Najadaceae, the Pondweed Family
Aquatic plants with submerged or floating leaves and inconspicuous flowers in summer.
| 1a. Leaves opposite or whorled — 2. | |
| 1b. Leaves alternate — 2c. | |
| 2a. Leaves thread-like, 3-8 cm. long | Horned Pondweed, Zannichellia palustris. |
| 2b. Leaves linear, toothed, abruptly dilated at the base, 3 cm. long or less (Naiad) — 3. | |
| 2c. Leaves entire, not abruptly dilated at base | 2Pondweed, Potamogeton spp. |
| 3a. Leaves about 2 mm. wide, sharply and coarsely toothed | Naiad, Naias marina. |
| 3b. Leaves very narrowly linear, with numerous minute teeth | Naiad, Naias flexilis. |