Mycena ustalis Aronsen & Maas Geest.

Persoonia 14(1): 61 (1989).

© A. Aronsen
VESTFOLD, Tjøme, Moutmarka 15 Oct. 2006

Gregarious to cespitose in grass near Juniperus or on needles of Juniperus. Not yet found outside the type locality, where it has been collected from three different places. The type was found on needles of Juniperus in a coastal area with scrub of Juniperus communis, Prunus spinosa, and Rosa sp. Listed as DD in the Norwegian red list (2021).

Pileus 10-40 mm across, parabolical to conical or campanulate, becoming broadly convex to applanate, then often umbonate, sulcate or not sulcate, very finely fibrillose (somewhat reminiscent of the pileus surface of some species of Inocybe), especially at the centre, translucent-striate, dry, slightly lubricous when moist (with dirt sticking to the surface), shiny, very dark sepia brown to black or even bluish black at the centre, sepia brown farther outwards, fading to grey-brown with age, margin straight to somewhat flaring with age, at first almost white, turning brownish. Flesh thin, very dark under the upper surface, paler farther below. Lamellae 16-24 reaching the stipe, tender, ascending, c. 2 mm broad, ventricose, narrowly adnate, sometimes uncinate, thin and smooth when young, much thickened, strongly veined or rugose, and intervenose with age, at first white, then dark grey; the edge convex, white to pale grey. Stipe 30-80 x 4-5 mm, stocky, hollow, terete or somewhat compressed and fissured lengthwise, straight or somewhat curved, smooth, at first conspicuously white-puberulous all over, glabrescent for the greater part (except at the apex), slate-coloured, dark bluish grey, particularly at the apex, gradually becoming paler and turning somewhat more brownish, the base densely covered with long, fairly coarse, somewhat woolly, white fibrils. Odour nitrous, taste not recorded.

Basidia either 25-35 x 6.5-8 µm, slender-clavate, 2-spored and clampless with sterigmata up to c. 8 µm long, or 30-45 x 8-9 µm, 4-spored and clamped. Spores (basidia 2-sp.) (7.6-)9.0-11.8(-14) x (5.0-)6.0-7.2(-8.5) µm, Q = 1.6-2.3, Qav ≈ 1.8, or (basidia 4-sp.) 7.6-9.0 x 5.4-5.6 µm, pip-shaped (those which are shorter and fairly broadly pip-shaped probably being immature), smooth, amyloid. Cheilocystidia 20-60 x 7-16 µm, originally forming a sterile band (lamellar edge homogeneous) but soon crowded out by vigoroulsy developing younger generations of basidia, clavate to fusiform, clampless (basidia 2-sp.) or clamped (basidia 4-sp.), smooth, apically broadly rounded or mucronate, more rarely with a longer, slender neck. Pleurocystidia similar, scanty, unobtrusive. Lamellar trama dextrinoid, brownish vinescent in Melzer's reagent. Hyphae of the pileipellis 2.5-6.5 µm wide, clampless or clamped, smooth. Hyphae of the cortical layer of the stipe 1.5-4.5 µm wide, clampless or clamped, smooth, the terminal cells (caulocystidia) 25-90 x 2-22.5 µm, cylindrical, narrowly to broadly clavate, ellipsoid to more or less irregularly shaped, simple or, more rarely, furcate, smooth. Clamps present in all tissues in 4-spored form, absent in 2-spored form.

Microphotos of cheilocystidia

Mycena ustalis is a member of the large section Fragilipedes. It is characterized by its very dark colour of the pileus, a white-puberulous, slate grey stipe, and nitrous smell. Important microscopic features are the smooth hyphae of the pileipellis and of the cortical layer of the stipe, as well as the smooth ceilocystidia.

M. leptocephala generally has a paler cap, strongly diverticulate hyphae of the pileipellis, and variously shaped, often much inflated caulocystidia. M. austera is another dark, nitrous smelling species, which can be distinguished by large fusiform to lageniform cheilocystidia, diverticulate hyphae of the pileipellis with very prominent terminal cells, sparsely diverticulate hyphae of the stipitipellis.



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© Arne Aronsen 2002-2023