| 1 | Leaves and involucre white-tomentose; shrubby perennial |
| 1' | Leaves and involucre not tomentose; plant annual |
| 2 | Capitula without rays, or ray-florets with very minute ligules |
| 2' | Capitula conspicuously radiate |
| 3 | Pappus-hairs twice as long as achene, 5-6 mm long; capitula in small terminal cymes or corymbs, or sometimes solitary |
| 3' | Pappus-hairs equalling or shorter than achene, less than 2 mm long; capitula numerous in rather large terminal cymes or corymbs |
| 4 | Leaves and stems arachnoid; involucre with a calyculus of blackish (sphacelate-)tipped bracts |
| 4' | Leaves and stems glabrous or glabrescent; involucre without a calyculus |
