Tochikagami - Tochikagami

A floating perennial plant of the family Hormonaceae (APG classification: Hormonaceae). The stem runs horizontally underwater, and white root hairs and leaves emerge from the nodes. The adult leaves are shield-shaped, and the stipules are membranous, egg-lanceolate, and 2.5-3.5 cm long. The floating leaves are almost cordate, 4-8 cm long, glossy on the upper surface, and densely packed in the center of the underside are 2-5 mm high swim bladders in a foam-like shape. The flowers are unisexual and monoecious. White flowers bloom for one day from July to October. Both male and female flowers have three sepals and three petals. There are 12 stamens and one pistil. The female flower has a thicker pedicel. The fruit is obovate, with spindle-shaped, pale pink seeds 1-1.5 mm long. It overwinters as seeds or buds. It grows in colonies in ponds and streams, and is found widely in temperate regions from Honshu to Okinawa. Its name means "horse chestnut mirror" and comes from its shiny round leaves.

[Sueo Otaki, September 19, 2018]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

トチカガミ科（APG分類：トチカガミ科）の浮葉性の多年草。茎は水中を横走し、節から白いひげ根と葉を出す。成長葉は楯(たて)状葉で、托葉(たくよう)は膜質で卵状披針(ひしん)形、長さ2.5～3.5センチメートル。浮水葉はほぼ心臓形で長さ4～8センチメートル、表面は光沢があり、裏面は中央部に高さ2～5ミリメートルの浮き袋が泡沫(ほうまつ)状に密生。花は単性で雌雄同株。7～10月、白色の一日花を開く。雄花・雌花ともに萼片(がくへん)3枚、花弁3枚。雄しべは12本、雌しべは1本。花柄は雌花のほうが太い。果実は倒卵形、中に紡錘形で長さ1～1.5ミリメートルの淡紅色の種子がある。種子または殖芽で越冬する。池沼や小川に群生し、本州から沖縄、および広く温帯に分布する。名は、トチ（スッポン）の鏡の意味で、円いつやのある葉に由来する。

［大滝末男　2018年9月19日］

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