Japan Flora: Scandent nearly glabrous or thinly puberulent perennial herb; stems slender, elongate, branched; lower leaves membranous, nar­rowly deltoid-ovate or narrowly ovate, 4-7 cm. long, 1.2-2.5 cm. wide, smaller in the upper ones, acuminate, shallowly cordate with an open sinus at base, glabrate to thinly puberu­lent, the petioles 5-15 mm. long; inflorescence branched, loosely many-flowered, longer than to nearly as long as the leaves, nearly glabrous, the pedicels 5-10 mm. long; calyx­lobes small, ovate-deltoid; corolla dark purple, 4-5 mm. across, the lobes spreading, narrowly ovate; corona-lobes shorter than the gynostegium; follicles lanceolate, glabrous, 4-5 cm. long, 4-5 mm. wide; seeds ovate, 4-5 mm. long. July-Aug. Thickets in lowlands and mountains;

Honshu, Shikoku, Kyu­shu.