Description from Flora of China
Didymocarpus Wallich sect. Paraboea C. B. Clarke in A. & C. de Candolle, Monogr. Phan. 5: 105. 1883; Buxiphyllum W. T. Wang & C. Z. Gao; Chlamydoboea Stapf.
Herbs, rarely subshrubs, perennial, epipetric or terrestrial, rhizomatous, stemmed or stemless. Leaves few to many, basal, clustered at stem apex, or spread along stem and opposite, rarely spirally arranged, equal to subequal in a pair; leaf blade adaxially woolly to glabrous, abaxially woolly, pannose, or velutinous, hairs dense, interwoven, usually branched at least near base, base attenuate to cuneate, rarely rounded to peltate-auriculate. Inflorescences cymes, sometimes umbel-like, corymbiform, or paniculate, lax, rarely dense, axillary or in terminal panicles, 1- to many flowered; bracts 1-3, opposite. Calyx actinomorphic, rarely slightly zygomorphic, 5-sect from base or from near base, rarely 2-lipped; segments equal. Corolla white, blue, or purple, zygomorphic, inside glabrous to glandular puberulent; tube oblique, campanulate, not swollen, longer than to occasionally nearly equalling limb, 2-13 mm in diam.; limb 2-lipped; adaxial lip 2-lobed; usually slightly shorter, rarely 1/4 X length to slightly longer than abaxial lip; abaxial lip 3-lobed, lobes equal or central lobe longer, apex rounded. Stamens 2, adnate to abaxial side of corolla tube near base, included; anthers dorsifixed, coherent, thecae divaricate, confluent at apex, dehiscing longitudinally; connective not projecting; staminodes 1-3, seldom absent, adnate to adaxial side of corolla tube. Disc inconspicuous. Ovary narrowly ovoid to oblong, rarely conical, 1-loculed; placentas 2, parietal, projecting inward, 2-cleft. Stigma 1, terminal, capitate, seldom subligulate, undivided. Capsule straight in relation to pedicel, linear to narrowly oblong or lanceolate, much surpassing calyx, dehiscing loculicidally to base; valves 4, spirally twisted, seldom straight. Seeds unappendaged.
About 87 species: Bhutan, China, Indonesia, Malaysia, Myanmar, Philippines, Thailand, Vietnam; 18 species in China.