オオミノアマタケ 

Collybia macrosperma Har.Takah., Mycoscience 42: 339-345 2001 

系統的な類縁関係がよく分からない種で、子実体の類型と顕微鏡的特徴に基づき暫定的にモリノカレバタケ属の仲間と考えましたが、やや大型の担子胞子(長さ 10-15µm) を有し、傘と柄が長い表皮シスチジアに被われ、毛状の縁シスチジアを持つ点で異質です。

  肉眼的特徴: 傘は径 7-12 mm, 最初半球形, のち饅頭形になりるかまたは平開し, 縁部は最初内側に巻き, ほぼ平坦もしくは老成時浅い溝線を表し, 表面は全体に細軟毛に被われ, 中央部淡褐色, 周縁に向かってほぼ白色を呈する. 肉は薄く (傘の中央部において 2.2 mm 以下), 軟質, 白色, 特別な味や匂いはない. 柄は 15-23×1-1.2 mm, ほぼ上下同大, 根本はやや拡大し, 中心生, 中空, 上部白色, 根本に向かって淡褐色を帯び, 平坦, 全体に表面と同色の細軟毛に被われ, 根本に発達した菌糸体は見られない. ヒダは上生, やや疎, 柄に到達するヒダは 17-22, 幅 1.2 mm以下, 白色, 縁部は細軟毛状, 縁取りを欠く.

  顕微鏡的特徴: 担子胞子は 10-15×4-5μm [Q = length/breadth: 2.5-3.0], 紡錘状円柱形, 側面観においてやや屈曲し, 平坦, 無色, 非アミロイド, 薄壁. 担子器は 40-50×8-10μm, こん棒形, ４胞子性. 偽担子器はこん棒形. 縁シスチジアは 42-80×4-6μm, 散生もしくは束生し, 子実層から著しく突出し, 糸状～円柱形, 鈍頭, 平坦, 無色, 非アミロイド, 薄壁. 側シスチジアはない. 傘の表皮は平行菌糸被で, 匍匐性の菌糸が不規則に配列し, 瘤状突起に著しく被われることはない; 菌糸は幅 3-10μm, 錯綜し, 円柱形, 平坦, 褐色の粒状色素が細胞壁に点在するかまたは無色, 薄壁, 時に隔壁にクランプを持つ; 傘シスチジアは 30-70×4-10 μm, 散生, 直立し, 片脹れ状紡錘形または類円柱形, 褐色の粒状色素が細胞壁に点在するかまたは無色, 薄壁, 時に隔壁にクランプを持つ. 柄シスチジアは 30-95×4-15 μm. 傘シスチジアと同形. 実質の菌糸はしばしば隔壁にクランプを有する.

  供試標本: KPM-NC0005074 (基準標本), Ikuta-ryokuchi, Kawasaki- shi, Kanagawa-ken, 4 Jul. 1999, coll. H.Takahashi; the same place, 10 Jul. 1999, coll. H.Takahashi. 

  コメント: 子実体は類白色で全体に細軟毛に被われ, 大型の担子胞子 (長さ 10-15µm) を持つ. 神奈川県川崎市生田緑地のイヌシデ, シラカシ, コナラを主とする林内の落枝上に発生.  本種は剛毛体様の毛を持たないが, 傘と柄が明瞭な無色薄壁の毛状皮嚢体に被われ, 長形の担子胞子を有し, 根本および基質上に発達した菌糸体を持たない性質は Marasmiellus Sect. Stenophylloides と共通している.

Collybia macrosperma Har.Takah., Mycoscience 42: 339-345, 2001

  Pileus 7-12 mm in diam, hemispherical to broadly conical, expanding to convex or applanate, with involute then deflexed or straight margin, smooth or slightly rugulose in age, finely pubescent, pale brownish at the center, almost white toward the margin. Flesh thin (up to 2.2 mm thick), soft, white; odor and taste indistinct. Stipe 15-23×1-1.2 mm, equal but subbulbous at the base, central, terete, hollow, whitish above, pale brownish toward the base, smooth, finely pubescent overall, denser toward the base, without basal mycelium. Lamellae adnexed, subdistant (17-22 reach the stipe), narrow (up to 1.2 mm broad), thin, white; edges finely pubescent, concolorous. 

  Basidiospores 10-15×4-5 μm [Q = length/breadth: 2.5-3.0], cylindrical- fusoid, slightly curved in profile, smooth, colorless, inamyloid, thin-walled. Basidia 40-50×8-10 μm, 

clavate, four-spored. Basidioles clavate. lamella-edge fertile, with long, hair-like cheilocystidia; cheilocystidia scattered or aggregated into fasciculate groups, strongly 

protruding beyond hymenium (up to 50 μm), 42-80×4-6 μm, filiform to cylindric, with obtuse apex, smooth, colorless, inamyloid, thin-walled. Pleurocystidia absent. Elements of 

hymenophoral trama 4-10 μm wide, cylindric, subparallel, smooth, colorless, thin-walled, occasionally with clamped septa. Pileipellis a layer of repent, branched hyphae, not radially arranged; constituent hyphae 3-10 μm wide, interwoven, cylindric, smooth, sometimes weakly encrusted with granules of brown pigment, thin-walled, occasionally with clamped septa; pileocystidia 30-70×4-10 μm, scattered, suberect to erect, fusoid-ventricose or subcylindric, with obtuse or subacute apex, colorless or weakly encrusted with granules of brown pigment, thin-walled. Pileitrama of cylindric or somewhat inflated, loosely interwoven hyphae 4-15(-24) μm wide, smooth, colorless, inamyloid, thin-walled, occasionally with clamped septa. Stipitipellis a cutis of parallel, repent hyphae 3-10 μm wide, cylindric, with scattered, suberect to erect caulocystidia, smooth, colorless, thin-walled, occasionally with clamped septa; caulocystidia similar to pileocystidia but longer and broader, 30-95×4-15 μm. Stipe trama composed of longitudinally running, cylindric hyphae 5-15 μm wide, unbranched, smooth, colorless, inamyloid, occasionally with clamped septa. 

  Known distribution: Japan (Kanagawa). 

  Habitat: Solitary to caespitose, on dead twigs in lowland forests dominated by Carpinus tschonoskii Maxim., Quercus myrsinaefolia Blume, and Quercus serrata Thunb. ex Murray, July, not common. 

  Specimens examined: KPM-NC0005074 (holotype), Ikuta-ryokuchi, Kawasaki- shi, Kanagawa-ken, 4 Jul. 1999, coll. H.Takahashi; the same place, 10 Jul. 1999, coll. H.Takahashi. 

  Japanese name: Oomino-amatake. 

  Notes: The collybioid habit, the inamyloid basidiospores and tramal tissues, and the Dryophila-type pileipellis structure suggest that this species is closely allied with the section Levipedes of the genus Collybia in Singer's (1986) classification. However, C.macrosperma is distinguishable from other taxa belonging to Collybia by its basidiomata densely covered with minute, soft hairs, the insititious stipe, the scattered, projecting, filiform cheilocystidia on the fertile lamella edges, and its relatively long basidiospores (reaching to 15 μm long). Until further taxonomic information concerning allied species becomes available, I prefer provisionally to relegate this taxon to the genus Collybia (s.l.).

Literature cited　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

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: 339-345.