Trees, shrubs or rarely herbs. Lvs either 2-paripinnate with few to numerous paired pinnae along the rachis and each pinna with usually numerous, sessile paired pinnules, or lvs reduced to simple phyllodes; glands present on petiole and rachis; stipules spinescent or membranous, often minute. Infl. a cylindric spike or globose head; spikes or heads axillary, solitary or arranged in simple or compound racemes or apparently terminal panicles; subtending bracts small, usually triangular; subtending bracteoles small, usually linear with expanded deltate apex. Fls small, actinomorphic, (3)-4-5-merous, usually yellow or cream; calyx shallowly or deeply divided; petals usually free, sometimes united at base. Stamens numerous, free, exserted; anthers uniform, versatile. Style filiform; stigma terminal. Pod 2-valved, straight, curved or twisted, dehiscent or indehiscent, few- to many-seeded; seeds with a variously folded and thickened fleshy aril.