Micropsalliota rufosquarrosa J. Q. Yan sp. nov. MycoBank: 842896
Etymology: Referring to its dull red squarrose pileus.
Diagnosis: Differs from M. gracilis in having smaller basidiomata and smaller cheilocystidia covered by an obvious brown deposition. (Figures 2I–K, 7, 10E)
Basidiomata stout (IG = 9.0–33). Pileus 6.0–12 mm in diameter, white to dirty white (1A1–1B1), convex, expanding to plane, surface dry, covered with red (11B7) to brownish violet (11C7–11D7) squarrose. Context less than 0.5 mm thick. Lamellae 0.3–1.5 mm broad, free, subdistant, with 2 series of lamellulae, white becoming light brown (7D5–7D6) as mature. Stipe 18–38 × 0.5–1.5 mm, cylindrical, white (1A1), surface with white (1A1) fibrils. Annulus single, membranous, superior, white, with a reddish margin, easily fall off.
Basidiospores 5.5–6.5 (7.0) × 3.0–3.5 (4.0) µm, av. = 6.1 × 3.3µm, Q = (1.60) 1.65–2.00 (2.25), elongated in face view, amygdaliform in profile view, light brown, wall 0.3– 0.4µm thick, most basidiospore with an apically thickened endosporium, without germ pore, inamyloid. Basidia 12.5– 16.5 × 5.5–7.0 (7.5) µm, clavate, hyaline, 4- or 2-spored. Pleurocystidia absent. Cheilocystidia 14–26 × 6.0–10µm, hyaline, utriform, apex broadly obtuse or capitate, 4.0–6.5µm in diameter, covered by light brown deposition. Pileipellis a cutis, hyphae 4.5–14 (17) µm in diameter, constricted at the septa on some hyphae, with dark brown granular incrusted in cellular vacuoles that dissolves in alkaline solution (vacuolar pigment).
Habit and habitat: Scattered on ground in mixed forests.
Specimens examined: CHINA. Jiangxi Province, Jiangxi Agricultural University, 20 May 2019, Jun-Qing Yan, HFJAU1208; 26 May 2019, Jun-Qing Yan, HFJAU1236, holotype.
Notes: Few species in the genus match the combination of small basidiomata, a pileus covered with dull red scurfy scales or fibrils, and small cheilocystidia covered by light brown deposition that characterizes M. rufosquarrosa. Some species have small basidiomata and a colored pileus but can be separated as follows: M. allantoidea has grayish brown scaly pileus, utriform, lageniform, or tiibiform capitate or subcapitate cheilocystidia (Zhao et al., 2010); M. atropurpurea Heinem., M. cymbispora Heinem. and Little Flower, and M. pseudovolvulata have smaller basidiospores averaging less than 5.5µm long (Heinemann and Flower, 1983; Heinemann, 1988; Zhao et al., 2010); M. cardinalis and M. purpureobrunneola have purple to brownish purple scales and different cheilocystidia (Heinemann, 1989; He et al., 2020); M. endophaea Heinem., M. megaspora, and M. roseipes have larger basidiospores that are longer than 6.5µm on average (Heinemann, 1988; Zhao et al., 2010); M. malabarensis Heinem. and Little Flower and M. subalpina Guzm.-Dáv. and Heinem. have longer cheilocystidia, up to 60µm (Heinemann and Flower, 1983; Guzmán-Dávalos and Heinemann, 1994); M. pruinosa Heinem. has grayish brown scaly pileus, and ellipsoid spores in face view (Heinemann, 1989).
