Japan Flora: Stoloniferous; stems somewhat thickened at the base, erect, simple, to I m. long, stout, glabrous or nearly so except for white hairs at nodes; leaves rather broadly lanceolate to narrowly elliptic, 8-15 cm. long, 1.5-4 cm. wide, acuminate at both ends, lustrous above, glabrous on both surfaces or thinly pilose on the nerves beneath, sessile or subsessile, the upper leaves slightly smaller; flowers white, about 5 mm. long; calyx 4-5 mm. long, 5- toothed, the teeth linear-lanceolate, spine-tipped; nutlets about 2 mm. long, entire and rounded-truncate at apex, broadly cuneate at base. Aug.-Oct. Wet places.

Hokkaido, Hon­shu, Shikoku, Kyushu. e. Asia and N. America.

var. hirtus Regel. Stems and underside of leaves long-pilose. Hokkaido and Honshu. Temperate e. Asia.