Ophiorrhiza acutiloba Hayata; O. cavaleriei H. Léveillé; O. eryei Champion; O. dimorphantha Hayata; O. dimorphantha f. brevistigma Hayata; O. dimorphantha f. longistigma Hayata; O. japonica var. acutiloba (Hayata) Ohwi; O. japonica var. minor J. Krause; O. labordei H. Léveillé; O. monticola Hayata; O. monticola f. brevistigma Hayata; O. monticola f. longistigma Hayata; O. nigricans H. S. Lo.

Herbs, weak to ascending, to 60 cm tall, often drying flushed with purple or darkened; stems subterete to slightly compressed, glabrous or with 2 hirtellous or pilosulous lines. Leaves in subequal pairs; petiole 0.3-2(-3) cm, glabrous to hirtellous or puberulent; blade drying papery, ovate, elliptic-ovate, elliptic, elliptic-oblong, lanceolate, or narrowly lanceolate, 1-11 × 0.7-3.5 cm, glabrous to strigillose or hispidulous adaxially, glabrous to puberulent, hirtellous, or villosulous abaxially, base cuneate to obtuse, margins flat to crisped, apex acute to acuminate or rarely obtuse (to rounded, Ophiorrhiza nigricans); secondary veins 4-8 pairs; stipules triangular, 0.8-2 mm, glabrescent, acute to bifid, caducous sometimes leaving 1 to several thickened scars to 0.3 mm. Inflorescence congested-cymose to cymose, few to many flowered, puberulent to strigillose, pilosulous, or hirtellous; peduncle 0.5-5 cm (to 6 cm, O. nigricans); axes congested-cymose becoming helicoid; bracts lanceolate-linear, spatulate, or linear, 1-6 mm, sometimes glabrescent, persistent. Flowers distylous, on pedicels 1-2 mm. Calyx glabrous to densely puberulent or pilosulous; hypanthium subturbinate to oblate or subglobose, 0.8-1 mm, 5-ribbed; lobes triangular, 0.4-1.2 mm. Corolla white or pink, funnelform to tubular-funnelform, outside glabrous to puberulent or pilosulous and longitudinally winged, inside pilose near middle and pilosulous above middle through throat and sometimes onto lobes; tube 9-14 mm; lobes triangular to ovate, (1.5-1.8 mm, O. nigricans) 2.5-4 mm, dorsally with wing to 0.5 mm wide, apex rostrate. Capsules submitriform, 2.5-4 × 6.5-9 mm, pilosulous to glabrous. Fl. winter, fr. spring and summer.

Duan and Lin (Acta Phytotax. Sin. 45: 873. 2007) synonymized Ophiorrhiza nigricans with O. japonica. They also synonymized O. kwangsiensis with O. japonica, but that species is provisionally separated here based on the characters given in the key to species pending further study. The reproductive biology of O. japonica was studied by Nakamura et al. (J. Plant Res. 120: 501-509. 2007), who found the Chinese plants sampled to be distylous and diploid. The corollas are apparently similar between the two floral forms, with the reciprocally placed anthers and stigmas positioned near the middle of the corolla tube vs. at or just above its throat, respectively.

Fertile soil of ravines in forests; 100-2400 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangxi, S Shanxi?, Sichuan, Taiwan, NE Yunnan, Zhejiang [Japan, Vietnam].