1Leaves 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
2Leaves bipinnate
2'Leaves simple pinnate, rarely unifoliate
3Plants armed with prickles, spines or thorns
3'Plants not armed
4Spines often branched, especially those on the trunks and branches
4'Spines simple
5Leaf-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
6Pods not winged
6'Pods winged
7Pods dehiscing at the apex
7'Pods dehiscing along the sutures, two-valved, rarely indehiscent (part of Caesalpinia)
8Seeds transversely oblong
8'Seeds often orbicular or globose, ellipsoid or reniform..
9Pods samaroid, winged above the seed-bearing part..
9'Pods winged along one suture side
10Pods indehiscent
10'Pods dehiscent, 2-valved
11Pods narrowly winged along one suture, valves thin-coriaceous
11'Pods not winged, valves distinctly woody or coriaceous
12Leaflets (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
13Leaves imparipinnate
13'Leaves paripinnate
14Pods winged
14'Pods not winged
15Pods surrounded by a broad, papery wing
15'Pods with a narrow wing along one suture
16Pods dehiscent, 1-3-seeded
16'Pods indehiscent, 1-seeded
17Pods often flattened. Cotyledons strongly folded (seen in section)
17'Pods often globose. Cotyledons solid, not folded
18Pods 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..
19Young leaves in pendent, linear, stipular or bracteate sheath buds (up to 20 cm long)
19'Young leaves not like above
20Pods often spiny outside
20'Pods not spiny outside
21Pods indehiscent
21'Pods dehiscent
22Leaves each with 1 pair of leaflets, pellucid-punctate.
22'Leaves each with 2-many pairs of leaflets, not pellucid-punctate
23Young 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
24Pods rugose, warty or smooth
24'Pods smooth
25Seeds endospermic
25'Seeds not endospermic
26Stipules foliaceous, (5-) 12.5-40 mm long
26'Stipules minute
27Stipules persistent
27'Stipules caducous
28Seeds arillate
28'Seeds not arillate
29Aril 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
30Seeds very small, usually 0.3-1 cm long
30'Seeds much larger, 2-4.5 cm long
31Valves of pods coiling during dehiscence
31'Valves of pods not coiling during dehiscence
32Valves of pods often straight or slightly twisting during dehiscence
32'Valves of pods twisting and enrolling, or coiling
33Leaflets 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
34Seeds 3-4 by 3 cm
34'Seeds often smaller, 2-3 by 1.25-2 cm