| 1 | Stamens inserted at the top of the tube with widest part of tube at the throat |
| 1' | Stamens not inserted at the top of the tube with widest part of tube distinctly below the throat |
| 2 | Corolla with scales at the throat above the stamens, pubescent inside; sepals 8-21 mm long |
| 2' | Corolla without scales, glabrous inside; sepals 4-8 mm long |
| 3 | Stamens inserted near corolla tube base; corolla tube 29-33 mm long; sepals 3-4 mm long |
| 3' | Stamens inserted around middle of corolla tube; corolla tube 8-25 mm long; sepals 4-19 mm long |
| 4 | Corolla glabrous inside, tube 8-20 mm long |
| 4' | Corolla puberulent at least in throat inside, tube 13-22 mm long |
