Harmajaea xizangense A. G. Xu & X. D. Yu 2024, sp. nov.

Harmajaea xizangense A. G. Xu & X. D. Yu, sp. nov. (Figs. 3, 4) MycoBank Number: 854093 Diagnosis:— H. xizangense differs from H. wellsiae by its relatively smaller pileus and unique geographical distribution, and differs from H. guldeniae by its larger and longer spores. Holotype:— CHINA. Tibet Autonomous Region, Linzhi City, Zayu County, on soil under mixed forests, 18 August 2021, A. G. Xu, holotype (SYAU-FUNGI-080). Etymology:—The epithet ‘ xizangense ’ refers to the type location, ‘Tibet’. Description:— Basidiomata small to medium. Pileus 4.5–6.0 cm broad, convex becoming plane and then slightly depressed at center, margin enrolled, light brown (5B2–3) to brown (5C4–7), towards centre with darker color, dry, margin striate. Lamellae short-decurrent, thin, moderately crowded, 2–3 tiers of lamellulae, undulating margin, light brown (5B3–4). Stipe 6.5–7.5 cm in length, about 0.8–1.0 cm in diam at the apex and up to 2.5 cm in diam at the base, central or somewhat eccentric, solid, subcylindrical to clavate, surface dry, longitudinally whitish-fibrillose with brown (5C4–7) background, abundant whitish mycelium. Context of pileus 2–4 mm thick, thinner at the margin, white. Odour faint, not distinct. Basidiospores (5.0–)5.5–6.5 (–7.7) × 3.0–3.8 μm, Q = 1.40–2.20, Qm = 1.65, ellipsoid to elongate-ellipsoid, surface slightly coarse under the SEM. Basidia 26.5–36.5 × 3.8–5.8 μm, 4-spored, with sterigmata 5.5 μm long, slightly amyloid. Cystidia absent. Hymenophoral trama regular, composed of cylindrical to inflated hyphae 5–10 μm wide. Pileipellis a cutis of radially arranged, inflated hyphae 5–12 μm wide, with intracellular yellow pigment. Stipitipellis composed of repent cylindrical hyphae 4–10 μm wide. Clamp connections absent in all parts of the basidiome. Habitat and distribution:—Solitary, on soil with rich humus, in montane coniferous forests, known from temperate zones of southwestern China; found during summer. Remarks:— Harmajaea xizangense is quite similar to H. guldeniae and H. wellsiae because they share a brownish pileus, decurrent lamellae, and a brownish stipe with a tomentose base. Geographically, H. guldeniae and H. wellsiae have been reported only from North America and Europe (Alvarado et al. 2018b); while H. xizangense has been found only in Tibet, China. The other three Harmajaea species have pileus diameters of 5–16 cm (see Alvarado et al. 2018b) whereas H. xizangense has a smaller pileus of 4–6 cm diameter. Furthermore, H. guldeniae has a spore size range of 4.3–5.1 × 3.0–3.8 μm, Q = 1.29–1.57, (see Alvarado et al. 2018b) so the spores are smaller and shorter than those of H. xizangense (5.5–6.5 × 3.0–3.8 μm, Q = 1.40–2.20).