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

Mycena fulvomarginata L. N. Liu sp. nov. Figs 4, 5 Diagnosis. Differs from the closest species, M. rubromarginata, in having yellow lamellae edges and light-yellow contents in cheilocystidia, hyphae of the pileipellis, and stipitipellis. Holotype. China • Hunan Province, Suining County, Hunan Huangsang National Nature Reserve, Shaoyang City, 26°25'41"N, 110°03'27"E, elev. 1075 m, 26 June 2021, LiNa Liu, HUIF 50088 (collection number NN 88). Etymology. Refers to the yellow color of the lamellae edges. Description. Pileus 4–8 mm diam., hemispherical when young, paraboloid or campanulate with age, sulcate, pellucid-striate, pruinose, apex with obtuse umbo, the margin infrequently out of flatness, dark reddish brown (7 C 8) at center, gradually becoming paler towards the margin to light brown (7 A 6), turning purple (12 B 5) with age. Context white, thin, fragile. Lamellae 10–12 reach the stipe, with 1 tier of lamellulae, adnexed, white (4 A 1), edge yellow (5 B 7), stipe 6.0–12.0 × 0.5–1.0 mm, central, cylindrical, hollow, fragile, finely white pruinose and pubescent, pale brown (6 D 7) to brown (6 F 7), fading to purple (12 B 5). Base slightly bulbous, covered with white fibrils. Odor and taste indistinctive. Basidiospores (7.8) 7.9–9.9 (10.0) × (4.5) 5.7–8.0 (8.2) μm, Q = 1.2–1.7, Q = 1.3 ± 0.1, subglobose to broadly ellipsoid, hyaline, smooth, thin-walled, amyloid. Basidia 24.8–33.5 × 8.2–13.5 μm, 4 - spored, clavate. Cheilocystidia 22.6–45.8 × 7.7–17.8 μm, abundant, fusiform to ventricose, clavate, subcylindrical, or somewhat irregularly shaped, smooth or covered with one or more apical simple to furcate excrescences, with light yellow contents. Pleurocystidia absent. Hyphae of the pileipellis 3.0–9.0 μm wide, covered with simple to much-branched excrescences, 2.0–6.0 × 2.0–4.0 μm, with light yellow contents. Hyphae of the stipitipellis 2.0–5.0 μm wide, covered with numerous simple to furcate cylindrical excrescences, 2.0–11.0 × 2.0–8.0 μm, with light yellow contents. Clamp connections are present in the basidia, pileipellis, and stipitipellis hyphae. Habitat. Gregarious on moss-covered bark of living deciduous trees. Known distribution. Hunan Province and Guangxi Zhuang Autonomous Region, China. Additional materials examined. China • Guangxi Zhuang Autonomous Region, Baise City, Leye County, Yachang Orchid National Nature Reserve, 24°46'29"N, 106°20'09"E, elev. 1080 m, 24 April 2024, LiNa Liu, HUIF 50089 (collection number NN 89). Notes. Mycena fulvomarginata belongs to sect. Rubromarginatae Singer ex. Maas Geest. due to the very small basidiomata, yellow lamellar edges, cheilocystidia with colored contents, diverticular pileipellis, and stipitipellis hyphae, along with exhibiting a growth habit on decaying wood. Mycena fulvomarginata is similar to the species described in this section: M. rubromarginata (Fr.) P. Kumm., M. seynii Quél., and M. bulliformis B. A. Perry & Desjardin. They resemble M. fulvomarginata in the shape of their cheilocystidia, are covered with excrescences on the pileipellis and stipe cortical hyphae, and have a similar brown pileus. However, M. rubromarginata differs in that it has longer pileipellis excrescences, up to 36 μm, and cheilocystidia that are 20–65 (up to 90) μm long, with reddish-brown contents (Robich 2003; Aronsen and Læssøe 2016). Mycena seynii should be easy to separate from the new species by its medium basidiomata, larger basidiospores measuring 10.5–15.0 × 6.0–7.5 μm, reddish-purple edge, larger cheilocystidia measuring 30–85 × 8–16 μm, pileipellis, and stipitipellis hyphae with brown to dark red granular contents (Robich 2003; Aronsen and Læssøe 2016). In addition, M. bulliformis differs from M. fulvomarginata by its violet to violet-brown edges, ellipsoid to broadly ellipsoid spores, and some smooth pileipellis hyphae (Perry and Desjardin 2016).