| 1 | Leaves simple, usually more or less bilobed, sometimes deeply divided (seemingly bifoliolate). 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. Flowers actinomorphic. Petals 3-5. Stamens 6-10 fertile |
| 4' | Spines simple. Flowers slightly zygomorphic or bilateral. Stamens 10, all fertile |
| 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 | Floral parts often punctate. Calyx lobes and petals usually (markedly) zygomorphic. Ovary 1-10(-13)-ovuled |
| 6' | Floral parts not punctate. Calyx lobes and petals slightly unequal. Ovary 1-3-ovuled. |
| 7 | Leaves often with only 1 pair of pinnae. Pods wingless, dehiscent |
| 7' | Leaves with 4-17 pairs of pinnae. Pods obliquely winged above, indehiscent |
| 8 | Petals 3-7 cm long, with long claw |
| 8' | Petals 0.25-2.5 cm long |
| 9 | Stamens 5 |
| 9' | Stamens 10 |
| 10 | Leaflets (1 or) 2 (3-6) pairs per pinna. Petals small, 2.5-5 mm long. Stamens with glabrous filaments. Pods dehiscent in two valves.. |
| 10' | Leaflets often more pairs (4-27) per pinna. Petals much larger, 12-25 mm long. Stamens with filaments pilose or villous at the base or basal part. Pods indehiscent or dehiscing at the apex only |
| 11 | Leaves imparipinnate |
| 11' | Leaves paripinnate |
| 12 | Petals 5. Pods winged |
| 12' | Petals absent, or greatly reduced (Dialium). Pods not winged |
| 13 | Stamens 5. Ovary 1-ovuled. Pods surrounded by a broad, papery wing |
| 13' | Stamens 7-9 (4 or 5 fertile, 2-4 staminodes). Ovary 3-5-ovuled. Pods with a narrow wing along one suture |
| 14 | Calyx lobes or sepals 4. Pods dehiscent, l-4(-6)-seeded |
| 14' | Calyx lobes or sepals usuallly 5. Pods indehiscent, 1-seeded |
| 15 | Inflorescences racemose. Ovary 1-6-ovuled. Pods l-4(-6)-seeded. Seeds exarillate |
| 15' | Inflorescences paniculate. Ovary 2-ovuled. Pods 1- or 2-seeded. Seeds arillate. |
| 16 | Fertile stamens 10. Ovary 1-ovuled. Pods often flattened. Cotyledons strongly folded (seen in section) |
| 16' | Fertile stamens usually 2. Ovary 2-ovuled. Pods often globose. Cotyledons not folded |
| 17 | Pods with a thin crustaceous, usually hairy exocarp, easily crushed or sometimes detached from mesocarp |
| 17' | Pods with a crustaceous, glabrous exocarp, united with a thick (c. 4-5 mm) and hard mesocarp, uncrushable by hard press between two hands |
| 18 | Inflorescences short, compact, nodding capitate, peduncle and rachis together less than5cm long, densely flowered. Young leaves in pendent, linear, stipular or bracteate sheath buds (up to 20 cm long) |
| 18' | Inflorescences and young leaves not like above |
| 19 | Bracteoles large, red, (4.5-)8-9 cm long, persistent |
| 19' | Bracteoles small or minute, not red, less than 2.5 cm long, often caducous. |
| 20 | Petals absent |
| 20' | Petals present, 1-5 |
| 21 | Only 1 petal developed, the others rudimentary or wanting |
| 21' | Often 2-5 petals developed |
| 22 | Calyx lobes often spiny outside. Fertile stamens often 10. Pods often spiny outside |
| 22' | Calyx lobes smooth outside. Fertile stamens 3-8 |
| 23 | Stamens often (5-)7 fertile. Seeds arillate |
| 23' | Stamens often 3 fertile. Seeds not arillate |
| 24 | Calyx lobes or sepals often 4. Pods indehiscent |
| 24' | Calyx lobes or sepals usually 5. Pods dehiscent |
| 25 | Petals often 2 or 3 developed, with or without reduced ones. Fertile stamens 3; filaments and staminodes connate about half their length into a pubescent tube. |
| 25' | Fertile stamens 2 or 10, free or filaments and staminodes connate at the base into a glabrous, very short incomplete ring |
| 26 | Fertile stamens 10, free |
| 26' | Fertile stamens 2, free, or filaments and staminodes connate at the base |
| 27 | Stipules foliaceous, persistent. Stamens and staminodes free |
| 27' | Stipules very small, caducous. Stamens and staminodes connate at the base.. |
| 28 | Stamens 15-80; filaments often connate at the base |
| 28' | Stamens (5-)10(-15); filaments free |
| 29 | Anther-thecae dehiscing lengthwise |
| 29' | Anther-thecae dehiscing by apical or basal pores or short slits |
| 30 | Calyx and corolla pellucid-glandular. Pods rather big, up to 36(-67) cm long, dehiscent |
| 30' | Calyx and corolla not as above. Pods rather small, less than 6 cm long, indehiscent |
| 31 | Stamens 10, 3 abaxial ones with long filaments sigmoidally curved, the anthers dehiscing by short slits; remaining 7 with short and straight filaments, the anthers dehiscing by basal pores |
| 31' | Stamens 10, 5-7 or all fertile; filaments straight, the anthers dehiscing by short slits or apical pores |
| 32 | Anther-thecae ciliolate along the sutures. Pods elastically dehiscent; valves coiling |
| 32' | Anther-thecae glabrous. Pods either indehiscent or dehiscent through 1 or both sutures; valves not coiling |
