肉眼的特徴: 原基は径0.5-2mm, 半球形の傘と盤状の柄からなり, 全体に橙黄色の毛被に
被われる.傘は径15-25 mm, 最初半球形, のち類紡錘形～釣り鐘形になり, 最後は平開し, し
ばしば中丘を具え, 放射状に走る明瞭な扇状の溝線を表し, ひだの線に沿ってしばしば裂け目
を生じる; 表面は淡黄色の地に橙黄色の毛被に被われ, 中央部は橙黄色～橙色の細鱗片状
をなす. 肉は非常に薄く (傘の中央部において1mm 以下), 淡黄色～類白色, 特別な味や匂
いはない. 柄は 20-30×1-2 mm, 頂部は1-1.5 mm, ほぼ上下同大または基部に向かってや
や拡大し, 中心生, やせ型, 中空; 表面は傘と同様に橙黄色の毛被に被われ,下半部は橙黄色
の細鱗片状をなし, 頂部は淡黄色～白色, 根本に発達した菌糸体は見られない. ヒダは離生,
やや疎, L = 30-45, 幅1-3 mm, 白色. 胞子紋は白色.
微鏡的特徴: 担子胞子は 5-7×3-4 μm, 無色, 表面は平坦, 卵形-楕円形～楕円形, 弱ア
ミロイド, 薄壁, 発芽孔を欠く. 担子器は15-20×6-8 μm, こん棒形, ４胞子性. 縁シスチジアは
群生し, 洋梨形または片脹れ状～糸状の付属糸を持つフラスコ形, 無色または淡黄色, 僅かに
厚壁, 平坦, 非アミロイド; シスチジア本体は 30-50×7.5-20 μm; 付属糸は 20-150×1.5-4 μ
m, 糸状, 曲がりくねり, 頂部に向かって細くなり, 無色. 側シスチジアはない. 傘の表皮は発達の
悪い平行菌糸被をなし, 匍匐性の菌糸 (30-80×6.5-15 μm) が平行に配列し, しばしば不明
瞭なクランプが見られ, 薄壁, 平坦, 淡黄色, 非アミロイド, 非ゼラチン質. 傘の皮嚢体は多生し,
傾伏性 (decumbent) , 淡黄色, 平坦, 非アミロイド, 厚壁(0.5-1.5 μm), 傘の表皮を形成する平
行菌糸被に直接つながる; 皮嚢体の本体はこん棒形～洋梨形 (30-45×7.5-15 μm) または
不規則な円柱形 (40-150×5-12.5 μm), 時に二次隔壁を有する; 付属糸は 50-250×1.5-6 μ
m, 長く, 曲がりくねり, 糸状, 頂部に向かって細くなる. 柄の皮嚢体は傘と共通する.
供試標本: CBM-FB-16150, on a dead fallen twig of Quercus serrata Thunb. in lowland
forest (60 m alt.), Yamato-shi, Kanagawa-ken, 3 Sept. 1996.
コメント: ヒトヨタケ型の子実体を形成し, 傘が平開すると一晩で萎れる特異な性質を持つ.
外観的および顕微鏡的な特徴からクヌギタケ属コガネハナガサ節 (Mycena sect. Radiatae
Singer) に所属すると思われる. コナラの枯れ枝上に発生．
分布は本州 (埼玉, 神奈川, 東京, 三重?, 兵庫?). タイプ標本は
千葉県立中央博物館の標本庫 (CBM)に登録, 収蔵されている.
Mycena auricoma H. Takah., Mycoscience 40: 73-80, 1999
Etymology: auri- = golden-yellow in Latin; coma = hair tuft in Latin: referring to yellowish
orange flocci enveloping the whole basidioma.
Primordium 0.5-2 mm in diam, hemispherical, with a discoid stipe, enveloped in orange
(5A6-5A7) to yellowish orange (4A6-4A7) flocci. Pileus 15-25 mm in diam, at first
hemispherical, then subfusiform, expanding to campanulate or obtusely conical, finally plane
but often narrowly subumbonate, radially plicate-striate almost to the disk, often split in
places along the lines of the lamellae, pale yellow (4A3) under yellowish orange (4A6-4A7)
flocci, yellowish orange (4A6-4A7) to orange (5A6-5A7) furfuraceous over the center,
orange (5A6-5A7) at the crenulate-pruinose margin. Flesh very thin (up to 1 mm in the
center of the pileus), yellowish white (4A2) to whitish, odor and taste none. Stipe 20-30×1-
2 mm, 1-1.5 mm above, almost equal or slightly enlarged at the base, central, slender,
terete, brittle, hollow, covered with yellowish orange (4A6-4A7) flocci as on the pileus,
yellowish orange (4A6-4A7) to orange (5A6-5A7) furfuraceous toward the dark orange
(5A8) base, yellowish white (4A2) to white pruinose at the apex, without basal mycelium and
disk. Lamellae free, subdistant, L = 30-45, 1-3 mm broad, thin, white, edge ascending, pale
orange especially near the margin of the pileus.
Spore print pure white. Basidiospores 5-7×3-4 μm, colorless, smooth, ovoid-ellipsoid to
ellipsoid, pale grey to dark grey in Melzer's reagent (weakly amyloid), thin-walled, without
germ pore. Basidia 15-20×6-8 μm, clavate, four-spored. Cheilocystidia forming a compact
sterile edge, pyriform or ventricose to lageniform with filiform appendages, colorless or pale
yellow, with thin to slightly thickened walls up to 0.5 μm, smooth, inamyloid; main cell bodies
30-50×7.5-20 μm; appendages 20-150×1.5-4 μm, filiform, flexuous, simple, colorless,
tapering to an obtuse or subacute apex. Pleurocystidia none. Trama of pileus and lamellae
composed of long-celled inflated hyphae 500-1500×15-50 μm, with the ends attenuating
into narrow septa, accompanied by a few uninflated and short-celled hyphae, walls thin,
smooth, colorless, inamyloid. Surface of pileus a poorly developed narrow cutis of parallel,
repent hyphae 30-80×6.5-15 μm, often with indistinctly clamped septa, walls thin, smooth,
pale yellow, inamyloid, not gelatinized. Dermatocysts of pileus numerous, dispersed,
decumbent, pale yellow, smooth, inamyloid, walls 0.5-1.5 μm thick, arising directly from the
cutis hyphae; main cell bodies simply clavate to pyriform (30-45×7.5-15 μm) or irregularly
cylindric to strangulated (40-150×5-12.5 μm), sometimes with a secondary septum;
appendages 50-250×1.5-6 μm, long, flexuous, filiform, simple, tapering to an obtuse or
subacute apex. Surface of stipe thinly coated with parallel, repent hyphae 5-10 μm wide,
often with indistinctly clamped septa, walls thin, smooth, pale yellow, inamyloid, not
gelatinized. Dermatocysts of stipe similar to those of the pileus but shorter and paler at the
apex of the stipe. Trama of stipe composed of longitudinally running, spindle-form hyphae
1000-2500×15-30 μm, walls thin, smooth, colorless, inamyloid.
Habitat: Solitary on dead fallen twig of Quercus serrata Thunb., from June to October,
not common. Distribution: Japan (Kanagawa, Saitama).
Holotype: CBM-FB-16150, on a dead fallen twig of Quercus serrata Thunb. in lowland forest (60 m alt.),
Yamato-shi, Kanagawa-ken, 3 Sept. 1996.
Japanese name: Kogane-hanagasa (first collected and named by Mr.Minoru Aoki).
Notes: This species is well characterized macroscopically by the yellowish orange flocci
on the pileus and stipe, the delicate, plicate- striate pilei, the insititious stipe lacking a basal
disc, the white, free lamellae and the lignicolous habit, and microscopically by the colorless,
amyloid basidiospores, the cheilocystidia often with filiform appendages and the thick-walled,
non-diverticulate dermatocysts tapering into filiform appendages apically. The combination
of these features suggests that it belongs to Mycena section Radiatae in the sense of
Singer (1975, 1986). However, its yellowish orange flocci enveloping the whole basidioma
distinguish the present fungus from other known species of the section Radiatae.
“Trogia” crinipelliformis Corner (1996) from Malaysia, which would belong to Mycena
section Radiatae following the Singer's system (1986), seems to be most closely allied with
M. auricoma. The former, however, has an acutely umbonate primordium, reddish orange
(not yellowish) tones in the fibrillose flocci on the pileus and stipe, inamyloid basidiospores,
and cheilocystidia with occasionally branched appendages.
Although numerous primordia occur initially, only a few grow into mature basidiomata.
The expanded basidiomata make basidiospores only for one night and soon collapse.
