| | 1. Stamens attached near base of corolla tube, apparently below level of stigma; seed with tuft of long hairs |
| |
| | 2. Leaves, stems, roots not fleshy; flower < 8 mm; inflorescence many-flowered |
| APOCYNUM |
| | 2' Leaves, stems, roots fleshy; flower > 15 mm, inflorescence few-flowered |
| CYCLADENIA (no key) |
| | 1' Stamens attached near top of corolla tube, near level of stigma; seed glabrous |
| |
| | 3. Leaves alternate to subwhorled; plant erect |
| AMSONIA (no key) |
| | 3' Leaves opposite; plant erect or sprawling |
| |
| | 4. Corolla pink, tube ± cylindric; stem erect |
| CATHARANTHUS (no key) |
| | 4' Corolla blue, tube funnel-shaped; stem sprawling |
| VINCA (no key)
|