| | 1. Style thread-like; fruit widely elliptic to ± round |
| |
| | 2. Inflorescence terminal, 1 per rosette; bracts subtending inflorescence ± round, ± = sepals |
| C. umbellatum |
| | 2' Inflorescence axillary, 2+ per rosette; bracts subtending inflorescence ovate to deltate, < sepals |
| |
| | 3. Perennial; taproot slender to thick; inflorescence umbel; anthers pink to rose |
| C. monospermum |
| | 3' Annual; roots ± fibrous; inflorescence panicle of head-like clusters; anthers yellow |
| C. pulchellum |
| | 1' Style 0, stigmas sessile; fruit ovate to narrowly oblong |
| |
| | 4. Flowers pedicelled, pedicels 1–3 mm; petals 2 or 4 |
| |
| | 5. Petals 2, ± 1 mm; sepals ± round to reniform — stamen 1 |
| C. roseum |
| | 5' Petals 4, 2–3 mm; sepals ovate to ± reniform |
| |
| | 6. Sepals ovate; ± fleshy; flowers persistent in fruit |
| C. pygmaeum |
| | 6' Sepals ± reniform, scarious; flowers deciduous in fruit |
| C. quadripetalum |
| | 4' Flowers subsessile; petals generally 3 |
| |
| | 7. Fruit > 2 × sepal length |
| C. monandrum |
| | 7' Fruit < 2 × sepal length |
| C. parryi |
| | 8. Flowers persistent in fruit; seeds fine-tubercled throughout; Transverse Ranges, s High Sierra Nevada |
| var. parryi |
| | 8' Flowers deciduous in fruit; seeds smooth throughout or margin fine-tubercled; San Francisco Bay Area, n Inner South Coast Ranges, East of Sierra Nevada |
| |
| | 9. Outer sepal ovate to ± round, margin membranous or narrowly scarious; San Francisco Bay Area, n Inner South Coast Ranges |
| var. hesseae |
| | 9' Outer sepal reniform, margin clearly white-scarious; East of Sierra Nevada |
| var. nevadense
|