Micropsalliota delicatula R.L. Zhao, J.X. Li & M.Q. He, sp. nov. Figure 3
Fungal Name: FN570748
Etymology: in reference to the delicate and tiny basidiomata.
Diagnosis: this species is characterized by its meagre basidiomes with thin transparent pileus and dentate margin. Holotype: CHINA, Zhejiang Province, Jingning county, Wangdongyang Wetland Park, 8 June 2015, Rui-Lin Zhao, ZRL2015234 (HMAS290752).
Macroscopic description: Pileus 3–7 mm in diam., sometimes papillate in the center, convex to applanate when young, then nearly plane, margin thin, exceeding the lamellae, surface dry, covered with fibrils, white or sometimes brownish red. Context less than 1 mm, Lamellae free, subdistant, with 1–2 series of lamellulae, 1–2 mm broad, brown. Stipe 12–19 × 0.5–1 mm, cylindrical, slender, hollow, smooth or slightly tomentose. Annulus peronate, single, fragile, white, up to 2–3 mm. odor not distinctive. Basidiomes discoloring yellow brown when bruised or dry. Microscopic description: Basidiospores 5.2–6.6 × 3–4.1 μm, [X = 5.8 ± 0.3 × 3.5 ± 0.3, Q = 1.4–1.8, Q m = 1.6 ± 0.12, n = 23], ellipsoid, sometimes amygdaliform, without germ pore, brown. Basidia 13.2–17.2 × 6–8.5 μm, clavate, 4-spored, sometimes 2-spored. Cheilocystidia 26–36.6 × 8–11.8 μm, apical capitate, up to 5.8–8.2 μm at the apex with a sinuous or straight neck and a thickened base. Pleurocystidia absent. Pileipellis composed of hyphae 6–13 μm diam., hyaline, constricted at the septa on some hyphae. Annulus composed of branched, smooth hyaline hyphae, 4–9 μm in diam., smooth, constricted, without internal pigment. KOH reaction bright yellow.
Habit and habitat: solitary on soil in forest. Known distribution: China.
Additional material examined: CHINA, Zhejiang Province, Jingning county, Wangdongyang Wetland Park, 9 June 2015, collected by Sheng-Yu Su, ZRL2015249 (HMAS290753)
Notes: Micropsalliota delicatula is characterized by meagre basidiomata with thin transparent pileus and dentate margin, KOH reaction staining bright yellow. Micropsalliota alba Heinem. & Little Flower, M. albella M.Q. He & R.L. Zhao M. albosericea Heinem. & Leelav. and Micropsalliota cymbispora Heinem. & Little Flower, all have tiny basidiomata (pileus less than 7 mm in diam.) which are similar to M. delicatula. Micropsalliota alba differs in having smaller cheilocystidia (Heinemann & Little Flower 1983). It is easy to distinguish M. albella from M.
delicatula through the papillate pileus of the latter, moreover，two species have different shapes of cheilocystidia, M. albella has smaller basidiospores (4.2–5.3 × 2.6–3.1 μm) and KOH reaction staining brown on pileus (He et al. 2020). Micropsalliota albosericea differs in having smaller cheilocystidia (18–30 × 6–11 μm), KOH reaction staining reddish brown and its thinner (5–8 μm) pileipellis hyphae (Zhao et al. 2010). Micropsalliota cymbispora has purple brown pileus (Heinemann & Little Flower 1983) and smaller basidiospores and cheilocystidia. In the phylogenetic analyses, M. subalba is close to M. delicatula and sister each other with a low support value. Micropsalliota subalba is distinguished by its medium-sized basidiomes (pileus 12–18 mm diam.) and positive KOH reaction staining brown (Zhao et al. 2010).
