Japan Flora: Rhizomatous and stoloniferous; stems 40-70 cm. long, simple or sparingly branched, wddish above the base; leaves oblanceolate to ob­long-oblanceolate, 4-7 cm. long, 1-1.5 cm. wide, obtuse, mu­cronate, entire, sessile, pellucid-dotted, pale green beneath; racemes erect, rather densely many-flowered, 10-20 cm. long, glabrous or minutely glandular-puberulent, the pedicels ob­liquely spreading, 3-4 mm. long, the bracts linear, as long as the pedicels; flowers white, 5-6 mm. across; calyx-segments ovate-oblong, obtuse, black-dotted on back; corolla-lobes spreading, obovate, rounded; capsules globose, 2-2.5 mm. in diameter.--- July-Aug. Wet margins of rivers and ponds in lowlands.

Honshu, Shikoku, Kyushu. Korea, China, Taiwan, and Indochina.