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| 1 Flowers sessile, opposite the petioles; sepals 3; petals 3; [section Polyanthemos] |
| 1 Flowers pedunculate, axillary; sepals usually 5; petals usually 5. |
| ..2 Petals 1-2 (-3) mm long; receptacles glabrous; [section Ranunculus] |
| ..2 Petals (3-) 4-12 mm long; receptacles pubescent. |
| ....3 Achenes bodies 1.5-3 mm long, 30-60 per head; achene beak ca. 0.5 mm long; achene with conical protuberances or short spines, to 0.16 mm long; achene beak 0.1-0.5 mm long; basal leaves compound; [section Polyanthemos]. |
| ......4 Achene with a few conical protuberances; petals 5-12 mm long; plant sparsely to densely hirsute; achenes 30-40 per head |
| ......4 Achene with numerous short spines; petals (3-) 4-5 mm long; plant with a few, widely scattered, long hairs; achenes 40-60 per head |
| ....3 Achenes 2.5-5 mm long, 4-20 per head; achene beak 1.5-3.0 mm long (or 0.8-1 mm long in R. marginatus); achene conspicuously spiny, the longer spines mostly 0.30-0.85 mm long (or only ca. 0.2 mm long in R. marginatus); basal leaves simple (but deeply lobed) or compound. |
| ........5 Achenes 4-9 per head, in a single whorl; achene margins spiny, as also the faces; beak of the achene 2.5-3 mm long; [section Echinella] |
| ........5 Achenes 10-20 per head, in several whorls; achene margins smooth, the spines restricted to the faces; beak of the achene 1.5-2.5 mm long; [section Polyanthemos]. |
| ..........6 Achene faces with short protuberances ca. 0.2 mm long; achene beak 0.8-1.0 mm long; peduncle usually longer than the subtending leaf |
..........6 Achene faces with stout spines ca. 0.5 mm long; achene beak 2.0-2.5 mm long; peduncle usually shorter than the subtending leaf |