Alloexidiopsis xantha J. H. Dong & C. L. Zhao 2024, sp. nov.

Alloexidiopsis xantha J. H. Dong & C. L. Zhao sp. nov. Figs 13, 14, 15 Diagnosis. Differs from other Alloexidiopsis species by its coriaceous basidiomata with cream to buff to yellow, smooth, slightly cracked hymenial surface, a monomitic hyphal system with clamped generative hyphae and allantoid to sickle-shaped basidiospores measuring 20–24 × 5–6.2 µm. Holotype. China • Yunnan Province, Lincang, Yun County, Dumu Village, 24 ° 32 ′ N, 100 ° 23 ′ E, altitude 2100 m, on the fallen branch of angiosperm, leg. C. L. Zhao, 20 October 2022, CLZhao 25093 (SWFC). Etymology. xantha (Latin or Greek origin): referring to the buff to yellow hymenial surface of the type specimen. Basidiomata. Annual, resupinate, closely adnate, coriaceous, very hard to separate from substrate, without odour or taste when fresh, becoming leathery upon drying, up to 10 cm long, 2 cm wide, 200–300 µm thick. Hymenial surface smooth, slightly cracked, cream when fresh, turning to cream to buff to yellow upon drying. Sterile margin cream, thinning out, up to 1 mm wide. Hyphal system. Monomitic, generative hyphae with clamp connections, colourless, thin- to thick walled, branched, interwoven, 2.5–3.5 µm in diameter; IKI –, CB –, tissues unchanged in KOH. Hymenium. Cystidia numerous, thin-walled, subcylindrical to subconiform with an obtuse apex, 12.5–17.5 × 3.5–6 µm, with a clamp connection at base; cystidioles absent. Hyphidia arising from generative hyphae, nodulose, frequently branched, colourless, thin-walled, 2.5–4 µm in diameter. Basidia ellipsoid to ovoid, obconical, longitudinally septate, two to four-celled, 18–20.5 × 12–15.5 µm; basidioles dominant, similar to basidia in shape, but slightly smaller. Basidiospores. Allantoid, curved, sickle-shaped, colourless, smooth, thin-walled, IKI –, CB –, (18.5 –) 20–24 (– 24.5) × 5–6.2 (– 6.5) µm, L = 21.66 µm, W = 5.63 µm, Q = 3.60–4.05, Q m = 3.85 ± 0.10 (n = 30 / 1).