Japan Flora: Dark green fragile aquatic herb; stems 20-100 cm. long, branched, slender; leaves verticillate, in 5's to 12's, sessile, 1.5-2.5 cm. long, much-divided, the ultimate segments filiform, with scattered minute spiny 'teeth; anthers oblong; achenes narrowly ovoid, sessile, 4-5 mm. long, with 2 spines near base; style persistent, spinelike, often longer than the body. June- July. Ponds, lakes, and shallow ditches;

Hokkaido, Honshu, Shikoku, Kyushu; common. Cosmopolitan.

var. quadrispinum Makino. Yotsubari-kingyo-mo. Achenes with 2 pairs of spines, one near base, the other on the shoulder.

Honshu, Kyushu. Manchuria, Ussuri, China, and Formosa.