| | 1. Pistils (and fruits) in 1 whorl; flowers bisexual, stamens generally 6 |
| |
| | 2. Fruits erect, beak < 1 mm; petals ± entire or slightly cut; pistils free at base |
| ALISMA |
| | 2' Fruits spreading, beak 3–6 mm; petals deeply cut; pistils ± fused at base |
| DAMASONIUM (no key) |
| | 1' Pistils (and fruits) in spheric cluster; flowers bisexual or unisexual, stamens 0 or > 6 |
| |
| | 3. Inflorescence axes and petioles generally angled; flowers bisexual, generally 3+ per node; fruit cluster bur-like |
| ECHINODORUS (no key) |
| | 3' Inflorescence axes and petioles generally smooth; flowers generally unisexual, staminate above, pistillate below, generally 3 per node; fruit cluster not bur-like |
| SAGITTARIA
|