| | 1. Middle and upper cauline leaves not clasping, petioled or not |
| |
| | 2. Sepal hairs ± dense; annual |
| C. hallii |
| | 2' Sepals generally glabrous or hairs sparse (if dense, perennial herb from woody caudex) |
| |
| | 3. Annual to weak perennial herb, caudex generally 0 or weak; leaves and lower stem conspicuously hairy |
| C. pilosus |
| | 3' Perennial from woody caudex; leaves and lower stem ± glabrous |
| |
| | 4. Basal and lower cauline leaves generally < 3 × longer than wide, narrowed abruptly to petiole, basal ± not rosetted; seed yellowish or light brown |
| C. glaucus |
| | 4' Basal and lower cauline leaves generally > 3 × longer than wide, tapered gradually to petiole (unless base deeply lobed), basal rosetted; seed dark brown |
| |
| | 5. Stem generally not inflated; sepals glabrous or tips sparsely hairy; stigma lobes < 0.5 mm |
| C. major |
| | 6. Sepals greenish white or cream-colored |
| var. major |
| var. nevadensis |
| | 5' Stem ± inflated; sepals glabrous or densely hairy; stigma lobes > 0.5 mm |
| C. crassicaulis |
| | 7. Sepals ± densely hairy |
| var. crassicaulis |
| var. glaber |
| | 1' Middle and upper cauline leaves clasping, sessile |
| |
| | 8. Sepals generally obviously darker in bud (except sometimes C. coulteri); longest filament pair fused at least at base (except sometimes C. californicus) |
| |
| | 9. Stem ± inflated; plant glabrous or sparsely hairy below |
| C. inflatus |
| | 9' Stem not inflated; plant generally obviously hairy below (except sometimes C. coulteri var. lemmonii) |
| |
| | 10. Sepals 4–8(10) mm; petals 6–11 mm; fruit 1–6 cm, compressed perpendicular to septum; seed ± spheric |
| C. californicus |
| | 10' Sepals (5)7–18 mm; petals (8)10–31 mm; fruit 4–13 cm, cylindric or ± compressed parallel to septum; seed compressed |
| C. coulteri |
| | 11. Leaves and lower stems generally densely hairy, generally some leaf hairs branched (except generally Southwestern California); lower and middle cauline leaves lanceolate to oblong, generally coarsely dentate to deeply cut; fruit generally reflexed |
| var. coulteri |
| | 11' Leaves and lower stems ± glabrous to sparsely hairy, leaf hairs unbranched; lower and middle cauline leaves lanceolate-oblong to ovate, entire to finely dentate; fruit generally erect or ascending |
| var. lemmonii |
| | 8' Sepals not or barely darker in bud; longest filament pair free |
| |
| | 12. Basal and lower cauline leaf length generally > 10 × width, sides ± parallel |
| C. heterophyllus |
| | 13. Sepals purple; petals whitish with purple veins or purplish |
| var. heterophyllus |
| | 13' Sepals yellowish or cream-colored, reddish blushed or not; petals yellowish green, purple-veined or not |
| C. heterophyllus var. pseudosimulans |
| | 12' Basal and lower cauline leaf length generally << 10 × width, sides generally not parallel |
| |
| | 14. Plant ± conspicuously spreading-hairy below |
| C. simulans |
| | 14' Plant glabrous (or stem inconspicuously appressed-hairy) |
| |
| | 15. Stem generally inconspicuously appressed-hairy; upper leaves ± narrowly oblong, hastate, tips acute |
| C. cooperi |
| | 15' Plant glabrous; upper leaves widely (ob)ovate, not hastate, tips ± obtuse |
| C. amplexicaulis |
| var. amplexicaulis |
| | 16' Sepals yellowish or cream-colored |
| var. barbarae
|