Scattered to gregarious among grass or on vegetable debris of both decidious and coniferous trees. Autumn. Known from Austria, Denmark, France, Germany, Hungary, Italy, the Netherlands, Sweden and UK. Never found in Norway.
Pileus 6-20 mm across, conical or parabolical to campanulate, flattening with age, shallowly sulcate, translucent-striate, glabrous, hygrophanous, whitish with a pinkish lilac flush, delicately pinkish lilac or flesh-colour, somewhat more strongly pink lilac at the centre, whitish towards the margin. Odour nitrous, also experienced as raphanoid or indistinctive. Taste mild to strongly raphanoid. Lamellae 15-21 reaching the stipe, ascending, adnate, not decurrent with a tooth, smooth to dorsally intervenose, white, the edge delicately pinkish. Stipe 40-70 x 1-1.5 mm, hollow, fragile, equal, straight, pruinose above, glabrous farther down or (not infrequently) covered with a conspicuous tomentum of long, flexuous, white hairs, watery white or delicately flushed with a pinkish hue, the base densely covered with long, coarse, flexuous, white fibrils.
Basidia 21-40 x 7-9 µm, clavate, 4-spored, with sterigmata up to 5 µm long . Spores 7.8-12 x 4.2-6 µm, Q 1.5-2.2, Qav ~ 1.8-2.0, pip-shaped to somewhat cylindrical, smooth, amyloid. Cheilocystidia 17-45 x 5-17 µm , forming a sterile band, clavate, fusiform, subcylindrical to somewhat irregularly shaped, smooth or covered with one or few unevenly spaced excrescences up to 20 x 2 µm. Pleurocystidia absent. Lamellar trama dextrinoid. Hyphae of the pileipellis 1.5-5 µm wide, densely covered with simple to branched excrescences 1-10 x 0.5-3 µm. Hyphae of the cortical layer of the stipe 1-5 µm wide, smooth to sparsely covered with simple to occasionally branched, straight to curved cylindrical excrescences 1-5(9) x 1-2.5 µm, terminal cells 2.5-7.5 µm wide, sparsely to densely covered with straight to curved excrescences; occasionally also with a few smooth caulocystidia 18-23 x 5-18 µm; the entire length of the sipe or only the lower part often denselycovered with long "hairs" 45-300 x 2-5 µm. Clamp connections present but often hard to find.
The macroscopic description has been taken from Maas Geesteranus (1986c) based on Kühner's description, complemented by a French collection kindly put to my disposal by Mr. H. Cochard, Clermont-Ferrand. The microscopic detailes are based on reexamination of this French collection and one Swedish and one Danish collection.
The French collection cited here, had microscopical characters somewhat deviating from the very few descriptions published on this species. The spores were distinctly narrower than indicated by Maas Geesteranus (1986c: 288). Kühner (1938: 420), however, measured spores almost of the same size as in the present collection. The cheilocystidia had much shorter excrescences than measured by Maas Geesteranus, but again Kühner illustrated only smooth cheilocystidia. The terminal cells of the stipitipellis were quite as illustrated by Maas Geesteranus, but I also observed many cystidia-like terminal cells, almost smooth or covered with very few excrescences. This shows that the variety of this rare species probably is wider than earlier believed.
M. albidolilacea is distinguished from the other species of the section Rubromarginatae by the mainly whitish pileus with a pinkish lilac tinge and the delicately pink-coloured lameallar edge, which generally is more visible near the pileus margin. Mycena decora Maas Geest., known from the Netherlands, is similar, but should be separated on account of a smaller number of lamellae reaching the stipe (12-14), smooth hyphae of the cortical layer of the stipe, and smooth caulocystidia curved outwards at right angles. More records are needed to decide whether they are two different species.
When describing the new species M. hepatica from Spain, the authors emphasized the relationship to M. albidolilacea (Villarreal et al. 1999). M. hepatica was, however, described as a much darker species both at the pileus and the stipe, the lamellar edge was said to be strongly dark reddish-brown, and the spores were somewhat shorter than in M. albidolilacea.
Wilhelm (2011) pointed to the similarity between dry, pale specimens of M. olivaceomarginata and M. albidolilacea. The former is a highly variable species, which may also appear with pale, pinkish colours and even a pinkish-red lamellar edge. The microscopical characters, however, will distinguish the two species, first of all the differently shaped cheilocystidia.
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