Amanita castanea

Amanita castanea Thongbai, Tulloss, Raspé & K.D. Hyde, sp. nov.

Basidiomata small to medium-sized. Pileus 50–75 mm wide, parabolic to hemispheric when young, convex to plane at maturity, sometimes depressed at center, dry, slightly viscid when moist, with shiny, sericeous or silky surface, chestnut to dark brown colored, darker at center, light brown to brownish orange (7D6–7C5) towards margin, with universal veil mostly towards margin, rarely over disc, as scattered gray to brownish gray, reddish brown to grayish brown warts or small floccose patches. Margin incurved to flaring upward, non-striate, non-appendiculate. Context 2–4 mm thick above stem, soft to slightly hard, pale yellowish or cream (4A2–3). Lamellae 4–6 mm broad, free to nearly free, subdistant when mature, yellowish white (3A2–3) to very pale greenish white (30A2–3). Lamellulae of 3–6 lengths, attenuate to nearly truncate. Stipe 50–95 × 10–15 mm (length includes bulb), nearly cylindrical or slightly tapering upwards, bulbous, white to dull white ground becoming brown (6D5, 6E5) at maturity, often covered with light orange grayish orange (6B3–6C3) squamules or fine flocculae, often with brownish cirrate scales formed from the outer layer of stipe below the partial veil in mature material (note: this is a common environmental effect seen in many amanitas), turning slightly yellow brown when bruised. Context stuffed to nearly hollow, thin, yellowish white (4A2). Bulb compressible, subglobose to hemispheric, marginate, up to 28 mm wide, white to dirty white (1A1–2). Universal veil on stipe base as very short volval limb on bulb margin, cottony, greenish gray (30A1–2). Partial veil subapical, membranous, robust, skirt-like, greenish gray or greenish yellow (3B2), darker grayish green at thickened edge (Fig. 1). Odor potato-like.

Lamellar trama bilateral, divergent, mediostratum 30–40 μm wide. Filamentous hyphae 1.8–6 μm wide, branching, hyaline, with slightly inflated elements, vascular hyphae not observed. Subhymenium (Fig. 1l) 22–35 μm thick, inflated cells dominating, in 3–4 layers, subglobose, ovoid, 10–20 × 8–12 μm, subtended by concatenated partially inflated hyphal segments. Basidia (Fig. 1l–o) 32–39(–44) × 11–13(–14) μm, narrowly clavate to clavate, mostly 4-, occasionally 2-spored, with sterigmata up to 5 μm long, clamps absent. Basidiospores ) (Fig. 1b–k) [53/1/1] (7.2–) 7.3–9.4 (–9.7) × (6.3–) 6.5–8.7 (–9.4) μm, (L’ = 8.2 μm, W’ = 7.6 μm, Q = 1.0–1.19 (–1.25), Q’ = 1.09 ± 0.06), smooth, hyaline, colorless, thin-walled, amyloid, globose to subglobose, infrequently broadly ellipsoid, occassionally adaxially flattened, apiculus rather variable, sublateral, very prominent to rather small, cylindric to truncate-conic. Contents monoguttulate or occasionally granular, white in deposit. Lamellar edge sterile, filamentous hyphae 3– 7 μm wide, hyaline, colorless or pale yellow, thin-walled, inflated cells dominating, mostly globose to subglobose and sometimes ovoid, 9–22 × 9–18(–22) μm, colorless, thin-walled. Pileipellis (Fig. 2c) up to 200 μm thick, 1- layered, loose, sometime branching, filamentous hyphae with slightly swollen tips, 4–10(–20) μm wide, minimal gelatinization limited to the pileipellis surface, thin-walled, with intracellular pale yellow pigment. Universal veil on pileus (Fig. 2b) filamentous hyphae, 2.5–6.2 μm wide, branching, with slightly inflated elements, with terminal subfusiform to narrowly clavate cells, 30–53 × 15–21 μm, hyaline, thin-walled, inflated cells, globose to subglobose to ovoid to elongate, dominating, 9–22 × 9–18(–22) μm, vascular hyphae occasional. Universal veil on stipe base filamentous hyphae 3–8.5 μm wide, more abundant than on pileus, branching, hyaline, or with intracellular pale brown pigment, inflated cells similar in form to but less frequent than those on pileus, vascular hyphae occasional, 7–8.5 μm wide. Stipe trama (Fig. 2d) longitudinally acrophysalidic, filamentous hyphae 2.2–8.8 μm wide, acrophysalides subfusiform to clavate, 120–310 × 25–45 μm, vascular hyphae rare. Partial veil (Fig. 2a) filamentous hyphae 2–5 μm wide, gelatinized, branching, hyaline, inflated cells terminal, thin-walled, subclavate to clavate, 114–120 × 25–36 μm, occasionally with intracellular pale brown pigment, vascular hyphae rare.

Index Fungorum number: IF552009, MycoBank: MB 818356, Facesoffungi number: FoF 02074

Etymology: castanea refers to the chestnut color of the pileus.

Holotype: THAILAND, Chiang Mai Province, Doi-saket District, Thep-sadet Subdistrict, elev. 1300 m, 30 June 2014, B. Thongbai (MFLU15-1424!).

            Habitat: scattered on the ground in forest of Fagaceae. Specimen examined: THAILAND, Chiang Mai Province, Doi-saket District, Thep-sadet Subdistrict, elev. 1,300 m, 30 June 2014, B. Thongbai BZ201405 (holotype MFLU15-1424!, isotype BBH 40844!).

Specimen examined: THAILAND, Chiang Mai Province, Doi-saket District, Thep-sadet Subdistrict, elev. 1,300 m, 30 June 2014, B. Thongbai BZ201405 (holotype MFLU15-1424!, isotype BBH 40844!).

Distribution: Only reported from northern Thailand.