Japan Flora: Leaves 5-12 cm. long and equally wide somewhat cordate, entire, smooth; stipules small in adult plants, large and leaflike in young vigorous plants; peduncles 3-10 mm. long; flowers about 12 mm. across; calyx hairy, the lobes short, recurved; capsules 15-17 mm. long and equally wide. Oct.-Nov.
Honshu (sw. part of centr. distr. and Aki Prov.), Shikoku; rare. China.