Micropsalliota pseudodelicatula J. Q. Yan sp. nov.
MycoBank: 842893
Etymology: Referring to its morphological similarity to M. delicatula.
Diagnosis: Differs from M. delicatula in having smaller basidiospores (4.3–5.5 × 2.7–3.3 µm). (Figures 2E–G, 5, 10C)
Basidiomata slender (IG = 50–93). Pileus 4.0–5.0 mm in diameter, white (1A1), convex to applanate, then nearly plane, surface dry, covered with white (1A1) scurfy scales or fibrils. Context less than 0.5 mm thick. Lamellae 0.5–1.0 mm broad, free, subdistant, with 2 series of lamellulae, white (1A1) becoming grayish red (7B2–7B3) to chestnut-brown (8D4– 8E5) as mature, edge white (1A1). Stipe 8.0–15 × 0.3–1.0 mm, cylindrical, slender, hollow, white (1A1), surface with white (1A1) fibrils, base unexpanded, or slightly expanded to the shape of suction cup. Annulus single, membranous, persistent, superior to medium, white (1A1).
Basidiospores (4.0) 4.3–5.5 × (2.5) 2.7–3.3µm, av. = 4.9 × 3.0µm, Q = (1.39) 1.48–1.83 (1.95), ellipsoid to elongated in face view, amygdaliform in profile view, light brown, wall 0.2–0.4µm thick, apically thickened endosporium indistinct, without germ pore, inamyloid. Basidia 11–14 × 3.5–6.0µm, clavate, hyaline, 4- or 2-spored. Pleurocystidia absent. Cheilocystidia 29–40 (43) × (4.0) 5.0–8.5 (9) µm, often in clusters, tibiiform, few lageniform, apex capitate 6.0–9.0µm in diameter. Pileipellis a cutis, hyphae 6.0– 15µm in diameter, hyaline, constricted at the septa on some hyphae.
Habit and habitat: Gregarious on red soil in forest.
Specimens examined: CHINA. Zhejiang Province, Suichang County, Sanren She nationality township, 29 May 2020, Jun-Qing Yan and Qin Na, HFJAU2228, holotype; Jiangxi Province, Jiangxi Agricultural University, 26 Jun 2019, Jun-Qing Yan, HFJAU1291.
Notes: Micropsalliota pseudodelicatula, which forms an independent lineage in subclade /bifida, is easily confused with M. delicatula. However, M. delicatula has larger basidispores, 5.2–6.6 × 3.0–4.1µm (Li et al., 2021). In addition, M. alba, M. albella M. Q. He and R. L. Zhao, M. albosericea, M. minor, M. pulverulenta Heinem. and Leelav., and M. pusillissima R. L. Zhao, Desjardin, Soytong and K. D. Hyde all have tiny basidiomata (pileus 5 mm in diameter or less) that are similar to M. pseudodelicatula. These species can be distinguished as follows: basidiospores of M. alba are larger, up to 5.8–6.6 × 3.3– 3.6µm (Heinemann and Flower, 1983); M. albella has narrowly utriform to utriform cheilocystidia, some of which are slightly subcapitate (He et al., 2020); cheilocystidia of M. albosericea are smaller (18–30 × 6.0–11µm) and clavate to ventricose capitate or subcapitate, without obviously elongated neck (Zhao et al., 2010); M. minor has forked cheilocystidia (this paper); M. pulverulenta has pleurocystidia (Heinemann and Leelavathy, 1991); M. pusillissima has smaller basidiomata (1.0–3.0 mm) and possesses broadly ventricose-capitate cheilocystidia without an obviously elongated neck (Zhao et al., 2010)
