| 1 | Fruit dehiscing circumscissile with an operculum. Ovary half-inferior. |
| 1' | Fruit valved or irregularly dehiscing. Ovary superior. |
| 2 | Leaves c. 4 mm long, opposite. |
| 2' | Leaves more than 6 mm long, the middle cauline leaves spirally arranged. |
| 3 | Seed glabrous. Fruit globular, 3-5 mm Ø. Calyx caducous or not. |
| 3' | Seed hairy. Fruit obpyriform, c. 10 by 8 mm. Calyx persistent, distinctly accrescent. |
