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| 1 Flowering stem scapose, leaves basal only; petals 8-16, white; [subfamily Chelidonioideae] |
| 1 Flowering stem with leaves at least low on the stem; petals 0-6, purple, red, orange-red, orange, yellow, cream. |
| ..2 Inflorescence a panicle; petals absent; [subfamily Chelidonioideae] |
| ..2 Inflorescence not a panicle; petals present, 4-6. |
| ....3 Leaves and fruits prickly; [subfamily Papaveroideae] |
| ....3 Leaves and fruits not prickly. |
| ......4 Sepals connate; leaves ternately dissected into linear segments; sap watery; [subfamily Eschscholzioideae] |
| ......4 Sepals separate; leaves pinnately lobed; sap yellow, orange, or milky. |
| ........5 Flowers several in a terminal umbel; [subfamily Chelidonioideae]. |
| ..........6 Stigma lobes, placentae, and capsule valves 2; style very short; fruit linear, glabrous |
| ..........6 Stigma lobes, placentae, and capsule valves (2-) 3-4; style ca. 1 cm long; fruit ellipsoid, pubescent with long white hairs |
| ........5 Flowers solitary, terminal. |
| ............ 7 Fruit 15-30 cm long, 2-locular (the partitions complete), dehiscent by elongate valves; stigmatic lobes 2; [subfamily Chelidonioideae] |
| ............ 7 Fruit 1-8 cm long, 4-20-locular (the partitions incomplete), dehiscent by small valves beneath the stigmatic disc; stigmatic lobes 4-20; [subfamily Papaveroideae] |
............ ..8 Ovaries and capsules glabrous |
| ............ ..8 Ovaries and capsules sparsely to densely setose-pubescent |