Xenasma bisterigmatae S. Y. He, H. M. Zhou & C. L. Zhao 2025, sp. nov.

Xenasma bisterigmatae S. Y. He, H. M. Zhou & C. L. Zhao sp. nov. Figs 8, 9 Diagnosis. Xenasma bisterigmatae differs from X. rimicola by its ellipsoid to subglobose and larger basidiospores (8.5–10.5 × 4.5–7 µm vs. 10–12.5 × 8–10.5 µm), two-sterigmata basidia. Holotype. China • Yunnan Province, Zhaotong, Wumengshan National Nature Reserve, GPS coordinates 27°29'N, 103°55'E, evel. 1900 m asl., on fallen angiosperm branch, leg. C. L. Zhao, 29 August 2023, CLZhao 32542 (SWFC). Etymology. Bisterigmatae (Lat.) refers to two-sterigmata basidia of the holotype. Basidiomata. Basidiomes annual, resupinate, smooth, without odor or taste when fresh, up to 6.5 cm long, 2.3 cm wide, and 100 µm thick. Hymenial surface smooth, membranaceous, ash-grey (19 C 2) when dry; sterile margin indistinct. Hyphal structure. Monomitic, generative hyphae with clamp connections, thin-walled, branched, interwoven, with dense crystal, 3.2–3.5 µm diam, IKI –, CB –; tissues unchanged in KOH. Cystidia abundant, tubular with obtuse apex, with slightly thick walls in the basal part that appears frequently collapsed, often with an apical amorphous globule, 64.5–93 × 5.5–7.5 µm. Cystidioles absent. Basidia clavate to subcylindrical, thin-walled, with two sterigmata and a basal clamp connection, with several guttules, 21.5–28 × 10–12 µm; basidioles in shape similar to basidia, but slightly smaller. Spores. Basidiospores ellipsoid to subglobose, thick-walled, verrucose, IKI –, CB –, 10–12.5 × 8–10.5 (– 11) µm, Lm = 11.15 µm, Wm = 9.3 µm, Q = 1.19–1.27 (n = 60 / 2). Additional specimens examined (paratype). China • Yunnan Province, Zhaotong, Wumengshan National Nature Reserve, GPS coordinates 27°29'N, 103°55'E, evel. 1900 m asl., on fallen angiosperm branch, leg. C. L. Zhao, 29 August 2023, CLZhao 32600 (SWFC). Notes. Based on the ITS analysis (Fig. 3), the new species Xenasma bisterigmatae was clustered with X. rimicola (P. Karst.) Donk. However, X. rimicola differs from X. bisterigmatae by its four-sterigmata basidia (Cunningham 1963).