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Marasmiellus gregarius Har. Takah., Mycoscience 42 (4): 343 (2001) [MB#474705]

子実体は小型で淡褐色を帯び、柄は白色粉状物に被われ、傘表皮は樹枝状分岐物を持つ菌糸(Rameales構造｢多分枝菌糸構造｣、図D)からなり、縁シスチジア(図C)は不規則な分岐物を形成します。

北半球温帯に広く分布する Marasmiellus ramealis (Bull.: Fr.) Singerの近縁種です。

肉眼的特徴: 傘は径 3-8 mm, 最初半球形で縁部は内側に巻き, のち饅頭形になり, 最初平坦であるがまもなく周縁に明瞭な放射状の溝線を表し, 表面は密綿毛状, 一様に淡褐色, まれに類白色. 肉は非常に薄く (1 mm以下), 淡褐色, 特別な味や臭いはない. 柄は 2-4×0.5-0.9 mm, ほぼ上下同大であるが時に根本がやや拡大し, 中心生, やせ型, 中空, 傘より濃色であるが頂部は淡色, ほぼ全面にわたって白色粉状, 根本は無毛で分化した菌糸体は見られない. ヒダは上生, 疎 (柄に到達するヒダは 8-11), 幅 1 mm以下, 白色または淡褐色; 縁部は長縁毛状 (fimbriate), 縁取りを欠く. 胞子紋は白色.

顕微鏡的特徴: 担子胞子は 6.5-8×4-5μm [Q = length/breadth: 1.6], 楕円形, 平坦, 無色, 非アミロイド, 薄壁. 担子器は 22-27×5-6.5 μm, こん棒形, 4 胞子性. 偽担子器はこん棒

形～類こん棒形, 縁シスチジアは 25-55×10-15μm, 群生し, 円柱形～類こん棒形, 多数の指状分岐物 (長さ 2-11μm)を具え, 無色, 薄壁. 側シスチジアはない. 子実層托実質はやや平列～不規則に配列する; 菌糸は傘実質と共通する. 傘の表皮は不規則に配列した匍匐性の菌糸からなり, 明瞭なRameales構造｢多分枝菌糸構造｣(図D)が発達する; 菌糸は幅 3-13μm, 錯綜し, 円柱形, 多数の瘤状～指状突起に被われ, 菌糸の間に褐色の色素顆粒が存在し, 薄壁, 時に隔壁にクランプを持つ. 傘実質の菌糸は幅 3-10μm, 錯綜し, 円柱形, 薄壁, 淡黄褐色, 非アミロイド, 時に隔壁にクランプを持つ. 柄の表皮は平行菌糸被; 菌糸は幅 2-5μm, 円柱形, 多数の瘤状分岐物に被われ, 非アミロイド, 細胞壁は褐色で厚さ 0.5μm, 時に隔壁にクランプを持ち, 柄シスチジアを欠く. 柄の実質は縦に沿って配列した円柱形の菌糸 (20-55×6-14μm) からなり, 無分岐, 平坦, 無色, 非アミロイド, 厚壁 (1.5μm), 時に隔壁にクランプを有する.

生態: テイカカズラおよびタマアジサイの枯枝上に群生.

コメント: 子実体は小型で淡褐色を帯び、柄は白色粉状物に被われ、傘表皮は樹枝状分岐物を持つ菌糸(Rameales構造｢多分枝菌糸構造｣、図D)からなり、縁シスチジア(図C)は不規則な分岐物を形成します。

北半球温帯に広く分布する Marasmiellus ramealis (Bull.: Fr.) Singerの近縁種です。

Marasmiellus gregarius Har. Takah., Mycoscience 42: 339-345, 2001　　　　

Pileus 3-8 mm in diam, at first hemispherical with involute margin, then convex, finally plano-convex, at first smooth but soon radially grooved at margin, entirely felted-

tomentose, usually entirely pale brown, rarely whitish overall. Flesh very thin (up to 1 mm), light brown; odor and taste not distinctive. Stipe 2-4×0.5-0.9 mm, almost equal but

sometimes subbulbous or slightly swollen at the base, central, slender, terete, hollow, deep concolorous with the pileus, paler toward the apex, pruinose to flocculose above, strigose toward the insititious base. Lamellae adnate, distant (8-11 reach the stipe), narrow (up to 1 mm broad), thin, whitish or pale brown; edges fimbriate, concolorous.

Spore print pure white. Basidiospores 6.5-8×4-5 μm [Q = length/breadth: 1.6], ellipsoid, smooth, colorless, inamyloid, thin-walled. Basidia 22-27×5-6.5 μm, clavate, four-spored. Basidioles clavate. Cheilocystidia 25-55×10-15 μm, abundant, cylindric to subclavate, with a variable number of digitate, 2-11 μm long projections, colorless, thin- walled. Pleurocystidia absent. Hymenophoral trama subregular to irregular; element hyphae similar to those of the pileitrama. Pileipellis a layer of repent, irregularly arranged hyphae, with strongly developed Rameales-structure; constituent hyphae 3-13 μm wide, interwoven, cylindric, with abundant warty or finger-like protuberances, with intercellular brown pigment among the hyphae, not incrusted, thin-walled, occasionally with clamped septa. Hyphae of pileitrama 3-10 μm wide, interwoven, cylindric, walls thin, smooth, pale melleous, inamyloid, occasionally with clamped septa. Stipitipellis a cutis of parallel, repent hyphae 2-5 μm wide, cylindric, diverticulate, inamyloid, brown walls up to 0.5 μm thick, occasionally with clamped septa, without caulocystidia. Stipe trama composed of longitudinally running hyphae, hyphal cells 20-55×6-14 μm, cylindric, unbranched, with smooth, inamyloid, colorless walls up to 1.5 μm thick, occasionally with clamped septa.

Known distribution: Japan (Tokyo).

Habitat: gregarious, on dead twigs of Hydrangea involucrata Siebold and Trachelospermum asiaticum (Siebold et Zucc.) Nakai, from June to July, not common.

Specimens examined: KPM-NC0005065 (holotype), Mt.Takao, Hachiouji-shi, Tokyo, 15 Jul. 1999, coll. W. Ikeda & H.Takahashi; the same place, 25 Jun. 1998, coll. W. Ikeda & H.Takahashi; the same place, 28 Jun. 2000, coll. H.Takahashi.

Japanese name: Satoyama-houraitake.

Notes: This species is characterized by its pale brown, small, collybioid basidiomata, the basidiospores less than 10 μm long, the cylindric to subclavate cheilocystidia with

numerous fine diverticula, and the pileipellis with a distinct Rameales-structure. This combination of characters suggests placement of this taxon in the section Rameales (J.E.

Lange) Singer, subsection Ramealini Singer (Singer, 1973, 1986).

Within the section, M.gregarius appears to be closely allied with North American Marasmiellus appalachienensis Desjardin (Desjardin, 1997) and Marasmiellus ramealis (Bull.: Fr.) Singer from Europe and North America. Marasmiellus appalachienensis differs from M. gregarius in having pure white pilei, a reddish stipe base, and broadly clavate or vesiculose caulocystidia. Marasmiellus ramealis differs in having pinkish brown or yellowish brown pilei, subcylindric, longer basidiospores (7.5-11 μm: Antonin and Noordeloos, 1993), and pileipellis strongly incrusted with brown pigment.

Literature

Antonfn, V. and Noordeloos,M.E. 1993. A Monograph of Marasrnius, Collybia and related genera in Europe. Part 1 .: Marasmius, Setulipes, and Marasmiellus. Lib. Bot. 8: 1-229.

Antonĺn V, Noordeloos ME. 1997. A Monograph of Marasmius, Collybia and related genera in Europe. part 2: Collybia, Gymnopus, Rhodocollybia, Crinipellis, Chaetocalathus, and additions to Marasmiellus. Lib Bot 17:1-256

Desjardin DE. 1997. A synopsis of Marasmiellus in the southern Appalachian Mountains. Mycotaxon 65: 237-261.

Singer, R. 1973. The genera Marasrniellus, Crepidotus and Sirnocybe in the Neotropics. Beih. Nova Hedwig. 44: 1-339.

Singer, R. 1986. The Agaricales in modern taxonomy, 4th ed. Koeltz Scientific Books, Koenigstein.

Takahashi, H. 2001. Notes on new Agaricales of Japan 1. Mycoscience. 42(4):339-345