| 1 | Flowers solitary; leaves to 1.7 cm long |
| 1' | Flowers 3-15 in an inflorescence; leaves to 15 cm long |
| 2 | Calyx fused into a 2-lipped tube |
| 2' | Calyx of free sepals or only irregularly fused and then not in a 2-lipped tube |
| 3 | Inflorescence puberulent, delicate, peduncle 1-1.3 mm wide; corolla tube 2.8-3 mm long, 1.1-1.6 times as long as lobes, c. 1.5 times as long as sepals; fruit articles 24.5-27 by 14-16 mm |
| 3' | Inflorescence glabrous, robust, peduncle c. 1.8 mm wide; corolla tube 7-7.5 mm long, 2.1-2.7 times as long as lobes, c. 3.2 times as long as sepals; fruit articles 10.4-11.2 by 7.5-8 mm |
| 4 | Corolla tube > 4 mm long |
| 4' | Corolla tube < 4 mm long |
| 5 | Leaves in whorls of 6, blade thickly coriaceous; sepal apex obtuse |
| 5' | Leaves in whorls of 3 or 4, blade coriaceous or subcoriaceous; sepal apex acute or acuminate |
| 6 | Leaves pubescent beneath, at least on midrib; corolla pubescent outside |
| 6' | Leaves glabrous beneath; corolla glabrous outside |
| 7 | Corolla lobes 4.5-4.8 mm long, 4.5-4.6 times as long as wide |
| 7' | Corolla lobes 2.1-2.4 mm long, 1.4-1.9 times as long as wide |
| 8 | Inflorescence simple and unbranched with 5 or fewer flowers |
| 8' | Inflorescence branched or with more than one whorl of flowers, 6 or more flowers altogether |
| 9 | Branchlets glabrous; leaf blade 1.8-4.7 cm wide; inflorescence glabrous |
| 9' | Branchlets puberulent; leaf blade 0.3-1 cm wide; inflorescence puberulent |
| 10 | Leaves in whorls of 3 or 4; inflorescence with 6-8 flowers |
| 10' | Leaves in whorls of 5; inflorescence with > 10 flowers |
