| 1 | Leaves completely sessile |
| 1' | Leaves obscurely to distinctly petiolate |
| 2 | Leaves of each pair united at the margins into a cup |
| 2' | Leaves of each pair not united at the margins |
| 3 | Inflorescence a sessile head of usually 3 sessile pairs of triads |
| 3' | Inflorescence a contracted raceme with an axis 1-4 mm long and usually 1 or 2 pairs of triads |
| 4 | Young internodes quadrangular; leaves shortly acuminate at the apex |
| 4' | Young internodes terete; leaves obtuse or rounded at the apex |
| 5 | Inflorescence axis 3-4 mm long; triads pedunculate; lateral flowers shortly pedicellate |
| 5' | Inflorescence axis c. 1 mm long; triads and lateral flowers sessile |
