Ludwigia

…An aquatic perennial plant of the Onagraceae family that grows in colonies in shallow ponds and marshes in the warm temperate and subtropical regions (illustration). It is found in Honshu, Shikoku, Kyushu, Taiwan, and Hainan Island. Its Japanese name comes from the fact that it produces yellow, free-petaled flowers that resemble those of the tumbleweed. The stem is soft and long, crawling through the mud and growing diagonally above the water. It produces aerating roots. The leaves are alternate and gathered at the top of the stem, oblanceolate, and about 5 cm long and 1 cm wide when mature. The flowers grow singly on the upper veins, about 2.5 cm in diameter, with 4 or 5 petals and sepals, 8 to 10 stamens, and one pistil, with an inferior ovary, and the fruit is a capsule that is club-shaped and 2 to 2.5 cm long. …

*Some of the terminology that mentions "Ludwigia" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…暖帯や亜熱帯地方の浅い池沼に群生するアカバナ科の水生多年草（イラスト）。本州，四国，九州のほか，台湾や海南島にもある。キンバイソウに似た離弁の黄色い花をつけるところから，和名がついた。茎は軟らかく，長く泥中をはい，斜めにのびて水上に出る。呼吸根を出す。葉は茎の上方に集まって互生し，倒披針形，成葉では長さ5cm，幅1cm内外。花は上部の葉脈に単生し，径約2.5cm，花弁と萼片は4または5枚，おしべは8～10本，めしべは1本で子房下位，果実は蒴果（さくか）で棍棒状，長さ2～2.5cmに及ぶ。…

※「Ludwigia」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報