Boletinellus rhytidophyllus (M. Zang) L.R. Liu, Yan C. Li & Zhu L. Yang, comb. nov., Figs. 3a–c, 4a–e.

MycoBank: MB840441

Basionym: Paxillus rhytidophyllus M. Zang, Acta Microbiol. Sin. 18 (4): 282, Pl. I: 6–11, 1978.

Protoglogue of Paxillus rhytidophyllus (Zang and Zeng 1978): “Pileus centralis, 6–9 cm diam., convexus dein planus, viscosus, rufobrunneus dein fusco-umbrinus. Stipes 2.5–4 × 1.5–2cm, late cylindricus et basim versus attenuates, laevigatus, flavidus. Lamellae citrino-flavidae, latiusculae, postice leviter sinuatae, breviter decurrentes et basi saepe venoso connexae. Basidiosporae ellipsoildeae vel oblongo-ellipsoildeae, 8–11.5 × 6–6.5 μm, pallido-flavae, laeves, 1-guttatae. Basidia 4-sporigera. Pleurocystidia 19–35 × 12–15 μm, clavata. Cheilocystidia non vidi. Hyphae medullarum tramata irregulares et paulo divergentes. Caro flavidula. Oder nullus.”

Description:— Basidiomata (Fig. 3a–c) small to medium-sized. Pileus 2–9 cm in diam., nearly applanate, reniform or convex, soon flattened, center slightly depressed when aged, margin incurved at first and then usually irregularly undulate when mature or aged; surface felted to glabrous or subvelutinous and subviscid when wet, brown (6E6–8) to yellowish brown (5E4–5) with dark brown (6F4–8) or grayish brown (6F2–3) tinge in the center, much paler towards margin. Stipe 1.2–4 cm × 0.7–2 cm in diam., eccentric to lateral, short, cylindrical, tapering at base, glabrous, yellow (3–4A5–6) to yellowish orange (2–3B6–7) when young, light brown (5D6–8) when old, unchanging in color when bruised. Hymenophore deeply decurrent, poroid-lamellate to alveolate with many cross-veins; pores large, up to 5 mm wide in the middle zone (seemingly much wider than 5 mm at the upper part of stipe, but the connecting walls inconspicuous and therefore not taken in consideration), angular, compound, radially elongate near the margin, about grayish yellow (4B5–6) to yellow (3A4–5) or light yellow (3A2) when young, and light brown (5D7–8) when old; tubes short, not easily separable, unchanging or staining brownish when injured. Context thick, pale yellow (1–3A4), always with slight orange-white (5A2) tinge, unchanging in color when bruised.

Basidiospores (Fig. 4a) [80/4/2] (7) 8.5–11 (11.5) × (5) 6–7 (8.5) μm [Q = (1.38) 1.40–1.69 (1.75), Q m = 1.57 ± 0.11], ellipsoid to oblong, yellow, yellowish brown to light brown in water and 5 % KOH, with one large oil drop when mature, without color change in Melzer’s Reagent (non-dextrinoid, non-amyloid), slightly thick-walled (0.6–1 μm), smooth. Basidia (Fig. 4b) (15) 22–34 × 7–12 μm, clavate, 2- to 4-spored, rarely 1-spored, hyaline to pale yellow in water and 5 % KOH. Pleurocystidia (Figure 4d) 26–44 × 7–12 μm, subclavate to subfusiform, attenuate at apex, sometimes with a septum, thin-walled, rare, hyaline to pale yellow in KOH, without epiparietal encrustations. Cheilocystidia (Fig. 4c) 40–50 × 8–10 μm, absent to rare, smooth, thin-walled, morphologically similar to pleurocystidia, subclavate, attenuate at apical part, always with a septum. Hymenophoral trama composed of 4–14 μm wide filamentous hyphae, thin-walled, non-amyloid, bilateral. Pileipellis (Fig. 4e) a trichoderm, composed of filamentous hyphae, 4–8 μm wide, hyaline to pale yellow in KOH, non-amyloid; terminal cells 50–90 × 4–10 μm, subclavate or cylindrical, hyaline to pale yellow in KOH. Clamp connections present in all tissues.

Habitat and distribution:—Scattered or gathered on the river beach or cliff by the tropical forests in China; fruiting in southwestern China.

Specimens examined:— CHINA. Yunnan Province: Xishuangbanna Dai Autonomous Prefecture, Jinghong, Mengla County, on the river beach by the forest, alt. 600 m, 2 September 1974, M. Zang 01030-HK1030 (KUN-HKAS 28975, type); Xishuangbanna Dai Autonomous Prefecture, Jinghong, Mengyang County, near the Wild Elephant Valley, alt. 800 m, 21 August 2019, L. K. Jia 353 (KUN-HKAS 113221).