Recognition of Mycenasect. Amparoina sect. nov. (Mycenaceae, Agaricales), including four new species and revision of the limits of sect. Sacchariferae Author Na, Qin Author Bau, Tolgor text MycoKeys 2019 52 103 124 http://dx.doi.org/10.3897/mycokeys.52.34647 journal article http://dx.doi.org/10.3897/mycokeys.52.34647 1314-4049-52-103 Mycena bicystidiata T.Bau & Q.Na sp. nov. Figs 2 c-d , 3 Diagnosis. Pileus furfuraceous to pruinose. Stipe without basal disc. Basidiospores small, 6.1-7.9 x 3.7-4.6 μm . Cheilocystidia clustered, sphaero-pedunculate to utriform with numerous sharp excrescences. Cherocytes absent. Acanthocysts pyriform to vesicular. Caulocystidia of two types, sphaero-pedunculate or clavate covered with conic spines. Clamps present. Holotype. CHINA. Chongqing City, Dafengbao Scenic Regions, 15 Aug 2017, Qin Na, HMJAU 43648. Etymology. Name refers to its two types of caulocystidia. Description. Pileus 2.8-5.2 mm in diam., conical when young, becoming nearly hemispherical with age, pure white all over, sulcate, translucent-striate, pruinose, furfur-like scattered, margin entire first, then nearly plane and finally fissile. Context very thin and fragile, pure white. Lamellae 0.5 mm thick, narrowly adnate, off-white, concolorous with the sides. Stipe slender, 15-28 x 0.5-1.0 mm, cylindrical, hollow, fragile, pure white, densely pruinose on the whole surface, base swollen and not forming a basal disc, hirsute. Odour and taste inconspicuous. Basidiospores (5.6-)6.1-7.9(-8.3) x (3.5)3.7-4.6(4.9) μm , Q=1.6-2.0, ellipsoid to oblong-ellipsoid, hyaline, with drops, thin walled, amyloid. Basidia 20-26 x 6-9 μm , clavate, hyaline, 4- or 2-spored. Cheilocystidia 19-32 x 12-18 μm , clustered, sphaero-pedunculate to utriform with numerous sharp spines, thin-walled and hyaline, inamyloid. Pleurocystidia absent. Pileipellis hyphae 4-7 μm wide, weakly dextrinoid; cherocytes absent; a cutis overlaid by elements of universal veil, not in chains; acanthocysts of one type, numerous, pyriform to vesicular, 29-62 x 24-51 μm , inamyloid. Hyphae of the stipitipellis 3-14 μm wide, smooth, dextrinoid; caulocystidia abundant, of two types, utriform, sphaero-pedunculate, 21-85 x 14-66 μm or clavate, long-elliptic, 21-85 x 11-26 μm , densely and evenly spinulose overall, hyaline, thin-walled, inamyloid. Clamps present in all tissues. Habit and habitat. Solitary to scattered on rotten wood in mixed forests, Bamboos, Cunninghamia , Ginkgo and Platycladus forests. Other specimens examined. CHINA. Hubei Province, Enshi Tujia and Miao Autonomous Prefecture, Lichuan County, Yandongwan, 19 Jul 2017, Qin Na, HMJAU 43589; Xingdou Mountain National Nature Reserves, 20 Jul 2017, Qin Na, HMJAU 43593; Zhejiang Province, Hangzhou City, Tianmu Mountain National Nature Reserves, 4 Jul 2018, Qin Na and Tolgor Bau, HMJAU 43774. Remarks. Mycena bicystidiata is unique in sect. Amparoina stirps Alphitophora because of the two types of caulocystidia covered with conic spines. Mycena alphitophora , which is the most widely distributed species of sect. Amparoina , shows the most morphological similarities to M. bicystidiatum ; however, the former differs in forming cylindric spores (7.5-10 x 4.5-5.5 μm ), sphaero-pedunculate cheilocystidia and caulocystidia that are only clavate in shape ( Desjardin 1995 ). Mycena depilata Singer is easily mistaken for M. bicystidiata by the stipe without a basal disc and the similar shape and size of spores and cheilocystidia, but M. depilata is distinguished from M. bicystidiata by its small basidiomata (pileus <0.3 mm), larger spores (8.5-10 x 4.5-5.2 μm ), and long-cylindrical and larger caulocystidia (30-120 x 5-20 μm ) ( Desjardin 1995 ). In contrast to M. bicystidiata , basidiospores of M. corynephora , M. distincta (Manim. & Leelav.) Aravind. & Manim., M. globispora (Manim. & Leelav.) Aravind. & Manim. and M. yalensis Singer are globose or broadly ellipsoid ( Desjardin 1995 ; Aravindakshan and Manimohan 2015 ). The bright or dark colour on the pileus distinguishes M. brunneospinosa Desjardin, M. incarnativelum Desjardin and M. roseotincta Aravind. & Manim. from M. bicystidiata ( Desjardin 1995 ; Aravindakshan and Manimohan 2015 ). In addition, M. hemitrichialis Singer produces caulocystidia that are only partially spinulose ( Singer 1989 ). Figure 2. Basidiomata of sect. Amparoina species. stirps Alphitophora : a-b Mycena alphitophora (Berk.) Sacc. c-d Mycena bicystidiata T.Bau & Q.Na e Mycena corynephora Maas Geest. f-g Mycena griseotincta T.Bau & Q.Na h Mycena hygroporoides T.Bau & Q.Na i Mycena miscanthi T.Bau & Q.Na; stirps Amparoina : j Mycena castaneicola T.Bau & Q.Na k-m Mycena heteracantha (Singer) Desjardin. Basidiomata of sect. Saccariferae species n-o Mycena hyalinostipitata T.Bau & Q.Na p-q Mycena substylobates T.Bau & Q.Na r Mycena tenerrima (Berk.) Quel . (= Mycena adscendens Maas Geest.) Scale bars: 10 mm ( a-g , i-m , r), 5 mm (h, n-q ). Photographs a-r by Qin Na. Figure 3. Microscopic features of Mycena bicystidiata (HMJAU 43648, holotype) a Basidiomata b Basidiospores c Basidia d Universal veil acanthocysts e Cheilocystidia f Caulocystidia g Pileipellis. Scale bars: 5 mm (a); 10 μm ( b-g ). Drawing by Qin Na.