| 1 | Midrib prominent on the upper surface. |
| 2 | Twigs hairy |
| 2' | Twigs glabrous |
| 2'' | Midrib impressed in the upper surface. |
| 3 | Corolla hairy |
| 3' | Corolla glabrous. |
| 4 | Underside of leaves glabrous. |
| 4' | Underside of leaves hairy. |
| 5 | Twigs hairy. |
| 5' | Twigs glabrous. |
| 6 | Leaves distichous. Calyx 2-4-lobed or symmetrically cleft, calyx lobes becoming longer by tearing. |
| 6' | Leaves spirally arranged. |
| 7 | Leaves crowded towards the end of the twigs. Twigs thick, tapering towards apex. Petiole more than 20 mm. Corolla more than 7 mm long. Apex of leaves rounded or acute. |
| 7' | Leaves evenly distributed. |
| 8 | Calyx and ovary glabrous |
| 8' | Calyx and/or ovary hairy. |
| 9 | Leaves longer than 10 cm. Nerves more than 10 pairs. Inflorescence a (basally branched) spike. Bracts persistent. Ovary glabrous, to c. 1 mm high, calyx lobes longer than l½ nim. Disk glabrous, clearly present. Fruits ampulliform, 1-celled. |
| 9' | Leaves shorter than c. 10 cm. Nerves less than 10 pairs. Inflorescence a raceme. Bracts caducous. Ovary hairy, 1-2 mm high, calyx lobes ½ -1½ mm long. Disk hairy, inconspicuous. Fruits ellipsoid, 3-celled |
| 10 | Nerves 4-5 pairs |
| 10' | Nerves more than 5 pairs. |
| 11 | Calyx and/or ovary hairy. |
| 11' | Calyx and ovary glabrous. |
| 12 | Leaves distichous |
| 12' | Leaves spirally arranged. |
| 13 | Leaves crowded towards the end of the tapering-off twigs |
| 13' | Plant different |
| 14 | Inflorescence not a spike. |
| 14' | Inflorescence a (basally branched) spike. |
| 15 | Inflorescence a fascicle. Stamens c. 50 |
| 15' | Inflorescence a raceme. |
| 16 | Stamens 40-60 |
| 16' | Stamens c. 100 |
| 17 | Twigs thick. Terminal buds large |
| 17' | Twigs not thick. Terminal buds small |
| 18 | Twigs glabrous. |
| 18' | Twigs hairy. |
| 19 | Leaves distichous. Petiole 1-4 mm. Corolla 3-5 mm |
| 19' | Leaves spirally arranged. Petiole more than 5 mm. |
| 20 | Inflorescence a fascicle. Bracts persistent, c. 2 mm. Calyx glabrous. Calyx lobes not becoming longer by tearing |
| 20' | Inflorescence a spike forming a cone in bud. Bracts caducous, 3-5 mm. Calyx hairy. Calyx lobes becoming longer by tearing |
| 21 | Leaves distichous. |
| 21' | Leaves spirally arranged. |
| 22 | Calyx usually hairy. Inflorescence a fascicle. Bracts persistent. Ovary c. 1 mm long. Calyx c. 1 mm long. Calyx lobes not becoming longer by tearing. Style base hairy. |
| 22' | Calyx often glabrous. Inflorescence a raceme or panicle of racemes. Bracts caducous. Ovary 1-1½ mm high. Calyx 2-3 mm. Calyx lobes becoming longer by tearing. Style base glabrous |
| 23 | Calyx and ovary glabrous. |
| 23' | Calyx and/or ovary hairy. |
| 24 | Leaf index 2 to 3. Nerves 8-12 pairs |
| 24' | Leaf index more than 3. Nerves 6-9 pairs. |
| 25 | Nerves less than 10 pairs |
| 25' | Nerves more than 10 pairs |
| 26 | Upper side of leaves hairy (pulverulent). Leaf margin and petiole beset with many closely spaced vesicular glands |
| 26' | Upper side of leaves glabrous. Leaf margin and petiole different. |
| 27 | Ovary glabrous. |
| 27' | Ovary hairy. |
| 28 | Nerves less than 10 pairs. Bracts caducous. Ovary 1-1½ mm high. Calyx 2½-4 mm. Calyx lobes becoming longer by tearing |
| 28' | Nerves more than 10 pairs. Bracts persistent. Ovary to c. 1 mm long. Calyx 1 to 2 mm long. Calyx lobes not becoming longer by tearing. |
| 29 | Leaves longer than 15 cm. |
| 29' | Leaves shorter than c. 15 cm. |
| 30 | Nerves 10-13 pairs |
| 30' | Nerves 12-17 pairs |
| 31 | Bracts to c. 1 mm long. |
| 31' | Bracts longer than 1 mm. |
| 32 | Leaf margin (and petiole) beset with closely spaced glands |
| 32' | Leaf margin (and petiole) often glandular but glands not closely spaced. |
| 33 | Nerves less than 10 pairs. Reticulation coarse. Inflorescence a fascicle. Bracts persistent. Ovary c. 1 mm high. Style base hairy |
| 33' | Nerves more than 10 pairs. Reticulation fine. Inflorescence a (basally branched) raceme. Bracts caducous. Ovary more than 1 mm high. Style base glabrous. |
| 34 | Angle of leaf base c. 90° |
| 34' | Angle of leaf base less than 60° |
