| | 1. Stolons conspicuous; flower bilateral (3 upper petals spotted, << 2 lower) |
| S. stolonifera |
| | 1' Stolons 0; flower radial or ± bilateral (3 upper petals spotted, ± = 2 lower in S. ferruginea) |
| |
| | 2. Leaves cauline on ± trailing stem |
| |
| | 3. Flowers in few-flowered racemes or panicles |
| S. nuttallii |
| | 3' Flowers at tip of long peduncle, 1–2 or in head-like clusters |
| |
| | 4. Leaf blade 3–5-lobed at tip; flowers 1–2 |
| S. cespitosa |
| | 4' Leaf blade entire; flowers in head-like clusters |
| S. tolmiei |
| | 2' Leaves basal, sometimes a few smaller and cauline |
| |
| | 5. Leaf blade generally 5–8 mm |
| S. rivularis |
| | 5' Leaf blade generally > 15 mm |
| |
| | 6. Filaments wider above than below |
| |
| | 7. Leaf blade base truncate to tapered; ovaries fused only at base; fruit 2 follicles |
| |
| | 8. Inflorescence open; sepals reflexed; petal spots 2; filaments generally much-widened above middle |
| S. marshallii |
| | 8' Inflorescence dense toward tips; sepals spreading; petal spots 0; filaments ± widened except near tip |
| S. rufidula |
| | 7' Leaf blade base generally cordate to reniform; ovaries fused throughout; fruit a capsule |
| |
| | 9. Leaf blade teeth irregular, rounded, base generally cordate; petiole hairy; petals not falling early, ovate to elliptic, spots 0; capsule dark purple |
| S. mertensiana |
| | 9' Leaf blade teeth regular, sharp, base generally reniform; petiole ± glabrous; petals ephemeral, round to elliptic, spots 2; capsule tip purple, base yellow-banded |
| S. odontoloma |
| | 6' Filaments wider below than above |
| |
| | 10. Ovary superior in flower and fruit |
| |
| | 11. Inflorescence bulblets 0; ovaries < half-fused; petal spots 0 |
| S. howellii |
| | 11' Inflorescence bulblets axillary to lower bracts; ovaries > half-fused; some petals spotted |
| |
| | 12. All petals spotted; leaf blade linear-elliptic, entire or teeth minute or sparse |
| S. bryophora |
| | 12' 3 upper petals spotted; leaf blade obovate, teeth generally coarse |
| S. ferruginea |
| | 10' Ovary ± half-inferior in flower, superior in fruit |
| |
| | 13. Leaf blade linear to oblanceolate, generally > 10 cm, long-tapered to an indistinct petiole; bogs and marshes |
| S. oregana |
| | 13' Leaf blade elliptic, obovate, or ovate, generally < 10 cm, short-tapered to a distinct petiole; many habitats but not bogs or marshes |
| |
| | 14. Leaf blade shallowly toothed; inflorescence ± open, often 1-sided; styles on fruit generally > 1.5 mm |
| S. californica |
| | 14' Leaf blade ± entire; inflorescence open between ± head-like clusters, not 1-sided; styles on fruit generally < 1 mm |
| |
| | 15. Petals generally < 2 mm, sepals ± reflexed to spreading |
| S. nidifica var. nidifica |
| | 15' Petals generally > 2 mm, sepals ± erect to spreading |
| |
| | 16. Inflorescence ± glabrous to sparsely glandular; leaves ± glabrous; > 1500 m |
| S. aprica |
| | 16' Inflorescence densely glandular; leaves ± hairy; < 1000 m |
| S. integrifolia
|