| 1 | Glands absent from both petioles and rachis |
| 1' | Glands present on either petioles or rachis. |
| 2 | Pedicels shorter than sepals; pods winged |
| 2' | Pedicels longer than sepals; pods flat or terete, but never winged |
| 3 | Perfect stamens 7; filaments almost equally long; pods terete, up to 23 cm long. |
| 3' | Perfect stamens 7, in 2 size classes; pods flat |
| 4 | Petiole 2.5-3.5 cm; pods flat, alternating bulging and depressed |
| 4' | Petiole 1.5-2.5 cm; pods flat, annulate septate |
| 5 | Petiolar glands only (N.B.: Lowest pair of leaflets may be caducous) |
| 5' | Glands only present on the rachis between the leaflets |
| 6 | Stinking; roughly villose to strigose plant; petiolar gland sessile, oblong, at the basal joint pods strigose, angulate, 10-14 cm long, c. 5 mm broad |
| 6' | Not stinking; glabrous or almost so; pods glabrous, terete or flat |
| 7 | Petiolar gland sessile, globose or ovoid, at the basal joint; pods flattened glabrous, brown with lighter coloured sutures |
| 7' | Petiolar gland narrow, clavate to subulate, above the basal joint; pods terete with lighter coloured sutures |
| 8 | Leaflets 2 pairs, obliquely ovate, very unequal-sided; upper pair much larger than lower one, 4-16.5 by 2-7 cm |
| 8' | Leaflets 3-more pairs, smaller than above |
| 9 | Leaflets 18-40 pairs; 1 conical gland between the lowermost pair (often early caducous) |
| 9' | Leaflets 3-16 pairs |
| 10 | Fertile stamens 10 |
| 10' | Fertile stamens less than 10 |
| 11 | Leaves 14-30 cm; leaflets 4-6 pairs; the stipe of the pod 10-20 mm |
| 11' | Leaves 8-18 cm; leaflets 6-10 pairs; the stipe of the pod 5-7 mm; |
| 12 | Leaflets 6-11 pairs; a clavate gland c. 2 mm between the lowest pair and one spindle-shaped gland between the uppermost pair of leaflets. |
| 12' | Leaflets 3-5 pairs accrescent; no gland between the uppermost pair |
| 13 | Leaflets lanceolate, acute, 4-11 by 2-3.5 cm |
| 13' | Leaflets obovate, obtuse, 1.5-4.5 by 1-2.5 cm |
| 14 | Leaflets 4 or 5 pairs, 2-2.5 by 1-1.5 cm |
| 14' | Leaflets 3 pairs |
| 15 | Flowers in slender, many-flowered racemes, 5-17 cm long, in upper leaf-axils; pods terete, inflated, 15-20 by 1-1.5 cm |
| 15' | Flowers in short, axillary, 1-3-flowered racemes, 3-5 mm; pods terete, linear falcate, 10-15 by 0.5 cm |
| 16 | A subulate gland between the 2 lower pairs of leaflets; pedicel of flower 0.5-1 cm, of pod up to 1.5 cm; 3 larger anthers abruptly rounded at apex.. |
| 16' | A subulate gland only between the lowermost pair of leaflets; pedicel of flowers 1-3.5 of pod 2-4.5 cm. |
