Plants of the World Online (Kew) recognises 96 species around 22 of which are native to Australia.
They can be shrubs, woody climbers or small trees up to 12 m high.
Side branches are often horizontal and new growth may have spines on the smaller branchlets.
The simple mostly evergreen leaves are typically opposite or rarely in whorls of three.
They have a short petiole with stipules between the petiole bases.
Stipules are free or their bases are fused to make a short sheath around the stem.
Typically roughly triangular the tip may be keeled.
They may persist or fall off, be smooth or occasionally hairy outside and some are leaf-like.
Veins, apart from the midrib are very faint and there may be pits, without hairs in the axils (domatia).
Almost all axillary inflorescences are a branched cluster of flowers with or without a peduncle.
They tend to all be on the same side of the branches.
Each inflorescence branch divides into two often with a single flower, on a long pedicel in or near the fork.
This is repeated a few times in each inflorescence.
Bracts near the top of the peduncle and bracteoles on the pedicels are usually small.
The sepals are fused into a calyx tube with a flat top or 4 or 5 tiny lobes.
Occasionally the lobes are around the same length as the tube.
The petal bases are fused into a cylindrical or bell-shaped corolla tube.
The lobes range from shorter to longer than the tube and spread out from it.
The cream, white to yellow lobes usually have a rounded tip.
There may be no hairs but usually there is a ring of hairs in the throat.
The bisexual flowers have 4 or 5 stamens inserted onto the top of the corolla tube.
Anthers, on sort filaments extend past the corolla.
The inferior ovary, of 2 fused carpels has 2 locules each with 1 pendulous ovule with axile placentation.
The long style, with the stigma extends well past the corolla.
Immediately below the stigma is a cylindrical pollen-presenter that is often split into 2 at the top.
Around the top of the ovary is an annular nectary disc that may have hairs on it.
The fruit are laterally compressed drupes with 2 (1) very hard-coated seeds or pyrenes.