Xanthagaricus flavosquamosus T.H. Li, Iqbal Hosen & Z.P. Song, sp. nov. MycoBank: MB822730 Figs 2a–b, 3, 5b
Diagnosis. Closely related to X. epipastus and X. subepipastus but differs in having larger basidiospores with verrucose surface, short but broadly clavate cheilocystidia, and found on the ground covered by fallen needles or debris of Pinus sp.
Typification. CHINA, Jiangxi Province, Jiulong Provincial Forest Park, 25 August 2015, Ming Zhang, Jun Ping Zhou & Hao Huang (GDGM 50918, holotype).
Etymology. The species epithet “flavosquamosus” (Lat.) refers to the yellow squamules on the pileus surface.
Description. Basidiomata small-sized. Pileus 8–13 mm broad, at first hemispherical to convex, then plano-convex to nearly applanate with age, yellow (2A4–7) to vivid yellow (2A8), lemon yellow or mustard yellow (3B8, 3B6), more or less yellow-brown to grayish brown at centre, concentrically fibrillose-squamulose, sometimes woolly to matted squamulose on the surface, more densely and darker at centre; margin incurved with appendiculate, often lacerated velar remnants, concolorous with the squamules; context 0.8 mm thick at the pileus center, elsewhere thin, no color change when cut or injured. Lamellae free, depressed around the stipe, broadly ventricose, yellowish white (3A2) to light pinkish white (10A2), with crenulate margin; 3–4 tiers of lamellulae. Stipe 20–30 × 1.5–2 mm, equal, central, cylindrical, slightly curved, fistulose, pale yellow (3A3) to slightly grayish yellow (3B3), some scattered squamules or scales on surface, with white mycelial tufts at base. Annulus absent. Odor and taste unknown.
Basidiospores [60/3/3] 5–5.5(–6) × 3–3.5 μm, [mean length = 5.38 μm, mean width = 3.25 μm, Q = (1.51–)1.61–1.68(–1.71),
Q m = 1.65 ± 0.052], ellipsoid to broadly ellipsoid, slightly thick-walled (0.5 μm), smooth under light microscope but minutely verrucose or warty under SEM, pale yellow to yellowish brown in H 2 O and 5% KOH, inamyloid. Basidia 10–12 × 5–6 μm, clavate, pale yellow in H 2 O, hyaline, thin-walled, 4-spored, with sterigmata up to 3 μm long. Lamellar trama regular to subregular, composed of thin-walled cylindrical hyphae 4–8 μm wide. Cheilocystidia 7–15 × 6–9 μm, abundant, clavate to broadly clavate, sometimes slightly fusoid to obovate, smooth, hyaline, thin-walled. Pleurocystidia absent. Pileipellis (squamules on pileus) epithelial, composed of agglutinated globose to subglobose, rarely clavate to ellipsoidal thin-walled cells, terminal cells 6–12 × 6–10 μm, slightly encrusted, with some vacuolar pigments when observed in KOH or H 2 O. Caulocystidia not found. Stipe trama composed of parallel hyphae 3–8 μm wide, yellowish brown in mass but pale yellow or subhyaline individually. Clamp connections absent in all tissues.
Habit, habitat and distribution. Gregarious to scattered, ground covered with fallen needles or debris of Pinus sp., currently only known from Jiangxi Province of China.
Additional specimens examined. CHINA, Jiangxi Province, Jiulong Provincial Forest Park, 26 Aug 2015, Ming Zhang, Jun Ping Zhou & Hao Huang (GDGM 50924); same location, 26 Aug 2015, Ming Zhang, Jun Ping Zhou & Hao Huang (GDGM 50613b).
