| 1 | Leaves simple, usually more or less bilobed, sometimes deeply divided (seemingly 2-foliolate). Venation palmate (or fan-like), or parallel |
| 1' | Leaves compound, rarely unifoliolate (or seemingly a simple leaf). Venation neither palmate (or fan-like) nor parallel |
| 2 | Leaves bipinnate |
| 2' | Leaves simple pinnate, rarely unifoliate |
| 3 | Plants armed with prickles, spines or thorns |
| 3' | Plants not armed |
| 4 | Spines often branched, especially those on the trunks and branches |
| 4' | Spines simple |
| 5 | Leaf-rachis very short, spine-like. Rachides of pinnae flattened, phyllodial. Leaflets tiny, numerous, caducous. Pods constricted externally between the seeds |
| 5' | Leaf-rachis not spine-like. Rachides of pinnae neither flattened nor phyllodial. Leaflets several to many, small to large, not caducous. Pods not like above |
| 6 | Pods not winged |
| 6' | Pods winged |
| 7 | Pods dehiscing at the apex |
| 7' | Pods dehiscing along the sutures, two-valved, rarely indehiscent (part of Caesalpinia) |
| 8 | Seeds transversely oblong |
| 8' | Seeds often orbicular or globose, ellipsoid or reniform.. |
| 9 | Pods samaroid, winged above the seed-bearing part.. |
| 9' | Pods winged along one suture side |
| 10 | Pods indehiscent |
| 10' | Pods dehiscent, 2-valved |
| 11 | Pods narrowly winged along one suture, valves thin-coriaceous |
| 11' | Pods not winged, valves distinctly woody or coriaceous |
| 12 | Leaflets (1 or) 2 (3-6) pairs per pinna. Pods 1-4-seeded; seeds large, 3-3.5 cm long |
| 12' | Leaflets 12-25(-40) pairs per pinna. Pods many-seeded; seeds smaller, up to 2.5 cm long |
| 13 | Leaves imparipinnate |
| 13' | Leaves paripinnate |
| 14 | Pods winged |
| 14' | Pods not winged |
| 15 | Pods surrounded by a broad, papery wing |
| 15' | Pods with a narrow wing along one suture |
| 16 | Pods dehiscent, 1-3-seeded |
| 16' | Pods indehiscent, 1-seeded |
| 17 | Pods often flattened. Cotyledons strongly folded (seen in section) |
| 17' | Pods often globose. Cotyledons solid, not folded |
| 18 | Pods with a thin crustaceous, usually hairy exocarp, easily crushed or sometimes detached from mesocarp |
| 18' | Pods with a crustaceous, glabrous exocarp united with a thick (4-5 mm) and hard mesocarp, uncrushable by hard press between two hands.. |
| 19 | Young leaves in pendent, linear, stipular or bracteate sheath buds (up to 20 cm long) |
| 19' | Young leaves not like above |
| 20 | Pods often spiny outside |
| 20' | Pods not spiny outside |
| 21 | Pods indehiscent |
| 21' | Pods dehiscent |
| 22 | Leaves each with 1 pair of leaflets, pellucid-punctate. |
| 22' | Leaves each with 2-many pairs of leaflets, not pellucid-punctate |
| 23 | Young leaves in two ranks, scaly buds; leaflets asymmetric, midrib more towards the upper margin. Pods often 2-many-seeded |
| 23' | Young leaves and leaflets not like above. Pods often 2-many-seeded |
| 24 | Pods rugose, warty or smooth |
| 24' | Pods smooth |
| 25 | Seeds endospermic |
| 25' | Seeds not endospermic |
| 26 | Stipules foliaceous, (5-) 12.5-40 mm long |
| 26' | Stipules minute |
| 27 | Stipules persistent |
| 27' | Stipules caducous |
| 28 | Seeds arillate |
| 28' | Seeds not arillate |
| 29 | Aril often 2-lobed, covering the seed for up to half or more of its length |
| 29' | Aril irregularly shaped, covering only the base of the seed |
| 30 | Seeds very small, usually 0.3-1 cm long |
| 30' | Seeds much larger, 2-4.5 cm long |
| 31 | Valves of pods coiling during dehiscence |
| 31' | Valves of pods not coiling during dehiscence |
| 32 | Valves of pods often straight or slightly twisting during dehiscence |
| 32' | Valves of pods twisting and enrolling, or coiling |
| 33 | Leaflets usually with 1 or 2 small crateriform glands at the basal part on lower surface. Valves of pods leathery or slightly woody |
| 33' | Leaflets without the glands as above. Valves of pods distinctly woody |
| 34 | Seeds 3-4 by 3 cm |
| 34' | Seeds often smaller, 2-3 by 1.25-2 cm |
