Description from Flora of China
Roettlera mekongensis Franchet, Bull. Mus. Hist. Nat. (Paris) 5: 252. 1899; Loxostigma forrestii J. Anthony.
Stems to 60 cm, densely villous, usually simple. Leaves opposite, spread along stem, unequal in a pair; petiole 0.8-2.5 cm, villous; leaf blade ovate to broadly ovate, 4-15 X 2-7 cm, villous to hirsute, base oblique, broadly cuneate to cordate, margin serrate, apex acuminate to acute. Cymes branched 2-4 , 5-12-flowered; peduncle to 7.5 cm, densely villous and glandular pubescent; bracts ovate to narrowly oblong, 4-6 X 1.3-2 mm, margin entire. Pedicel 0.8-2 cm. Calyx 5-sect from base; segments equal, lanceolate, 7-9 X ca. 2 mm, margin shallowly dentate. Corolla white, flushed purple, 3.5-4 cm, outside glandular puberulent, inside glabrous; tube 1.8-2.8 X 1.4-1.7 cm; adaxial lip lobes semiorbicular, 2-5 X 2-4 mm; abaxial lip lobes oblong, 3-4 X ca. 4 mm. Adaxial stamens ca. 1.5 cm, abaxial ones ca. 1 cm, glabrous. Pistil 2-3 cm; ovary glabrescent. Style ca. 1 cm, pubescent to densely pubescent. Immature capsule to 5.5 cm. Fl. Jul, Oct, fr. Oct.
* Rocks or cliffs in valleys; ca. 2100 m. NW Yunnan.