1	Petals yellow, golden, or bronze.		(2)
+	Petals white or pale lavender.		(4)
2 (1)	Stamens 150 or more, filaments red or purplish; flowers 7–12 cm wide; petals bright yellow to golden or bronze.		3 Argemone aenea
+	Stamens 20–75, filaments yellow; flowers 3–7 cm broad; petals pale lemon yellow to bright yellow.		(3)
3 (2)	Flower buds subglobose, body length ± equal to breadth; petals mostly bright yellow.		1 Argemone mexicana
+	Flower buds oblong, body length 1.5–2 times breadth; petals mostly pale lemon yellow.		2 Argemone ochroleuca
4 (1)	Leaf surfaces prickly on veins, often also minutely prickly or hispid between veins; stems usually closely prickly.		(5)
+	Leaf surfaces rarely prickly except on veins or unarmed; stems with widely spaced prickles or almost unarmed (copiously long-prickly in A. arizonica).		(9)
5 (4)	Longest capsular prickles simple, 5–8(–10) mm.		(6)
+	Longest capsular prickles branched, usually 8–35 mm.		(7)
6 (5)	Distal leaf blades not clasping; leaf surfaces densely crisped-hispid between main veins.		6 Argemone hispida
+	Distal leaf blades usually definitely clasping; leaf surfaces variously prickly but not crisped-hispid.		7 Argemone munita
7 (5)	Longest capsular prickles 15–35 mm.		4 Argemone aurantiaca
+	Largest capsular prickles about 8–15 mm.		(8)
8 (7)	Apices of leaf lobes angular, marginal teeth 3 mm or more; flowers usually closely subtended by 1–2 foliaceous bracts.		5 Argemone squarrosa
+	Apices of leaf lobes usually definitely rounded, marginal teeth usually less than 1 mm; flowers usually not closely subtended by foliaceous bracts.		7 Argemone munita
9 (4)	Longest capsular prickles branched, usually 8–35 mm.		(10)
+	Longest capsular prickles simple, 4–10(–12) mm.		(11)
10 (9)	Longest capsular prickles 15–35 mm.		4 Argemone aurantiaca
+	Longest capsular prickles 8–15 mm.		5 Argemone squarrosa
11 (9)	Prickles (when present) of sepals and sepal horns ascending, or sepals unarmed; blades of proximal leaves often lobed less than 1/2 distance to midrib.		(12)
+	Prickles (when present) of sepals and sepal horns patent; blades of proximal leaves mostly lobed more than 1/2 distance to midrib.		(17)
12 (11)	Leaf blades thick and leathery; stamens 100–120.		12 Argemone corymbosa
+	Leaf blades often succulent, but not leathery; stamens 150 or more.		(13)
13 (12)	Flower buds obovoid or oblong; sepal horns usually flattened adaxially.		(14)
+	Flower buds usually subglobose, rarely ellipsoid or ellipsoid-oblong; sepal horns terete.		(15)
14 (13)	Flower buds obovoid; surface of sepal horns prickly; blades of proximal leaves lobed ca. 3/4 distance to midrib, apices of lobes angular, marginal teeth prominent.		9 Argemone pleiacantha
+	Flower buds oblong; surface of sepal horns unarmed; blades of proximal leaves lobed ca. 1/2 distance to midrib, apices of lobes rounded, marginal teeth very short.		7 Argemone munita
15 (13)	Distal leaves not evidently clasping; stems with scattered prickles, the longest 7–10 mm.		13 Argemone gracilenta
+	Distal leaves clasping; stems with shorter prickles.		(16)
16 (15)	Sepal horns 6–10(–15) mm; flower buds ellipsoid-oblong; capsules narrowly to broadly ellipsoid.		14 Argemone polyanthemos
+	Sepal horns 3–6(–10) mm; flower buds subglobose to broadly ellipsoid; capsules oblong to oblong-ellipsoid or narrowly ellipsoid.		15 Argemone albiflora
17 (11)	Blades of distal leaves usually definitely clasping; blades of proximal leaves lobed ca. 1/2–3/4 distance to midrib.		(18)
+	Blades of distal leaves not definitely clasping; blades of proximal leaves lobed 4/5 distance to midrib or more.		(19)
18 (17)	Blades of proximal leaves lobed ca. 3/4 distance to midrib, apices of lobes angular.		9 Argemone pleiacantha
+	Blades of proximal leaves lobed 1/2 or less distance to midrib, apices of lobes usually rounded.		7 Argemone munita
19 (17)	Flower buds usually subglobose; sepal horns terete, usually slender, unarmed.		13 Argemone gracilenta
+	Flower buds oblong to obovoid or ellipsoid; sepal horns terete or flattened or angular, usually prickly.		(20)
20 (19)	Stems copiously long-prickly, often decumbent, diffusely branched; blades of basal and proximal leaves lobed nearly to midrib, lobe length often 5 times width; sepal horns 12–15 mm.		8 Argemone arizonica
+	Stems sparsely to copiously prickly, erect, not diffusely branched; blades of basal and proximal leaves lobed 4/5 distanct to midrib or less, lobes proportionately broader; sepal horns 5–12 mm.		(21)
21 (20)	Flower buds usually oblong-obovoid, rarely subglobose; sepal horns usually flattened adaxially, rarely terete.		9 Argemone pleiacantha
+	Flower buds broadly ellipsoid to ellipsoid-oblong; sepal horns terete or angular.		(22)
22 (21)	Stems often closely prickly; capsules narrowly ellipsoid-ovoid; seeds 1.8–2.2 mm.		11 Argemone chisosensis
+	Stems not closely prickly; capsules narrowly to broadly ellipsoid; seeds about 1.5 mm.		10 Argemone sanguinea