シモフリアシグロタケ
Marasmiellus atrostipitatus Har. Takah., Mycoscience 41: 467 (2000) [MB#466182]
子実体は小形(傘の径4-12 mm)で成熟するとニンニク臭を発し、傘は乳白色で明瞭な放射状の溝線を表し、柄は下部に向かって黒色を呈し、白色の粉状物に密に被われ、傘の表皮組織は平行菌糸被で, * Rameales構造「多分枝菌糸構造」 が発達。シラカシとヒサカキを中心とする林内の落枝及び落ち葉上に発生。
Jul.1998, Yamato, Kanagawa Pref.
神奈川県大和市
A. Basidiospores. B. Basidium and basidioles. C. Cheilocystidia. D. Terminal elements of the pileipellis. E. Caulocystidia. Scales: 10µm. All figures from the holotype.
A. 担子胞子. B. 担子器および偽担子器. C. 縁シスチジア. D. 傘表皮組織の末端細胞 (* Rameales構造). E. 柄シスチジア.
肉眼的特徴: 傘は径 4-12 mm, 最初半球形で縁部は内側に巻き, のち饅頭形からほぼ平開し, しばしば中央部がやや凹み, 最初平坦であるがまもなく明瞭な放射状の溝線を表し, ほぼ平滑または僅かに密綿毛状, 純白色, しばしば縁部は波状 (undulating). 肉は非常に薄く (0.5 mm以下), 白色; 老成するとニンニク臭がある. 柄は 6-18×0.2-1 mm, ほぼ上下同大または下方に向かってやや細くなり, 中心生またはやや偏在生, やせ型, 中空, 上部は淡褐色で白色粉状, 下部は黒褐色で密に細かい羊毛状, 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 10-15), 幅 1.5 mm以下, 白色; 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 7-9×3.5-4.5 μm [Q = length/breadth: 2], 楕円形～長楕円形, 平坦, 無色, 非アミロイド, 薄壁. 担子器は 22-29×5-8 μm, こん棒形, ４胞子性. 偽担子器は類こん棒形～紡錘形. 縁シスチジアは 19-55×8-15 μm, 群生し, こん棒形～不規則なこん棒形, しばしば上部に複数の指状突起 (長さ 2-12 μm)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. 傘の表皮は平行菌糸被で, * Rameales構造「多分枝菌糸構造」 (図D)が発達する; 菌糸は幅 2-11 μm, 互いに平行に走り, 円柱形, しばしば肥大し, 多数の瘤状～指状突起に被われ, 無色, 薄壁, 隔壁にクランプを欠く. 傘実質の菌糸は幅 3-17 μm, 円柱形, しばしば肥大し, 薄壁, 無色, 非アミロイド, 隔壁にクランプを欠く. 柄の表皮は平行菌糸被; 菌糸は幅 2.5-6 μm, 円柱形, しばしば褐色の粒状色素に被覆され, 非アミロイド, 細胞壁は褐色で厚さ 1 μmに達し, 隔壁にクランプを欠く; 柄シスチジアは 15-28×5-15 μm, 群生し, こん棒形～類円柱形, 時に瘤状分岐物 (5-12×3-8 μm)を有し, 無色または褐色, 非アミロイド, 厚壁 (1 μm). 柄の実質は縦に沿って配列した円柱形の菌糸(幅 4-9 μm)からなり, 無分岐, 無色または淡褐色, 非アミロイド, 厚壁 (1 μm), 時に隔壁にクランプを有する.
* Rameales構造「多分枝菌糸構造」(Fig. g): 不規則に分岐する多数の樹枝状, 短指状またはこぶ状の突起 (diverticula)に被われた菌糸細胞からなる表皮構造. シロホウライタケ属 (Marasmiellus Sect.Rameales)において典型的であるが, モリノカレバタケ属 (Collybia Sect.Subfumosae) 並びにヒトヨタケ属 ヒメヒトヨタケ亜節(Coprinus Sect.Coprinus Subsect.Alachuani)にも類似の構造が見られる. また Campanella 及び Resupinatus の両属には二叉糸状体と ラメアレス構造の中間型が見られる. 平行菌糸被の特殊型.
傘表皮組織の類型 (Antonĺn and Noordeloos 1997)
a, b: ホウライタケ属における子実層状被, a 箒状細胞, b 平滑細胞;
c: 平行菌糸被; d: 粘性平行菌糸被; e: 珊瑚状菌糸からなる平行菌糸被;
f: モリノカレバタケ型表皮構造（瘤状分岐物を持ち且つ凝着色素に被われた菌糸が絡み合い, 放射状に並列しない構造);
g: 多分枝菌糸構造.
Marasmiellus atrostipitatus Har. Takah., Mycoscience 41: 467-472, 2000
Pileus 4-12 mm in diam, at first hemispherical with involute margin, then plano-convex, often with slightly depressed center, at first smooth but soon radially sulcate-striate almost to the disk, glabrous or slightly tomentose under lens, pure white, often with undulating marginal zone. Flesh very thin (up to 0.5 mm), white; odor alliaceous in age; taste none. Stipe 6-18×0.2-1 mm, almost equal, slightly tapering toward the base, central or somewhat eccentric, slender, terete, hollow, pale brownish above, blackish brown to almost black below, white pruinose in upper part, becoming flocculose toward the insititious base. Lamellae adnexed, distant (10-15 reach the stipe), somewhat broad (up to 1.5 mm broad), thin, white; edges fimbriate, concolorous.
Spore print pure white. Basidiospores 7-9×3.5-4.5 μm [Q = length/breadth: 2], ellipsoid to oblong, smooth, colorless, inamyloid, thin-walled. Basidia 22-29×5-8 μm, clavate, four-spored. Basidioles subclavate to fusiform. Cheilocystidia 19-55×8-15 μm, abundant, clavate to irregularly clavate, often with a variable number of digitate, 2-12 μm long projections, colorless, thin-walled. Pleurocystidia absent. Hymenophoral trama subregular to irregular; element hyphae similar to those of the pileitrama. Pileipellis a cutis with well-developed Rameales-structure; constituent hyphae 2-11 μm wide, parallel, cylindric, inflated or not, with abundant warty or finger-like protuberances, colorless, thin-walled, without clamped septa. Hyphae of pileitrama 3-17 μm wide, subparallel, cylindric, often inflated, walls thin, smooth, colorless, inamyloid, without clamped septa. Stipitipellis a cutis of parallel, repent hyphae 2.5-6 μm wide, cylindric, often encrusted with granules of brown pigment, with inamyloid, brown walls up to 1 μm thick, without clamped septa; caulocystidia 15-28×5-15 μm, abundant, clavate to subcylindric, smooth or with a few broad, irregular to knob-like diverticula 5-12×3-8 μm, colorless or brown, inamyloid, slightly thick- walled (up to 1 μm thick). Stipe trama composed of longitudinally running, cylindric hyphae 4-9 μm wide, unbranched, smooth, colorless or light brown, inamyloid, slightly thick- walled (up to 1 μm thick), occasionally with clamped septa.
Known distribution: Japan (Kanagawa).
Habitat: Solitary to caespitose, on dead leaves and twigs in lowland forests dominated by Quercus myrsinaefolia Blume and Eurya japonica Thunb., from June to September, not common.
Holotype: KPM-NC0005075, on dead leaves and twigs under broad-leaved trees, Yamato-shi, Kanagawa-ken, 24 Jul. 1998.
Other specimens examined: on dead leaves and twigs under broad-leaved trees, Yamato-shi, Kanagawa-ken, 4 Jul. 1999; ibid. 12 Jul. 1999.
Japanese name: Shimofuri-ashiguro- take.
Notes: This species is characterized by its pure white pileus, the conspicuously white pruinose to flocculose, blackish stipe, basidiospores less than 10 μm long, clavate cheilocystidia with a few finger-like projections, and the pileipellis with a distinct Rameales-structure. The combination of these features suggests that this species belongs in the section Rameales (J.Lange) Singer, subsection Opacini Singer (Singer, 1973, 1986).
Within the section Rameales, the closest related species is Marasmiellus stypinoides (Petch) Pegler (Pegler, 1986) from Sri Lanka, which differs in having an umbilicate pileus, a nigrescent (at first white) stipe, and absence of garlic odor. Marasmiellus nigripes (Schwein.) Singer, the type species of the section Nigripedes Singer, has superficial resemblance to Marasmiellus atrostipitatus, but it can be readily differentiated because of its stellate-cruciform basidiospores. European Marasmiellus trabutii (R.Maire) Singer (Antonin and Noordeloos, 1993), which belongs in the section Tricolores Singer, is also similar in appearance but differs in having adnate to subdecurrent lamellae, much longer basidiospores (12.5-17.5 μm: Antonin and Noordeloos, 1993), and irregularly cylindric cheilocystidia and caulocystidia.
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
Pegler, D.N. 1986. Agaric flora of Sri Lanka. Kew Bulletin Add. Ser. XlI. Her Majesty's Stationery Office, London.
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. 2000. Two new species of Marasmiellus from eastern Honshu, Japan. Mycoscience. 41:467-472