| 1 | Midrib prominent on the upper surface. |
| 1' | Midrib impressed on the upper surface. |
| 2 | Twigs hairy. |
| 2' | Twigs glabrous. |
| 3 | Leaves evenly distributed, underside glabrous |
| 3' | Leaves crowded towards the end of the twigs, minutely sparsely appressedly hairy beneath. |
| 4 | Leaves crowded towards the end of the twigs |
| 4' | Leaves evenly distributed |
| 5 | Corolla hairy |
| 5' | Corolla glabrous. |
| 6 | Twigs hairy. |
| 6' | Twigs glabrous. |
| 7 | Leaves distichous. |
| 7' | Leaves spirally arranged. |
| 8 | Underside of leaves glabrous |
| 8' | Underside of leaves hairy. |
| 9 | Bracts persistent. |
| 9' | Bracts caducous |
| 10 | Inflorescence a true fascicle. Ovary c. 1 mm high. Calyx 1 mm long. |
| 10' | Inflorescence a short, often clustered spike. Ovary 1-2 mm high. Calyx 1 ½-4 mm long |
| 11 | Upper side of leaves hairy. |
| 11' | Upper side of leaves glabrous. |
| 12 | Angle of leaf base more than 90°. Bracts and bracteoles caducous. Hairs on twigs more than 2 mm long |
| 12' | Angle of leaf base less than 90°. |
| 13 | Leaf margin (and petiole) beset with closely spaced glands. Bracts to c. 1 mm long. Calyx to c. 1 mm long, calyx lobes ½-l mm long. Disk glabrous. Style base not conical. Fruits to c. 10 mm long |
| 13' | Leaf margin (and petiole) often glandular but glands not closely spaced. Bracts longer than 1 mm. Calyx l½-4mm, calyx lobes longer than ½-1mm. Disk hairy. Style base conical. Fruits 13-18 mm long |
| 14 | Leaves crowded towards the end of the twigs |
| 14' | Leaves evenly distributed. |
| 15 | Underside of leaves glabrous. |
| 15' | Underside of leaves hairy (pulverulent, nearly glabrous, in S. adenophylla). |
| 16 | Calyx glabrous. Inflorescence a fascicle. Disk pulvinate or cylindric. Fruits cylindrical. Seeds straight |
| 16' | Calyx hairy. Inflorescence a (basally branched) spike. Disk annular. Fruits ampulliform. Seeds not straight |
| 17 | Calyx and ovary glabrous. |
| 17' | Calyx and/or ovary hairy. |
| 18 | Inflorescence a spike |
| 18' | Inflorescence a fascicle |
| 19 | Ovary glabrous. |
| 19' | Ovary hairy. |
| 20 | Nerves less than 10 pairs. Bracts and bracteoles caducous. Ovary 1-1½ mm high, calyx longer than 2 mm, calyx lobes 1-1½ mm long, becoming longer by tearing. Fruits 22-40 mm long, 3-celled |
| 20' | Nerves more than 10 pairs. Bracts and bracteoles persistent. Ovary to c. 1 mm high, calyx c. 2 mm long, calyx lobes longer than l½ mm, not becoming longer by tearing. Fruits 5-7 mm long, 1-celled |
| 21 | Ovary more than 1 mm high. |
| 21' | Ovary to c. 1 mm high. |
| 22 | Leaf margin (and petiole) beset with closely spaced glands. Bracts to c. 1 mm long. Calyx to c. 1 mm long |
| 22' | Leaf margin (and petiole) often glandular but glands not closely spaced. Bracts longer than 1 mm. |
| 23 | Nerves 6-11 pairs. Reticulation faintly prominent. Bracts and bracteoles persistent. Calyx lobes not becoming longer by tearing. Fruits 13-18 mm long. |
| 23' | Nerves 12-17 pairs. Reticulation much prominent. Bracts and bracteoles caducous. Calyx lobes becoming longer by tearing. Fruits to c. 10 mm long. |
| 24 | Leaves longer than 15 cm |
| 24' | Leaves shorter than c. 15 cm. |
| 25 | Bracts and bracteoles caducous (Reticulation fine.) |
| 25' | Bracts persistent. (Reticulation coarse.) |
| 26 | Inflorescence an often clustered short spike. Bracts 1-4 mm. Calyx 2½-3 mm. Stamens more than 60. Fruits not ampulliform, 13-18 mm long |
| 26' | Inflorescence a fascicle. Bracts to c. 1 mm long. Calyx c. 1 mm long. Stamens 12-35. Fruits ampulliform, 5-7 mm long |
| 27 | Nerves more than 10 pairs. |
| 27' | Nerves less than 10 pairs. |
| 28 | Underside of leaves hairy. |
| 28' | Underside of leaves glabrous. |
| 29 | Inflorescence a spike |
| 29' | Inflorescence a fascicle |
| 30 | Petiole more than 20 mm. Inflorescence a spike or a cone. Fruits 3-celled |
| 30' | Petiole less than 20 mm. |
| 31 | Inflorescence terminal |
| 31' | Inflorescence axillary. |
| 32 | Calyx and/or ovary hairy. Corolla 2-5 mm |
| 32' | Calyx and ovary glabrous. |
| 33 | Intramarginal vein far from margin. Inflorescence a fascicle. Bracts persistent, hairy, shorter than 3 mm. Ovary c. 1 mm high, calyx 1-2 mm long, calyx lobes not becoming longer by tearing. Corolla 4-5 mm. Stamens less than 50. Fruits 7-10 mm long. |
| 33' | Intramarginal vein close to margin. Inflorescence a raceme or panicle of racemes. Bracts caducous, glabrous, longer than 3 mm. Ovary 1½-2 mm high, calyx 3-5 mm, calyx lobes becoming longer by tearing. Corolla 8-10 mm long. Stamens c. 100 or more. Fruits c. 15 mm long |
| 34 | Underside of leaves hairy. |
| 34' | Underside of leaves glabrous. |
| 35 | Leaves crowded towards the end of the twigs |
| 35' | Leaves evenly distributed. |
| 36 | Bracts persistent. Disk glabrous. Fruits 13-18 mm long |
| 36' | Bracts caducous. Disk hairy. Fruits 7-12 mm long |
| 37 | Calyx and/or ovary hairy. |
| 37' | Calyx and ovary glabrous. |
| 38 | Disk hairy. |
| 38' | Disk glabrous. |
| 39 | Leaves distichous |
| 39' | Leaves spirally arranged |
| 40 | Inflorescence a short, often clustered spike. Bracts persistent |
| 40' | Inflorescence a raceme. Bracts caducous |
| 41 | Inflorescence a (basally branched) spike. Bracts persistent |
| 41' | Inflorescence not a spike. Bracts caducous. |
| 42 | Inflorescence a panicle of racemes. Stamens more than 100 |
| 42' | Inflorescence a (basally branched) raceme. Stamens 25-60. |
| 43 | Calyx lobes becoming longer by tearing |
| 43' | Calyx lobes not becoming longer by tearing |
