Japan Flora: Usually glabrous perennial with slender creeping rhizomes; stems erect, terete, branched at base; leaves 5- to 12-verticillate, the sub-merged ones filiform, 2-3 cm. long, 2-lobulate at apex, the aerial ones linear, 5-10 mm. long, 0.7-1 mm. wide, obtusely truncate to obscurely bimucronate at apex, scarcely narrowed at base; flowers solitary in axils, sessile, the bracteoles linear, shorter than the calyx-tube; calyx-tube about 0.7 mm. long, glo¬bose in fruit, the lobes 4, deltoid, short; petals obovate, about twice as long as the calyx-lobes, retuse; stamens 4; capsules glo¬bose, about 1.5 mm. across; styles short and slender, the stigmas capitellate. Sept.-Oct. Wet places in lowlands;

Honshu (Owari and Ise Prov.); very rare.