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

Mycena roseolamellata L. N. Liu sp. nov. Figs 10, 11 Diagnosis. Differs from M. pura in having a brown pileus and pink lamellae. Holotype. China • Hunan Province, Ningxiang City, Biandan’ao, Lijingpu Subdistrict, 28°12'07"N, 112°32'43"E, elev. 110 m, 28 November 2023, ShengQiang Liu, HUIF 60001 (collection number NN 601). Etymology. Refers to the pink colors of lamellae. Description. Pileus 7–17 mm diam., parabolic when young, then campanulate or broadly conical with age, apex with an obtuse umbo, sulcate, translucent-striate, glabrous, dark brown (6 F 5–6 F 8) at first, then turning pale brownish yellow (6 A 4) to pale brown (6 E 4) with age, margin brownish white (6 A 2) to pale brown (6 D 4–6 D 6). Context white, fragile, thin. Lamellae 24–26 reach the stipe, with 1–2 tiers of lamellulae, adnate or slightly adnex, white (4 A 1) when young, pinkish to light pink (9 A 3–9 A 2) at maturity, concolorous with faces. Stipe 29–30 × 2.0–3.0 mm, central, cylindrical, hollow, dark brown (6 F 5-6 F 8), pale brownish yellow (6 A 4) to pale brown (6 D 7) with age, base covered with long, dense, white fibrils. Odor and taste indistinctive. Basidiospores (8.3) 8.6–10.8 (11.5) × (5.3) 5.4–6.3 (6.4) μm, Q = 1.5–2.0, Q = 1.7 ± 0.1, ellipsoid to elongated, hyaline, smooth, thin-walled, amyloid. Basidia 21.7–30.8 × 6.8–8.9 μm, 2 - spored, clavate. Cheilocystidia 26.7–84.9 × 8.6–18.7 μm, abundant, fusiform, ventricose-rostrate, obtuse apex, base tapered, with short to long stalk, smooth, hyaline, amyloid, thin-walled. Pleurocystidia similar to cheilocystidia, 52.3–105.7 × 12.3–20.9 μm. Pileipellis 1.0–6.0 μm wide, smooth, terminal hyphae sometimes diverticulate, 1.0–6.0 × 1.0–2.0 μm. Stipitipellis 2.0–5.0 μm, smooth, terminal hyphae sometimes diverticulate, 1.0–4.0 × 1.0–2.0 μm. Clamp connections are absent in the basidia, pileipellis, and stipitipellis hyphae. Habitat. Gregarious on decayed twigs of bamboo or woody debris of deciduous trees. Known distribution. Ningxiang City, Hunan Province. Additional materials examined. China • Hunan Province, Ningxiang City, Biandan’ao, Lijingpu Subdistrict, 28°12'07"N, 112°32'43"E, elev. 110 m, 22 December 2023, ShengQiang Liu, HUIF 60002 (collection number NN 602). Notes. Mycena roseolamellata is classified into sect. Calodontes based on the smooth cheilocystidia and stipitipellis. Microscopically, M. pura (Pers.) P. Kumm. is the most similar to M. roseolamellata; however, M. pura is distinguished from M. roseolamellata by its purple pileus with pinkish or brown tints, lamellae interveined with age, the presence of clamp connections in all tissues, and the absence of a root-like, pruinose stipe (Robich 2003; Aronsen and Læssøe 2016). Mycena rosea Gramberg is somewhat similar to M. roseolamellata; they have pink lamellae, smooth cheilocystidia, and pleurocystidia. Mycena rosea can be distinguished from M. roseolamellata by having a pink pileus with a dull yellow center, a white or pink stipe, and the presence of clamp connections in all tissues (Robich 2003; Aronsen and Læssøe 2016). Mycena roseolamellata is very different from any species of sect. Calodontes, owing to its brown pileus. Mycena galericulata (Scop.) Gray shares some similarities with M. roseolamellata in terms of pileus color, but M. galericulata is differentiated by the presence of non-smooth cheilocystidia, pileipellis, and stipitipellis (Maas Geesteranus 1992 a, 1992 b).