| 1 | Foliage in the form of 'cladodes' or flattened shoots |
| 1' | Foliage of individual leaves. |
| 2 | Foliage in the form of scales, needles, or linear leaves less than 2 mm wide. |
| 2' | Foliage in the form of broad flat leaves more than 2 mm wide. |
| 3 | Foliage not dimorphic. |
| 3' | Foliage dimorphic, leaves of ultimate branchlets longer and narrower than on main shoots may be bilaterally flattened |
| 4 | Leaves not bilaterally flattened |
| 4' | Leaves bilaterally flattened |
| 5 | Leaves bilaterally flattened |
| 5' | Leaves bifacially flattened. |
| 6 | Leaves with a groove over the midvein, (spirally placed,) lacking hypoderm, with a sweet taste |
| 6' | Leaves flat or with a ridge over the midvein, with hypoderm, without a sweet taste. |
| 7 | Leaves opposite, many with multiveined leaves |
| 7' | Leaves spirally placed, uninerved |
