| 1 | Erect trees or shrubs without a prickle below the leaf-scars |
| 1' | Scandent shrubs or climbers with an unpaired, often recurved prickle below the leaf-scar |
| 2 | Main vein of leaflets forming the front (i. e., the acroscopic) margin, or nearly so |
| 2' | Main vein of leaflets distant by at least ¼ of the width of the leaflet from the acroscopic margin |
| 3 | Peduncles arranged as a corymb or a raceme at the end of branches. Stamens pink- red distally. Subtropical or warm temperate mainland Asia. |
| 3' | Peduncles aggregated into terminal, branched panicles. Stamens usually yellowish green distally |
| 4 | Stipules lanceolate to ovate-lanceolate, with one central main vein, 0.4-0.7 by 0.14- 0.21 cm. Petiolar gland elliptic, strongly raised and convex, 2.5-4.5 mm. Corolla appressed puberulous |
| 4' | Stipules auriculate-cordate, with several veins, 1-1.8 by 0.6-3 cm. Petiolar gland circular to broadly elliptic, raised and sometimes slightly depressed in the central part, 0.8-3 mm in diameter. Corolla most often hirsute by patent hairs |
| 5 | Stipules 1-1.5 by 0.6-3 cm. Petiolar gland elliptic, c. 2-3 mm. Calyx (2-)2.5-5 mm; corolla 6-10 mm |
| 5' | Stipules c. 1.8 by 1.3 cm. Petiolar gland broadly elliptic to circular, 0.8-1.5 mm in diameter. Calyx 1.5-2 mm; corolla (4-)4.2-4.5 mm. |
| 6 | Leaves with one pair of pinnae only |
| 6' | At least some leaves with more than one pair of pinnae |
| 7 | Flowers sessile or subsessile |
| 7' | Flowers pedicellate |
| 8 | Petiolar gland c. 4-7 mm, usually sunken into the rachis, often with raised margins, situated at the junction of the pinnae. Corolla glabrous or puberulous at the apex of the lobes only |
| 8' | Petiolar gland 1-2.5 mm in diameter, raised, often with a depressed central part, situated just above the base of the petiole. Corolla densely appressed puberulous to sericeous all over |
| 9 | Main vein distant by ⅓-¼ of the width of the leaflet from the front margin |
| 9' | Main vein central or subcentral |
| 10 | Leaflets drying yellowish green to dark green. Petiolar gland situated well below the junctions of the pinnae, usually about the middle of the petiole. Monsoon areas of mainland Asia |
| 10' | Leaflets drying a brownish colour. Petiolar gland situated at the junction of the pinnae or slightly (to 2 mm) below |
| 11 | Petiolar gland flat or slightly depressed, sessile, rhombic to obtriangular in outline, up to 3 mm in diameter. Pedicel of marginal flowers 1-1.5 mm |
| 11' | Petiolar gland usually raised, often stipitate, ± circular in outline, 0.5-1.2 mm in diameter. Pedicel of marginal flowers 3—5(—8.5) mm |
| 12 | Flower clusters (glomerules) 20-40-flowered. Calyx of marginal flowers tubular, narrowly campanulate, cup-shaped (to obconical). Petiolar gland (sessile or) raised, ± rimmed, concave, when narrow with an orifice, 0.5-1.2 mm in diameter |
| 12' | Flower clusters (glomerules) 10-15-flowered. Calyx of marginal flowers campanulate. Petiolar gland substipitate to stipitate, concave, c. 0.5-1 mm high, 0.5 mm in diameter |
| 13 | All flowers within a glomerule uniform and of the same size |
| 13' | Flowers within a glomerule dimorphic, i.e., with an enlarged central flower. |
| 14 | Flowers glabrous all over. Solomon Islands |
| 14' | At least a part of the flower pubescent |
| 15 | Calyx glabrous. Inflorescence glabrous or sparsely puberulous. |
| 15' | Calyx pubescent. Inflorescence pubescent |
| 16 | Main vein of leaflets central, subcentral, or subdiagonal |
| 16' | Main vein of leaflets excentric, situated at (2/5-) ⅓-¼ of the width of the leaflet from the front margin |
| 17 | Petiolar gland raised, circular to elliptic, with a narrow orifice, c. 2.5 mm in diameter |
| 17' | Petiolar gland raised, elliptic to slit-like, concave, but without a narrow orifice |
| 18 | Leaves with (9—)11—12 pairs of pinnae, each with 13-17 pairs of rounded and mu- cronulate leaflets; petiolar gland bowl-shaped, 1.5-2.5 mm in diameter. Calyx 2-2.5 mm; corolla 7-8.5 mm |
| 18' | Leaves with (2-)3-7 pairs of pinnae, each with (5-) 10-25 pairs of (rounded-) acute, mucronate leaflets. Petiolar gland circular, raised, flat to slightly concave, 0.5-0.8 mm in diameter. Calyx 1-1.5 mm; corolla 4-5 mm |
| 19 | Marginal flowers sessile |
| 19' | Marginal flowers pedicellate |
| 20 | Main vein of leaflets subcentral; leaflets 1-3 (or 4) pairs per pinna, not oblong |
| 20' | Main vein of leaflets distant by ⅓-1/5 of the width of the leaflet from the front margin; leaflets (7-)10-16 pairs per pinna, broadly oblong. Monsoon areas of mainland Asia |
| 21 | Stipules first erect and rigid, then becoming recurved and hook-like |
| 21' | Stipules inconspicuous and caducous, not transformed into two recurved hooks 22 22a. Leaflets 19-29 pairs per pinna, oblong-falcate, acute, 0.1-0.2 mm wide. Northern tropical South America |
| 21'' | Leaflets 1-12 pairs per pinna, more than 0.5 cm wide |
| 22 | Main vein of leaflets distant by ⅓-¼ of the width of the leaflet from the front margin and nearly parallel to that |
| 22' | Main vein of leaflets diagonal to subcentral |
| 23 | Petiolar gland circular, slightly concave, c. 1-1.2 mm in diameter; leaflets subses- sile. Flowers in pedunculate corymbs axillary to the distal leaves. |
| 23' | Petiolar gland circular-elliptic, sessile, with slightly raised margins, 1-4 mm in diameter; leaflets 1-5 mm stalked. Flowers usually in peduncled panicles, sometimes with some leaves developing |
| 24 | Flowers in an open corymb, the marginal ones situated below the central one; pedicels 2.5-5 mm. Stamens purple to pink |
| 24' | Marginal flowers arranged in a dense umbel below the central one; pedicel 0.5-2 mm. Stamens white, turning yellow. Monsoon areas of mainland Asia |
| 25 | Pinnae 8-20 pairs; leaflets 25-60 pairs per pinna, narrowly oblong to linear, 0.4-0.8 by 0.08-0.2 cm |
| 25' | Pinnae (1—)3—7 pairs; leaflets 3-14 pairs per pinna, obovate-ovate, subtrapezoid-oblong; (0.7-)0.9-2.2 by 0.4-1 cm |
| 26 | Distal parts of branches and inflorescences glabrous to scarcely puberulous. Pinnae (l-)3 or 4 pairs; leaflets with a tiny mucro |
| 26' | Distal parts of branches and inflorescence with an often flocculent, reddish brown, tomentose indumentum. Pinnae 5-7 pairs; leaflets with a triangular cusp |
