Gymnopus schizophyllus J.P. Li, T.H. Li & Y. Li
MycoBank number: 837642
Basidiomata gymnopoid or collybioid. Pileus 10–20 mm broad, membranous, hemispherical when young, then convex, with slightly inflexed margin, expanding to plano -convex , with a depressed disc, undulating at the margin, glabrous, radially striate or grooved towards the margin, often pale orange (6A3) to light brown (6D8), darker at the centre, sometimes to dark brown (6F8), white to light brown (6D8) towards the margin. Lamellae adnate, linear to arcuate, sometimes furcate to branched or venose, generally split at the edge, dull white to brownish orange (7C7), pale at the edge, sometimes with brown (7E8) to dark brown (7F8) tints somewhere, L = 10–20, l = 3–4. Stipe 11–21 mm long, 0.8–1 mm thick in middle, central, cylindrical, straight or sometimes curved, insititious, hollow, fibrous, glabrous, rooting deep in the substrate, but eventually attaches to the stump, white to orange-white (6A2) at first, slightly darker at base, then darker towards the apex, finally entirely light brown (7D8) to brown (7E8). Odour not distinctive.
Basidiospores [n=80] 4–6 (–6.5) × 2.5–3 (–3.5) μm (average = 4.90 × 2.93 μm, E = (1.29–) 1.33–2.00 (–2.20), Q = 1.68) or [n=20] 6.5–8 × 2.5–3 μm (average = 7.35 × 2.86 μm, E = 2.17–3.2, Q = 2.65), obovoid, ellipsoid to subellipsoid, sometimes amygdaliform. Basidia [n=20] 15–32 × 4–6 μm, clavate, 4-spored, rarely 1–3-spored. Basidioles [n=20] 17–27.5 × 4–6.5 μm, clavate, cylindrical. Lamellar edge sterile. Cheilocystidia [n=20] 20–43 × 4.5–9 μm, irregularly clavate, tending to inflated, with finger-like apical projection(s) or more or less diverticulate elements. Pileipellis a cutis composed of thin-walled, cylindrical hyphae up to 18 μm wide, smooth or with scattered diverticula, hyaline to slightly greyish; Rameales-like structures present but very few; terminal elements short, broad, mostly inflated, vesiculose or pyriform to cystidioid (clavate), obtuse and sometimes diverticulate, mixed with a few irregularly branched elements, some resembling Dryophila-type structures. Stipitipellis a cutis composed of cylindrical hyphae, up to 19 μm wide, thin- to thick-walled, smooth, non-dextrinoid, diverticulate, parallelly arranged. Caulocystidia absent. Clamp connections present.
Habitat: Saprotrophic, gregarious or in small clusters, usually rooting around roots and stumps in broadleaf forests.
Additional specimens examined: China, Guangdong Province, Xinyi City, Yunkaishan National Nature Reserve, 26 July 2019, B. Song, H.S. Wen & J.P. Li (GDGM 77038); Guangdong Province, Xinyi City, Yunkaishan National Nature Reserve, 29 May 2019, B. Song, H.S. Wen & J.P. Li (GDGM 76287); Yunnan Province, Maguan County, Laojunshan Moutain, 11 August 2016, X.H. Wang (KUN-HKAS 96494).
Notes: Gymnopus schizophyllus is a very distinct species by the orange to brown pileus that becomes paler with age; by the lamellae with generally split edge; by the two sizes of basidiospores: 1) 4–6 (–6.5) × 2.5–3 (–3.5) μm from the usual 4-spored basidia and 2) a few larger basidiospores up to 8 μm long from the 1–3-spored basidia; and by a pileipellis often with scattered cystidioid (clavate) or vesiculose to pyriform terminal elements. Morphologically, among the known species of Gymnopus with a striate or grooved pileus and similarly sized basidiospores, G. discipes, G. expallens (Peck) Murrill, G. fusipes (Bull.) Gray, G. micromphaloides R.H. Petersen & K.W. Hughes, G. oculatus Murrill, G. omphalinoides, G. pseudomphalodes (Dennis) J.L. Mata, G. purpureicollus (Corner) A.W. Wilson, Desjardin & E. Horak, G. sepiiconicus (Corner) A.W. Wilson, Desjardin & E. Horak and G. subflavescens Murrill are similar to the new species. However, G. discipes has a subfleshy pileus with a wide umbo, free and ventricose lamellae and a white stipe (Murrill 1916); G. expallens has basidiomata with a distinct odour, a hygrophanous pileus, adnexed and ventricose lamellae, and a broad stipe up to 4 mm (Murrill 1916); G. fusipes has a fleshy pileus and a fusoid stipe with pseudorrhiza (Antonín and Noordeloos 2010); G. micromphaloides, sect. Vestipedes [= Collybiopsis micromphaloides (R.H. Petersen & K.W. Hughes) R.H. Petersen], has adnexed and ventricose lamellae, a scurfy-vestured stipe, and strongly encrusted hyphae of the pileipellis (Petersen and Hughes 2014); G. oculatus has a white pileus in general, nearly free lamellae and a whitish pruinose, larger stipe (Murrill 1916); G. omphalinoides generally has a deeply umbilicate pileus, broad, adnate and ventricose lamellae; G. pseudomphalodes has a cream pileus and regularly cylindrical cheilocystidia (Dennis 1961); G. purpureicollus has a hygrophanous pileus, subfree to adnate lamellae with a decurrent tooth and a lamellar edge without cheilocystidia (Wilson et al. 2004); G. sepiiconicus, sect. Levipedes, has hyphae with annular incrustations in the stipitipellis (Wilson et al. 2004); and G. subflavescens has white basidiomata overall, crowded lamellae and small, globose basidiospores (Murrill 1916).
Fig. 1 Phylogram generated by ML analysis of the combined dataset (ITS1-5.8S-ITS2-LSU region). ML-BP ≥ 70 % and BI-PP ≥ 0.95 are shown above and below the branches, respectively.