| | 1. Leaf blades entire; anthers glabrous |
| |
| | 2. Leaf blade generally 3–10 mm, margin inrolled to midrib |
| C. intricatus |
| | 2' Leaf blade 10–40 mm, margin plane to inrolled (but not to midrib) |
| C. ledifolius |
| | 3. Leaf oblanceolate to elliptic-lanceolate, glabrous to sparsely woolly below, midrib & veins visible |
| var. intermontanus |
| | 3' Leaf narrowly lanceolate, densely woolly below, midrib and veins obscure |
| var. ledifolius |
| | 1' Leaf blades toothed to crenate; anthers hairy |
| |
| | 4. Leaf ± leathery, woolly below; hypanthium densely white-tomentose — s Channel Islands (Santa Catalina Island) |
| C. traskiae |
| | 4' Leaf ± thin, not leathery, ± sparsely hairy below; hypanthium glabrous to sparsely hairy |
| |
| | 5. Leaf ± glabrous below; hypanthium rim 2–5 mm diam |
| C. minutiflorus |
| | 5' Leaf hairy below; hypanthium rim 4–7 mm diam |
| C. betuloides |
| | 6. Leaf blade with 4–7 lateral veins, 1–4 cm |
| var. betuloides |
| | 6' Leaf blade with 6–12 lateral veins, 2–8 cm |
| |
| | 7. Flowers (and fruits) generally 5–12 per cluster; leaf blade generally ovate, teeth ± deltate |
| var. blancheae |
| | 7' Flowers (and fruits) 1–3 per cluster; leaf blade generally obovate, long, narrowly triangular |
| var. macrourus
|