苦草 ku cao

Physkium natans Loureiro, Fl. Cochinch. 2: 663. 1790; Vallisneria asiatica Miki; V. asiatica var. higoensis Miki; V. gigantea Graebner; V. gigantea var. higoensis (Miki) Kitamura; V. higoensis (Miki) Ohwi; V. natans var. higoensis (Miki) H. Hara; V. physcium Jussieu ex Sprengel, nom. illeg. superfl.; V. spiraloides Roxburgh.

Rhizome tuberous; stolons ca. 2 mm in diam., usually smooth. Leaves 0.2-2 m × 0.5-2 cm, veins 5-9, margin entire or inconspicuously serrulate, apex obtuse. Male spathe ovate-conic, 1.5-2 cm × 5-10 mm, with more than 200 male flowers; sepals strongly convex; stamens 1, filaments sometimes 2-lobed at apex, with hairs at base. Female spathe 1.5-2 cm; peduncle 30-50 cm or longer, slender; sepals greenish purple, 2-4 × ca. 3 mm, apex obtuse; petals white, minute; staminodes 3. Fruit cylindric, 5-30 cm × ca. 5 mm. Seeds narrowly obovoid, glandular hairy. 2n = 20.

Rivers, streams, ponds, lakes. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Shaanxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [India, Japan (including Ryukyu Islands), Korea, Malaysia, Nepal, Russia (Far East), Vietnam; SW Asia, Australia].