KEY TO THE GENERA based on flowering material

1Stamens free, not united into a ligule; petals not clawed, ovary uni- or bilocular.
1'Stamens united into a strap-shaped ligule; the 2 anterior petals unguiculate and enveloping the ligule in buds; ovary unilocular
2Ovary unilocular, inserted at or near base of receptacle.
2'Ovary bilocular, inserted at mouth or midway up receptacle.
3Inflorescence a panicle of cymules; fertile stamens 7-26.
3'Inflorescence racemose; fertile stamens 2 or 5
4Stamens 15-26, the filaments hairy, exserted
4'Stamens 7-10, the filaments glabrous, included
5Fertile stamens 6-8(-9), markedly unilateral, the filaments equal or not exceeding the calyx lobes.
5'Fertile stamens 10-50, usually inserted around complete circle; the filaments far exserted beyond calyx lobes.
6Lower leaf surface glabrous or lanate, with stomatal cavities; bracteoles not enclosing small groups of flowers; inflorescence a panicle of cymules; ovary inserted midway up receptacle
6'Lower leaf surface usually areolate with stomatal cavities; bracteoles enclosing small groups of flowers; inflorescence a much-branched panicle; ovary inserted at mouth of receptacle
7Stamens 10-25; inflorescence little branched panicles, or racemes
7'Stamens c. 45; inflorescence much-branched corymbose panicles