Convolvulaceae, the Morning Glory Family
Twining or trailing herbs (except one species), with regular flowers; sepals 5; corolla 5-angled or 5-lobed; stamens 5, attached to the corolla; ovary superior, 2-3-celled.
| 1a. Plants with green foliage and conspicuous flowers (summer) — 2. | |
| 1b. Leafless brown or yellow plants, with very small flowers (Dodder) — 7. | |
| 2a. Style divided at the top into linear or oblong stigmas (flowers white or pink) (Bindweed) — 3. | |
| 2b. Style not divided at the top; stigmas sessile, capitate (Morning Glory) — 6. | |
| 3a. Stem erect; leaves rounded or somewhat cordate at base, not hastate or sagittate (1-3 dm. high) | Bindweed, Convolvulus spithamaeus. |
| 3b. Stem trailing or twining; leaves sagittate or hastate — 4. | |
| 4a. Calyx almost concealed by two large heart-shape bracts — 5. | |
| 4b. Bracts at base of calyx none | Bindweed, Convolvulus arvensis. |
| 5a. Leaves triangular-hastate, with sharp basal lobes | Bindweed, Convolvulus sepium. |
| 5b. Leaves oblong-ovate, the basal lobes obtuse | Bindweed, Convolvulus sepium var. pubescens. |
| 6a. Stem smooth or nearly so; ovary 2-celled (flowers white) | Wild Potato Vine, Ipomoea pandurata. |
| 6b. Stem with reflexed hairs; ovary 3-celled (flowers of various colors) | Morning Glory, Ipomoea purpurea. |
| 7a. Introduced weed, growing as a parasite on clover | Dodder, Cuscuta epithymum. |
| 7b. Native species, on various shrubs and herbs — 8. | |
| 8a. Flowers sessile — 9. | |
| 8b. Flowers distinctly pedicelled — 12. | |
| 9a. Sepals united below into a gamosepalous calyx — 10. | |
| 9b. Sepals separate from each other — 11. | |
| 10a. Calyx-lobes obtuse | Dodder, Cuscuta arvensis. |
| 10b. Calyx-lobes acute | Dodder, Cuscuta obtusiflora. |
| 11a. Flowers in dense rope-like twists on various species of herbs | Dodder, Cuscuta paradoxa. |
| 11b. Flowers in dense clusters on various species of shrubs | Dodder, Cuscuta compacta. |
| 12a. Tips of the petals inflexed | Dodder, Cuscuta coryli. |
| 12b. Tips of the petals erect or spreading — 13. | |
| 13a. Capsule depressed at the summit | Dodder, Cuscuta cephalanthi. |
| 13b. Capsule pointed at the summit | Dodder, Cuscuta gronovii. |