二瓣小蘑菇

2.1.1 二瓣小蘑菇（Micropsalliota bifida R.L.Zhao, Desjardin, Soytong & K.D. Hyde，图 1）
子实体小型；菌盖直径 6~21 mm，幼时斗笠形或钟形，成熟后凸镜形至平展或平凹，幼时淡黄色，中间褐色，表面干，无毛或被白色细纤毛，具条纹，成熟后光滑，纯白色，边缘略内卷，在 KOH中变红褐色；菌肉薄，白色，不变色；菌褶离生，不等长，具小菌褶，密，幼时苍白色、浅灰色至淡黄褐色，成熟后灰褐色、褐色至深褐色；菌柄长 30~46 mm，粗 1~2 mm，圆柱形，白色，近光滑或稍被绒毛；菌环白色，膜质，上位，易脱落；无明显的气味和味道。担 孢 子 3.8~4.7 µm×2.3~2.8 µm ， [x=(4.2±0.21)µm×(2.6±0.14)µm, Q=1.4~1.9, Q m =1.59±0.09,n=40]，椭圆形至杏仁形，有时顶部变厚，褐色，光滑，薄壁，无芽孔；担子 9.8~12.3 µm×3.9~5.6 µm，短棒状，具 4 个小梗，有时具 2 个，无色，薄壁；褶缘囊状体 17.6~32 µm×4.6~7.4 µm，宽棒状至近槌形，顶部有时分裂成两瓣，簇生，无色，光滑，薄壁；侧生囊状体缺失；菌盖皮层由平伏菌丝组成，菌丝直径 1.6~5.6 µm，圆柱形，无色，薄壁；锁状联合缺失。生境：群生于阔叶林中地上或枯枝上。分布：泰国（模式产地）、中国广东。研究标本：2020 年 8 月 22 日，广东省惠州市罗浮山风景区，23°15′54″N，114°3′27″E，海拔90 m，张锦花、潘雪玉（RITF4915，RITF4917）。
该属中还有一些具有白色菌盖的物种，如亚白小蘑菇（M.subarginea） 、 M.arginea 、 砖红小蘑菇（M.lateritia) #注——更多时候，该物种的菌盖呈现红褐色（非原文内容）# 、 拟白色小蘑菇（M. pseudoarginea） 、 白小蘑菇（M. alba），宏观特征不易与二瓣小蘑菇区分 。但M.subarginea有更长、弯曲、圆柱形至近头状的缘生囊状体（30~60 µm×4~8 µm）；M. arginea有膨大近头状的缘生囊状体；M. lateritia有更长的孢子（4.5~5.8 µm×2.6~3.2 µm）、近头状的缘生囊状体（20~40 µm×9~18 µm）及菌盖成熟后变红褐色；M. pseudoarginea的担子更长（17~19 µm×6~6.7 µm），有椭球形至宽棒状的缘生囊状体；M. alba 有更小的子实体、更大的担孢子（5.8~6.6 µm×3.3~3.6 µm）及宽头状的缘生囊状体 。

6. Micropsalliota bifida R.L. Zhao, Desjardin, K. Soytong &K. D. Hyde sp. nov. Fig. 10; Plate 1g. MycoBanknumber:MB 518415
Pileus 9–15 (−25) mm diam., obtuse conicus ad con-vexum, glaber vel leviter pulveraceo-squamosus, niveus.Lamellae liberae, maxime densae, cinnamomeae, brunneae,castaneae. Stipes 15–30 (−40)×1–2 mm, cylindraceus, albus,annulatus. Sporae 3.8–5×(2−)2.5–3.2 μm, ellipsoideae,amygdaliformes, brunneae, apicem versus crassitunicatae.Cheilocystidia 14–27 (− 30)×5–9 μm, late clavata adsubcapita, bifida, hyalina, glabra. Pleurocystidia absentia.Pileipellis cutis, ex hyphis 3–5 μm diam., glabris.Pileus 9–15 (−25) mm diam., obtuse ly conical toconvex, becoming plano-convex with slightly incurvedmargin with age; surface dry, glabrous to finely powdery-fibrillose, pure white overall. Context membranous, thin,white. Lamellae free, very crowded, with 4 series oflamellulae, narrow (0.5–0.8 mm), orange-gray to brownishyellow, becoming grayish brown (8E3) to light brown(6B4), brown (7E4) or dark brown (7F5) in age, edgespaler. Stipe 15–30 (−40)×1– 2 mm, cylindrical, smooth orsilky, white. Annulus persistent, pendent or percurrent,membranous, superior, edge entire or torn. Odor notdistinctive. No color staining when bruised or cut. Driedspecimens brown.Macrochemicial reaction: KOH reaction strong reddishbrown; ammonia reaction blue then green.Spores 3.8-5×(2-)2.5-3.2μm, ellipsoid to amygdaliform, some with apical thickening, nogerm pore, brown. Basidia 8–12×4–5 μm, short-clavate, 4-spored. Cheilocystidia 14–27 (− 30)×5–9 μmbroadlyclavate to subcapitate, bifid with two irregular toe-likelobes, hyaline, smooth. Pleurocystidia absent. Pileipellis acutis composed of hyphae 3– 5 μm diam., hyaline, smooth.Etymology: bifidus (L)=split into two parts, referring tothe two-lobed cheilocystidia.Habit: gregarious on red soil along roadsides.Known distribution: Thailand.Material examined: THAILAND, Chiang Mai Prov., DoiSuthep-Pui National Park, Sangasabhasri Lane to Huai KokMa Village, N18°48.62′ E98°54.60′, elev. 1145 m, 13 June2006, collected by Mari a Alice Neves, ZRL3067 (Holotype: BBH#19583; Isotype: SFSU); Chiang Mai Prov., MaeTaeng, Ban Mae Sae Village, on Highway 1095 near 50 kmmarker, N19°14. 599′ E98°39.456′, elev. 962 m, 17 July2005, collected by Ruilin Zhao, ZRL2103 (BBH#19485;SFSU); Chiang Mai Prov., Chom Thong, Ob LuangNational Park, elev. 1812 m. 23 June 2005, collected byThanh Huyen Le, ZRL2026 (BBH# 19413; SFSU); ChiangMai Prov., Doi Inthanon National Park, Highway 1009 at25 km marker, N18°32.54′ E98°33.51′, elev. 1076 m, 27June 2005, collected by Amy Honan, ZRL2057(BBH#19441; SFSU); Chiang Mai Prov., Mae Taeng Dist.,Ban Pha Deng Village, Pathummikaram Temple, foresttrail, N 19°06′28.8″ E 98°44′47.3″, elev. 1050 m. 8 June2006, collected by Ruilin Zhao, ZRL3042 (BBH#19558;SFSU); Chiang Mai Prov., Mae Taeng Dist., New Waterfall,30 June 2005, collected by Thanh Huyen Le, ZRL2070(BBH#19454; SFSU); Chiang Mai Prov., Mae Taeng Dist.,Tung Joaw Village, forest trail, N19°08.07′ E98°38.90′,elev. 1300 m, 30 June 2006, collected by Ruilin Zhao,ZRL3076 (BBH#19592; SFSU).
Notes: This new species is distinguished by a white glabrous pileus, a red KOH-reaction and blue-greenammonia reaction, small spores and bifid cheilocystidia. Micropsalliota bifida is similar to a number of small whitespecies, but differs as itemized below. Micropsalliotasubarginea Heinem. has long, cylindrical, flexuous, sub-capitate cheilocystidia 30–60×4 – 8 μm (Heinemann 1980).Micropsalliota arginea has cheilocystidia with a broadlyventricose base and a distinct apical capitulum that arisesfrom a long elongate neck (Pegler 1986). Micropsalliotasubalba has larger spores 5.5–6.5×3.5–4 μm, and ventri-cose-capitate cheilocystidia 32–40×7–13 μm (Heinemannand Little Flower 1983). Micropsalliota lateritia Heinem.has slightly longer spores 4.5–5.8×2.6–3.2 μm, clavate toventricose cheilocystidia 22–40×9–18 μm, and pilei thatstain reddish brown with age (Heinemann 1980). Micro-psalliota pseudoarginea has clavate, basidia-like cheilocys-tidia, and a yellow KOH reaction (Heinemann 1982).Micropsalliota plumaria has smaller basidiomes (pileus 4–10 mm diam., stipe 10–25×0.5–1 mm), pilei with rustybrown disc, broadly clavate, subcapitate cheilocystidia, andbasidiomes that dry purple brown (Pegler 1986). Micro-psalliota albahas smaller pilei (4–6 mm diam.), largerspores 5.8–6.6×3.3–3.6 μm, and broadly capitate cheilo-cystidia (Heinemann and Little Flower 1983). Finally, M.albosericea Heinem. & Leelav. has smaller basidiomes(pileus 5 mm diam., stipe 8– 12×0.5 mm), cymbiformspores and ventricose-capitate cheilocystida (Heinemannand Leelavathy 1991). The two geographical ly isolatedspecimens included in the combied ITS+LSU analysesformed a well-supported clade (89% BS, 100% PP) sister to M. subarginea.