On debris and decayed wood of deciduous
trees, among conifers, and often on burnt places. Also in
moss, apparently not on wood.
Pileus up to 20 mm across, conical to campanulate, sulcate, translucent-striate, at first pruinose, then dull, becoming somewhat shiny, slightly lubricous, black-brown to black at the centre, appearing bluish grey or bluish black when pruinose, dark sepia brown towards the margin. Lamellae 15-18 reaching the stipe, ascending, adnate, decurrent with a short tooth, becoming dorsally interveose with age, white, with age turning more greyish or brownish with a whitish edge. Stipe up to 65 x 2 mm, hollow, equal, terete or somewhat compressed, straight to curved, entirely pruinose, glabrescent except for the apex, exuding a milk white fluid when broken, dark brown above, almost black below, densely covered with long, coarse, whitish fibrils at the base. Odour raphanoid to indistinctive.
In Europe, this taxon traditionally has been regarded as no more than a variety of M. galopus. Kühner (1938:226) and Moser (1983: 170) used the name M. galopus var. nigra, while Lange (1936: 36) introduced the name M. galopus var. leucogala. In recent years Horak (2005); Robich (2003: 454) treated it as a variety, and Emmett et al. (2008: 360) merely said that "some authors treat the white and dark forms as varieties, viz. var. candida J.E. Lange and var. leucogala (Cooke) J.E. Lange, or even as species; this view is not accepted here (see Chard et al. 1983)".
Chard et al. (1983: 510) found that "the results reported here suggest that these taxa (M. galopus, M. galopus var. candida, M. leucogala) are only different forms of a single variable species". Maas Geesteranus ( 1988d: 388), however, claimed that Mycena leucogala is a species in its own right, and that it can be told apart from M. galopus as follows:
Mycena leucogala: (1) stipe apically dark brown; (2) terminal cells with strongly developed excrescences, and (3) often with side-branches which have grown out into diverticulate lateral heads.
Mycena galopus (var galopus): (1) stipe apically pale brown to white; (2) terminal cells (often hard to find) with less strongly or even weakly developed excrescences; (3) without diverticulate lateral heads.
I have not been able to confirm the differences in the terminal cells as a constant character.
Mycena galopus var. leucogala has often been collected from burnt places indicating that it could be a species of its own with a narrower habitat demand, but it also appears in other habitats as debris and decayed wood of both deciduous trees and conifers.
Selected images on the Internet:
Mycology in Holland