| LYTHRUM |
| 1' Hypanthium bell- to urn-shaped |
| |
| 2. Flowers in axillary clusters; fruit irregularly dehiscent |
| AMMANNIA |
| 2' Flowers 1 per axil; fruit dehiscent by 2 or 4 valves |
| |
| 3. Annual; stem prostrate to decumbent; leaf ± petioled; hypanthium partly enclosing fruit |
| Lythrum portula |
| 3' Perennial; stem ascending to erect; leaf sessile; hypanthium > fruit |
| ROTALA
|