Hydrotrophus echinospermus C. B. Clarke, J. Linn. Soc., Bot. 14: 8. 1873; Blyxa aubertii Richard var. echinosperma (C. B. Clarke) C. D. K. Cook & Lüönd; B. bicaudata Nakai; B. ceratosperma Maximowicz ex Ascherson & Gürke; B. shimadae Hayata; B. somae Hayata.

Stems shortened. Leaves all in basal rosette, strap-shaped, 10-20(-40) cm × 4-7 mm, veins 7-9, apex acuminate. Spathes green, 2-5 cm × ca. 2 mm, with slender peduncle 2-12 cm. Flowers bisexual. Sepals green, linear, ca. 6 × 1 mm. Petals 1-1.4 cm × 0.5-0.8 mm. Stamens 3, 4-6 mm. Ovary narrowly cylindric, 3-7 cm; styles 0.6-1.5 cm. Fruit 4-7 cm. Seeds 30-50, fusiform or oblong-fusiform, 1.5-2 × ca. 0.8 mm, with filiform projections or ridges 2-12 mm from each end, and with prominently acute spines on surface. Fl. and fr. Jun-Oct. 2n = 42.

Paddy fields and channels. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Hunan, Jiangsu, Jiangxi, S Shaanxi, Sichuan, Taiwan, Zhejiang [Bangladesh, India, Indonesia, Japan, Korea, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Sri Lanka, Thailand, Vietnam; Australia].