Shrubs or small trees. Young branches and leaves with peltate scales. Leaves alternate; stipules small, sheathing bud, fugacious; petiole swollen at base and apex; leaf blade simple, palmately veined. Inflorescence a terminal panicle. Flowers bisexual, actinomorphic. Sepals 5, free, imbricate, with basal, abaxial glands, fugacious. Petals 5, imbricate, large and conspicuous. Stamens many, free or slightly united at base; anthers oblong, with 2 inverted, U-shaped thecae, dehiscing by short, apical slits on bend. Ovary superior, 1-loculed; ovules many on 2 parietal placentas; style slender; stigmas 2-lobed. Fruit a capsule, loculicidally 2-valved, usually spiny. Seeds many; testa red, slightly fleshy; embryo large; cotyledons broad, incurved at apex; endosperm copious.
One genus and five species: native to tropical America; one species widely cultivated in tropical regions, including China.
Molecular data suggest that the genus Diegodendron Capuron, endemic to Madagascar, is related to Bixa and could be included within the Bixaceae.
Zhang Pengyun & Zhang Yaojia. 1990. Bixaceae. In: Li Hsiwen, ed., Fl. Reipubl. Popularis Sin. 50(2): 180.
"Ovary superior, 1-celled, with 2 parietal placentas; ovules numerous; style slender, recurved in bud; stigma 2-lobed"
"Stamens numerous, hypogynous; filaments free; anthers horse-shoe-shaped, opening by short slits at the top"
"Seeds obovoid; testa rather fleshy, red; endosperm copious; embryo large; cotyledons broad, incurved at the apex"
"Fruit a densely echinate-setose or smooth capsule, 2-valved; valves thick, with the placentas in the middle"