Pantropical - especially the New World tropics with a few temperate taxa. Fossil pollen and plant parts in the Eocene. Zygomorphic to almost actinomorphic and perfect.
Flowers are large and as a solitary flower or in a cyme, raceme or panicle.
Sympetalous with a corolla tube. Seed is generally winged and flat with no endosperm. Placentation is axile or parietal. Some leaflets may be modified into a tendril. Stipules are lacking, but often with a gland at the base of the petiole.