Agaricus albiceps R.L. Zhao & B. Cao, sp. nov. 2020
Fungal Names: FN 570665
Holotype: CHINA. INNER MONGOLIA: Hulun Buir, Genhe, Chaocha River (50°44′31″N, 121°12′20″E; 740 m above sea level [asl]), scattered on ground in coniferous forest, 25 Aug 2017, Zhilin Ling ZRL20170538 (holotype HMAS 279924).
Morphological description
Pileus 60–120 mm wide, at first broadly parabolic or hemispherical, then convex, and finally applanate with uplifted margin and center slightly depressed; surface dry, completely white or with yellowish tone at disc; edge slightly exceeding, appendiculate with remnants of universal veil when young. Lamellae free, up to 5–6 mm broad, crowded, with intercalated lamellulae, at first pink or pinkish brown, finally dark brown. Stipe 90–135 × 10–15 mm, cylindrical to slightly clavate with bulbous base, hollow, surface white, smooth above the annulus, squamulose-floccose below the annulus, becoming yellowish when bruised. Annulus superior, membranous, white, smooth on the upper surface, floccose on the lower surface. Context white on cutting, unchanging or becoming yellowish toward the base. Odor of almond. KOH reaction yellow; Schäffer’s reaction reddish orange on pileus and stipe.
Basidiospores (5.5–)6–7 × (4–)4.5–5 μm [x¯= 6.3 × 4.6 μm, Q = (1.2–)1.3–1.5, Qm = 1.4, n = 30], ellipsoid or ovoid, smooth, thick-walled, brown. Basidia 21–27.5 × 7.5–9 μm, 4-spored, clavate or slightly truncate at the apex, hyaline, smooth. Cheilocystidia 12–22 × 5–11 μm, hyaline, simple, ellipsoid, cylindrical, or catenulate, variable but often broadly globose. Pileipellis a cutis of cylindrical hyphae, 3.5–8 μm wide, not or slightly constricted at septa, hyaline.
Habitat: on ground in coniferous (Pinus) forest.
Distribution: northeast China.
GenBank Accession: ITS MK617917; 28S MK617829; tef1 MK614424
Notes: Agaricus albiceps is represented by eight specimens from the Greater and Lesser Hinggan Mountains in northeast China in a well-supported clade (85/1.0 BS/ PP) (FIG. 1). The species is similar to A. sylvicola (Vittad.) Lév.; however, A. sylvicola has smaller basidiospores (Parra 2013; Kerrigan 2016).
Reference: Bin Cao , Mao-Qiang He , Zhi-Lin Ling et al. (2020): A revision of Agaricus section Arvenses with nine new species from China.
Agaricus albiceps (ZRL20170538, holotype). A, B. Basidiomes. C. Basidiospores. D. Cheilocystidia. E. Basidia. F. Pileipellis hyphae. Bars: A, B = 2 cm; C–F = 5 μm.
