Mycena subroriduliformis L. N. Liu 2025, sp. nov.

Mycena subroriduliformis L. N. Liu sp. nov. Figs 8, 9 Diagnosis. Differs from M. surculosa in having a viscid pileus and stipe. Holotype. China • Hunan Province, Suining County, Hunan Huangsang National Nature Reserve, Shaoyang City, 26°24'47"N, 110°05'20"E, elev. 542 m, 25 April 2024, LiNa Liu, HUIF 50540 (collection number NN 540). Etymology. Refers to the viscid pileus and stipe of the new species. Description. Pileus 2–8 mm diam., hemispherical when young, campanulate with age, with obvious depression at the center, sulcate, translucent-striate, surface wet, glabrous, brownish white (7 A 1), light brown (7 C 3), brownish grey (7 D 1–6 D 2) when old. Context white, thin, and fragile. Lamellae 18–20 reach the stipe, with 1–2 tiers of lamellulae, decurrent, white (4 A 1), concolorous with the sides. Stipe 2–45 × 1–2 mm, cylindrical, hollow, fragile, surface glutinous, white (4 A 1) to brownish grey (5 A 1–5 D 3) towards the apex, light brown to brown (5 D 6–6 D 6) towards the base, base swollen. Odor and taste indistinctive. Basidiospores (6.2) 6.6–8.5 (9.0) × (3.6) 3.8–5.2 (5.3) μm, Q = 1.5–2.1, Q = 1.7 ± 0.1, pip-shaped, cylindrical, hyaline, amyloid, smooth. Basidia 19.3–26.9 × 5.6–8.0 μm, 4 - spored, clavate, hyaline. Cheilocystidia 16.8–26.9 × 6.3–17.1 μm, abundant and variably shaped, clavate to cylindrical with short, more or less branched projections, 1.0–6.0 × 1.0–2.0 μm, thin-walled, hyaline. Pleurocystidia absent. Pileipellis hyphae somewhat gelatinized, 2.0–5.0 μm wide, with irregular simple to branched warts or cylindrical excrescences, 1.0–4.0 × 1.0–2.0 μm. Hyphae of the stipitipellis 1.0–6.0 μm wide, covered with cylindrical excrescences. 1.0–4.0 × 1.0–2.0 μm. Clamp connections are present in the basidia, pileipellis, and stipitipellis hyphae. Habitat. Gregarious on decaying leaves of deciduous trees. Known distribution. Shaoyang City, Hunan Province. Additional materials examined. China • Hunan Province, Suining County, Hunan Huangsang National Nature Reserve, Shaoyang City, 26°24'39"N, 110°05'25"E, elev. 588 m, 25 April 2024, LiNa Liu, HUIF 50546 (collection number NN 546). Notes. The following characteristics placed this new species in the sect. Insignes Maas G. due to the viscid pileus and stipe, decurrent lamellae, pip-shaped spores, clavate cheilocystidia with coarse excrescences, hyphae of the pileipellis embedded in gelatinous matter, and diverticulate (Maas Geesteranus 1989). The three other similar species in sect. Insignes are M. surculosa Maas G. & de Meijer, M. odorifera (Peck) Sacc., and M. calceata Robich. All are differentiated from M. subroriduliformis as follows: M. surculosa has a dry pileus, with only the stipe being viscid. The apical side branches of the pileipellis are densely covered and simple to forked, with cylindrical excrescences. The stipitipellis is somewhat gelatinized (Maas Geesteranus and De Meijer 1997). Mycena odorifera has a distinctive alkaline-like odor, a pruinose stipe, pubescence, and cheilocystidia occasionally with forked apices (Smith 1935). Mycena calceata has dark brown basidiomata and relatively large spores (11.0–13.5 × 5.5–8.0 μm), smooth cheilocystidia, or one or two branches at the apex (Robich 2003).