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.

Japan Flora: Perennial; stolons terminated by a fusi­form tuber; stems erect, 20-40 cm. long, somewhat branched, soft-puberulent, purplish; leaves membranous, rhombic-ovate or narrowly ovate, obtuse or acute with an obtuse tip, cuneate or acute at base, scattered obtuse-toothed, glabrate or thinly puberulent and glandular-dotted on both sides, short-petiolate; flowers few in each verticil, dense, white, about 2 mm. long; calyx membranous, 1 mm. long at anthesis, to 1.5 mm. long in fruit, 5-fid, the teeth ovate; nutlets broadly cuneate at base, thickened on margin, compressed-trigonous, smooth, truncate, with 4 obsolete undulate teeth on the broad anterior apex.  Aug.-Sept. Wet places.

Hokkaido, Honshu, Shikoku, Kyu­shu. Sakhalin, Kuriles, Korea, Manchuria, e. Siberia, and N. America.