China, Hunan Province, Zhangjiajie City, Zhangjiajie Campus of Jishou University, on the ground of a forest dominated by Quercus fabri and Q. serrata, elev. ca. 220 m, 29°8'24"N, 110°27'42"E, 26 May 2019, W.Q. Qin (GDGM73213, Holotype!), ITS MN378318.

“brunneo-”: brown, “-discus”: pileus disc. The species epithet “brunneodiscus” (Lat.) refers to the brown pileus disc of this new taxon.

Hygrophorus brunneodiscus differs from H. cossus by the smaller pileus (20–50 mm broad), brownish pileus disc, thinner stipe (4–7 mm wide) and the shorter basidia (32–48 µm long); differs from H. fuscopapillatus and H. griseodiscus by the low elevation distribution and brown pileus disc.

Figure 3. 

Hygrophorus brunneodiscus. a, b Basidiomata (GDGM73213, Holotype) c, d Basidiomata (GDGM75489) e Basidiospores (GDGM73213) f Basidia (GDGM73213) g Elements of pileipellis (GDGM73213). Scale bars: 2 cm (a–d).

Pileus 20–50 mm broad, hemispherical or conical with a slightly involute or slightly revolute margin when young, becoming convex with an expanded margin when mature, whitish to brownish as a whole, brownish-orange, light brown, yellowish-brown (5C4–5, 5D4–5, 5E5–8) at the disc (about one fourth part of the radius from the centre to the margin), becoming paler to greyish-yellow (4B3–4), greyish-white (4B1) or whitish outwards and white at the margin or with a white marginal zone of 1–2 mm wide, viscid, covered with a glutinous layer of transparent materials when wet. Lamellae short decurrent to decurrent, white, waxy, with 36–40 complete lamellae and 1–3 lamellulae between two complete lamellae; lamella edge concolorous, entire. Stipe 40–90 × 4–7 mm, cylindrical, hollow, nearly equal to slightly thinner at apex and tapering towards the base; pale yellow to greyish-yellow (4A3, 4B3), white to yellowish-white (4A2) at apex, sometimes white at base; sticky, covered with a layer of transparent materials when wet, easily-sticking debris on the slime layer, usually fibrillose or with scattered white fibrillose dots at apex. Context thin, white to light brown, with slight fishy odour.

Basidiospores (6.5)7–9(9.5) × 4–5.5(6) μm [mean length = 7.6 µm, mean width = 4.6 µm], Q = (1.3)1.4–2(2.1), Qm = 1.68, ellipsoid to oblong, smooth. Basidia 32–48 × 6–8.5 µm, Q = 4.1–6.6, Qm = 5.3, clavate, thin-walled, 4-spored, with sterigmata 5.5–7(9) µm long. Pileipellis an ixotrichoderm, composed of septate cylindrical hyphae, covered with a gelatinous layer; hyphae thin-walled, 2.5–5 μm wide, slightly yellowish and glutinous in KOH. Hymenophoral trama divergent, composed of septate, thin-walled and cylindrical hyphae; hyphal cells 45–70 × 6–10 μm, hyaline. Clamp connections present.

Solitary to scattered, on the ground of subtropical broad-leaf forest dominated by Quercus, so far only known from Hunan Province in South Central China.

China, Hunan Province, Zhangjiajie City, Zhangjiajie Campus of Jishou University, 26 October 2018, W.Q. Qin (GDGM75489); ibidem, 30 June 2019, W.Q. Qin (GDGM76934).

Hygrophorus brunneodiscus is characterised by its brown tint on pileus disc, sticky pileus and stipe surface, basidiospores (6.5)7–9(9.5) × 4–5.5(6) μm, basidia 32–48 × 6–8.5 µm and subtropical and low elevation distribution.

Hygrophorus brunneodiscus can be easily recognised within subsect. Hygrophorus for its brownish colour on the pileus disc. Apart from that, H. cossus differs from H. brunneodiscus by having pale ochraceous grey colour at the pileus centre and more slender basidia (48–60 × 7–8.5 μm) (Larsson and Jacobsson 2004). Hygrophorus discoxanthus differs in the pure white mature basidiomata as young, rusty-brown pileus margin and discolouration of rusty brown at the lamellar edge and different host-association (with Fagus) (Candusso 1997, Larsson and Jacobsson 2004). Hygrophorus eburneus differs from it by having more carnose pileus and thicker stipe (4–10 mm wide), forming an ectomycorrhizal relationship with Fagus (Larsson and Jacobsson 2004). Hygrophorus hedrychii differs from it by having larger and more robust fruit-bodies (pileus 30–80 mm in diam. and stipe 5–10 mm in width), forming an ectomycorrhizal relationship with Betula (Larsson and Jacobsson 2004, Campo 2015). Hygrophorus scabrellus differs from it by owning smaller (24–28 mm in diam.) and off-white with dark green colour pileus, smaller basidiospores (mean length = 6.5 µm, mean width = 3.84 µm) and distribution in temperate forests under Quercus trees (Naseer et al. 2019).

China, Sichuan Province, Panzhihua City, Yanbian County, Gesala Ecotourism Area, elev. ca. 2900 m, 27°08'10"N, 101°11'33"E, 25 August 2013, M. Zhang & C.Q. Wang (GDGM44412, Holotype!), ITS MN378337.

“fusco-”: dark brown, “-papillatus”: papillate. The species epithet “fuscopalillatus” (Lat.) refers to the dark brown or grey brown papilla on the pileus of the new species.

Differs from H. griseodiscus by the host association with Fagaceae, solitary habit, adnate to subdecurrent lamellae and slightly smaller basidispores measuring (6)7–9.5(10) × (4)4.5–5.5(6) µm. The ITS sequence is 95% similar to H. griseodiscus.

Figure 4. 

Hygrophorus fuscopapillatus. a, b Basidiomata (GDGM44412, Holotype) c, d Basidiospores Basidiomata (LJW1858) e, f Basidiospores and Basidia (XHW6609) g, h Basidiospores and Basidia (GDGM44412) i, j Basidiospores and Basidia (LJW1858). Scale bars: 2 cm (a–f).

Pileus 20–30 mm broad, convex to hemispherical when young, applanate to plano-concave when mature, with a papilla or small umbo in the centre, white to pale grey (1B1), grey or brownish-grey to olive brown (4E2–3,4F1–3) at papilla, gradually becoming lighter from centre to margin, white to pale grey (1B1) at margin, glutinous when wet; margin even, occasionally split. Lamellae adnate to subdecurrent, white, thick, with 30–36 complete lamellae per pileus and 1–3 lamellulae between two entire lamellae. Stipe 40–60 × 4–5 mm, cylindrical, white to yellowish-grey (4B2), covered by a glutinous layer. Context thin, whitish.

Basidiospores (6)7–9.5(10) × (4)4.5–5.5(6) µm [mean length = 8.2 µm, mean width = 5 µm], Q =1.3–1.9, Qm =1.65, broadly ellipsoid, ellipsoid to oblong, smooth, hyaline. Basidia (32)35–46(48) × (6)6.5–8.5(9) µm, Q = 4.4–6.8, Qm = 5.5, clavate, thin-walled, 4-spored, with sterigmata 5–7.5 µm long. Pileipellis an ixotrichoderm, composed of septate and thin-walled cylindrical hyphae, covered with a gelatinous layer; hyphal cells 3–5 μm broad. Hymenophoral trama divergent, composed of septate, thin-walled and cylindrical hyphae; hyphal elements 13–31.5 μm broad. Clamp connections present.

Solitary, on the ground of Fagaceae-dominated forests, so far only known from Sichuan and Yunnan provinces in Southwest China.

China, Yunnan Province, Yulong County, Jade Dragon Snow Mountain, Lijiang Alpine Botanic Garden, on the ground of Quercus pannosa dominated forest, elev. ca. 3267 m, 27°00'02"N, 100°10'52"E, 31 August 2019, J.W. Liu (LJW1858); Binchuan County, Jizushan, on the ground of Castanopsis and Lithocarpus dominated forest, elev. ca. 2853 m, 25°58'06"N, 100°21'39"E, 18 September 2019, X.H. Wang (XHW6609).

Hygrophorus fuscopapillatus is distinguished by the solitary basidiomes, the brownish-grey to olive brown papilla in the pileus centre, the broadly ellipsoid, ellipsoid to oblong basidiospores measuring (6)7–9.5(10) × (4)4.5–5.5(6) µm.

Amongst the members of subsect. Hygrophours, H. griseodiscus closely resembles H. fuscopapillatus; however, H. griseodiscus differs from H. fuscopapillatus by the host association with Pinaceae, the larger pileus (2–4.5 cm broad), the emarginate lamellae with decurrent tooth, the larger basidispores measuring (7)8–10(10.5) × (4)4.5–6(6.5) µm and the broader basidia (7–11 mm broad). In addition, H. brunneodiscus is distinguished from H. fuscopapillatus by the broader pileus (2–5 cm in diam.) and the brownish pileus disc. Hygrophorus cossus is separated by the larger pileus (3–9 cm in diam.), greyish-white lamellae with a cream yellow tint and a thicker stipe (0.6–2 cm broad) (Larsson and Jacobsson 2004). Hygrophorus discoxanthus differs by the rusty brown lamellae when mature and the wider stipe (up to 1.2 cm broad); H. eburneus is distinguished by the gregarious habit, the more robust basidiomes and the white pileus (Candusso 1997, Larsson and Jacobsson 2004). Hygrophorus glutiniceps differs by the subtropical to tropical distribution and smaller basidiospores measuring (5)6–8.5(10) × (3.5)4–6 µm. Hygrophorus hedrychii is separated by the larger basidiomes (pileus up to 8 cm in diam.) and the reddish-yellow pileus centre (Larsson and Jacobsson 2004). Hygrophorus scabrellus is distinguished by the off-white with dark green pileus, the off-white to beige lamellae and the much smaller basidiospores measuring 6.5 × 3.84 µm (Naseer et al. 2019).

China, Guangdong Province, Guangzhou City, Tianluhu Forest Park, on the ground of a forest dominated by Castanopsis fissa, elev. ca. 250 m, 23°13'39"N, 113°25'53"E, 6 September 2012, M. Zhang (GDGM42188, Holotype!), ITS MN378313.

“glutini-”: glutinous, “-ceps”: pileus. The species epithet “glutiniceps” (Lat.) refers to the glutinous surface of pileus.

Hygrophorus glutiniceps differs from H. discoxanthus by the subtropical to tropical distribution, the darker lamellae and the thinner stipe (3–6 mm broad).

Figure 5. 

Basidiomata of Hygrophorus glutiniceps. a, b GDGM42140 c GDGM42154 d GDGM42188 (Holotype) e GDGM42217 f GDGM45220. Scale bars: 2 cm.

Pileus 8–40 mm broad, hemispherical to convex, often with an inconspicuous umbo and a usually involute margin when young, broad-convex to depressed with a slightly incurved to rarely uplifting margin when mature, covered with a layer of gelatine-like or transparent gluey materials when wet, white with cream or light yellow to orange tint (4A2–4) at disc, becoming light to yellowish-brown (5E8) with age (especially at margin and in wounded area), usually brownish-orange (5C5) to brown (6E8) when exsiccated. Lamellae broadly adnate or with decurrent tooth when young, short to moderately decurrent when mature, white when young, then changing to ochraceous or even brown (6E8), waxy when wet, with 25–30 complete lamellae reaching to stipe and 1–3 lamellulae between two entire lamellae. Stipe 25–60 × 3–6 mm, equal but often thinner at the base, cylindrical but usually curved, white, occasionally with yellowish tint (2A2), covered with transparent glutinous materials when wet. Context thin, white when young, changing to brown when old.

Basidiospores (5)6–8.5(10) × (3.5)4–5.5(6) µm [mean length = 7.1 µm, mean width = 4.7 µm], Q = (1.2)1.3–1.77(2), Q_m = 1.52, ellipsoid to oblong, smooth, hyaline. Basidia 35–47 × 5–8.5 µm, Q values usually more than 5, clavate, thin-walled, 4-spored, with sterigmata up to 7.5 µm long, hyaline. Pileipellis an ixotrichoderm, composed of septate hyphae, usually covered with a gelatinous layer; hyphae thin-walled, 3–5 μm wide, with yellowish gluten in KOH. Stipitipellis an ixotrichoderm, hyphae 3–5 μm wide, similar to those of pileipellis. Hymenophoral trama divergent, composed of septate, thin-walled and cylindrical hyaline in 4–17 μm diam. Clamp connections present.

Gregarious to scattered, on the ground of subtropical broad-leaf forest dominated by Castanopsis, currently only known from subtropical to tropical areas of China.

China, Guangdong Province, Guangzhou City, Tianluhu Forest Park, 6 September 2012, M. Zhang (GDGM42217); ibidem, 6 September 2012, J. Xu (GDGM42140). Hainan Province, Changjiang County, 3 July 2013, M. Zhang (GDGM45220); Baisha County, Yinggeling National Nature Reserve, elev. ca. 600 m, 1 August 2015, N.K. Zeng 2452 (FHMU1578); Ledong County, Yinggeling National Nature Reserve, elev. ca. 650 m, 4 June 2017, N.K. Zeng 3052 (FHMU2013).

Hygrophorus glutiniceps is macro-morphologically characterised by its subtropical-tropical distribution, white and sticky pileus and stipe, darkening lamellae when mature or wounded. The size of basidiospores [(5)6–8.5(10) × (3.5)4–5.5(6) µm] and basidia [35–47 × 5–8.5 µm] can be used to confirm the recognition. The association with Castanopsis fissa is also helpful for its identification.

Hygrophorus glutiniceps can be morphologically distinguished from closely-related species by the following differences. Hygrophorus cossus looks different from H. glutiniceps in the different ectomycorrhizal connection (with Quercus), the temperate distribution, the longer basidiospores [(7–9.5 μm long in Candusso (1997), 7–9 μm long in Larsson and Jacobsson (2004)] and the higher ratio of length to width [Qm = 1.7–1.75 in Candusso (1997)]. Hygrophorus eburneus differs in the different host-connection (with Fagus), thicker stipe (7–10 mm in width) and larger basidiospores (8–10 × 4.5–5.5 μm) with larger Qm (1.78–1.82); H. discoxanthus differs in the different host-connection (with Fagus), the more rusty brown tint on pileus and lamellae and the thicker stipe (5–12 mm in width); H. hedrychii differs in the different host-connection (with Betula) and larger pileus (30–60 mm broad); H. laurae Morgan has a much larger basidioma (with pileus 20–40 mm broad) and a wash of red or brown on the disc; and H. laurae var. decipiens Peck, described from New York, USA, differs in the absence of the pileus discolouration when dry and the nearly unchangeable lamellae (Morgan 1883, Peck 1905, Candusso 1997, Larsson and Jacobsson 2004).

Figure 6. 

Macro- and microscopic features of Hygrophorus glutiniceps. a Basidiomata (GDGM42217) b Basidiospores (GDGM42188) c Basidia (GDGM42188) d Terminal cells of pileipellis (GDGM42188).

China, Sichuan Province, Jiuzhaigou, elev. ca. 3100 m, 11 September 2012, X.L. He (SAAS462, Holotype!), ITS MN378338.

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

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.

Figure 7. 

Hygrophorus griseodiscus (SAAS462, Holotype). a, b Basidiomata c Basidiospores d Basidia e Elements of pileipellis.

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.

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.

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).

Pileus 10–50 mm broad when dried, subglobose when young, becoming hemispherical, convex to nearly plane when mature; margin incurved when young, even, expanded to sometimes slightly upturned when mature; surface covered with a thick layer of transparent and sticky materials, white, with pinkish (7A2) to yellowish (4A2) tones or cream colour (1A2) on the disc. Lamellae adnate to short decurrent, white at first, changing to pinkish-white (7A2) or pale yellow (4A3) or cream colour (1A2), waxy, with 1–3 lamellulae between two entire lamellae. Stipe 20–85 × 3–10 mm when dried, cylindrical or nearly so, often thinner at apex, usually slightly enlarged at base, uneven, with white short fibrils at apex, sometimes longitudinally lacerated when mature, covered with a layer of transparent sticky materials, white, changing to orange white (5A2, 6A2) where touched. Context thick, white when young, pale to pinkish-yellow when mature, with Cossus smell.

Basidiospores (6)7–8(9) × (3.5)4–4.5(5) µm, Q = 1.5–2(2.3), Qm = 1.8, ellipsoid to subcylindrical, colourless, thin-walled, smooth. Basidia 30–40 × 6–9 µm, Q = 4.1–5.7, clavate, 4-spored; sterigmata 4–5 µm long; basal clamp connections common. Pileipellis an ixotrichoderm, composed of septate hyphae, covered with a gelatinous layer; hyphae thin-walled, 4–5 μm wide. Stipitipellis a trichoderm; hyphae 7–10 μm wide, light yellowish-brown intracellular pigment presented in a few hyphae when immersed in 5% KOH solution. Hymenophoral trama composed of septate, thin-walled and cylindrical hyaline hyphae, size 58–105 × 3–23 μm. Clamp connections present.

Figure 8. 

Hygrophorus hedrychii. a Basidiospores b Basidia c Basidiomata (CFSZ2851) d Basidiomata (CFSZ18159) e Basidiomata (CFSZ18269) f Sold at a local market, named as “baizhenmo”.

Scattered to gregarious in the north temperate forests dominated by Betula, known from north-eastern China (this study), as well as from Europe where the species was firstly discovered.

China, Inner Mongolia Autonomous Region, Chifeng City, Harqin Banner, Wangyedian village, 30 August 2007, T.Z. Liu (CFSZ2851); ibidem, 8 August 2017, T.Z. Liu, Y.Q. Guang & N. Liu (CFSZ18159); Hexigten Banner, Jingpeng Town, 15 August 2017, T.Z. Liu & G.L. Yu (CFSZ18269).

Macroscopically, Hygrophorus hedrychii is a distinctive waxycap, which is relatively easily recognised in the field by its white pileus disc and lamellae changing to pale ochraceous pink when mature and the host association with birch. Microscopically, the Chinese specimens agree with the descriptions by Larsson and Jacobsson (2004) for the Swedish samples and Campo (2015) for the French collections. Molecular phylogenetically, they are also identical to the European species. The Chinese samples from Inner Mongolia are traded as edible fungi at some local markets. The European H. hedrychii was not, however, treated as an edible mushroom (Larsson, personal communication). This difference may indicate different dietary habits in different areas.