Xanthoconium fusciceps N.K. Zeng, Zhi Q. Liang & S. Jiang, 2017

Liang, Zhi-Qun, Chai, Hui, Jiang, Shuai, Ye, Zheng-Kun & Zeng, Nian-Kai, 2017, The genus Xanthoconium (Boletaceae, Boletales) in tropical China, Phytotaxa 295 (3), pp. 246-254 : 249-250

Xanthoconium fusciceps N.K. Zeng, Zhi Q. Liang & S. Jiang , sp. nov. ( Figs. 2a–d and 3 )

MycoBank:—MB 819378

Etymology: — Latin “ fusci- ” meaning dark brown, “-ceps” meaning pileus, referring to the species having a dark brown pileus when young.

Diagnosis:—Characterized by a dark brown pileus with a rugulose or pitted surface, a non-staining hymenophore and context, golden yellow basidiospores, cystidia with pale yellowish brown, yellowish brown to golden brown pigments, and uninflated hyphae in the pileipellis.

Holotype:— CHINA. Hainan Province: Qiongzhong County, Yinggeling Nature Reserve , elev. 750 m, 3 August 2015, N. K. Zeng 2483 ( FHMU).

Description:— Basidiomata small to medium-sized. Pileus 3–7.5 cm in diameter, convex, sometimes applanate when old; surface dry, nearly glabrous, usually rugulose or pitted, dark brown (7E2–3) when young, then pale brown (7C2) to brown (7D3–4); margin incurved; context 0.5–1.7 cm thick in the center of the pileus, white (1B1), unchanging in color when injured. Hymenophore poroid, adnate to slightly decurrent; pores angular to almost round, about 0.5 mm in diameter, white (2A1) when young, then yellow (3A4), unchanging in color when injured; tubes 2–6 mm in length, yellowish (3A3), unchanging in color when injured. Stipe 4–7 × 0.5–2.3 cm, central, subcylindric, solid, sometimes flexuous; surface dry, nearly glabrous, brown (6C4) to dark brown (7E2–3) when young, then pale brown (7C2), base white (2A1); context white (1B1), unchanging in color when injured; annulus absent; basal mycelium white (2A1). Odor indistinct.

Basidiospores [80/4/4] 9–12(–13) × 3–4 μm, Q = (2.25–)2.50–3.43(–3.71), Q m = 2.93 ± 0.33, ellipsoid to subfusiform, slightly thick-walled (up to 0.5 μm), golden yellow in KOH, smooth. Basidia 21–30 × 6–9 μm, clavate, thin-walled, 4-spored, colorless to hyaline in KOH; sterigmata 4–5 μm in length. Hymenophoral trama bilateral, composed of thin- to slightly thick-walled (up to 0.5 μm thick) hyphae, 6–12 μm wide, colorless in KOH. Cheilocystidia 35–62 × 9–13 μm, abundant, ventricose, fusiform or subfusiform, thin-walled, usually containing yellowish brown, golden brown to dark brown pigments, with no encrustations. Pleurocystidia 32–70 × 8–15 μm, abundant, ventricose, fusiform or subfusiform, thin-walled, usually containing yellowish brown, golden brown to dark brown pigments, with no encrustations. Pileipellis a trichoderm about 100 μm thick, composed of more or less vertically arranged, thin- to slightly thick-walled (up to 0.5 μm thick), occasionally branched hyphae, 5–9(–13) μm wide, colorless, pale yellowish brown to yellowish brown in KOH; terminal cells 20–61 × 5–9(–13) μm, narrowly clavate or subcylindrical, with obtuse apex. Pileal trama made up of thin- to slightly thick-walled (up to 0.5 μm) hyphae 3–12 μm in diameter, colorless in KOH. Stipitipellis a hymeniform layer composed of thin- to slightly thick-walled (up to 0.5 μm) emergent hyphae with narrowly or broadly clavate terminal cells (10–25 × 5–11 μm), colorless, pale yellowish brown to yellowish brown in KOH, and occasionally with clavate, 4-spored basidia (15–20 × 7–8 μm). Stipe trama composed of longitudinally arranged, parallel hyphae 5–10 μm wide, cylindrical, thin- to slightly thick-walled (up to 1 μm), hyaline to colorless in KOH. Clamp connections absent in all tissues.

Habitat: — Scattered to gregarious on the ground in forests of Fagaceae .

Known distribution:—Southern China (Hainan Province).

Additional materials examined:— CHINA. Hainan Province: Qiongzhong County, Yinggeling Nature Reserve , elev. 850 m, 26 July 2009, N. K. Zeng 349 ( FHMU) ; same location, 28 July 2009, N. K. Zeng 365 ( FHMU) ; Baisha County, Yinggeling Nature Reserve , elev. 380 m, 10 September 2016, N. K. Zeng 2941 ( FHMU) .

Figures

FIGURE 2. Basidiomata of Xanthoconium species. a–d. X. fusciceps (a–b, d from N.K. Zeng 2483, holotype; c from N.K. Zeng 2941); e–i. X. sinense (e, g–h from N.K. Zeng 1575; f, i from N.K. Zeng 1583). Photos by N.K. Zeng.

FIGURE 3. Microscopic features of Xanthoconium fusciceps (N.K. Zeng 2483, holotype). a. Basidia and pleurocystidia. b. Basidiospores. c. Cheilocystidia. d. Pleurocystidia. e. Pileipellis. f. Stipitipellis. Bars = 10 μm. Drawings by N.K. Zeng.