Agaricus endoxanthus Berk. & Broome
Index Fungorumnumber: 226162
Pileus 65 mm diam., convex to plano-convex; disc with a broad, flattened or slightly depressed umbo; pileus margin exceeding the lamellae as a white edge; surface dry, covered by brownish-grey (8E2) to grey (8E5) fibrils, radially fissured exposing the underlying white context that turns pink in wet conditions; at disc fibrils darker and aggregated into small, scattered fibrillose squamules. Context firm, white. Lamellae free, crowded, with 10 or more series of lamellulae, up to 4 mm broad, straight or ventricose, greyish red to dull red (8C3) when young, brown to dark brown (8F4) with age; edges paler than the sides. Stipe 60 × 4–12 mm, cylindrical below, with a slightly tapered apex: base slightly swallowed with white rhizomorphs, hollow; surface both above and below the annulus glabrous, brownish grey (8E2). Annulus superior, persistent, pendent, single, up to 11 mm broad; lower surface slightly floccose; edge entire, white, and sometimes with brown granules. Odor indistinct, not phenolic or almond-like. Base of stipe and centre of disc strongly staining yellow on cutting, without color change on touching.
Spores 5–6 × 3–4 µm [x = 5.4 ± 0.6 × 3.5 ± 0.5 µm, Q = 1.25–2, Qm = 1.55 ± 0.45, n = 20], ellipsoid with attenuate apex in most cases, without germ pore, smooth, brown. Basidia 12–17 × 5–7 µm, clavate, 4-spored. Cheilocystidia (9–)11–17 × 8–12 µm, rarely seen in old specimens, mostly pyriform, some turbinate or subsphaerical, hyaline, smooth. Pleurocystidia absent. Pileipellis a cutis, composed of cells variable in size and shape, many 25–44 × 17–25 µm, others 17–25 × 5–7.5 µm, distinctly constricted at the septa, with dark brown vacuolar pigments. Annulus composed of hyphae of 5–7.5 µm diam., which are hyaline, smooth and curved. Stipitipellis with hyphae similar to those of the pileipellis, but slightly smaller. Macrochemical reactions KOH reaction yellow; Schäffer reaction negative. (Figs. 1–2)
Habit solitary in soil, in open areas of forest.
Material examined: THAILAND, Chiang Mai Prov., Mae Taeng Dist., Ban Pha Deng Village, 19°17.123’N 98°44.009’E, elev. 900m., 13 August 2006, coll.:Rui-lin Zhao ZRL3095(BBH 19611, SFSU).
Fig. 1 Agaricus endoxanthus (BBH 19611): F. Basidiomata; G. Cheilocystidia; H. Pileipellis hyphae.
Fig. 2 Agaricus endoxanthus (BBH 19611): A. Cheilocystidia; B. Basidiospores and basidia; C. Pileipellis hyphae. Scale bars: A–B = 10 µm; C = 25 µm.
Zhao RL, Desjardin DE, Callac P, Parra LA, Guinberteau J, Soytong, K, ... & Hyde K D 2013–Two species of Agaricus sect. Xanthodermatei from Thailand. Mycotaxon, 122(1), 187-195.