Agaricus ignicolor R.L. Zhao.
Index Fungorum number: IF 570201, MycoBank: MB 570201, Faces of Fungi: FoF01193
Pileus 55 mm in diam., 2 mm thick at the disc, broadly conic, convex; surface dry, with flaky to sharp warty squamules, erect at the disc then recurved to margin, deep orange, and fading in rain, margin distinctly exceeding. Lamellae free, more crowded, intercalated with lamellulae, 4–5 mm broad, at first white, greyish pink, then dull red (8B3), finally brown, to dark brown. Stipe 22× 5–7 mm, cylindrical, curved, with rhizomorphs at the base, hollow; smooth and white above the annulus; with thick flaky squamules and deep orange below annulus, not staining on touching. Annulus pendent, superous, and mixed with the stipe squamules, deep orange. Context firm, white to cream in both pileus and stipe, not discolouring on cutting. Odour mushroomy. Macrochemical reaction: KOH and Schäffer’s reactions negative. Basidiospores 5–6×3–4 μm [x = 5.4 ± 0.4× 3.6 ± 0.4, smooth, thick-walled, without germ pore. Basidia 12–16× 6–7 μm, clavate, smooth, hyaline. Cheilocystidia 21–30 × 7–13 μm, clavate, broadly clavate, mostly subcapitate with apex 4–7 μm in diam., smooth or with slightly fine spines, hyaline. Pleurocystidia absent. Pileipellis a cutis composed of hyphae 2.5–5 μm in diam., equal, branched, even light yellow, smooth or fine spiny, without constriction at the septa. Annulus and stipitipellis hyphae similar to those of pileipellis. Q= 1.3–2, Qm= 1.53± 0.47, n=20], ellipsoid, reddish-brown. (Fig. 1 g-i; Fig. 2)
Etymology: “igno” refers to fire, and the species epithet “ignicolor” refers to fire-coloured basidiomes of this species.
Holotype: THAILAND, Chiang Mai Prov., Mae Taeng Dist., Ban Pha Deng village, N 19°17.123′ E 98°44. 009′, elev. 900 m, 21 August 2005, collected by Ruilin Zhao, ZRL2132 (BBH 19512, holotype; HMAS 274009, isotype).
Habitat: solitary in soils of road banks.
Specimen examined: THAILAND, Chiang Mai Prov., Mae Taeng Dist., Ban Pha Deng village, N 19°17.123′ E 98°44. 009′, elev. 900 m, 21 August 2005, collected by Ruilin Zhao, ZRL2132 (BBH 19512, holotype; HMAS 274009, isotype).
Notes: Agaricus crocopeplus Berk. & Br., A. erythrotrichus Heinem., and A. trisulphuratus are species from section Trisulphurati. All including this new species, are covered by a developed orange universal veil, which is very distinctive in the field. Agaricus crocopeplus has a white membranous annulus, which differs from the others, which have orange, flaky annuli. Agaricus erythrotrichus has much larger basidiospores (6.2–7.4 × 3.8–4.3 μm) than all others (Heinemann 1956b, 1980). Agaricus ignicolor is most similar to A. trisulphuratus; however, it could be separated by the following characteristics: (i) the edge of annulus of A. ignicolor is orange, while in A. trisulphuratus it is not coloured or slightly white; (ii) the cheilocystidia of A.ignicolor are often capitate, but in A. trisulphuratus they are clavate to cylindrical; and (iii) squamules of A. ignicolor are much more stable, and not easily removed by rain drops.