Agaricus inthanonensis L.J. Chen, K.D. Hyde & R.L. Zhao
Index Fungorum number: IF 814603; Facesoffungi number: FoF 01209
Pileus 61 mm in diam., 4 mm thick at the disc, convex to hemisphaerical; surface dry, appressed with fibrillose squamules near the margin and thick fibrils at the disc, brown (7E6) against white background, dense at the disc; margin inflexed and eroded. Lamellae free, crowded, intercalated with lamellulae, 4 mm in width, ventricose, reddish grey (8B2) to brown, dark brown with age. Stipe 136 × 6– 8 (−12 at the base) mm, cylindrical and subbulbous at the base, with rhizomorphs at the base, hollow, surface smooth and white above the annulus, appressed fibrillose brown squamulose below the annulus, discolouring yellowish brown on touching. Annulus 12 × 15 mm, membranous, white, lower side with brown to margin, upper side smooth, lower side fibrillose floccose, skirt-like. Context firm, discolouring on cutting unknown. Odour woody. Macrochemical reaction: KOH reaction yellow, Schäffer’s greyish violet or negative. (Fig. 2 j−i)
Basidiospores 5.5–6 ×3.2–4 μm [x = 5.9 ± 0.7 × 3.9 ± 0.7, Q= 1.37–1.81, Qm= 1.51 ± 0.3, n = 20], ellipsoid, brown, smooth, thick-walled, without germ pore. Basidia 16–24× 7–9 μm, clavate, hyaline, 4-spored. Cheilocystidia 15–19 × 10–14 μm, globose, cystiform, smooth, hyaline. Pleurocystidia absent. Pileipellis a cutis composed of hyphae 5–10 μm in diam., smooth, some constricted at the septa, with dark brown and membranous pigments, rarely branched. (Fig. 3)
Habitat: solitary on leaf litter in the forest dominated by Castenopsis and Lithocarpus.
Material examined: THAILAND, Chiang Mai Prov., Doi Inthanon, Sit 1, N 19°06′28.8″ E 98°44′47.3″, elv. 1050 m., 1 July 2010, collector, Jie Chen, LD014 (MFLU10-0747, holotype). CHINA, Yunnan Prov., Xishangbanna, Mengsong, 25 May 2012, collector Samantha C. Karunarathna LDMS22 (MFLU15-2400; HMAS274018).
Fig. 1 Phylogeny of Agaricus subgenus Spissicaules generated from Bayesian analysis of ITS sequences, rooted with A. campestris. Bootstrap support (BS) values > 50 % and Bayesian posterior probability (PP) values > 80 % (or >50% in some main clades) are given at the internodes (PP/BS). BT^ means the sequence is from type specimen; a clade with thick branch is corresponding a certain section in Fig. 1