Agaricus xanthodermulus Callac & Guinb., Mycologia

Tarafder, Entaj, Dutta, Arun Kumar, Karunarathna, Samantha C., He, Mao-Qiang, Tian, Fenghua & Acharya, Krishnendu, 2023, Agaricus sect. Xanthodermatei (Agaricales) of West Bengal, India, Phytotaxa 630 (4), pp. 245-265 : 258

Agaricus xanthodermulus Callac & Guinb., Mycologia 97(2): 421 (2005) ( Figures 2g –h , 6 )

Index Fungorum Number: 501381

Pileus 35–79 mm in diameter, broadly convex to conico-convex when young, then expanding to plano-convex at maturity, often depressed at the center; surface semi moist, distinctly covered with light brown (3F1) squamules on a white background that is cracked irregularly when young, on maturity squamules diminishes and the surface apparently looks almost smooth; margin with traces of white velar remnants, sometimes rimose; context 5 mm thick at centre, fleshy, white (1A1), not discolouring on cutting. Lamellae free, 5–8 mm broad, close to crowded; with 2–3 series of lamellulae, pinkish white (12A2) to pastel pink (11A4) when young, becoming dark brown (6F6-8) on maturity; irregular, forked near the middle towards the stipe, edge even, concolorous. Stipe 30–80 × 5–11 mm, central, slightly curved at the upper half, fusiform, surface smooth at apex, slightly fibrillose towards the base, white to cream, reddish brown (9D6) at the extreme apex, turning yellowish on bruising; context fleshy, white, discolouring light yellow on cutting, slightly bulbous without rhizomorphs. Annulus superous to supramedian, double, membranous, upper surface smooth, lower surface fibrillose, thick, 40 mm diam., white (1A1). Odour phenolic.

Basidiospores [30,1,1] (5.9–)6.4–7.3(–8.2) × (3.5–)4.4–5.2(–5.6) μm, X m = 7.2 ± 1.02 × 4.6 ± 0.6 µm, Q = 1.3–1.9, Q m = 1.6 ± 0.2, ellipsoid to elongate, smooth, brown to dark brown with KOH, slightly thick-walled. Basidia 15–22 × 6–7.5 μm, clavate, hyaline, gluttulate, thin-walled, smooth, 4-spored, sterigmata 1.2–3.2 μm long. Basidioles 10–15 × 6–7 μm, clavate, hyaline, thin-walled, smooth. Cheilocystidia 12–16 × 8–10 μm, clavate, sphaeropedunculate, rarely subglobose, sometimes in chains, hyaline, thin-walled, smooth. Pleurocystidia absent. Pileipellis a cutis, hyphae 7–12 μm broad, branched, cells hyaline, thin-walled, smooth. Stipitipellis hyphae 5–7.5 μm broad, hyaline to light brown with KOH, thin-walled. Annulus composed of long cylindrical hyphae, 5–9 μm broad, hyaline with KOH, not constricted at the septa, smooth, thin-walled.

Macrochemical reactions:—KOH reaction positive, pileus surface and context turning light yellow (1A5) to yellow (2A6); stipe surface and context changing light brown (6-7D6); Schäffer reaction on pileus surface negative.

Habit and habitat:—caespitose, terrestrial on humus soil under a dicotyledonous tree.

Specimen examined:— INDIA: West Bengal, Kalimpong District, Mongbol Busty, 27°3’47.41”N, 88°27’39.25”E, alt. 1128.0 m asl., 02 June 2019, E. Tarafder & J. Tamang, CUH AM759.

Remarks:— Agaricus xanthodermulus was originally described from France ( Callac and Guinberteau 2005) and later reported to occur in Ethiopia ( Sitotaw et al. 2015). Our collection constitutes the first record for India.

Our collection matches the type description ( Callac and Guinberteau 2005), but it differs in having a pileus covered with light brown squamules on a white background that is cracked irregularly when young. However, the Ethiopian collection ( Sitotaw et al. 2015) and some French collections ( Parra 2013) match very well with our collection.

Figures

FIGURE 2. Field photographs of the basidiomata of (a–c) Agaricus endoxanthus. (d–e) A. melanocarpus. (f) A. punjabensis. (g–h) A. xanthodermulus. Scale bars: a–c = 20 mm, d–e = 10 mm, f = 20 mm, g = 15 mm, h = 10 mm. Photographed by: E. Tarafder

FIGURE 6. Agaricus xanthodermulus. (a) Basidiospores (b) Basidia (c) Basidioles (d) Cheilocystidia (e) Pileipellis hyphae. Scale bars: a–d = 5 μm, e = 10 μm. Drawing by: E. Tarafder