Lentibulariaceae, the Bladderwort Family
Small herbs, growing on rocks, in mud, or in water; calyx and corolla both 2-lipped; stamens 2, attached to the corolla; ovary 1-celled.
| 1a. Corolla purple — 2. | |
| 1b. Corolla yellow (flowers in summer) (Bladderwort) — 4. | |
| 2a. Leaves oval to elliptical, entire (about 1 dm. high, on rocks; flowers in summer) | Butterwort, Pinguicula vulgaris. |
| 2b. Leaves dissected or none, submerged (flowers in summer) (Bladderwort) — 3. | |
| 3a. Flower-stalk with a single bract near the middle | Bladderwort, Utricularia resupinata. |
| 3b. Flower-stalk without bracts, except at the base of the pedicels | Bladderwort, Utricularia purpurea. |
| 4a. Stem and numerous dissected leaves floating in water | Bladderwort, Utricularia vulgaris var. americana. |
| 4b. Stem and minute leaves creeping on the bottom of ponds or in mud, while the flowers are borne on erect stalks, easily detached from the delicate stems — 5. | |
| 5a. Upper lip of corolla conspicuous, as long or nearly as long as the lower lip; lower lip with a prominent raised palate — 6. | |
| 5b. Upper lip of corolla half as long as the lower lip, or less — 7. | |
| 6a. Spur of corolla very short and blunt | Bladderwort, Utricularia gibba. |
| 6b. Spur of corolla very long and slender | Bladderwort, Utricularia cornuta. |
| 7a. Spur of corolla very short and blunt, or almost none | Bladderwort, Utricularia minor. |
| 7b. Spur of corolla long and slender | Bladderwort, Utricularia intermedia. |