Recognition of Mycenasect. Amparoina sect. nov. (Mycenaceae, Agaricales), including four new species and revision of the limits of sect. Sacchariferae Na, Qin Bau, Tolgor MycoKeys 2019 52 103 124 44T9B 829099 T. Bau & Q. Na Agaricomycetes Mycenaceae Mycena CoL Fungi Mycena hygrophoroides Agaricales 0 103 Basidiomycota species hygrophoroides  Diagnosis. Pileus concave with slight pruinose. Lamellae distant. Stipe with dense white fibrils and swollen base. Acanthocysts forming two types. Caulocystidia long-elliptic with conical excrescences, up to 120 μmlong.  Holotype. CHINA. Guangdong Province, Shaoguan City, Chebaling National Nature Reserve, 8 May 2017, Qin Na, HMJAU 43417.  Etymology. Name refers to its sparse lamellae.  Description. Pileus 1.5-2.5 mm in diam., campanulate to hemispherical, applanate or slightly concave at centre, white with greyish shade (6B1), shallowly sulcate, translucent-striate, slightly pruinose, pubescent. Context white, thin and very fragile. Lamellae distant, sparse, white, concolorous with the sides. Stipe 4.5-8.2 x0.5-0.8 mm, cylindrical, hollow, fragile, pure white (5A1) with a greyish (5B1) base, covered with dense white fibrils, base swollen and not forming basal disc, hirsute. Odour and taste indistinctive. Basidiospores (6.9-)7.2-8.9(-9.3) x(5.3-)6.4-6.7(-7.1) μm, Q=1.2-1.5, Qav=1.31, broadly-ellipsoid, hyaline in water and 5% KOH, amyloid, smooth. Basidia 15-21 x7-9 μm, 4- or 2-spored, clavate, hyaline. Cheilocystidia 23-37 x19-28 μm, subglobose, sphaero-pedunculate to utriform with numerous sharp spines, thin-walled and hyaline, inamyloid. Pleurocystidia absent. Pileipellis hyphae 3-9 μmwide, dextrinoid; cherocytes absent; a cutis overlaid by elements of universal veil, not in chains; acanthocysts forming two types, pyriform to vesicular, 13-29 x11-24 μm, clavate to ovoid or obovoid, 29-42 x14-20 μm, inamyloid. Hyphae of the stipitipellis 3-7 μmwide, smooth, dextrinoid; caulocystidia abundant, clavate, long-elliptic, 32-122 x8-11 μm, with numbers of conical spines, inamyloid. Clamps present in all tissues.  Habit and habitat. Scattered on rotten wood of coniferous trees, ex. Cunninghamia.  Other specimens examined. Guangdong Province, Shaoguan City, Liangjiang Town, Shangxie Village, 7 May 2017, Qin Na, HMJAU 43421.  Remarks.  Mycena hygrophoroidescould be considered to be a member of HemimycenaSinger owing to the tiny basidiomata and sparse lamellae, but the absence of a basal disc, amyloid spores and spinulose cheilocystidia, acanthocysts and caulocystidia are diagnostic characters for M. hygrophoroides, which should be placed in Mycena sect. Amparoinastirps Alphitophora. Mycena acanthophilaJ.C.Zamora& Catala, of which the holotype was collected from Spain growing on dead branches of Leguminosae, most resembles M. hygrophoroides, but differs in having a yellow pileus, smaller cheilocystidia (13.5-22 x8.5-12 μm) and diverse caulocystidia (Zamora and Catala2012). Mycena depilata, a species of stirps Alphitophora, shows some morphological similarities to M. hygrophoroidesin possessing white and tiny basidiomata, distant lamellae (L = 7-9) and globose-pedicellate acanthocysts with hyaline contents. However, M. depilatadiffers in producing ellipsoid spores (Q = 1.64 +/-0.11), broadly clavate cheilocystidia and shorter caulocystidia (16-50 x5-16 μm; Singer 1989). Mycena hemitrichialisis difficult to distinguish from M. hygrophoroides, but M. hemitrichialishas free to subfree lamellae, longer caulocystidia (100-300 x5-15 μm) and ellipsoid spores ( Singer 1989). In comparison with M. hygrophoroides, M. alphitophoraand M. distinctahave larger basidiomata and longer caulocystidia of more than 400 μmand 300 μm, respectively ( Desjardin 1995; Aravindakshan and Manimohan 2015). Their noticeably pigmented pileus enables discrimination of M. brunneospinosa, M. incarnativelumand M. roseotinctafrom M. hygrophoroides( Desjardin 1995; Aravindakshan and Manimohan 2015). The significantly larger basidiomata and globose spores can be used to distinguish M. corynephora, M. globisporaand M. yalensisfrom M. hygrophoroides.  Figure 5. Microscopic features of Mycena hygrophoroides(HMJAU 43417, holotype) a Basidiomata b Basidia c Basidiospores d Cheilocystidia e Universal veil acanthocysts f Caulocystidia g Pileipellis. Scale bars: 2 mm (a); 10 μm( b-g). Drawing by Qin Na.