| 1 | Lateral sepals (alae) caducous at the beginning of fruit-setting. Disk present. Leaves usually with distinct petioles. |
| 1' | Lateral sepals (alae) persistent. Disk (apparently) absent. Leaves hardly petiolate. Annual to perennial herbs, sometimes woody at base. Spp. 9-20. |
| 2 | Annual herbs up to 30 cm high. Flowers, fruits and seeds up to 3 mm long. Spp. 1-3. |
| 2' | Shrubs, small trees, or lianas. Flowers, fruits and seeds at least 5 mm long. |
| 3 | Keel without appendages at apex. Seed without tubercles, without black appendage at chalazal side |
| 3' | Keel with a pair of appendages near apex. Seed tuberculate, with a small or large black appendage at chalazal side. |
| 4 | Capsule narrowly winged, longer than wide. Seed at chalazal side with a cylindrical appendage one third as long as the seed itself |
| 4' | Capsule broadly winged, much wider than long. Seed at chalazal side with a small, knob-like appendage |
| 5 | Fruit much longer than wide, at base with 3 small, persistent sepals. Seed very long-hairy, without aril. Upper sepal flat. Lianas. Sp. 4. |
| 5' | Fruit about as long as wide, without persistent sepals. Seed glabrous or shortly hairy, partly covered by an aril. 'Upper' sepal saccate. Shrubs or small trees. Spp. 5-8. |
| 6 | Flowers 5-6 mm long. Style straight to near stigma. Seed nearly completely covered by the aril |
| 6' | Flowers at least 10 mm long. Style curved in apical half. Seed usually covered up to halfway by the aril. |
| 7 | Capsule covered by a white layer of dense papillae, the wall not with prominent veins. Racemes in the forks |
| 7' | Capsule without white layer, with prominent longitudinal veins. Racemes (supra-)axillary. |
| 8 | Appendages of the keel undivided. Racemes mostly reflexed or patent from the base |
| 8' | Appendages of the keel divided into 7—10 ± connate lobes. Racemes erect or very rarely pendulous |
| 9 | Lateral sepals (alae) broadly ovate, hairy. |
| 9' | Lateral sepals (broadly) elliptic or narrower, glabrous or hairy marginally, or rarely covered by stiff hairs. |
| 10 | Alae yellowish. Ovary and fruit hairy all over. Capsule narrowly winged. Stigma not recurved at apex, with 2 minute lobes |
| 10' | Alae green. Ovary and fruit only hairy at margin. Stigma strongly recurved at apex, at inner side with one stigmatic lobe |
| 11 | Alae nearly symmetric, petaloid (coloured). |
| 11' | Alae asymmetric, falcate, not petaloid (green). |
| 12 | Alae 1.5-2 mm long. Stem set with small, shortly stalked glands. Capsule unwinged. Style obliquely cup-shaped at apex, at one end with a tuft of hairs |
| 12' | Alae 3-10 mm long. Stem eglandular. Capsule winged. Style not or hardly widened at apex, without a tuft of hairs. |
| 13 | Alae mucronate. Style (nearly) straight, (sub)apically with 2 small stigmatic lobes. Filaments nearly completely connate |
| 13' | Alae rounded at apex. Style curved in apical half, with one stigmatic lobe. Filaments free for at least one third. |
| 14 | Alae 6-7 mm long. Capsule hairy along margin. Racemes in the forks (but terminal on side-branches). Bracts and bracteoles persistent |
| 14' | Alae 3-4 (in fruit up to 5) mm long. Capsule glabrous. Racemes mostly terminal. Bracts and bracteoles early caducous |
| 15 | Capsule and vegetative parts stiffly hairy. Appendages of keel little incised. Stigma apically neither widened nor sharply reflexed |
| 15' | Capsule glabrous or hairy only at margin. Plants not stiffly hairy. Appendages of keel divided into a number of filiform or finger-shaped lobes. Stigma apically widened or sharply reflexed. |
| 16 | Capsule c. 2 mm long. Alae c. 3 mm long. Style apically widened, at one side with the stigmatic lobe |
| 16' | Capsule (3—)3.5—5 mm long. Alae 4-6 mm long. Style apically strongly reflexed. |
| 17 | Plant with stiffly erect, long inflorescences. Apical part of the style very asymmetrically winged. Free parts of filaments triadelphous |
| 17' | Plant with short inflorescences or, if with long ones, then these ascending. Style apically symmetrically winged. Free parts of filaments not connate. |
| 18 | Appendages of the keel finely divided into hair-like segments. Capsule almost orbicular, c. 4 by 4 mm |
| 18' | Appendages of the keel divided into finger-shaped lobes. Capsule somewhat longer than wide, 2.5-4 by 2.5-3.5 mm. |
| 19 | Upper petals shorter than the keel, 2.5-3.5 mm long. Capsule at the margin both with curved as well as with short straight hairs. Inflorescences 0.5-2 cm long |
| 19' | Upper petals slightly longer than the keel, 2.5-4.5 mm long. Capsule at the margin with curved hairs only. Inflorescences 0.5-7 cm long |
