竹节水松 zhu jie shui song

Stems to 1--2 m, basally rhizomatous and glabrescent, apically rust colored pubescent. Submersed leaves petiole 0.3--1.5 cm; blade palmately dissected, 2--5 × 2.5--7 cm in overall diam., ultimate segments linear to slightly spatulate, to 1.8 mm wide. Floating leaves petiole 1.5--2 cm; blade 1.4--2 × ca. 0.3 cm. Flowers 0.6--1.5 cm in diam. Sepals white, with margin tinged purple, or yellow, rarely purplish, 5--12 × 2--7 mm, apex obtuse. Petals colored as sepals, 4--12 × 2--5 mm, base clawed, apex broadly obtuse or emarginate; basal nectiferous auricles yellow. Stamens (3--)6, ca. 3.5 mm. Pistils (2--)3, 3.5--4 mm, short pubescent. Fruit 4--7 mm. Seeds 1--3, 1.5--3 × 1--1.5 mm. Fl. and fr. summer--autumn. 2n = 26, 78, 104.

In rivers. Jiangsu [native to SE North America and S South America].