| 1 | Flowers actinomorphic, in axillary bundles or racemes. Seeds not winged. Shrubs or trees. |
| 1' | Flowers zygomorphic. |
| 2 | Woody climbers. Flowers in elongate inflorescences. Seeds winged. |
| 2' | Herbs, sometimes with woody base. Flowers solitary in the leaf axils. Seeds not winged. |
| 3 | Leaves (sub)sessile. Pedicels jointed. Seeds ribbed lengthwise. |
| 3' | Leaves stalked. Pedicels not jointed. Seeds smooth. |
