密刺苦草 mi ci ku cao

Vallisneria spiralis Linnaeus var. denseserrulata Makino, Bot. Mag. (Tokyo) 28: 27. 1914.

Rhizome erect, 1-6 cm, 4-6 mm in diam.; stolons with minute spines. Leaves 20-70 cm × 6-12 mm, veins 3, midvein with minute spines, margin densely serrulate, apex obtuse or acute. Male spathe triangular, 1-1.5 cm × ca. 6 mm, many flowered; sepals reflexed; stamens 2. Female spathe 1.5-2 cm, with slender and very long peduncle; sepals ca. 3 × 2 mm, apex acute. Fruit triangular-cylindric. Seeds not winged. Fl. and fr. Sep-Oct. 2n = 20.

Streams, lakes. Anhui, Guangdong, Guangxi, Hubei, Liaoning, Zhejiang [Japan].