Most species are herbaceous perennials or subshrubs but a few are woody shrubs or small trees. The phyllotaxy is usually opposite and decussate, but leaves have a spiral or alternate arrangement in some groups. As with other members of the Lamiales the flowers have a (usually) zygomorphic corolla whose petals are fused into a tube and there is no one character that separates a gesneriad from any other member of Lamiales. Gesneriads differ from related families of the Lamiales in having an unusual inflorescence structure, the "pair-flowered cyme", but some gesneriads lack this characteristic, and some other Lamiales (Calceolariaceae and some Scrophulariaceae) share it. The ovary can be superior, half-inferior or fully inferior, and the fruit a dry or fleshy capsule or a berry. The seeds are always small and numerous. Gesneriaceae have traditionally been separated from Scrophulariaceae by having a unilocular rather than bilocular ovary, with parietal rather than axile placentation.