| | 1. Peduncle bracts tipped by 1 tack-like gland; chaff scales generally without tack-like glands; plant often > 1.5 dm |
| |
| | 2. Corollas yellow; ray fruits decidedly rough-wrinkled |
| C. truncata |
| | 2' Corollas white; ray fruits smooth (except some C. hooveri) |
| |
| | 3. Heads 2–4-flowered, inconspicuous; branchlets many, ± thread-like, flexible; ray fruit glabrous |
| C. hooveri |
| | 3' Heads 6–many-flowered, conspicuous; branchlets 0–many, rigid; ray fruit hairy |
| |
| | 4. Peduncle bracts ± cylindric distally, tip truncate to strongly concave |
| C. spicata |
| | 4' Peduncle bracts flat, tip rounded to truncate (terminal gland sometimes 0) |
| C. villosa |
| | 1' Peduncle bracts, chaff scales, or both generally with 1 tack-like gland (or in plants < 1.5 dm of Butte Co., peduncle bracts with 1 tack-like gland and chaff scales without such glands) |
| |
| | 5. Leaves opposite throughout; heads appearing whorled |
| C. oppositifolia |
| | 5' Leaves generally alternate at least above; heads not appearing whorled |
| |
| | 6. Central ligule lobe << and narrower than lateral lobes, widest at base |
| C. multiglandulosa |
| | 6' Central ligule lobe < or = lateral lobes, widest near middle |
| |
| | 7. Stem ± densely soft-hairy; peduncle bracts oblanceolate, flexible, tack-like glands small, ± sessile, ± marginal; chaff scale tack-like glands generally 0; ray fruit rough-wrinkled |
| C. mollis |
| | 7' Stem short-stiff-hairy (and sparsely soft-hairy); peduncle bracts club-shaped or acuminate, rigid, tack-like glands stalked, on margins and surfaces; chaff scales generally with tack-like glands; ray fruit smooth |
| |
| | 8. Ray flowers (2)3–6; disk flowers 6–20; branches generally few, ± rigid, main axis generally obvious; receptacle cup width = length; corollas sometimes yellow |
| C. fremontii |
| | 8' Ray flowers generally 1(2); disk flowers 2–5; branches many, flexible, often ± zigzag and without obvious axis; receptacle cup width ± 1/2 length; corollas not yellow |
| C. pauciflora
|