| 1 | Erect trees or shrubs without a recurved prickle below the leaf-scars |
| 1' | Scandent shrubs or climbers with an unpaired, often recurved prickle below the leaf-scars |
| 2 | Main vein of leaflets forming the front margin or nearly so |
| 2' | Main vein of leaflets distant by at least ¼ of the width of the leaflet from the front margin |
| 3 | Pods with distinct transverse veins, valves strongly bullate over the seeds, dehiscent. Subtropical and warm temperate mainland Asia |
| 3' | Pods with inconspicuous veins, valves not strongly bullate over the seeds, indehiscent |
| 4 | Seeds with a closed, subcircular areole at the micropyle end. |
| 4' | Seeds with an elliptic to oblong, open areole |
| 5 | Petiolar gland strongly raised, convex, elliptic, 2.5-4.5 mm. Pod dark brown. Seeds (elliptic-)oblong, 5.3 by 3 mm |
| 5' | Petiolar gland raised, flat to slightly depressed in the central part, elliptic to circular, 0.8-1.5 mm in diameter. Pod yellowish brown. Seeds broadly ovate-elliptic, 7-8 by 6 mm |
| 6 | Areole of seeds U-shaped |
| 6' | Areole of seeds ellipic, oblong or circular |
| 7 | Pods straight to slightly curved |
| 7' | Pods contorted into a circle |
| 8 | Valves of pod rigidly coriaceous, thick, bullate over the seeds. Seeds c. 21-22 by 12.5-19 by 8-9 mm |
| 8' | Valves of pod rigidly chartaceous-subcoriaceous, not particularly bullate over the seeds. Seeds c. 13-16 by 10-14 by 4-4.5 mm |
| 9 | Petiolar gland (sessile or) raised, ± rimmed, when narrow with an orifice, 0.5-1.2 mm in diameter. Lateral part of pleurogram continuous |
| 9' | Petiolar gland substipitate to stipitate, concave, c. 0.5-1 mm high, 0.5 mm in diameter. Lateral face of seed with two discontinuous straight lines or pleurogram closed at the edge of the seed |
| 10 | Pods indehiscent or irregularly breaking up |
| 10' | Pods dehiscent, splitting along the sutures |
| 11 | Areole in the micropylar half of the seed obtriangular |
| 11' | Areole reaching well above the middle of the seed, usually elliptic, obovate or oblong |
| 12 | Stipules erect when young, later on recurved and thorn-like, often caducous. Leaflets sessile |
| 12' | Stipules inconspicuous, very early caducous. Leaflets stalked |
| 13 | Pod subwoody, dark brown, finely transversely ribbed, 30-36 by (5-)6.5-7.5 cm. Solomon Islands (Bougainville) |
| 13' | Pod chartaceous, yellowish to golden brown, with prominulous or hardly visible veins, up to 22 by 5.5(-6) cm |
| 14 | Petiolar gland with slightly raised margin. Pod drying yellowish, strongly bullate over the seeds. Seeds 7-9 by 3.5-4.5 by 1.5 mm |
| 14' | Petiolar gland strongly raised, with a narrow orifice. Pod drying golden brown, not remarkably bullate over the seeds. Seeds unknown |
| 15 | Leaves often with 1 pair of pinnae only. Seeds orbicular; areole circular, pleurogram parallel to the margin of the seed. Monsoon areas of mainland Asia |
| 15' | Leaves usually with at least 2 pairs of pinnae. Seeds usually distinctly longer than wide; if occasionally orbicular, then areole ovate-elliptic with pleurogram not parallel to the margins |
| 16 | Main vein of leaflets subcentral, central, or diagonal |
| 16' | Main vein of leaflets distinctly excentric, distant by ⅓-1/5 of the width of the leaflet from the front margin |
| 17 | Petiolar gland strongly raised, with a narrow orifice. |
| 17' | Petiolar gland flat or with slightly raised margins, circular, elliptic or slit-like in outline |
| 18 | Pod glabrous with inconspicuous transverse veins, margins not thickened. Seeds obovate-elliptic to elliptic |
| 18' | Pod puberulous when young, glabrescent, with a prominent, dense, reticulate, transverse venation. Seeds ovate, ovate-elliptic or oblong |
| 19 | Leaves with 1 or 2 (or 3) pairs of pinnae; terminal pair of pinnae with 2 or 3 (or 4) pairs of leaflets; apex of leaflets acuminate to broadly rounded, obtuse, rarely mucronulate; petiolar gland circular to elliptic in outline |
| 19' | Leaves with (2 or) 3 or 4 pairs of pinnae; terminal pair of pinnae with 4 or 5 pairs of leaflets; apex of leaflets acute to rounded; petiolar gland elliptic to slit-like |
| 20 | Leaflets sessile or nearly so, stalk up to 0.5 mm long |
| 20' | Leaflets stalked for at least 1 mm |
| 21 | Leaflets 0.3-0.6 by 0.1-0.2 cm. Seeds elliptic to narrowly obovate-elliptic, 3.2-3.8 by 1.5-1.8 mm. Northern tropical South America |
| 21' | Leaflets 0.6-2(-2.7) by 0.2-0.6(-1.4) cm. Seeds obovate-suborbicular or broadly elliptic, 7-8 by 5-6.2 mm |
| 22 | Leaves with (9-) 11 pairs of pinnae; petiolar gland circular to elliptic in outline, sharply rimmed by raised margins, 1.5-2.5 mm in diameter. Pod light brown, puberulous at least when young |
| 22' | Leaves with (2-)3-7 pairs of pinnae; petiolar gland circular in outline, ± raised, flat to slightly concave, 0.5-0.8 mm in diameter. Pod dark brown, glabrous |
| 23 | Fruiting peduncles axillary to leaves. Pods straw to light brown. Seeds elliptic to sub-orbicular, 8-10 by 6-7.5 mm |
| 23' | Fruits in panicles. Pods dark brown. Seeds ovate, 9 by 6 mm. Monsoon areas of mainland Asia |
| 24 | Pinnae 8-20 pairs; leaflets 25-60 pairs per pinna, narrowly oblong to linear, 0.4-0.8 by 0.08-0.2 cm |
| 24' | Pinnae (1—)3—7 pairs; leaflets 3-14 pairs per pinna, obovate-ovate or subtrapezoid-oblong, (0.7-)0.9-2.2 by 0.4-1 cm |
| 25 | Distal parts of branches glabrous to scarcely puberulous. Pinnae (l-)3 or 4 pairs; leaflets with a tiny mucro |
| 25' | Distal parts of branches with an often flocculent, reddish brown, tomentose indumentum. Pinnae 5-7 pairs; leaflets with a triangular cusp |
