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

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

Fig. 3 View Figure 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).