Phaeocollybia attenuata Singer

Phaeocollybia attenuata (A. H. Sm.) Singer, Lilloa 22: 567 (1951) [1949] Figs 2 E, 2 F, 3 E, 3 F, 6 Chinese name. 渐尖暗金钱菌 (Jian jian An Jin Qian Jun). Description. Pileus 1.0– 2.5 cm diam, convex to hemispherical with subumbonate in center, seen from above, sometimes appearing as a rounded triangle, margin straight to slightly inflexed and even edge; surface smooth, overall moderate orange (# c 57753), sometimes pale orange at the center, often with abundant, radially arranged pale orange (# ffe 1 ae) streaks; streaks shorter near the margin; pileus context 2 mm at the center, pale orange (# ffefe 1). Lamellae ventricose, nearly free, even to slighly undate edges, 3–5 irregularly arranged tiers, 1–2 mm wide, close, light grayish red (# dabdc 2) when young, deepening to grayish red (# d 7 aba 5) at maturity. Stipe central, cylindrical, hollow, 4–5 cm long, including pseudorhiza, 2–3 mm diam, smooth in surface, mostly desaturated dark red (# 996 a 6 a) on the upper portion, which gradually darkens into a dark grayish pink (# 504247) on the lower half. Pseudorhiza 2–3 cm long, root-like, cylindrical and hollow in the upper part, tapering and becoming solid towards the base. Basidiospores [96 / 2 / 2] 7.9–9.8 (– 11.0) × (4.3 –) 5.3–6.5 (– 7.5) μm, (N = 96, Q = 1.11–1.8, Q m = 1.51 ± 0.15, av. 8.80 ± 0.73 × 5.87 ± 0.55 μm, limoniform with apical papilla, apical and apiculus smooth, the remaining surface verruculose to verrucose, brown-toned in 1 % Congo Red and 5 % KOH solution. Basidia 24–33 × 7–8 μm (N = 20), av. 28.1 ± 2.2 × 7.4 ± 0.4 μm, mostly 4 - spored, rarely 2 - spored, sterigmata 3.1–5.0 μm long, cylindrical to clavate, occasionally curved, guttulate. Cheilocystidia 17–38 × 3–6 μm (N = 20), av. 27.2 ± 5.7 × 4.3 ± 0.6 μm, intermixed with basidia, narowly cylindrical, narrowly clavate or flexuose, frequently septate. Pleurocystidia not observed. Subhymenium thin-walled, 5–10 μm thick, with 2–3 layers of ovoid, fusiform to narrowly cylindrical, and 2.3–10.7 × 2.7–7.7 μm, av. 4.5 ± 1.8 × 4.4 ± 1.4 μm. Hymenophoral trama regular, 25–45 μm wide, consisting of thin and hyaline hyphae, narrowly cylindrical hyphal elements, 20–70 × 6–11 μm. Pileipellis two-layered: upper layer ≤ 20 μm thick, of thin, parallel hyphae 3–7 μm wide; lower layer ≥ 60 μm thick, of coarse, parallel hyphae 15–25 μm wide. Stipitipellis parallel aligned, thin-walled, hyphae 8–20 µm wide, sometimes constricted at the septal areas. Tibiiform diverticula abundant on pseudorrhizal pellis, 5–17 × 1–3 μm (N = 20), av. 11.4 ± 2.9 × 1.9 ± 0.3 μm, narrowly cylindrical to narrowly conical with capitate apex, transparent and colorless, thin-walled. Clamp connections absent in all tissues. Additional specimens examined. China • Yunnan Province, Dali City, Jianchuan County, elev. 2,441 m, 7 September 2024, Rui-Yu Li, (HKAS 154131); • ibid., Song-Ming Tang, (HKAS 154132). Notes. Phaeocollybia attenuata is reported here for the first time from China (Smith 1937; Wei et al. 2012). In the phylogenetic tree (Fig. 1), P. attenuata (HKAS 154131) forms a sister clade to P. attenuata (LLN 2071029 -51) and P. attenuata (RLE 2007-026). The Chinese material closely matches the holotype description by Smith in essential diagnostic features, including the presence of a long tapering pseudorhiza, a hollow cartilaginous stipe, the absence of clamp connections (except for very rare and scattered ones in the stipitipellis), and undifferentiated cystidia (Smith 1937). However, the Chinese collections exhibit some morphological variation and provide refined microcharacters not detailed in the protologue. The pileus in Chinese specimens is moderate orange with conspicuous pale orange radial streaks, a feature not mentioned in the original description. The basidiospores are slightly larger (av. 8.80 ± 0.73 × 5.87 ± 0.55 μm) and limoniform with a distinct apical papilla and verrucose ornamentation, whereas Smith described them as smaller (7–8 × 4–4.5 μm) and almond-shaped. Furthermore, detailed microscopic examination of the Chinese material reveals abundant tibiiform diverticula on the pseudorhizal pellis, a characteristic structure of the genus not noted in the original description. Despite these differences, the comprehensive analysis of morphological characteristics and phylogeny supports the identification of the Chinese collections as P. attenuata, indicating that the known distribution range of this species extends into East Asia, in addition to its type locality in the USA.