Basidiomata light green to yellowish-green and turning blue when dried, umbonate to plano-convex pileus covered with dark gray to black granulose to squamules and with light green appendiculate margin, free and light green to yellowish-green lamellae, subcylindrical and yellowish-green support with light green fibrillose remnants, oblong to ovoid basidiospore with a germ pore, 5.8-7.2 × 3.8-5 μm, clavate to utriform cheilocystidia with short to long appendages, 18-32 × 8-15 μm, a hymenodermal pileus covering made up of some cylindrical elements, a cutis support covering made up of hyaline hyphae and cylindrical elements, absence of clamp-connections in all tissues. Pileus 15-35 mm diam, umbonate, explanding via campanulate to applanate to plano-convex, with low umbo, with straight margin; when young granulose, dark gray (1-30F1) to black, soon breaking up into concolourous squamules to squamules fibrillose around granulose umbo toward margin, on light green to yellowish-green (30A5-8) background, attached with light green (30A5) appendiculate margin, fringed and lamellae exceeding when mature. Lamellae free, broadly ventricose, light green to yellowish-green (30A5-6), slightly crowded, with 5 lamellulae series. Support 23-40 × 3-8.5 mm, subcylindrical or wider at base zone and slightly tapering to apex, with green to yellowish-green (30A5-6) fibrillose background. Annulus membranous, rarely present or often fragile, with green to yellowish-green (30A5-6) fibrillose remnants at middle to upper part of support. Context in pileus 2.0-3.0 mm wide, concolourous with surface; in support hollow, concolourous with surface. Odor and taste not observed. Spore print white. Basidiospores [75, 3, 3] l × w = 5.8-7.2 × 3.8-5 μm, avl × w = 6.5 × 4.3 μm, Q = 1.4-1.7, Qav = 1.5, in side-view oblong or ovoid, in frontal view ovoid, oblong, thick -walled, hyaline, with a germ pore, dextrinoid, cogophilous, cyanophilous, metachromatic. Basidia 12-15 × 6-8 μm, clavate, 4-spored, hyaline. Lamella edge sterile. Cheilocystidia 18-32 × 8-15 μm, clavate to utriform, with short to long appendages (l × w = 5-20 × 2.5-3.5 μm), Pleurocystidia absent. Pileus covering a hymenoderm made up of some layers of cylindrical elements, rarely with narrowly clavate elements, 23-47 × 4-7 μm, hyaline to pale brown-walled, under layer with hyaline hyphae, cylindrical, 2.5-6.5 μm wide. Stipe covering a cutis made up of cylindrical elements, 1-2.5 μm wide, hyaline, with cylindrical hyphae in lower layer, 1-4 μm wide, hyaline. Clamp connections absent in all tissues. (Figs. 1-2)
Etymology: The name is referred to the first collecting site of this species at Houay Nhang Preserved Forest.
Habitat: solitary, saprotrophic, on humus soil; widespread in deciduous forests of Houat Yang Preserved Forest, Xaythany District, Vientiane Capital, Lao PDR.
Specimens examined: Laos, Vientiane Capital, Xaythany District, Houay Nhang Preserved Forest, collected date 12 July 20014, P. Sysouphanthong (PS2014-1448, HNL502947, holotype); ibidem collected date 20 August 20014, P. Sysouphanthong (PS2014-1463, HNL502962, paratypes); ibidem collected date 2 September 20014, P. Sysouphanthong (PS2014-1483, HNL 502982, paratypes).
FIG. 1 Fresh basidiomata of La. houaynhangensis . ac (HNL502947), d (HNL502962), ef (HNL502982).
FIG. 2 Micromorphology of La.houaynhangensis with scale bars (HNL502947). a hymeniderm structure of pileus covering, b a cutis structure of support covering, c oblong ovoid basidiospoes, d clavate to utriform cheilocystidia with appendages.
Sysouphanthong P, Bouamanivong S, Salichanh T, Xaybouangeun N, Sucharitakul P, Osathanunkul M and Suwannapoom C, 2018 –Leucoagaricus houaynhangensis (Agaricaceae), A New Yellowish-green Species from Lao People’s Democratic Republic. Chiang Mai Journal of Science, 45, pp.1287-1295.
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