The family is characterized by bilaterally symmetrical, bisexual flowers, each of which has a two-lipped corolla of five fused petals; five-lobed calyx (sepals); two or four, rarely five, anthers that are joined lightly together or in pairs; and a superior or partly inferior ovary (i.e., positioned above the attachment point of the other flower parts, or slightly below them) with a single chamber in which numerous small seeds are produced on the walls of the ovary (parietal placentation).