Description from Flora of China
Roettlera Vahl (1804), not Willdenow (1797).
Herbs, rarely shrubs or subshrubs (outside China), perennial, terrestrial or epipetric, rhizomatous, stemless or simple stemmed. Leaves few to many, along stem, then opposite, whorled, or alternate or basal, equal to subequal in a pair; leaf blade sparsely to densely puberulent to pubescent, rarely nearly glabrous, short strigose, or woolly, base cuneate to cordate, rarely auriculate. Inflorescences axillary, sometimes umbel-like, lax or sometimes dense, 1- to many-flowered cymes; bracts 2, opposite. Calyx actinomorphic and 5-fid, or zygomorphic and 2-lipped or 5- or 3-sect from base to shallowly lobed; segments equal to unequal. Corolla blue to wine-red, rarely pink, white, or yellow, zygomorphic, inside glabrous, rarely sparsely puberulent; tube cylindric to funnelform-tubular, not swollen, rarely saccate at base, longer than limb, 2-13 mm in diam.; limb 2-lipped; adaxial lip 2-lobed, 1.5-3 X shorter than abaxial lip; abaxial lip 3-lobed, lobes equal or central lobe longer, apex rounded, rarely obtuse to acute. Stamens 2, adnate to abaxial side of corolla tube near or above middle, included; anthers dorsifixed, coherent by adaxial surfaces, thecae divaricate, confluent at apex, dehiscing longitudinally; connective not projecting; staminodes (absent or)2 or 3, adnate to adaxial or adaxial and abaxial sides of corolla tube. Disc ringlike, rarely cupular. Ovary linear, 1-loculed; placentas 2, parietal, slightly projecting inward, 2-cleft. Stigma 1, terminal, depressed-globose to disclike or truncate, undivided. Capsule straight in relation to pedicel, usually linear, much surpassing calyx, dehiscing loculicidally to base; valves 2 or 4, straight, not twisted. Seeds unappendaged.
About 180 species: SE Asia; 31 species in China.
The delimitation of Chirita and Didymocarpus is somewhat problematic. As defined here, the genera are based entirely on stigma shape. Thus, more than a few Chinese taxa described in Didymocarpus (see especially Wang et al., Edinburgh J. Bot. 49: 54. 1991) and some included here (e.g., D. cortusifolius and D. heucherifolius) were included in Chirita by other recent workers (see D. Wood, Notes Roy. Bot. Gard. Edinburgh 33: 123-205. 1974). Didymocarpus nigrescens H. Léveillé & Vaniot and D. violaceus H. Léveillé (1912, not Ridley 1896) cannot be placed reliably in any genus because they are
only known from fruiting specimens. The senior author suggests that both taxa probably belong in Didymocarpus, but Burtt suggested that D. nigrescens belongs in Petrocodon
(Notes Roy. Bot. Gard. Edinburgh 38: 471. 1980) or Tengia (Notes Roy. Bot. Gard. Edinburgh 22: 314. 1958).