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| 1 Leaves with an odd number of pinnae (lateral pinnae paired, but an additional pinna present in a terminal position on the rachis); [Caesalpinoideae]. |
| ..2 Leaflets 0.9-1.6× as long as wide; terminal pinna with about 2× as many leaflet pairs (8-20) as the lateral pinnae (3-7) |
| ..2 Leaflets 1.8-4× as long as wide; terminal pinna with about the same number of leaflet pairs as the lateral pinnae. |
| ....3 Lower surfaces of leaflets eglandular |
| ....3 Lower surfaces of leaflets densely glandular punctate, the glands orange when fresh and drying black |
| 1 Leaves with an even number of pinnae (lateral pinnae paired). |
| ......4 Coarse climbing or sprawling suffruticose herbs, the stems to 6 m long, and usually armed with retrorsely curved prickles; [Caesalpinoidaeae] |
| ......4 Perennial herbs, less coarse; [Mimosoideae] |
| ........5 Stamens > 10; [tribe Acacieae] |
| ........5 Stamens 10 or fewer; [tribe Mimoseae]. |
| ..........6 Petiole with 1-several glands; stems ascending to erect; flowers greenish-white |
| ..........6 Petiole without glands; stems prostrate to weakly arching; flowers pink-purple, yellow, or greenish-yellow. |
| ............ 7 Flowers pink-purple; legume ribbed, the ribs with prickles |
| ............ 7 Flowers yellow to greenish-yellow; legume not ribbed or prickly |