51. Ophiorrhiza petrophila H. S. Lo, Bull. Bot. Res., Harbin. 10(2): 66. 1990.
法斗蛇根草 fa dou she gen cao
Herbs, ascending, to 100 cm tall; stems drying dark brown or purplish black and shiny, slightly compressed to subterete, glabrous. Leaves in subequal pairs; petiole 0.5-1 cm, glabrous; blade drying papery, grayish green adaxially, pale abaxially, ovate or narrowly ovate, 2-7(-9) × 1.5-3(-3.5) cm, glabrous, base cuneate to obtuse, margins entire, apex cuspidate to shortly caudate; secondary veins 7-9 pairs; stipules caducous, not seen. Inflorescence 3-5 cm, many flowered, pilosulous to glabrescent; bracts filiform to subulate, 4-5 mm, obtuse, persistent. Flowers reportedly distylous, subsessile or on pedicels to 1.5 mm. Calyx glabrous; hypanthium turbinate, ca. 1.5 mm, 5-ribbed; lobes triangular, 0.7-1 mm, with 1 gland in each sinus. Corolla reddened, tubular-funnelform, outside glabrous; tube 10-11 mm, sparsely villous to scabrous throughout inside; lobes ovate-triangular, 1.5-1.8 mm, dorsally with broad lunate wing. Capsules purple, ca. 2.5 × 8 mm. Fl. May.
● Dense forests in limestone regions. Yunnan.
The protologue described this species as distylous but noted that long-styled flowers had not been seen; the putative short-styled flowers were said to have the anthers positioned in or shortly above the corolla throat and the stigmas situated near the middle of the corolla tube.