| | 1. Stems glabrous, puberulent, or gland-dotted |
| |
| | 2. Herbage gland-dotted; corollas yellow |
| |
| | 3. Involucres 6–8 mm, obconic; phyllaries weakly vertically ranked, tips not swollen |
| C. paniculatus |
| | 3' Involucres 7–9.5 mm, cylindric; phyllaries strongly vertically ranked, tips swollen, green |
| C. teretifolius |
| | 2' Stems (and generally leaves) not gland-dotted; corollas generally yellow (white) |
| |
| | 4. Corollas white; leaves gland-dotted |
| C. albidus |
| | 4' Corollas yellow; leaves not gland-dotted |
| |
| | 5. Fruit glabrous; leaves flat, rigid, persistent |
| |
| | 6. Involucres generally 10–13 mm; phyllaries strongly keeled |
| C. depressus |
| | 6' Involucres generally 12–15 mm; phyllaries not keeled |
| C. gramineus |
| | 5' Fruit (generally densely) hairy; leaves generally twisted |
| |
| | 7. Heads overtopped by leaves; flowers 2–3(4) per head |
| C. humilis |
| | 7' Heads not overtopped by leaves; flowers 3+ per head |
| |
| | 8. Phyllaries acuminate to bristle-tipped; leaves < 1 mm wide |
| C. greenei |
| | 8' Phyllaries obtuse to acute; leaves 1–10 mm wide |
| C. viscidiflorus |
| | 9. Upper stems (and generally leaves) hairy |
| |
| | 10. Stems bristly near inflorescence; leaves > 2 mm wide, ± rough-hairy |
| subsp. lanceolatus |
| | 10' Herbage finely puberulent; leaves 1–2(4) mm wide, glabrous |
| subsp. puberulus |
| | 9' Stems glabrous; leaves glabrous (except generally ciliate) |
| |
| | 11. Leaves ± 1 mm wide; flowers 3–4(5) per head; involucre ± obconic |
| subsp. axillaris |
| | 11' Leaves 1–10 mm wide; flowers generally 4+ per head; involucre cylindric |
| subsp. viscidiflorus |
| | 1' Stems tomentose to felted |
| |
| | 12. Phyllaries long-acuminate, weakly keeled; inflorescence generally raceme-like; heads 5–18-flowered |
| C. parryi |
| | 13. Leaves generally > 3 cm, > 5 mm wide |
| subsp. latior |
| | 13' Leaves generally < 3 cm, 4 mm wide or less |
| |
| subsp. imulus |
| |
| | 15. Leaves oblanceolate, glands short-stalked |
| subsp. asper |
| | 15' Leaves linear to oblanceolate, stalked glands 0 |
| |
| | 16. Heads 1–3 per inflorescence; corolla 8–9 mm |
| subsp. monocephalus |
| | 16' Heads many per inflorescence; corolla > 9 mm |
| |
| | 17. Phyllaries tips recurved; corolla 10–11 mm |
| subsp. nevadensis |
| | 17' Phyllaries straight; corolla 11–12.5 mm |
| subsp. vulcanicus |
| | 12' Phyllaries obtuse to acute, strongly keeled; inflorescence generally panicle-like; heads 5-flowered |
| C. nauseosus |
| | 18. Involucre subglabrous to tomentose; stems generally whitish; leaves generally dark green to grayish white |
| |
| | 19. Fruit glabrous except white-hair-tufted at top |
| subsp. washoensis |
| |
| subsp. bernardinus |
| | 20' Involucre 7–10(11) mm |
| |
| | 21. Corolla lobes 1–2 mm; style appendage > stigma |
| subsp. albicaulis |
| | 21' Corolla lobes 0.5–1 mm; style appendage < stigma |
| subsp. hololeucus |
| | 18' Involucre glabrous (outer phyllaries sometimes ciliate or scaly-margined); stems greenish or brownish; leaves greenish yellow or 0 |
| |
| subsp. leiospermus |
| |
| | 23. Leaves 1–3 mm wide, 1–5-veined; involucre > 10 mm |
| subsp. bernardinus |
| | 23' Leaves 1 mm wide or less, 1-nerved; involucre < 10 mm |
| |
| | 24. Phyllaries abruptly pointed, recurved |
| subsp. ceruminosus |
| | 24' Phyllaries acute, erect |
| |
| | 25. Involucres 6–10 mm; stems generally leafy |
| subsp. consimilis |
| | 25' Involucres 8.5–12 mm; stems often leafless |
| subsp. mohavensis
|