| 1 | Herbs or subshrubs; stems unarmed; flowers bisexual; leaves opposite or subopposite |
| 1' | Shrubs, trees or woody climbers; stems armed or unarmed; flowers bisexual or unisexual; leaves alternate, opposite or subopposite |
| 2 | Inflorescence a panicle; without involucre; perianth 0.7-1 cm long |
| 2' | Inflorescence a terminal cyme; calyx-like involucre coloured; perianth 3-5.5 cm long, corolla-like |
| 3 | Leaves alternate; branches often with supra-axillary spines; flowers bisexual, perianth 1.5-3 cm long, in groups of 3 surrounded by an involucre of leafy, bright-coloured bracts |
| 3' | Leaves opposite, subopposite or in part verticillate; branches unarmed or with axillary spines; flowers unisexual, perianth less than 1 cm long, bracts minute, not forming an involucre |
| 4 | Scrambling shrub or liana, often with axillary, slightly curved spines; perianth and anthocarp with stipitate glands |
| 4' | Shrubs or trees, unarmed; perianth and anthocarp without glands |
| 5 | Perianth of male flowers obconic-campanulate; stamens exserted; female flower buds rounded or obtuse at apex |
| 5' | Perianth of male flowers urceolate, globose or elongate; stamens included; female flower buds long-acuminate at apex |
