Three new species of Micropsalliota (Agaricaceae, Basidiomycota) from central and southern Vietnam Author Ivanova, Daria 0000-0002-8302-8337 Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Str., 2, 197376 St. Petersburg, Russia & divanova @ binran. ru; https: // orcid. org / 0000 - 0002 - 8302 - 8337 divanova@binran.ru Author Morozova, Olga 0000-0002-7329-528X Komarov Botanical Institute of the Russian Academy of Sciences, Prof. Popov Str., 2, 197376 St. Petersburg, Russia & omorozova @ binran. ru; https: // orcid. org / 0000 - 0002 - 7329 - 528 X omorozova@binran.ru Author Pham, Thi Ha Giang 0000-0002-4137-7213 Joint Vietnam-Russia Tropical Science and Technology Research Centre, Nguyen Van Huyen, Nghia Do, Cau Giay, Hanoi 122100, Vietnam & giangvietnga @ gmail. com; https: // orcid. org / 0000 - 0002 - 4137 - 7213 giangvietnga@gmail.com text Phytotaxa 2023 2023-11-28 626 4 247 258 https://phytotaxa.mapress.com/pt/article/download/phytotaxa.626.4.2/51317 journal article 10.11646/phytotaxa.626.4.2 1179-3163 10212911 Micropsalliota appendiculata D.D. Ivanova & O.V. Morozova , sp. nov . ( Fig. 3 ) Mycobank: MB849326. Type: — VIETNAM , Dong Nai Province , Vinh Cuu District , Dong Nai Cultural and Nature Reserve , on destroyed termite mound, in tropical polydominant mixed forest, 13 June 2011 , coll. O.V. Morozova ( holotype : LE F-315913!, isotype : VRTC 267VN11 !). Etymology:—Referring to appendiculate margin of the pileus. Diagnosis:—The species is characterized by having very small beige basidiomata with obtuse umbo, strongly appendiculate margin of pileus with relatively long veil remnants, and drop-shaped cheilocystidia. Description:— Basidiomata very small and fragile, cream and grey when fresh, fading to grey-brown when dry (6C5, 6D5–6). Pileus 4–6 mm in diameter, subumbonate or umbonate when young, soon expanding to convex, always with well distinguished obtuse umbo; surface fine tomentose, covered with appressed fibrillose squamules, light brown and greyish brown (7D3–5) around umbo, turning cream or reddish grey (7B2) towards the margin; the margin incurved with appendiculate veil remnants; the surface reddish brown (8E4) in KOH. Lamellae free, crowded, ventricose, 0.5–1 mm broad, intercalated with lamellulae, creamy, greyish red (7B3). Stipe 10–15 × 1 mm , cylindrical, smooth, concolorous with the pileus, with brown spots (9E6– 8, 8E 5–7). Annulus fugacious, leaving fibrillose scalelike remnants concolorous with the pileus. FIGURE 3 . Micropsalliota appendiculata (LE F-315913, holotype): (a) basidiomata in situ : (b) pilei with partial veil, (c) basidiospores, (d) basidia, (e) cheilocystidia, (f) pileipellis hyphae. Bars: a–b = 1 cm; c–e = 10μm; f = 20μm. Basidiospores 5.6–6.6 × 3.3–4 µm, Q = 1.5–1.9, Q m = 1.71 (n = 21) amygdaliform, with an apical endosporal thickening. Basidia 13–15.6 × 6.4–9 µm, clavate, 4-spored. Cheilocystidia 11.1–37.3 × 7.4–11.8 µm, ovoid, obovoid, broadly-cylindrical and subglobose, some are drop-shaped. Pleurocystidia absent. Pileipellis a cutis, composed of cylindrical hyphae 10–15 µm wide, constricted at the septa with suballantoid cells. Stipitipellis consists of cylindrical hyphae 6–8 µm wide. Habitat and distribution:—In large group on a destroyed termite mound on roadside in tropical evergreen mixed forest. Known only from the type locality in southern Vietnam . Notes:— Micropsalliota appendiculata is characterized by the following features: small, creamy, discoloring to brown basidiomes, umbonate pileus, cylindrical stipe with a fugacious fibrillose annulus, and ovoid, obovoid, subglobose cheilocystidia. The most distinctive feature is the appendiculate margin with relatively long veil remnants that resemble teeth. At least two other previously studied species are known to have a denticular pileus margin and small basidiomata: M. dentatomarginata R.L. Zhao, J.X. Li & M.Q. He (2021: 174) and M. albosericea Heinemann & Leelavathy (1991: 341) . However, the teeth of the both species are much lesser than those of M. appendiculata . Micropsalliota dentatomarginata has also larger pure white basidiomata (pileus of 12–15 mm in diameter) and capitate cheilocystidia with a thickened base ( Li et al. 2021 ). M. albosericea has white basidiomata and clavate or subcapitate cheilocystidia ( Zhao et al. 2010 ). In the phylogenetic tree, M. appendiculata is clustered with M. megaspora R.L. Zhao, Desjardin, K. Soytong & K. D. Hyde (2010: 64) , which possesses fibrillose pileus ( 5–12 mm diam.), with erect brown (7E6) squamules, bigger spores (6–8 × 3.8–4.5 µm) and ventricose cheilocystidia with a long obtuse neck or pyriform.