5 x 4.5-5.8 μm, Q 1.5 - 2.2, Qav ~ 1.8, pip-shaped, smooth, amyloid. Cheilocystidia 17-34 x 6.5-11 x 0-4.5 μm, occuring mixed with basidia (lamellar edge heterogeneous), cylindrical, subclavate, fusiform, sublageniform, occasionally sigmoid, smooth, rarely with a few, very coarse excrescences, apically generally broadly rounded but also more or less narrowed to form a neck. Pleurocystidia absent. Lamellar trama dextrinoid, vinescent in Melzer's reagent. Hyphae of the pileipellis 4.5-16 μm wide, densely covered with cylindrical, straight excrescences 1-2.5 x 0.9 μm, terminal cells up to 17 μm wide, clavate, some more globose. Hyphae of the cortical layer of the stipe 1.5-4.5 μm wide, more or less densely covered with cylindrical, sometimes more thorn-like, straight to curved excrescences 1-3.5 x 0.9 μm. Clamp connections present in all tissues, but clamps infrequent and easily missed.

Mycena terena is characterized by its occurence on fallen Salix leaves, the minute size, the greyish-white pileus, and the black stipe (the latter feature easily seen in young specimens, but in older specimens it may be present only at the very apex, or may even be entirely disappeared). It's a member of sect. Polyadelphia, and has many features in common with the section's type species, Mycena polyadelpha. There is one character, however, by which it at once can be separated from the latter: the cheilocystidia are smooth.

A similar looking, species, also growing on fallen Salix leaves and with equally smooth cheilocystidia, is the recently described M. guldeniana. It can be distinguished by the the grey-brown pileus, somewhat broader spores, and occurence in alpine sites. ITS sequences obtained by the Norwegian Barcoding Project (NorBOL), however, are indicating that the two taxa are conspecific. More collections and further analyzes are needed to conclude. For now they are retained as separate species on this web site.

Quite often M. terena grows together with a tiny, white species of Marasmius. More confusion, however, may be caused by specimens of M. mirata. They can be equally white, usually growing on small twigs but also on fallen leaves of Salix, and even the black apex of the stipe can be present. A microscopic investigation, however, will readily separate the two species.

. Microscopic features