Growing solitary or in small groups among vegetable debris under various deciduous trees but also on fallen needles in Picea woods on calcareous soil. In Europe it grows typically under Fagus but in Norway it had mainly been found under Alnus until it was collected under Fagus in Vestfold 2000. Listed as vulnerable (VU) in the Norwegian Red List (2021). Autumn.

Pileus 15-50 mm across, hemispherical to campanulate, becoming plano-convex, shallowly sulcate, translucent-striate, hygrophanous, glabrous, slightlylubricous when moist, date brown to pale dingy purplish brown or pale lilaceous brown, from centre outwards drying pale ochraceous or beige, with or without a pinkish shade. Odour strong, raphanoid. Taste similar. Lamellae 29-50 reaching the stipe, ascending, becoming horizontal, at first narrowly adnate or emarginate, then adnate to decurrent with a tooth, smooth to transversely ribbed, dorsally intervenose, pale lilaceous grey-brown, pale purplish brown, densely punctate by minute, dark purplish brown dots (pleurocystidia), the edge crenulate, dark purplish brown. Stipe 25-80 x 2-8 mm, hollow, fragile to firm, equal or somewhat broadened downwards, straight, curved below, terete or laterally compressed, coarselly fibrillose or even floccose, whitish with slight yellowish, brownish or lilaceous tint, lenghtwise striate by dark purplish brown fibrils, the base densely white-villose.

Basidia slender-clavate, 4-spored. Spores 6-7.5(-8) x 3.1-4.1(-4.5) µm, Q 1.7-2.1, Qav ~ 1.9-2, pip-shaped, smooth, amyloid. Cheilocystidia 40-70 x 6-14 µm, mostly occuring mixed with the basidia, but often very much protruding, and then locally forming a sterile band, fusiform, smooth, with purplish brown contents. Pleurocystidia numerous, similar, with purplish brown contents. Hyphae of the pileipellis 1.5-4.5 µm wide, smooth. Hyphae of the cortical layer of the stipe 2.5-3.5 µm wide, smooth, terminal cells 2-8 µm wide, cylindrical, simple or apically somewhat branched. Clamps present in all tissues.

Mycena pelianthina is easily recognized as a member of sect. Calodontes on account of the large size, the purplish or violaceous tints, and the raphanoid odour. Within this section it is placed in subsection Marginatae J. E. Lange together with M. lammiensis and M. rutilantiformis (Murrill) Murrill because of the intensely coloured lamellar edge. The latter has only been recorded from the United States. Redhead & al. (2001) transferred Mycena pelianthina to the genus Prunulus, a point of view that has not been followed at this web site.

Harmaja (1985) described the until then unknown species M. lammiensis from Finland under Alnus incana (and more rarely Picea abies). It shares many features with M. pelianthina, like the violaceous tints, the raphanoid smell, and the dark violet lamellar edge. Microscopically the two species are quite similar too, the only distinct difference being the spore size. In M. pelianthina the spores rarely are more than 4 µm broad, while in M. lammiensis they are almost always broader than 4 µm. (According to my measurements (6.0-)7.5-9.0 x (3.5-)4.0-5.0 µm). The shape of the spores may be somewhat different too. In M. pelianthina the spores are somewhat narrowly pip-shaped, while in M. lammiensis they are pip-shaped to somewhat cylindrical. This is, however, hardly a distinct specific character. Harmaja claimed that the cystidia of M. lammiensis were narrower than the counterparts in M. pelianthina, and that they had longer and narrower necks. Although the outer measurements do not differ much, my impression is that Harmaja is right on this point. The cheilocystidia generally seem to be narrower and with narrower and longer necks in M. lammiensis. Another difference is that the cheilocystidia are much more protruding in M. lammiensis than the counterparts in M. pelianthina.

It is not clear to me whether the colour of the pileus is different between the two species. In Mycena pelianthina the colour is date brown to pale brown with purplish to violaceous tinges, drying to pale ochraceous or beige, with or without a pinkish shade. The descriptions of M. lammiensis suggest a more dingy lilac colour, which is turning more brownish with age. The blackening process when drying seems to be similar in both species.

Harmaja (1985) and Maas Geesteranus (1992) discussed the very slight differences between M. lammiensis and the American species M. rutilantiformis, and concluded somewhat hesitantly that M. lammiensis is a species in its own right.

Mycena lammiensis is known from 15 collections in Finland and red listed as Near Threatened (NT) (Finnish Biodiversity Information Facility 2023). An interesting question is if the Norwegian collections of M. pelianthina, collected under Alnus, from central and Northern parts of the country actually would prove to represent M. lammiensis, as suggested by Harmaja (2002: 25). Examination of three collections from the herbarium in Oslo, and five collections from Tromsø, however, showed without doubt that they are M. pelianthina. This has been cofirmed by sequences in the Norwegian Barcoding Project (NorBOL). However, in 2021 M. lammiensis was collected for the first time in Norway (see M. lammiensis).

I will express my thanks to the authorities of the herbarium in Helsinki for the loan of the holotype of M. lammiensis and an additional collection from Turku (Leg. S. Huhtinen, 30 Aug. 1985). I am also grateful for the loan of several collections of M. pelianthina from the herbaria in Oslo and Tromsø.

Go to Mycena lammiensis.