| 1 | Stamens partially to almost completely exserted |
| 1' | Stamens completely included in corolla tube |
| 2 | Corolla tube 5-14 mm long; upper part absent or up to 2 mm long |
| 2' | Corolla tube 23-37 mm long; upper part 5-9(-10) mm long |
| 3 | Corolla tube 9-14 mm long; leaves 8-20 by 2-7.5 cm; secondary veins (6-)7-14 on each side |
| 3' | Corolla tube 5-8(-9) mm long; leaves 3.5-14 by 0.8-6 cm; secondary veins 5-8 on each side |
| 4 | Corolla mouth glabrous or glabrate; inflorescences 1-7-flowered, tertiary venation largely obscure |
| 4' | Corolla mouth densely pubescent; inflorescences 8-25-flowered, tertiary venation easily visible, ± perpendicular to midrib and oblique to secondary veins |
| 5 | Corolla lobes glabrous at the apices; leaves 3-8.1 times as long as wide |
| 5' | Corolla lobes pubescent all over; leaves 2.1-4.8 times as long as wide |
| 6 | Corolla tube 23-26 mm long; lobes 15-20 mm long; leaves obtuse or acute at the apex; ovary glabrous or only very sparsely puberulent |
| 6' | Corolla tube 34-37 mm long; lobes 25-33 mm long; leaves acuminate with obtuse point at the apex; ovary pubescent |
| 7 | Corolla lobes 3-4 mm wide, 7.5-10 times as long as wide; lower part of the corolla tube 4-5 mm long; calyx without colleters |
| 7' | Corolla lobes (5-)7-22 mm wide, 1.5-5 times as long as wide; lower part of the corolla tube 5-19 mm long; calyx with colleters |
| 8 | Stamens inserted 6-8 mm from corolla base; lower part of the tube 5-8 mm long; inflorescences 1- or 2-flowered |
| 8' | Stamens inserted 15-19 mm from corolla base; lower part of the tube 7-17(-18) mm long; inflorescences 1-12-flowered |
| 9 | Leaves 1.5-2.2 times as long as wide; corolla tube 18-23 mm long; colleters in the calyx 5-15 |
| 9' | Leaves 2.7-4.2 times as long as wide; corolla tube 25-33 mm long; colleters in the calyx 50-60 |
| 10 | Anther apex 1-1.5 mm from throat; upper part of the tube densely pubescent inside |
| 10' | Anther apex 3-30 mm from throat; upper part of the tube glabrous or sparsely pubescent inside |
| 11 | Leaves ≤ 2.5 times as long as wide, 8-13 cm wide |
| 11' | Leaves > 2.5 times as long as wide, 1-6.5 cm wide |
| 12 | Leaves ≤ 11 cm long; corolla tube 11-31 mm long; lobes 1.1-4 times as long as the tube; anther apex 4-6 mm from throat |
| 12' | Leaves 9-20 cm long; corolla tube (20-)33-37 mm long1; lobes 0.5-0.9 times as long as the tube; anther apex (3-)9-11 mm from throat1 |
| 13 | Leaves 3-6.1 times as long as wide, acuminate or caudate at the apex; leaf axils with colleters; sepals 2-3.8 times as long as wide; pedicels c. 5 mm long |
| 13' | Leaves 2.6-2.8 times as long as wide, acute at the apex; leaf axils without colleters; sepals 0.8-1.7 times as long as wide; pedicels 30 mm long |
