Solitary to gregarious among grass and moss in open areas or in mixed woods, or on tree stumps, on decayed and often moss-covered wood of both deciduous and coniferous trees, or on fallen branches. Spring to late autumn. Widely distributed in Norway.

Pileus up to 25 mm across, at first ovoid-cylindrical, then conical or parabolical to campanulate, without or with small to large umbo, flattening with age, translucent-striate, sulcate, pruinose, glabrescent, hygrophanous, at first fairly dark brown, often blackish brown, with whitish margin, then very dark grey to paler grey, or dark grey-brown to almost black-brown, pallescent when drying, turning grey-brown, the margin paler to whitish. Lamellae 14 - 26 reaching the stipe, ascending, narrowly to fairly broadly adnate, occasionally decurrent with a short tooth, becoming rugulose to veined, dorsally intervenose, fairly dark grey-brown to grey, paler with age, the edge concolorous with the sides or paler to whitish. Stipe 20-65 x 1-2.5 mm, hollow, fragile, equal or somewhat broadened below, terete, straight to curved, minutely puberulous all over, glabrescent for the greater part except at the apex, shiny, dark brown, grey-brown to grey, darker below, paler above, the apex generally greyish, but in younger specimens often bluish-black, the base densely covered with long, coarse, flexuous, white fibrils. Odour nitrous.

Basidia slender-clavate, generally 4-spored (but see remark). Spores 8-11.2 x 4-5.8 µm, Q 1.6-2.1, Qav ~1.8, pip-shaped, smooth, amyloid. Cheilocystidia 27-80 x 9-19 µm, forming a sterile band, fusiform, lageniform, subcylindrical, clavate, apically broadly rounded or mucronate or gradually to more abruptly passing into a longer or shorter neck, sometimes with a few excrescences. Pleurocystidia similar, if present. Hyphae of the pileipellis covered with cylindrical, simple to branched excrescences which may form dense masses and tend to become somewhat gelatinized. Hyphae of the cortical layer of the stipe smooth or occasionally with a few coarse excrescences just below the terminal cell; terminal cells 4.5-20 µm wide, often much inflated, variously shaped and branched, usually curved outwards or constituting caulocystidia. Clamp connections generally present at all tissues (but see remark).

Microphoto of cheilocystidia

Microphotos of caulocystidia

Microphotos of hypahae of the pileipellis

Mycena leptocephala is a member of sect. Fragilipedes (Fr.) Quél. and belongs to a group of quite similar looking species with or without a nitrous smell. M. aetites (Fr.) Quél. lacks the nitrous smell, the hyphae of the cortical layer of the stipe are diverticulate, and the terminal cells are unobtrusive, not inflated and easily overlooked. M. austera Aronsen can be distinguished on account of the absence of clamps, the conspicuously inflated terminal cells of the pileipellis, and the differently shaped caulocystidia. M. parca Aronsen is very close, but the cheilocystidia are generally more lageniform, the hyphae of the pileipellis are generally unbranched and the terminal cells of the stipe cortex are scarce and fairly narrow. The rare and poorly known M. aronsenii Maas Geest. can be separated on account of the smaller spores and the peculiar hyphae of the cortical layer of the stipe.

Among the species not found in Norway, M. fragillima A.H. Sm. seems to be very close, and in my opinion the arguments for keeping it as a separate species are rather weak. Maas Geesteranus (1992: 246) pointed out that M. fragillima had been found on fern debris, that its stipe was described as very pale watery grey, and that it was very fragile, and stated that these characters do not fit with M. leptocephala. I do not agreee. According to my experience this is within the variation of this very variable species.

Mycena leptocephala is a variable species but usually easy to identify. In the field it can be confused with several other nitrous-smelling species (e.g. M. stipata, M. abramsii, M. parca) but is readily identified on account of the smooth hyphae of the cortical layer of the stipe and the conspicuously shaped terminal cells of these hyphae, combined with the diverticulate hyphae of the pileipellis.

M. leptocephala is generally 4-spored and clamped, but Smith (1947: 243) mentioned to have found 2- and 3-spored forms. According to Maas Geesteranus (1992: 259) one of these collections proved to be devoid of clamps. Maas Geesteranus (1991b) also reported a 2-spored and clampless collection from Germany and I have myself seen both 2-spored and 4-spored collections devoid of clamp connections!

I suspect M. leptocephala to comprise more than one phylogenetic species, and this should be investigated with molecular methods.

Further images on the web:

Flemming V. Larsen

Die Pilze Pilze Galerie

kulakbiocampus/paddestoelen/