1	Plant generally wind-pollinated or self-pollinated, capitula small and not showy; all florets unisexual, or if bisexual then capitula aggregated into glomerules; ray florets absent		(2)
+	Plant generally adapted for attracting pollinating insects, capitula colorful and attractive; some or all florets bisexual; ray florets present, sometimes inconspicuous, rarely absent		(4)
2 (1)	Florets all bisexual; capitula aggregated into glomerules surrounded by leaflike bracts; achenes free and not surrounded by modified phyllaries into a bur or into spiny, tuberculate, or winged coat.		228 Lagascea
+	Florets unisexual; capitula not aggregated into glomerules and lacking any outer leaflike bracts; achenes surrounded by modified phyllaries into a prickly bur or spines, tubercles, or wings		(3)
3 (2)	Phyllaries in male capitula 1- or 2-seriate, free to base; phyllaries in female capitula 6-12-seriate, their distinct tips mostly ± hooked (distal 1-3 usually longer, stouter, and not hooked), whole becoming a hard, prickly perigynium or bur; florets 2.		232 Xanthium
+	Phyllaries in male capitula 1-seriate, connate; phyllaries in female capitula 1-8-seriate, usually with free tips forming tubercles, spines, or wings; florets 1(-5).		233 Ambrosia
4 (1)	Leaves and phyllaries with obvious oil glands		(5)
+	Leaves and phyllaries lacking oil glands		(6)
5 (4)	Phyllaries connate into a tube, sometimes splitting with age; style arms relatively long, spreading or arcuate; leaves lacking basal cilia.		202 Tagetes
+	Phyllaries free; style arms minute, scarcely bifurcated; leaf bases distinctly ciliate.		203 Pectis
6 (4)	Only ray florets fertile, ray achenes much longer than those of sterile disk florets		(7)
+	Disk florets fertile; ray florets present and fertile or sterile or absent		(9)
7 (6)	Leaves alternate; ray achenes strongly flattened, each achene ± enclosed by and often attached to subtending phyllary and 2 adjacent paleae, all falling as a unit.		234 Parthenium
+	Leaves opposite; ray achenes thick, rounded or weakly compressed, without wings; achenes thick, not obviously flattened, not falling as unit with adjacent paleae		(8)
8 (7)	Achenes enveloped and enclosed by prickly inner phyllaries.		214 Acanthospermum
+	Achenes merely subtended by unarmed phyllaries.		217 Smallanthus
9 (6)	Ray florets with or without short tubes, persistent with corollas fused to apex of achene.		211 Zinnia
+	Ray florets deciduous, of if ray florets absent (i.e., capitula disciform or discoid) then corollas not fused to apex of achene		(10)
10 (9)	Pappus of subulate to acerose scales, or spatulate, entire to erose, fimbriate, or laciniate, sometimes aristate, scales 1-seriate, or plumose, setiform scales (or flattened bristles) 1-seriate, or an apical peg		(11)
+	Pappus absent, or awned		(13)
11 (10)	Pappus of plumose setae.		212 Tridax
+	Pappus of aristate or linear scales with erose or fimbriate margins, or absent		(12)
12 (11)	Pappus of 6-12 aristate, rarely linear scales with erose margins; capitula > 10 mm in diam.		235 Gaillardia
+	Pappus absent or of fimbriate, sometimes aristate scales; capitula 3-5 mm in diam.		213 Galinsoga
13 (10)	Achenes compressed		(14)
+	Achenes all relatively plump, or 3-5-angled in ray florets and compressed in disk florets		(21)
14 (13)	Pappus of retrorsely barbed awns; leaves opposite or upper alternate		(15)
+	Pappus absent, or persistent, of 2 bristly cusps or scales; leaves opposite		(17)
15 (14)	Style branches with long hairs; pappus of 2 scabrid awns.		205 Glossocardia
+	Style branches with short minute papillae; pappus of 2-4 scabrid awns		(16)
16 (15)	Anther filaments pubescent; achene apex beaked.		206 Cosmos
+	Anther filaments glabrous; achene apex narrow, not beaked.		207 Bidens
17 (14)	Phyllaries 2-seriate, outer few and smaller, inner membranous, connate at base; pappus of 2-4 awns or scales or absent.		208 Coreopsis
+	Phyllaries free, outer leathery, subequal, inner shorter, similar with paleae; ray achenes narrowly oval and winged, with 2 triangular scales		(18)
18 (17)	Achenes markedly dimorphic, those of ray florets with conspicuous, lacerate winged margin, others wingless.		219 Synedrella
+	Achenes all ± alike, wingless or somewhat thickly winged distally, not lacerate		(19)
19 (18)	Shrubs or small trees; synflorescence of numerous capitula in congested panicles or corymbs; achenes wingless.		223 Clibadium
+	Annual or perennial herbs; synflorescence of solitary capitula or capitula several in dense clusters; achenes winged or angled		(20)
20 (19)	Capitula radiate; pappus of 2 stout awns.		220 Calyptocarpus
+	Capitula discoid; pappus peglike.		221 Eleutheranthera
21 (13)	Achenes enclosed by inner phyllaries or outer paleae		(22)
+	Achenes not enclosed by inner phyllaries		(24)
22 (21)	Capitula tightly or loosely aggregated on short peduncles in corymbose panicles.		204 Flaveria
+	Capitula axillary or in sparse cymes or panicles		(23)
23 (22)	Female florets 1-seriate; phyllaries 5, spreading; capitula in sparse panicles, peduncles long.		216 Sigesbeckia
+	Female florets multiseriate; phyllaries 4, broad, in 2 pairs; capitula axillary, peduncles very short.		209 Enydra
24 (21)	Paleae narrow, long, flat; ray florets 2-seriate, lamina small; pappus absent or of 2 short awns		(25)
+	Paleae concave or folded, ± enclosing florets		(26)
25 (24)	Ray floret lamina white; achene body tuberculate.		222 Eclipta
+	Ray floret lamina yellow; achene body striate.		215 Guizotia
26 (24)	Achenes in ray florets broadly ovate or elliptic, 3-angled; disk achenes ellipsoid, strongly compressed; pappus absent or of up to 10 awnlike bristles.		210 Acmella
+	Achenes in bisexual florets 4- or 5-angled, or compressed		(27)
27 (26)	Ray florets sterile		(28)
+	Ray florets fertile		(31)
28 (27)	Paleae completely investing and falling with accompanying achene, each forming a hardened perigynium.		227 Sclerocarpus
+	Paleae sometimes conduplicate, ± enfolding achenes, not forming perigynium		(29)
29 (28)	Pappus absent, a small crown of minute scales, or of 2-4 small scales; receptacles conical to columnar.		229 Rudbeckia
+	Pappus of 2 awns sometimes with a few scales, or a crown of fused scales, or of 2 awns with fused scales, or absent; receptacles flat to shallowly convex		(30)
30 (29)	Peduncles usually distally dilated, always fistulose; pappus absent or coroniform, of connate scales, 1 or 2 scales sometimes subulate to aristate.		230 Tithonia
+	Peduncles never fistulose; pappus absent or readily deciduous, of 2(or 3) usually lanceolate, aristate, or erose scales, plus 0-8 usually shorter scales.		231 Helianthus
31 (27)	Pappus elements 2-5, unequal, spinelike or squamalike, persistent, base connate; ray florets female, ray floret lamina short or very short, apex 2-4-dentate; capitula small.		218 Blainvillea
+	Pappus absent, or scalelike, cyathiform, coroniform, or of 1 or 2 setae; capitula relatively large		(32)
32 (31)	Corollas orange to yellow; outer phyllaries herbaceous and larger than inner; leaves sessile or very shortly petiolate; plants mainly prostrate; achenes triangular (ray) or compressed (disk); capitula always solitary, terminal (but appearing axillary) on erect peduncles; achene beak and pappus obscured at maturity by corky collar.		224 Sphagneticola
+	Corollas white or yellow; outer phyllaries ± equal in size to inner; leaves usually conspicuously petiolate; plants mostly erect or ascending [sometimes vines or subshrubs outside of our area]; synflorescence of 1-3(-6) capitula, terminal or axillary; pappus of obvious setae (rarely absent)		(33)
33 (32)	Ray florets female and sterile or neuter; pappus awns caducous.		225 Melanthera
+	Ray florets female and fertile; pappus absent or single awn persistent.		226 Wollastonia