Hygrophorus griseodiscus C.Q. Wang & T.H. Li sp. nov. Figure 7

Typification.

China, Sichuan Province, Jiuzhaigou, elev. ca. 3100 m, 11 September 2012, X.L. He (SAAS462, Holotype!), ITSMN378338.

Etymology.

" griseo -": grey, "- discus ": pileus. The species epithet " griseodiscus " (Lat.) refers to the grey disc of the pileus.

Diagnosis.

Hygrophorus griseodiscus is distinguished from H. brunneodiscus by the greyish pileus with a darker grey pileus disc and larger basidiospores measuring (7)8-10(10.5) × (4)4.5-6(6.5) µm .

Description.

Pileus 20-45 mm broad, convex, obtusely umbonate at disc, grey to light grey (1C1, 1D1), medium to dark grey or olive grey (1E1, 1F1-4) at disc, white to pale grey (1B1) at margin, glutinous when wet; margin even, slightly involuted to extended. Lamellae emarginate with decurrent tooth or subdecurrent, white, thick, subcrowded, unequal, with 1-3 lamellulae between two entire lamellae. Stipe 40-70 × 4-6 mm, cylindrical, white to pale grey (1B1), covered with transparent glutinous materials when wet. Context slightly thick, white.

Basidiospores (7)8-10(10.5) × (4)4.5-6(6.5) µm [mean length = 9 µm, mean width = 5.2 µm], Q = 1.4-2.1, Qm = 1.74, ellipsoid, oblong to subcylindrical, smooth, hyaline. Basidia 29-56.5 × 7-11 µm, Q = 3.05-6(6.9), Qm = 4.39, clavate to cylindrical, thin-walled, 4-spored, with sterigmata up to 6 µm long. Pileipellis an ixotrichoderm, covered with a gelatinous layer; hyphae thin-walled, 2.5-6 μm wide. Hymenophoral trama divergent, composed of septate, thin-walled and cylindrical hyphae; hyphal cells 5.5-20 μm in width, hyaline. Clamp connections present.

Habit, habitat and distribution.

Scattered, on the ground of subalpine coniferous forest dominated by Abies and Picea, often surrounded by mosses, so far only known from Sichuan Province in Southwest China.

Remarks.

Hygrophorus griseodiscus is characterised by its convex and grey pileus with a dark grey to olive grey disc, emarginate to subdecurrent lamellae. The Asian subalpine coniferous habitat may be a helpful character for its identification.

Morphologically, H. brunneodiscus is distinguished from H. griseodiscus by the brownish pileus disc and smaller basidiospores (6.5-9.5 × 4-5 µm). Hygrophorus cossus differs in the greyish-white lamellae with a cream yellow tint and a thicker stipe (6-20 mm wide) (Candusso 1997, Campo 2015). Hygrophorus discoxanthus can be separated by the pure white pileus when young and rusty brown lamellae when mature (Candusso 1997, Campo 2015). Hygrophorus eburneus is different by the white pileus and the wider basidiospores (8-10 × 4.5-5.5, Qm = 1.78-1.82) (Candusso 1997). Hygrophorus glutiniceps is separated by the white pileus with cream or light yellow to orange tint at the disc, shorter basidiospores [(5)6-8.5(10) × (3.5)4-6 µm] and subtropical to tropical distribution. Hygrophorus hedrychii is distinguished by the presence of a pale orange tint on the pileus disc and an orange-pink tint on the lamellae (Larsson and Jacobsson 2004). Hygrophorus scabrellus is readily distinguished from H. brunneodiscus by its smaller basidiomata (pileus 2.4-2.8 cm broad), dark green tint on pileus and much smaller basidiospores (6.5 × 3.84 µm) (Naseer et al. 2019).