Solitary on fallen, decaying Quercus leaves. Autumn. Known from the Netherlands, Spain and Sweden.

Pileus up to 10 mm across, obtusely conical to parabolical, shallowly sulcate, glabrous, at first white, then very pale pink. Flesh thin, whitish. Lamellae ascending to somewhat arcuate, adnate, decurrent with a tooth, white, becoming pale pink, with white edge. Stipe 20-65 x 1-1.5 mm, hollow, equal, terete, smooth, apically minutely puberulous, glabrescent farther below, very pale pink, the base fastened to the substratum by radiating white fibrils. Odour nitrous, taste not recorded.

Basidia 22-36 x 7-9 µm, slender-clavate, 4-spored, with sterigmata up to 7 µm long. Spores 7-9.5 x 4-5.5 µm, elongated pip-shaped, almost cylindrical, smooth, amyloid. Cheilocystidia 13-50 x 5-15 x 2.5-4.5 µm, occuring mixed with basidia, not embedded in gelatinous matter, fusiform to clavate, smooth or covered with one or few coarse excrescences apically or sometimes laterally. Pleurocystidia absent. Lamellar trama dextrinoid, vinaceous brown in Melzer's reagent. Hyphae of the pileipellis 1.8-4.5 µm wide, covered with simple to somewhat branched, cylindrical, more or less curved excrescences up to c. 20 µm long which are difficult to discern because of gelatinous matter. Hyphae of the cortical layer of the stipe 2-3.5 µm wide, gelatinized, smooth to fairly sparsely covered with cylindrical, simple or furcate excrescences 2-21.5 x 1.5-2.5 µm, the terminal cells 2.5-7 µm wide, coarsely and densely diverticulate. Clamp connections present.

Examined material: SWEDEN: Blekinge, Olofström, Snöfleboda 23 Aug 2008, 'Auf faulenden Blättern von Quercus robur im Auwald', leg. E. Ludwig & A. Rydberg (M-0160123).

The macroscopic description above is based on the type description (Maas Geesteranus 1992) and Ludwig & Ryberg (2009). The microscopic details are complemented by my own observations on a Swedish collection, kindly put to my disposal by the Botanische Staatssamlung München. In the type description, nothing was mentioned about the smell, but the collectors of the Swedish collection emphasized a distinct nitrous smell (Ludwig & Ryberg 2009).

When Mycena mitis was described from the Netherlands by Maas Geesteranus (1992), he placed it in sect. Insignes Maas Geest. mainly on account of the gelatinized hyphae of the pileipellis and stipitipellis. Later, Villarreal et al. (1999) transferred it to sect. Fragilipedes and stated that all members of sect. Insignes, in addition to having a gelatinous layer embedding the hyphae of the pileipellis and the stipitipellis, also have invariably arcuate lamellae.

The essential characters of M. mitis are:

Another pink species growing on fallen Quercus leaves is Mycena smithiana but it is a completely different species with cheilocystidia densely covered with small warts and short cylindrical excrescences, and with 2-spored basidia.