Agaricus padanus Lancon.

Wang, Zhuo-Ren, Callac, Philippe, Zhou, Jun-Liang, Fu, Wen-Jin, Dui, San-Han & Zhao, Rui-Lin, 2015, Edible species of Agaricus (Agaricaceae) from Xinjiang Province (Western China), Phytotaxa 202 (3), pp. 185-197 : 191

Agaricus padanus Lancon. in Rivista Micol. 1 (2002: 31). (Figure 2: D–H; Figure 4)

Basidiomata developed underground and completely covered by universal veil when young, then the center of the pileus emerges from soil or the whole basidiomata still stays in soil when mature. Pileus 40–80 mm in diameter, pulvinate or irregular pulvinate to convex, plane to slightly depressed at center in age and margin distinctly involute; surface covered by appressed, light brown to yellowish-brown squames on a dirty white background, reddish-brown on bruising. Lamellae free, crowded, brown to dark brown, very narrow, with paler and even edge, with 2–4 series of lamellulae. Stipe 40–80 × 30–38 mm, cylindrical and tapering sharply or round base; covered by a peronate sheath, and disrupted into coarse scales, sometimes in circles, light yellowish-brown; surface smooth or fibrillose, white to dirty white. Annulus superous, single, membranous, around 4 mm broad, pendant, white to yellowish-white. Context firm, first light greyish-white, discolouring pink, then violaceous purple. Odour mushroomy.

Macrochemical reactions: KOH negative; Schäffer reaction negative.

Basidiospores 7.3–8.8 × 5.4–6.8 μm, avX = 8 ± 0.4 × 6.6 ± 0.4 μm, Q = 1.1–1.4, avQ = 1.22, n = 20, subsphaerical to broadly ellipsoid, thick-walled, brown, without apical pore, smooth. Basidia 18–30 × 6–7 μm, clavate, hyaline, 2 or 4-spored with short sterigmata (less than 2 μm long). Cheilocystidia clavate, broadly clavate or irregularly clavate, often with 1–2 septa at the base, hyaline or with yellowish-brown vacuolar pigment. Terminal element 25–30 × 10–16 μm (7 μm wide at the base). Pleurocystidia absent. Pileipellis a cutis composed of cells 4–6 μm wide, cylindrical, hyaline or with yellowish-brown parietal pigments, occasionally branched, not or slightly constricted at septa. Annulus composed of cells 5–10 μm wide, cylindrical not constricted at septa or elongate-ellipsoid constricted at septa, hyaline, smooth, branched, curved.

Habit, habitat and distribution:—gregarious, sometimes in fairy rings, in soil of poplar forest and reedy grassland. Only known from Italy and China.

Materials examined:— CHINA, Xinjiang Province, Bortala, Ebinur Lake, 2011, WZRxinjiang2, ibidem, 10 May 2012, WZR2012 8213, WZR2012 903, WZR2012 904, all collected by Zhuo-Ren Wang. All in SWFC! and HMAS!

Notes:— Agaricus padanus was initially described from Italy and these are the first records outside Italy. The samples from western China match very well the European descriptions of the species, in having yellowish-brown, appressed squames on pileus, a stipe covered by a sheath when young, broken in squamose circles when mature; large spores and broadly clavate cheilocystidia with a septate base ( Parra 2008). This species had been thought to be a member of section Bivelares ( Didukh 2004) because of its partial morphological similarity to A. bitorquis (the type species of section Bivelares ). However, the two sequences KJ575603 and KJ575604 which were from specimens provided by the author of the species ( Lanconelli 2002) and collected in the type locality, do not belong to section Bivelares , but to section Nigrobrunnescentes according to Parra et al. (2014) and this study.