Nuphar japonicum - Nuphar japonicum

Japanese: コウホネ(河骨) - コウホネ（英語表記）Nuphar japonicum

A perennial aquatic plant of the Nymphaeaceae family. It is also called Kawahone. It grows in ponds and marshes throughout Japan. The rhizomes run horizontally through the mud at the bottom of the water, and leaves emerge from the tips. The leaves have cylindrical petioles that pierce the water surface. The leaf blades are oblong or oblong, pointed at the tip, and arrowhead-shaped at the base. Thin, submerged leaves are also often produced. In summer, yellow flowers about 5 cm in diameter with cylindrical pedicels longer than the petioles bloom. The flower has five petal-like sepals, numerous small petals, and numerous stamens arranged in a spiral, and in the center is a broad ovate ovary. The top of the ovary is disc-shaped (stigma plate), and the stigmas are arranged radially. In Hokkaido and northern Honshu, there is another species, N. pumilum , whose leaves float on the water surface like water lilies and whose stigma plate is slightly reddish. This species is widely distributed in the cool temperate zone of the Northern Hemisphere.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

スイレン科の多年生の水草。カワホネともいう。日本各地の池沼中に生じる。根茎は水底の泥中を横走し，その先端部から葉が出る。葉は円柱形の葉柄があり水面上に突き抜けて葉を出す。葉身は長卵形ないし長楕円形で先はとがり，基部は鏃 (やじり) 形をしている。しばしば細長い沈水葉も生じる。夏に，葉柄よりも長く，円柱形の花柄をもつ径 5cmほどの黄色の花が咲く。花は花弁状化した萼片5枚と多数の小型の花弁，おしべ多数が螺旋状に並び，その中心に広卵形の1子房がある。子房の頂部は盤状 (柱頭盤) をなし，放射上に柱頭が並ぶ。北海道や本州北部には別種のネムロコウホネ N. pumilumがあり，葉はスイレンのように水面に浮び，柱頭盤はやや赤みを帯びる。北半球の冷温帯に広い分布をもつ種である。

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