Herbs or shrubs, usually tomentose or silky pubescent. Leaves alternate, simple and entire or rarely 3-foliolate. Stipules deciduous. Inflorescence consisting of terminal racemes or flowers solitary in the leaf-axils. Bracts 2, opposite, foliaceous, adnate at or above the middle of the pedicels. Flowers irregular, rather large. Sepals 4 or 5, unequal, imbricate. Petals 5, the 3 upper ones long-clawed, free or partly united, the 2 lower ones shorter or even reduced to small, thick, fleshy scales. Stamens 3—4; filaments free or united; anthers basifixed, opening with terminal pores. Ovary sessile, uni-locular; style cylindric, acute. Ovules 2, collateral, pendulous, anatropous. Fruit globose or slightly compressed, indehiscent, spiny, 1-seeded. Endosperm wanting. Only one genus with about 20 species in tropical and warm-temperate America.