Agaricus planipileus

Agaricus planipileus R.L. Zhao

Index Fungorum number: IF 570226, MycoBank: MB570226, Faces of Fungi: FoF01198

Pileus 70–110 mm in diam., 6–10 mm thick at the disc, applanate, top flat; surface dry, covered by fibrillose squamules, triangular, appressed, light brown (oac646) and easily removed by rain drops, then displaying white background, margin straight and slightly lacerate. Lamellae free, 5–8 mm broad, normal to slightly ventricose, crowded, pink, reddish brown, dark brown (oac610, 636). Stipe 80–200 × 6–20 (apex) – 15–35 (base) mm, cylindrical with a bulbous base, hollow, surface smooth to slightly fibrillose and white above the annulus, floccose squamose and white with light brown tips below the annulus, staining light yellow on touching. Annulus membranous, simple, pendant, upper surfaces smooth and lower surface floccose, 8–12 mm broad, white. Context fleshy, on cutting white, in both pileus and stipe, quickly turning rubescent on exposure. Odour strong of almonds. Macrochemical reactions: KOH reaction unknown, Schäffer’s reaction negative. Basidiospores 5.7–7.3× 3.6–4.6 μm, [x = 6.3 ± 0.4× 4.1±0.3 μm, Q= 1.3–1.8, Qm= 1.5 ± 0.2, n = 20], ellipsoid, brown, smooth, thick-walled, without germ pore. Basidia 14–17×7–9 μm, clavate to broadly clavate, hyaline, smooth, 4-(2-) spored. Cheilocystidia 10.7–24× 7.8–11.8 μm, abundant, simple, pyriform, irregular ellipsoid, wide clavate, hyaline, smooth. Pleurocystidia absent. Pileipellis a cutis composed of 3–11.4 μm diam., long cylindrical, smooth, hyphae, with brownish membranous pigments, not constricted at the septa. (Fig. 1 g-h; Fig.2)

Etymology: the epithet “planipileus” refers to the applanate pileus of this species.

Holotype: CHINA, Yunnan Prov., Tengchong county, Datang, Danlonghe Village, 28 July 2011, collected by R.L. Zhao, ZRL2011250 (HMAS273997, holotype).

Habitat: solitary in the forest.

Specimen examined: CHINA, Yunnan Prov., Tengchong county, Datang, Danlonghe Village, 28 July 2011, collected by R.L. Zhao, ZRL2011250 (HMAS273997, holotype). China, Yunnan Prov., Tengchong county, Datang, Danlonghe Village, 28 July 2011, collected by S.Y. Liu, ZRL2011248 (HMAS253916).

Distribution: China.

Notes: Several species have light brown to ochre squamules on the pileus, and smaller basidiospores (>7 μm) such as A. bresadolanus and A. litoralis However, A. litoralis differs from A. planipileus in having a depressed pileus at the disc and a stipe not bulbous at the base. Agaricus bresadolanus has wider ellipsoid spores (Q = 1.24).