1	"Leaves not spiny"	2
1	"Leaves spiny or spiny-toothed"	7
2	"Phyllaries spine-tipped"	3
2	"Phyllaries not spine-tipped"	5
3	"Phyllary tip-spines hooked"	Arctium
3	"Phyllary tip-spines not hooked"	4
4	"Phyllary tip fringed with spines or slender teeth"	Centaurea
4	"Phyllary tip entire or minutely spiny-toothed, tapered to spine"	Volutaria
5	"Phyllary tips (at least inner) +- prominently expanded, +- fringed with short spines or irregular teeth"	Centaurea
5	"Phyllary tips not expanded or fringed"	6
6	"Proximal leaves linear to oblong or oblanceolate, often lobed or divided; attachment scar of fruit lateral"	"Acroptilon {Acroptilon repens}"
6	"Proximal leaves lanceolate to triangular, sharply dentate; attachment scar of fruit basal"	"Saussurea {Saussurea americana}"
7	"Corolla yellow to orange-red"	8
7	"Corolla white to blue, red, or purple"	9
8	"Pappus of many, unequal, narrow scales in several series (sometimes 0), generally 0 on outer fruits; flowers all fertile; fruit 4-angled"	Carthamus
8	"Pappus of 20 stiff bristles or awns in 2 series, on all fruits; outer flowers sterile [corolla 3-lobed; ovary vestigial]; fruit cylindric, 20-ribbed"	"Centaurea benedicta"
9	"Pappus of long-plumose bristles"	10
9	"Pappus of +- rough or barbed bristles or slender scales"	11
10	"Largest leaves toothed to deeply lobed; involucre body 1--6 cm diam; receptacle generally not fleshy; phyllaries linear to ovate"	Cirsium
10	"Largest leaves often +- compound; involucre body 4--15 cm diam; receptacle fleshy; phyllaries ovate"	Cynara
11	"Stem spiny-winged"	Carduus
11	"Stem not spiny-winged"	12
12	"Leaf not blotched along veins; heads not long-peduncled; pappus of many, unequal, narrow scales in several series"	"Carthamus leucocaulos"
12	"Leaf white-blotched along veins; heads long-peduncled; pappus of many long bristles, deciduous in a ring"	"Silybum {Silybum marianum}"