On decaying wood of deciduous trees. Autumn. Rare.

Pileus up to 28 mm across, convex, with a low umbo, glabrous, somewhat waxy-shiny, sulcate, translucent-striate, dark brown, blackish brown at the centre, fairly pale at the margin. Lamellae subdistant, ascending, narrowly adnate, fairly broad and thick, whitish. Stipe up to 55 x 3 mm, hollow, straight to curved, somewhat widened towards the base, glabrous except for a pruinose apex, somewhat fibrillose in lower parts, brown, the apex greyish, the base dark brown.

Basidia 27-33 x 6.5-9 µm, clavate, 4-spored, clamped. Spores 7 - 9 x 4.8 - 5.5 µm, Q = 1.4-1.6, pip-shaped, amyloid. Cheilocystidia 55 - 77 x 11 - 19 µm, smooth, fusiform to lageniform, clamped, occurring mixed with the basidia (lamellar edge heterogenous). Pleurocystidia similar. Lamellar trama dextrinoid. Hyphae of the pileipellis smooth, clamped, embedded in gelatinous matter. Hyphae of the cortical layer of the stipe smooth, clamped, caulocystidia 29 - 44 x 5 - 9 µm, clavate, smooth.

The description above has been taken from one single Norwegian record and unfortunately it is somewhat insufficient. The identification is in accordance with Maas Gesteranus' (2016) concept. He examined the collection and confirmed the identity.

Mycena algeriensis was described as a new species from Algerie by Kühner (1938), and seems to be rare in Europe (Kühner & Romagnesie 1953: 106). The species is still poorly understood. Kühner (1938: 493) pointed at the close relationship to Mycena jacobi Maire (= M. niveipes (Murill) Murill) but accepted M. algeriensis, somewhat reluctantly, as a separate species. Malençon & Bertault (1975: 225) also discussed the relationship to M. niveipes.

It seems that Mycena algeriensis can be separated from M. niveipes on account of a darker pileus, and that the cystidia are more obtusely rounded at the apex. Typical M. niveipes has a grey, almost white pileus and a pale silvery-grey or whitish-grey stipe. According to Maas Geesteranus (1988a) Mycena algeriensis can be separated from M. niveipes as follows: In M. niveipes the stipe is (very) fragile and bluish white to greyish white when young, turning white later on; the hyphae of the pileipellis are not embedded in gelatinous matter. In M. algeriensis, the stipe is elastic-cartilaginous and grey-brown to dark sepia brown; the hyphae of the pileipellis are embedded in gelatinous matter.

In the original description it is pointed out that Mycena algeriensis sometimes resembles M. galericulata, and M. polygramma sometimes is quite similar too. Both species can be distinguished by the cystidia.

The odour in the original description was described as 'nitreuse parfois faible' (Kühner 1938: 492). Malençon & Bertault (1975: 224) described the odour as 'chlorée ou de pétales froissées de Papaver rhoseas(!)'. Maas Geesteranus (1988a: 58), however, hesitated to accept that Malençon & Bertault had identified the correct species. He claimed that the odour is 'nitrous, although sometimes weak'.

Emmett et al. (2008: 387) referred to a Finnish record indicating absence of clamps. It seems relevant to point at the related species M. niveipes which appears both with and without clamps.

Emmett (pers. comm.) has recently studied the type of M. algeriensis and believes the northern European taxon belongs elsewhere (see Aronsen & Læssøe 2016). In my opinion, it is not likely that the taxon Maire described from eucalypt trunks in Algeria is identical with the various collections from Northern Europe. Some of the collections indicate some species of Hydropus, but at least a part of Scandinavian material is a genuine yet not fully understood species of Mycena.