Leaves differentiated into lamina and petiole, laminas orbicular or cordate to ovate or elliptic.
Inflorescences unisexual.
| | Key to the species | |
| 1 | Undersurface of lamina with an orbicular or ovate pad of honeycomb-like aerenchymatous tissue smaller than and clearly delimited from the rest of the lamina; male flowers with staminal filaments free; female flowers with petals well-developed | Hydrocharis dubia |
| Undersurface of lamina mostly covered with well-developed large-cell aerenchyma; male flowers with staminal filaments connate at least 1/2 their length; female flowers with petals usually undeveloped | Hydrocharis laevigata |
