Xanthagaricus heinemannii Kun L. Yang, Jia Y. Lin, Zhen-Chao Liu & Zhu L. Yang

Yang, Kun L., Lin, Jia Y., Li, Guang-Mei, Liu, Zhen-Chao, Hosen, Md. Iqbal & Yang, Zhu L., 2024, Heinemannomyces, Hymenagaricus and Xanthagaricus revisited (Basidiomycota, Agaricaceae), Phytotaxa 659 (2), pp. 112-164 : 134-136

Xanthagaricus heinemannii Kun L. Yang, Jia Y. Lin, Zhen-Chao Liu & Zhu L. Yang , sp. nov. ( Fig. 8 )

Registration identifier:— FN571941

Etymology:— Named after the Belgian mycologist Paul Heinemann.

Diagnosis:— Differing from other Xanthagaricus species by remarkable floccose to fibrous squamules on pileus and stipe.

Type:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and Landscape Architecture , on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, August 25, 2023, Jia Y. Lin & Kun L. Yang, L 23317 ( HKAS133458 , holotype! (ITS: PP736714; nrLSU: PP732944; rpb2: PP746799; tef-1α: PP746829 ); HTBM1298 , isotype!) .

Description:— Basidiomata small. Pileus 10–16 mm in diameter, convex to plano-convex, sometimes slightly umbonate; background ceramic white (#FEFEFA); squamules more or less flaky at center, becoming floccose to fibrous towards margin, meat brown (#D7B19D), sandal brown (#BA8B70), dirty thatch red (#BFA5A5) to dull thatch red (#B29B9C), becoming lighter towards margin; margin with appendices concolorous with the squamules on the pileus; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, becoming darker after damaged. Lamellae free, nearly crowded, ceramic white (#FEFEFA), linen brown (#E6DECB) to dirty milky brown (#B7A48D), with a slightly serrate edge; lamellulae abundant. Stipe cylindrical to subcylindrical, sometimes tapering downwards, slightly curved, 19–36 mm long, 1.5–4.5 mm thick; background ceramic white (#FEFEFA) to linen brown (#E6DECB); squamules fibrous, usually more abundant below the annulus, concolorous with the squamules on the pileus; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, becoming darker after damaged; base without specialized tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the pileus. Odor unknown. Taste unknown.

Basidiospores [40/3/2] 5.5–6.5 (7) [5.98 ± 0.39, 6.00] × 3–4 [3.41 ± 0.42, 3.00] µm, Q = 1.50–2.17 [1.77 ± 0.21, 1.50], ellipsoid to oblong, slightly thick-walled, smooth under LM, densely verrucose under SEM, tinged cardamon yellow (#E0E091) to dusk orange (# CEAD 64) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 14–15.5 × 6.5–8 μm, clavate, mostly 4-spored, occasionally 2-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounding by basidioles measured 11–13.5 × 6.5–8 μm. Lamella trama regular to subregular, composed of 3–9 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in both water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia abundant, 12–18 × 3–4 µm, clavate to subcylindrical, thin-walled, smooth, nearly colorless in both water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid to intricate trichoid at center, becoming entirely intricate trichoid towards margin, composed of slightly thick-walled and encrusted, globose, subglobose, broadly ellipsoid, subcylindrical to clavate cells measured 8–22.5 × 9–15.5 µm or subcylindrical to cylindrical, interwoven, moderately to frequently branching hyphae 3.5–7.5 µm wide, tinged pale beige brown (#E0CDA5) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of slightly thick-walled and encrusted, subcylindrical to cylindrical, interwoven, moderately to frequently branching hyphae 4–7 µm wide, tinged pale beige brown (#E0CDA5) in both water and 5% KOH. Clamp connections absent in all tissues.

Habitat and distribution:— Solitary to gregarious, scattered on soil as individuals in southern subtropical monsoon forests or urban green belts. Currently known from China (South China).

Additional collections examined:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and Landscape Architecture , on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, June 27, 2023, Jia Y. Lin, L 23110 ( HTBM0943 (ITS: PP736708; nrLSU: PP732938; rpb2: PP746793; tef-1α: PP746821 )) ; China, Guangdong Province, Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11’31”N, 113°32’48”E, elevation 150 m, September 6, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S 23611 ( HTBM1722 (ITS: PP736757; nrLSU: PP732987 )) .

Additional notes: This species is similar to Hy. splendidissimus because the hyphae form an irregular trichoderm in pileus squamules. However, Hy. splendidissimus presents subhymeniform to hymeniform elements in the pileus squamules, context becoming reddish after damaged and bluish lamellae, differing from the epithelioid to subhymeniform elements in the pileus squamules, context not turning reddish after damaged and brownish lamellae of this species.

Figures

FIGURE 8. Xanthagaricus heinemannii (Photos by Jia Y. Lin, Kun L. Yang & Zhen-Chao Liu; drawings by Kun L. Yang & Jia Y. Lin, from HKAS133458 (holotype) & HTBM0943). a–g. Basidiomata (a–b. HTBM0943; c–e. HKAS133458 (holotype); f–g. HTBM1722). h–i. Basidiospores (h. Line drawing; i. SEM photo of HKAS133458 (holotype)). j. Cheilocystidia. k. Hymenium and subhymenium. l. Squamules at pileus center. m. Stipe squamules. Bars: a–b = 5 mm, c–g = 10 mm, h–k = 5 µm, l–m = 20 µm.