| 1 | Leaves orbicular to elliptical, more than 7 mm wide |
| 1' | Leaves filiform to linear, up to 4 mm wide |
| 2 | All leaves submerged, amplexicaul |
| 2' | With many floating petiolate leaves |
| 3 | Floating leaves translucent; fruits 1.5-1.75 mm long |
| 3' | Floating leaves opaque; fruits 3-4 mm long |
| 4 | Leaf lamina arising directly from the node |
| 4' | Leaf lamina arising from the top of a sheath (which surrounds the stem above the node) |
