Marasmius xingshanensis J. Q. Yan & H. Chen 2025, sp. nov.

Marasmius xingshanensis J. Q. Yan & H. Chen sp. nov. Fig. 3 Etymology. “xingshanensis” refers to its type specimen originating from the Xingshan County of China. Holotype. China • Hubei Province, Xingshan County, Yichang City, 29 June 2024, collected by Jun-Qing Yan, Lin-Gen Chen, Hong Chen, Ling Ding, HFJAU 5544. Diagnosis. Marasmius xingshanensis is mainly characterized by the rather small basidiomata, pileus dark brown, reddish brown at center, slightly paler to white towards margin; lamellae rarely forked; basidiospores mainly shorter than 7.0 μm; well-developed pleurocystidia, up to 100 μm long, subcylindrical, ventricose, narrowly utriform, apex with obtuse or short papilla, the base is constricted into a curved long or short stipe; lamellae edge is composed of a large number of basidioles and rarely basidia; cheilocystidia absent. It differs from M. riparius Singer by having smaller spores which are shorter than 7 μm. Description. Pileus 15–30 mm, plano-convex to plane, center with slightly obtuse umbo, smooth, hygrophanous, dark brown (7 F 7), reddish brown (8 D 5–6) at center, slightly paler to white towards margin, striate up to 1 / 3 from the margin, drying out to white, with grayish orange at center. Context thin, white. Lamellae 2.0–3.0 mm broad, adnexed, ventricose, moderately close, grayish red (7 B 3), light brown (7 D 5), with 2–3 tiers of lamellules, rarely forked, edges even, white. Stipe 20–41 mm long, 1.5–3.0 mm thick, central, cylindric, equal, fibrous, hollow, grayish red (7 B 3), light brown (7 D 5), smooth, the base covered with white mycelium. Basidiospores (5.0) 5.5–7.0 (7.5) × 2.2–3.5 μm (av = 6.3 × 2.9 μm), Q = (1.6) 1.8–2.7 (3.0), elongated-ellipsoid to cylindrical, slightly flattened on one side in profile, 2.3–3.5 μm broad, elongated-ellipsoid to cylindrical in face view, smooth, colorless, hyaline, inamyloid, thin-walled. Basidia 24.5–33.5 × 4.0–6.5 μm, clavate, 4 - spored. Pleurocystidia (43.0) 53.0–90.0 (100.0) × (5.7) 7.0–16.0 μm, variously, subcylindrical, ventricose, narrowly utriform, rarely branched, apex obtuse or with short papilla, the base is constricted into a curved long or short stipe, surface rarely with nodulose, smooth, slightly thick-walled, yellowish in 5 % KOH. Lamellae edge is composed of a large number of basidioles and rarely basidia, cheilocystidia absent. Pileipellis a hymeniderm composed of cells 19.0–38.0 × 7.5–18.0 μm, pyriform or broadly clavate, smooth, hyaline, thin-walled. Lamellae trama interwoven, with hyphae 5.0–8.8 μm in diam, hyaline, dextrinoid, thin-walled. Stipitipellis a cutis composed of cylindrical hyphae 4.0–8.5 μm wide, parallel, smooth. Caulocystidia absent. Clamp connections present. Habitat. Scattered on soil in broad-leaved forest or mixed coniferous and broad-leaved forests. Additional specimens examined. China • Hubei Province, Xingshan County, Yichang City, 29 June 2024, collected by Jun-Qing Yan, Lin-Gen Chen, Hong Chen, Ling Ding, HFJAU 5344; 4 July 2024 collected by Jun-Qing Yan, Lin-Gen Chen, Hong Chen, Ling Ding, HFJAU 5540. Note. Based on molecular systematics and morphological analysis, M. xingshanensis belongs to subg. Globulares ser. Brunneospermi (Oliveira et al. 2020 b; Oliveira et al. 2024). Within this series, only M. magnus lacks cheilocystidia. However, M. magnus has a larger pileus (31–122 mm), fulvous to rusty orange in color, a longer stipe (70–94 mm), and a pileipellis composed of Siccus - type broom cells (Magnago et al. 2016). Morphologically, among the known species of sect. Globulares, only M. riparius and M. ochraceus Berk. & Broome. share similar morphological characteristics with the new species M. xingshanensis, including a hymenidermal pileipellis composed of Globulares - type cells, well-developed pleurocystidia, and lack of cheilocystidia. However, M. riparius has a cinnamon pileus, with larger basidiospores (8.2–10 × 4.8–5.5 μm), smaller pleurocystidia (40–44 × 8–9 μm) (Singer and Digilio 1952); M. ochraceus has a larger pileus (30–80 mm), a longer stipe (60–110 mm) and smaller pleurocystidia (30–35 × 6–8 μm) (Berkeley and Broome 1873). In addition, morphologically, M. pallidibrunneus J. S. Oliveira, and M. pinicola Jing Si, S. H. He & Hai J. Li have the aspect of M. xingshanensis with similarly basidioma size and colored pileus. However, M. pallidibrunneus has basidiospores up to 9 μm long, and presence of cheilocystidia (Oliveira et al. 2020 b); M. pinicola has smaller pleurocystidia (26–46 × 5–12 μm), and presence of cheilocystidia (Li et al. 2023).