5. Micropsalliota arginophaea Heinem., Bull. Jard. Bot.Nat. Belg. 50:51. 1980. Fig. 9 ; Plate 1f.
Pileus 6–20 mm diam., hemispherical to convex or campanulate, expanding to plano-convex, often subumbonate to umbonate; surface fibrillose-squamulose, dense-ly so on the disc, sometimes glabrescent, brown over all when young. Context 0.5–0.8 mm thick, white. Lamellae free, crowded, with 3 series of lamellulae, 1–1.5 mm broad, straight to slightly ventricose, light brown to brownish-gray (7C2) or brown (7E4), edges paler. Stipe size variable, 7–40×0.5–2 mm, cylindrical, slender orstout, smooth above annulus, fibrillose to floccose below the annulus, white. Annulus persistent, pendent, single, rigid, superior, membranous, 0.5–2mmbroad,white.Odor not distinctive. No color staining when bruised orcut. Macrochemicial reaction: KOH reaction reddish brown.Spores 4 5:5 2:5 3 m m½x ¼ 4:8 0:5 2:80:3mmQ ¼ 1:3 2; Qm¼ 1:74 0:44; n ¼ 20, ellipsoid to amygdaliform, no germ pore, brown. Basidia 9–12×4–5 μm, clavate, 4-spored. Cheilocystidia 17–30 (−42)×4–8 μm, apex 3.5–6 μm diam., shape variable, subcylindrical to clavate, mostly with long elongated neck, somesubcapitate with swollen base, some with a spear-like apex, hyaline, smooth. Pleurocystidia absent. Pileipellis a cutis composed of hyphae 3–8(−12) μm diam., cylindrical, lightbrown or brown, sometimes slightly constricted at septa, with membranous and incrusting pigments. Annulus hyphae5–8 μm diam., hyaline, smooth. Habit: 2–4 basidiomes cespitose, clusters gregarious inred soil.
Known distribution: Malaysia (type locality); Thailand.Mate rial examined: THAILAND, Chiang Mai Prov.,Chom Thong, Ob Luang National Park, elev. 1,812 m, 23June 200 5, collected by Than h Huyen Le, ZRL2027(BBH#19414; SFSU); Chiang Mai Prov., Mae Taeng, BanMae Sae Village, on Highway 1095 near 50 km marker, N19°14. 599′ E98°39.456′, elev. 962 m, 3 July 2005, collected byThitiya Boonpratuang, ZRL2088 (BBH#19471; SFSU) andZRL2091 (BBH#19474; SFSU); same location, 3 July 2005,collected by Amy Honan, ZRL2089 (BBH#19472; SFSU);same location, 18 August 2005, collected by Ruilin ZhaoZRL2130 (BBH#19510; SFSU); Chiang Mai Prov., MaeTaeng Dist., Ban Pha Deng Village, N 19°17.123′ E98°44.009′, elev. 900 m, 2 September 2006, collected by ThanhHuyen Le, ZRL3097 (BBH#19613; SFSU); same location, 20September 2006, collected by Ruilin Zhao, ZRL3106(BBH#19622; SFSU); same location, 10 October 2006,collected by Ruilin Zhao, ZRL31 10 (BBH#19626; SFSU).
Notes: Micropsalliota arginophaea is distinguished by abrown fibrillose-squam ulose pileus, small spores, no stain-ing reaction when bruised or cut, but a strong reddishbrown reaction with KOH. Although the basidiome featuresand cheilocystidia shape are quite variable in this speci es,the ITS data indicate that this variability can be accepted asinfraspecific one. The LSU data suggest that specimensZRL 3097 and ZRL 3110 fall outside of the cladecontaining other specimens of M. arginophaea, but withoutstatistical support. Micropsalliota arginophaea is similar inpileus coloration and ornamentation and spore size to M.brunneolaHeinem. and M. brunneosperma (Singer) Pegler.Micropsalliota brunneola differs, however, in forming alarger, more strongly squamose pileus (20–30 mm diam.with erect or recurved squamules up to 1 mm high), andbroader pileipellis hyphae (8–20 μm diam.). Unf ortunately,there are no published data on cheilocystidia morphology for M. brunneola (Heinemann 1980). Micropsalliota brunneosperma differs in having broader spores (3.2–4.5 μm diam.), and consistently capitate cheilocystidia witha long and narrow neck (Pegler 1977).
