| 1 | Leaves verticillate. |
| 1' | Leaves opposite and decussate. |
| 2 | Sepals imbricate. Ovary semi-inferior with 2(-3) connate carpels |
| 2' | Sepals valvate. Ovary superior, with 2-5 free carpels. |
| 3 | Sepals imbricate. |
| 3' | Sepals valvate. |
| 4 | Ovary semi-inferior, 2(-3)-carpellate. Flowers apetalous. |
| 4' | Ovary superior, 2-carpellate. Petals small, ± obovate-spathulate. |
| 5 | Leaves simple or unifoliolate. |
| 5' | Leaves trifoliolate or pinnately compound (occasionally some simple/unifoliolate leaves on the same tree). |
| 6 | Flowers apetalous and unisexual (plants dioecious). Ovary with 2-5 free carpels. |
| 6' | Flowers with petals, each split distally into 3 acute lobes; flowers bisexual or male (plants hermaphrodite or andromonoecious). Ovary with 2-3 connate carpels. |
| 7 | Flowers apetalous. |
| 7' | Flowers with petals. |
| 8 | Flowers 4-7(-8)-merous; ovary superior with as many carpels as sepals; styles short-conical, closely adpressed. |
| 8' | Flowers 4(-5)-merous (4-6-merous outside Malesia); ovary semi-inferior, 2-carpellate; styles subulate-terete, spreading. |
| 9 | Flowers protandrous. Petals ± obovate-spathulate, apex rounded, often with a few hairs along the midline on lower surface. Stipules 1 pair per node, interpetiolar |
| 9' | Flowers homogamous. Petals cuneate, bifurcating towards apex, each tooth with a small gland. Stipules 4 per node, lateral. |
| 10 | Carpels 2-6, the styles not far exserted beyond the perianth. Ovules 6-16 per locule. Indumentum including stellate hairs and in most species spherical glandular trichomes. Stipules ± orbicular with a rounded apex or reniform, not stalked. |
| 10' | Carpels 2, the styles far exserted beyond the perianth. Ovules up to 40 per locule. Indumentum of simple hairs only. Stipules obovate to reniform, the apex usually bifid with two obtuse apices and the base distinctly stalked |
