| 1 | Lianas or vines, often bearing a pair of coiled tendrils at the base of inflorescence; stems usually producing milky sap; leaves always with a well develop distal leaflet; stipules present although usually minute or early deciduous |
| 1' | Shrubs or trees (without tendrils); not producing milky sap; leaves with a rudimentary or a well developed distal leaflet; stipules absent |
| 2 | Fruit a schizocarp, splitting into 3, indehiscent, winged mericarps (samaras) |
| 2' | Fruit a septicidal or septifragal, marginicidal capsule |
| 3 | Leaves trifoliolate; thyrses with umbel-like units; flowers actinomorphic with an annular disc; mericarps with a distal wing |
| 3' | Leaves biternate, 5-foliolate or sometimes trifoliolate; thyrse racemiform; flowers zygomorphic with a unilateral disc modified into 2-4 lobes; mericarps with a proximal wing |
| 4 | Capsules coriaceous or woody; seeds often sarcotestal |
| 4' | Capsules membranous; seeds not sarcotestal |
| 5 | Leaves biternate; capsules inflated, with unwinged locules |
| 5' | Leaves trifoliolate; capsules flattened or slightly inflated, with winged locules |
| 6 | Leaves simple; plant viscous |
| 6' | Leaves pinnately compound, trifoliolate or unifoliolate; plant not viscous |
| 7 | Leaves trifoliolate or less often unifoliolate (recognized by the swollen distal portion of the petiole) |
| 7' | Leaves pinnately compound, with distal rudimentary leaflet |
| 8 | Flowers apetalous, solitary and axillary or in short racemes; nectary disc cupular; stamens 5-6 |
| 8' | Flowers petaliferous, in lateral cincinni along racemiform or paniculate thyrse; nectar disc unilateral, semiannular, or 2- 4-lobed; stamens 8 |
| 9 | Fruits baccate, indehiscent |
| 9' | Fruit a capsule or a schizocarp |
| 10 | Fruit 1(2)-coccate, with 2(1) rudimentary cocci, late schizocarpic, separating into indehiscent globose mericarps, with fleshy pericarp containing much saponin; seeds globose, exarillate |
| 10' | Fruit ellipsoid or nearly globose, usually with a single locule; seed arillate or sarcotestal |
| 11 | Fruits light brown; seeds with a thin, translucent-white, fleshy aril, easily removable to show a shiny dark brown testa (cultivated) |
| 11' | Fruits green, yellow, orange or rusty brown; seed with a fleshy testa |
| 12 | Petals with 2 marginal projections or appendages, on or above the base, or lacking appendages; stamens spreading, broadly exposed |
| 12' | Petals with a well-developed single, adaxial, erect, petaloid appendage; stamens mostly erect, partially exposed (hidden by the petal’s appendages) |
| 13 | Fruit red, with echinate pericarp (cultivated) |
| 13' | Fruit green, orangish yellow, reddish or rusty brown; pericarp not echinate |
| 14 | Fruit a woody or leathery capsule; seeds covered at base by a detachable fleshy arillode |
| 14' | Fruit a schizocarp |
| 15 | Petals without appendages; capsule reddish, of 1(2) subglobose cocci, one of the coccus usually rudimentary |
| 15' | Petals with adaxial appendage; capsule otherwise, if bicoccate, the coccus slightly flattened, and of similar size |
| 16 | Ovary of two carpels; seeds with a large, triangular carunculate aril at base |
| 16' | Ovary of three carpels; seeds with non-prominent, cup-shaped aril |
| 17 | Sepals connate at base into a cupular calyx; sepals as long as wide, subimbricate |
| 17' | Sepals free at base; sepals > twice as long as wide, imbricate |
| 18 | Petals with an adnate appendage forming a pocket along most of its extension, the whole structure with 2 short marginal projections; leaflet entire or crenate on margins |
| 18' | Petals with a pair of marginal tomentose appendages; leaflet usually serrate or dentate on margins (C. diphylla entire) |
| 19 | Capsules ferruginous-pubescent, 1.5-2 cm long, 3-locular |
| 19' | Capsules glabrous, red, 5-7 cm long, 3-4-locular (cultivated) |
| 20 | Ovary 2-carpellate; schizocarps (1)2-coccate, woody, unwinged |
| 20' | Ovary 3-carpellate; schizocarps splitting into 3 chartaceous or membranous mericarps |
| 21 | Fruits splitting into 3, samaroid mericarps, each with a proximal wing and a papery, inflated coccus |
| 21' | Fruits splitting into 3 membranous, inflated, unwinged, wrinkled mericarps |
