Infundibulicybe confusa L. Fan & Y.X. Zhang sp. nov. Figs. 3, 4

MycoBank:—MB852897

Diagnosis:—Basidiomata small to medium; pileus 1.7–3.9 cm diam, infundibuliform; surface dry, smooth to finely felty, brownish flesh to pale brown, center and margin always much lighter, pale brown to cream; stipe cylindrical, coarser towards the base, hollow, surface with longitudinally fibrils, yellowish brown, base inflated with abundant white tomentum, and shorter basidiospores (5–)5.5–6.5(–7) × 3.5–4.5 μm.

Etymology:— confusa, refers to this species being confused with Infundibulicybe alkaliviolascens due to the appearance of the basidioma.

Holotype:— CHINA. Shanxi Province, Jiaocheng County, Guandi Mountain, Chailugou Village, on soil, in mixed forest of Larix gmelinii var. principis-rupprechtii and Picea asperata, elev. 1,600 m, 111°24’2’’E, 37°47’25’’N, 29 July 2020, H. Liu, J. Yang LH970 (BJTC FM1281).

Description:—Basidiomata small to medium, clitocyboid. Pileus 1.7–3.9 cm diam, infundibuliform; dry, smooth to finely felty, brownish flesh (#e0b89a) to pale brown (#c19472), center and margin always much lighter, pale brown (#edceba) to cream (#d8d0bb), margin straight, sometimes slightly involute. Lamellae long-decurrent, white (#eef0e8) to light cream (#f1f0de), moderately crowded, with lamellulae of 1 or 3 tiers, edges smooth and concolorous with faces. Stipe 2.5–3.9 × 0.6–1 cm, central, cylindrical, coarser towards the base, hollow, longitudinally fibrillose, concolorous with the pileus, base inflated with abundant white tomentum. 5 % KOH on the surface of the dried pileus produced no color change.

Basidiospores (5–)5.5–6.5(–7) × 3.5–4.5 μm, Q=1.4–1.6, Qm=1.5±0.1, ellipsoidal in face view, lacrymoid in lateral view, hyaline, smooth, inamyloid, cyanophilous, color not changed in KOH. Basidia 21–37.5 × 4–7 μm, clavate, hyaline, 4-spored or 2-spored, sterigmata 2–5 μm long. Cystidia absent. Lamellar trama regular; hyphae 3–8 µm wide, colorless, hyaline, cylindrical. Pileipellis a cutis composed of repent, cylindrical, subparallel, septate, thin-walled hyphae, with intracellular yellowish brown pigment 3–11 μm wide. Stipitipellis a cutis composed of subparallel cylindrical hyphae 5–8 μm wide. Clamp connections present in all parts of the basidiomata.

Ecology and distribution:—associated with the mixed forest of Larix gmelinii var. principis-rupprechtii and Picea asperata, at elevation 1,600 m, only known from Shanxi Province, northern China.

Additional specimen examined:— CHINA. Shanxi Province, Jiaocheng County, Guandi Mountain, Chailugou Village, on soil, in mixed forest of Larix gmelinii var. principis-rupprechtii and Picea asperata, elev. 1,600 m, 111°24’2’’E, 37°47’25’’N, 29 July 2020, H. Liu, J. Yang LH974 (BJTC FM1285).

Notes:—In the ITS phylogenetic tree (Fig. 1), Infundibulicybe confusa and I. bresadolana are phylogenetically closely related to each other, but I. bresadolana has smooth basidiomata, more reddish colors, brownish gills in mature basidiomata, longer and narrower basidiospores (5.5–8.0 × 3.1–4 μm), which are usually lacrymoid, or ellipsoid to oblong, and usually grows on grasslands associated with Dryas sp. (Harmaja 1969). Morphologically, I. alkaliviolascens shares similarities with I. confusa in the yellowish brown basidiomata, but it can be differentiated from the latter by the violet to purplish pink reaction to KOH on the dried pileus, and long basidiospores (6–8.5(9) × (3)3.5–4.5 μm) (He & Yang 2023).