On decaying Scirpus and Carex in wet areas. Probably rare in Norway.

Pileus 2-4 mm across, hemispherical with more or less depressed centre or sometimes papillate, shallowly sulcate, translucent-striate, pruinose, very pale brown with a faint pinkish shade, darker in the centre; the margin very pale, almost white. Lamellae c. 10 reaching the stipe, ascending to subhorizontal, the ege concave, fairly broad, broadly adnate, somewhat decurrent, whitish with pure white edge. Stipe up to 25 mm long, cartilaginous, equal, straight to somewhat flexuous, minutely puberulous,whitish or grey, becoming somewhat yellowish from the base with age; the base covered with short, white fibrils.

Basidia clavate, 4-spored, clampless. Spores 7.8- 10.5 x 3.8-4.5 µm, pip-shaped, smooth, amyloid. Cheilocystidia c. 25 x 7-15 µm, forming a sterile band (the lamellar edge homogeneous), clampless, clavate or somewhat irregularly shaped, covered with fairly few, more or less unevenly spaced, simple to branched, straight to somewhat curved excrescences. Hyphae of the pileipellis and of the cortical layer of the stipe diverticulate, clampless.

The description is taken from one Norwegian collection. Mycena riparia is a member of Sect. Polyadelphia Singer ex Maas Geest. and can be confused with M. culmigena Maas Geest. and M. juncicola (Fr.) Gillet, but is readily identified by the clampless hyphae and the differently shaped cheilocystidia. M. tubarioides (Maire) Kühner can be distinguished by the gelatinous matter covering the hyphae of the pileipellis, the gelatinous lamellar edge, the arcuate, very broad lamellae, the possessing of clamp connections, and the larger spores.

Go to key to sect. Polyadelphia.

Norwegian collections:

VESTFOLD, BORRE, Falkensten 26 Sept. 1987, at the base of Carex acuta, A. Aronsen M 22/87 (O-F65213 ). (Aronsen, 1988b); same locality on Carex sp. 1990.10.07, Marstad, Per (55-90) - Det. Aronsen, Arne (O-F165186).