| 1 | Lateral aerial branches with basal internodes much elongated in form of stolons |
| 1' | Lateral branches not elongated at their bases into stolons |
| 2 | Plants stemless; inflorescences and leaves appearing to arise directly from tuber |
| 2' | Plants with obvious stems; inflorescences axillary or terminal |
| 3 | Leaf venation subpalmate |
| 3' | Leaf venation pinnate |
| 4 | Stems much shorter than leaves or with leaves crowded at apex |
| 4' | Stems becoming longer than leaves and leaves not crowded at apex |
| 5 | Corollas red p.p. |
| 5' | Corollas white, sometimes with lobes lavender |
| 6 | Peduncles about as long or longer than leaves and pedicels very short. |
| 6' | Peduncles shorter than leaves and pedicels obviously present |
| 7 | Leaf blades round to acute at base |
| 7' | Leaf blades long attenuate at base |
| 8 | Leaf blades with indumentum p.p. |
| 8' | Leaf blade glabrous or nearly so |
| 9 | Leaves sessile or subsessile; inflorescences bracteate |
| 9' | Leaves obviously petiolate; inflorescences ebracteate |
| 10 | Plants terrestrial, decumbent to erect |
| 10' | Plants epiphytic or if terrestrial then lianescent or clambering |
| 11 | Ovary almost completely inferior; plants rhizomatous |
| 11' | Ovary superior or almost completely superior (Sinningia); plants with tubers, or lacking underground perennial stems, not rhizomatous |
| 12 | Corollas purple or if orange-red then lobes tiny and green |
| 12' | Corollas orange, including spreading lobes |
| 13 | Inflorescences lacking bracts and always with peduncles (except Besleria insolita) and pedicels |
| 13' | Inflorescences with bracts, or lacking peduncles |
| 14 | Stems erect at apex, decumbent at base |
| 14' | Stems erect |
| 15 | Leaf blades with indumentum p.p. |
| 15' | Leaf blade glabrous or nearly so |
| 16 | Inflorescence clearly pedunculate |
| 16' | Inflorescence epedunculate or obscurely pedunculate |
| 17 | Corollas spurred at base, strongly oblique in calyx |
| 17' | Corollas not spurred at base, erect in calyx |
| 18 | Plants from tubers; fruit a capsule |
| 18' | Plants without tubers; fruit a berry |
| 19 | Herbs or shrubs without tubers; corolla yellow; fruit a red berry |
| 19' | Herbs from tubers; corollas orange to red; fruit a dry green to brown capsule |
| 20 | Anthers dehiscing by pores; stems glabrous, except sometimes at apex |
| 20' | Anthers dehiscing by longitudinal slits; stems usually pubescent |
| 21 | Fruit a red to dark red berry; extrafloral nectaries present |
| 21' | Fruit a capsule and often brightly colored inside; no extrafloral nectaries |
| 22 | Corollas white or whitish, rarely yellow or cream-colored (in Paradrymonia maculata and then 4 lobes spreading and the 5th covering mouth of corolla tube, and nearly equal leaves) |
| 22' | Corollas red or yellow |
| 23 | Leaves equal to unequal in a pair, smaller one shaped like larger one, not deciduous p.p. |
| 23' | Leaves strongly unequal in a pair, smaller one usually stipule-like or deciduous |
| 24 | Ventral lobe of corolla entire |
| 24' | Ventral lobe of corolla long fimbriate p.p. |
| 25 | Calyx lobes ovate to cordate at base, if corolla red then lower lobe yellow and not reflexed; fruit a green fleshy capsule |
| 25' | Calyx lobes narrowed at base, or if cordate then all 5 corolla lobes red and lower lobe reflexed (Columnea oerstediana); fruit a white or colored berry |
