Agaricus badioniveus Linda J. Chen, R.L. Zhao & K.D. Hyde
Facesoffungi number: FoF 02283.
Pileus 3.5 cm diam, 3 mm thick at disc; convex and truncated at disc; surface dry, with yellowish brown fibrils, densely at disc, and progressively sparse towards the margin, on a white background. Margin straight, not exceeding the lamellae, with appendiculate remains of the annulus. Lamellae free, crowded, 3 mm broad, with intercalated lamellulae, ventricose, pinkish to brown with time. Stipe 45 × 7 mm (12 mm at base), cylindrical with a bulbous base, surface above the ring smooth, below the ring fibrillose, white, strongly flavescent when bruised. Annulus simple, membranous, superous, white, fragile. Context firm, white, flavescent when cut. Odour of strong almonds.
Spores (5–)5.4–5.8(–6.2) × 3.1–3.5(–3.8) µm, (x = 5.6 ± 0.12 × 3.3 ± 0.11 µm, Q = 1.54–1.86, Qm = 1.67 ± 0.01, n = 20), ellipsoid, smooth, brown, thick-walled. Basidia 15–19 × 6.5–7 µm, clavate to broadly clavate, hyaline, smooth, 4-spored. Cheilocystidia 23–35(–40) × 9–12(–16) µm, abundant, simple, or septate at base, pyriform, clavate or narrowly clavate, with yellowish pigments, smooth. Pleurocystidia absent. Pileipellis a cutis constituted of cylindrical hyphae of 6–9 um wide, not or slightly constricted at the septa, with brownish pigment. Macrochemical reactions — KOH reaction positive, yellow. Schäffer’s reaction positive, reddish orange on dry specimen. (Figs. 1–2)
Etymology: Refers to the pileus with tawny fibrils on a white background.
Habitat: Solitary on soil, in forest.
Material examined:THAILAND, Chiang Rai Prov., Doi Pui site1, 25 July 2012, J. Chen, LD2012131 (holotype MFLU12-0964).
Notes: Agaricus badioniveus is characterized by a pileus surface covered with yellowish brown fibrils, simple cheilocystidia and spores on average size of 5.6 × 3.3 μm. In gross morphology, A. badioniveus is highly similar to A. megalosporus. However, the latter species has larger sporocarps (the pileus diameter can reach 10 cm) and spores (6 × 3.5 μm on average). According to phylogenetic results, A. badioniveus is closely related to A. flammicolor, a species easily distinguished by its bright orange colour.