| 1 | Stems square in cross-section, winged |
| 1' | Stems round in cross-section, not winged |
| 2 | Leaves with 1-2 pairs of strongly bent (arcuate) secondary veins |
| 2' | Leaves with more than 5 straight or nearly so (pinnate) secondary veins |
| 3 | Calyx 26-40 mm long, half as long as corolla, barely ridged to smooth; corolla lobes coiled at anthesis |
| 3' | Calyx 8-26 mm long, 1/3 or less of corolla length, connate for 1/2 of length, ridged to slightly winged; corolla lobes flat at anthesis |
| 4 | Corolla cream to yellow to orange, tube slightly to broadly widening towards mouth |
| 4' | Corolla white, tube not widening towards mouth |
