Involucral scales rigid, with spreading herbaceous tips 1, 2
Involucral scales without green tips.
Heads in a compound terminal corymb, not at all racemose 37–40
Heads small, mostly clustered in the axils of feather-veined leaves 3–7
Heads mostly large, in a terminal thyrse; leaves feather-veined.
Western species 8, 9
Northern or mountain species 10–12
Heads mostly small or middle-sized; inflorescence paniculate (sometimes thyrsoidal).
Leaves 3-ribbed; heads in 1-sided spreading panicled racemes.
Stem and leaves smooth and glabrous 29–32