1 Inflorescence an involucrate head subtended by phyllaries, the heads solitary or many and variously arrayed in secondary inflorescences, the ovary inferior, the corolla connate and tubular at least basally, the calyx absent, the stamens 5, the fruit a cypsela

1 Inflorescence, flower, and fruit structure various, but not with the combination of features as above (sometimes the flowers in a head, e.g. Eryngium in APIACEAE, or the fruit a cypsela in Cevallia in LOASACEAE, but then with other features differing, such as stamens 4, or green calyx present, or fruit a schizocarp of mericarps, etc.).

  2 Perianth uniseriate, with only undifferentiated tepals; flowers many and small, greenish or brownish, inconspicuous individually; inflorescence of glomerules that are usually further aggregated into racemes or panicles; fruit an achene or utricle

  2 Perianth biseriate, both sepals and petals present and differentiated (except uniseriate and of 2 white to cream-colored sepals 5-10 mm long in Macleaya in PAPAVERACEAE); flowers larger, usually with the petals prominently colored; inflorescence various, but not as above; fruit a capsule, silique/silicle, or a schizocarp of 2 mericarps.

    3 Corolla bilaterally symmetrical and the petals connate into a tube (or the corolla 2-lipped but the corolla lobes twisted so as to make the flower asymmetrical); stamens 4; fruit a 2-locular and loculicidal capsule opening by 2 valves

    3 Corolla radially symmetrical and either connate into a tube or distinct (except Reseda in RESEDACEAE, with bilateral symmetry but separate petals); stamens 5 or more; fruit a silique/silicle, a schizocarp of 4 mericarps, or a 1-, 3-, or 4-locular capsule (2-locular in Ipomoea in CONVOLVULACEAE and Glaucium in PAPAVERACEAE), opening variously.

      4 Ovary inferior; fruit either a schizocarp of 2 mericarps (Eryngium), a 4-loculicidal (Oenothera) or apically dehiscent (Mentzelia) capsule with a persistent perianth (Mentzelia), or a cypsela (Cevallia).

        5 Flowers 4-merous, in a diffuse inflorescence; fruit a 4-locular capsule

        5 Flowers 5-merous (sometimes superficially 10+ in Mentzelia, the numerous "petals" actually a combination of 5+ petaloid stamen filaments and 5 petals).

          6 Flowers aggregated into a head; fruit a schizocarp of 2 mericarps

          6 Flowers solitary or in dichasia (Mentzelia) or if headlike, then plants with abundant trichomes, flowers yellow and fruit a cypsela with a persistent perianth (Cevallia); [LOASACEAE]

             7 Stamens 5; fruits indehiscent (a cypsela with a persistent perianth), bearing one seed each; plants with four trichome types (knobbed, retrorse, dendritic, and stinging), these sometimes but not always all present on the same plant.

             7 Stamens numerous (8-50+), often strongly exerted; petals 5 (sometimes superficially appearing to have ca. 10+ due to the presence of 5+ petaloid stamen filaments and 5 petals), fruits dehiscent (capsules with apical dehiscence); plants with two types of trichomes (antrorse/smooth or retrorse)

      4 Ovary superior; fruit either a silique/silicle, or a 1-, 2-, or 3-locular capsule, or a berry.

               8 Sepals and petals of different numbers, the sepals 2-3, the petals 0, 4, or 6; stamens many

               8 Sepals and petals the same number, 4-8 each; stamens 5 or 6 (10-25 in Reseda in RESEDACEAE).

                 9 Corolla bilaterally symmetrical; stamens 10-25

                 9 Corolla radially symmetrical; stamens 5 or 6.

                   10 Petals 4, distinct; stamens 6; fruit a silique/silicle

                   10 Petals 5, connate into a tube; stamens 5; fruit either a capsule or a berry.

                     11 Plant a twining vine.

                       12 Corolla with a long tube, much longer than the lobes, scarlet, white, pink, or blue; leaves shallowly to deeply pinnately parted into 3-many lobes

                       12 Corolla with a short tube, the lobes longer than the tube, purplish; leaves with a single large terminal l lobe, and 2 small basal lobes (these almost separate as leaflets)

                     11 Plant an erect or sprawling herb.

                          13 Fruit a capsule, 1-locular; corolla white, pink, lavender, or blue, the tube short (< 4 mm long), the lobes flaring, the corolla < 15 mm long or wide

                          13 Fruit either a capsule, 2- or-3 locular, or a berry; corolla scarlet, blue, white, yellow, greenish-yellow, or purple, the tube long (>10 mm long) and cylindrical, the corolla > 10 mm long or wide.

                            14 Stigmas 3; fruit a capsule with 3 valves; leaf lobes 0.5-5 mm wide, often themselves lobed, the sinuses very deep, often nearly to the leaf midvein

                            14 Stigmas 2; fruit either a capsule with 2 valves or a berry; leaf lobes > 5 mm wide, not lobed themselves, the sinuses shallow, often < 1/2 way to the midvein