Key for Tachia Aubl.

1Stems square in cross-section, winged
1'Stems round in cross-section, not winged
2Leaves with 1-2 pairs of strongly bent (arcuate) secondary veins
2'Leaves with more than 5 straight or nearly so (pinnate) secondary veins
3Calyx 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
4Corolla cream to yellow to orange, tube slightly to broadly widening towards mouth
4'Corolla white, tube not widening towards mouth