Fl. Peruv. Prodr., 95. 1794.
Herbs, perennial; caudex herbaceous or woody, herbage tending to dry black. Stems prostrate, ascending, erect, or spreading, glabrous. Leaves cauline, opposite; petiole present; blade not fleshy, not leathery, margins weakly or sharply serrate. Inflorescences axillary, flowers solitary; bracts present. Pedicels present; bracteoles smaller than calyx lobes, not surrounding calyx of flowers they subtend. Flowers bisexual; sepals 5, proximally connate, calyx bilaterally symmetric, campanulate, lobes ovate, outer lobes ± as wide as inner; corolla white or lemon yellow with purple or reddish veins in throat, bilaterally symmetric, weakly bilabiate, campanulate [salverform], tube base not spurred or gibbous, throat not densely pilose internally, lobes 5, abaxial 3, adaxial 2, abaxial lip projecting to spreading; stamens 4, medially or distally adnate to corolla, didynamous, filaments glabrous; staminode 0; ovary 2-locular, placentation axile; stigma 2-lobed. Fruits capsules, dehiscence septicidal, slightly loculicidal at apex. Seeds 40–80, black or brown, angled, wings absent. × = 11.
c, e United States, Mexico, Central America, South America, introduced in Asia (India, Sri Lanka), Africa (Cameroon, Sierra Leone), Australia.
Species ca. 10 (2 in the flora).
|1||Stems erect; leaf blade margins weakly serrate; corollas white with purple veins in throats, adaxial lobes connate 1/2–2/3 lengths; seeds: radial walls of reticulum smooth.||Mecardonia acuminata|
|1||Stems spreading, prostrate, or ascending; leaf blade margins sharply serrate; corollas lemon yellow with reddish veins in throats, adaxial lobes connate nearly to apices; seeds: radial walls of reticulum mamillate.||Mecardonia procumbens|