Olive Family (Oleaceae)

The flowers of most species have radial symmetry, in that any longitudinal section through the center of the flower would divide it into two identical halves. The flowers of some species are bisexual, in which both male and female organs are present. The flowers of other species are unisexual, in that they have male organs or female organs, but not both. The flowers of most species have four sepals (the typically green, leaf-like parts which constitute the outermost whorl of flowers) and four petals (the typically pigmented, leaf-like parts which are interior to the sepals, but exterior to the sexual organs). Most species have flowers with two stamens (male organs) and one pistil (female organ). The pistils of most species contain four ovules, which develop into seeds after fertilization.

The fruit of some species, such as the ash, is a samara, or a dry, one-seeded fruit which is indehiscent (lacks a suture), and has wing-like structures to facilitate dispersal by the wind. The fruit of other species, such as the olive, is a drupe, or a fruit with a fleshy outer layer and a hard inner layer containing one seed. The fruit of other species is a berry, a fruit that is fleshy throughout and has one or more seeds.

Some species, such as ash, have seasonally deciduous leaves, which fall off in the autumn after they become non-functional. Other species, such as olive, have persistent leaves, in that there are always some leaves attached to the tree, even when they are no longer functional. In most species in this family, the leaves arise opposite to one another on the stem. The leaves of some species, such as lilac and golden bell, are simple in that they consist of a single blade. The leaves of other species, such as ashes, are compound, and are composed of many separate leaflets.