| 1 | Leaves alternate, opposite or scattered |
| 1' | Leaves verticillate in whorls of 4 or more |
| 2 | Leaves mostly alternate, petiolate; inflorescence axis c. 55 mm long, bearing c. 20 flowers; corolla yellow |
| 2' | Leaves opposite, sessile or nearly so; inflorescence axis 140-190 mm long, bearing 40 or more flowers; corolla red |
| 3 | Inflorescence axis 20-40 mm long |
| 3' | Inflorescence axis more than 200 mm long |
| 4 | Leaves in whorls of c. 8; inflorescence axis lacking a sterile tip; flowers yellow |
| 4' | Leaves in whorls of 4; inflorescence axis with a sterile tip more than 150 mm long; flowers pink or red |
