Agaricus dolichopus R.L. Zhao
Pileus 40–45 mm in diam., 3–5 mm thick at disc, plane, surface dry, covered by fibrillose squamules, triangular with slightly upturned tip, brown, dense at the disc and spreading towards the margin; margin straight to decurved and sometimes appendiculate. Lamellae free, 3 mm broad, crowded, intercalated with lamellulae, dark brown when mature. Stipe75–80 × 3–5 mm, equal, hollow, surface smooth or slightly fibrillose, white, not discolouring or slightly red on touching. Annulus thick membranous, 5 mm in diam., entire or torn, pendant, white, upper surface smooth and lower surface heavily floccose with brown patches at the margin. Context firm, on cutting, at first white in both pileus and stipe, then quickly turning slightly rubescent at the centre of pileus and stipe, finally after 15 min uniformly light brown. Odour mushroomy, phenol. Macrochemical reaction: KOH not distinct or yellow, Schäffer’s reaction negative. Basidiospores 4.5–5.4 × 2.9–3.7 μm [x = 5.1 ± 0.3× 3.4 ± 0.2, Q= 1.4–1.8, Qm = 1.5 ± 0.1, n = 20], ellipsoid, brown, smooth, thick-walled, without germ pore. Basidia14– 19 × 5.6–7.4 μm, clavate, hyaline, smooth, 2- or 4-spored. Cheilocystidia abundant, pyriform, broad clavate, (10–) 14– 21 × 10–14 μm, smooth, hyaline. Pleurocystidia absent. Pileipellis a cutis composed of hyphae 3.2–13 μm in diam., slightly constricted at the septa, containing light brown, to brown pigments. Annulus composed of hyphae 3.2–9 μm in diam., hyaline, branched, cylindrical. (Figs. 1–2)
Etymology: the epithet Bdolichopus^ refers to relatively long stipe of this species.
Holotype: CHINA, Yunnan Prov., Dali, Cangshan Mountain, 27 July 2014, collected by M.Q. He. ZRL2014120 (HMAS273989, holotype).
Habitat: solitary in forest.
Specimens examined: CHINA, Yunnan Prov., Dali, Cangshan Mountain, 27 July 2014, collected by M.Q. He. ZRL2014120 (HMAS273989, holotype). China, Yunnan Prov., Yimeng County, Dalongkou Forest Park, 17 August 2012, collected by Xie Meng, ZRL2012715 (HMAS273950).
Notes: These three species differ from A. magnivelaris Pegler as the latter has oblong-ellipsoid basidiospores (Qm = 1.9), while the spores of all new species are ellipsoid with a Qm = 1.5–1.6. The basidiomes of the new species are more or less reddish brown on touching or cutting or in KOH reaction, but in A. variabilicolor and A. dolichopus discolouration is very weak or indistinct; while A. kunmingensis has a distinct reddish brown discolouration in all cases. In the field, A. variabilicolor has a light brown cap which is not darker at the disc of pileus, and has a floccose stipe surface, while A. dolichopus has distinct brown triangular scales, which are darker at the disc, and a smooth to slightly fibrillose stipe surface.