Mostly densely fasciculate in grassland. Autumn. Originally described from Austria and also known from Switzerland, Italy and the Netherlands (Arnolds et al. 2015). There are also matching sequences from Sweden and Denmark (Olariaga et al. 2015).
Pileus 20-60 mm wide, conical, becoming flattened and conical-campanulate, with age radially rugulose, translucent-striate when moist, glabrous, hygrophanous, at first very dark brown with some purplish shade, soon becoming paler, greyish brown or pinkish-purplish brown, then losing all purplish or pinkish tints and turning greyish orange, with a yellowish beige margin. Lamellae >30 reaching the stipe, ascending, narrowly adnate, without decurrent tooth, often basally interveined and anastomosing, pale pink to white; edge concolorous. Stipe 35-80 x 5-13 mm, tough, cylindrical but often somewhat distorted, longitudinally sulcate, glabrous except for a puberulous apex, white with a silvery lustre; base white-tomentose. Odour and taste raphanoid.
Basidia 30-36 x 7-10μm, slenderly clavate, 4-spored, with sterigmata 3.5-6.5 μm long. Spores 8-11 x 4.5-6 μm, Q 1.5-2.2, Qav ≈ 1.8, pip-shaped, smooth, amyloid. Cheilocystidia 38-118 x 11-22.5 μm, occuring mixed with basidia, fusiform, clavate to lageniform, mostly long-stalked. Pleurocystidia not numerous, similar to the cheilocystidia. Lamellar trama dextrinoid. Hyphae of the pileipellis 2-6 μm wide, smooth, with terminal cells 5-17 μm wide, smooth, fusiform, subcylindrical to lageniform. Hyphae of the cortical layer of the stipe 2-4 μm wide, smooth. Caulocystidia 35-60 x 3.5-8 μm, fusiform, subcylindrical to narrowly clavate. Clamp connections abundant in all tissues.
The macroscopic description has been taken from Maas Geesteranus & Hausknecht (1994), and the microscopic details are based on re-examination of coll. WU 18414, leg. Hausknecht, 23.09.1998, Austria, NE Eggenburg, Grafenberg, Koglstein, Silikat-Trockenrasen, Brandstelle.
Mycena dura differs from the other members of the Mycena pura group by the dark pileus lacking deep purple and pink colours. Instead, the typical colour of the pileus is said to be ochre brown. Laskibar et al. (2001) and Olariaga et al. (2015) emphasized the weak raphanoid odour in contrast to the strong odour in the other members of sect. Calodontes (except for M. diosma). The protologue of M. dura, however, describes the odour and taste as "very much resembling those of Mycena pura". The lamellar edge in M. dura is heterogenous with cheilocystidia occuring in clusters among basidia while the cheilocystidia are forming a sterile edge in f. ex. M. pura. Olariaga et al. (2015) suggested that the preference for grassland habitats should be regarded as a key character of M. dura.
Mycena dura is close to M. pura but is different on account of densely fasciculate growth, dark cap when young, tough and white stem, base of stem without coarse fibrils and cheilocystidia mixed with basidia. It was confirmed via the holotype as a good species from a molecular phylogenetic point of view in Harder et al. (2010).
Olariaga et al. (2015) demonstrated the synonymy of Porpoloma aranzadii. Based on this, it is clear that the morphological variation and ecological preferences of this taxon are greater and more varied than given above based on the holotype.
Microphotos of cheilocystidia
Microphotos of pileipellis with terminal cells
Microphotos of stipe cortex with caulocystidia
Microphoto of spores
I want to express my thanks to the curator of the herbarium of the Institute of Botany in Wien (WU) for the loan of one collection of M. dura and to A. Hausknecht for the loan of the photo.