1	Leaf blade margins coarsely crenate to serrate-dentate; petioles with 2 cuplike glands at apex.		12 Croton glandulosus
+	Leaf blade margins entire, denticulate, or serrulate; petioles without cuplike glands at apex (sessile or stipitate glands often present at apex in C. linearis, stipitate-glandular in C. ciliatoglandulifer)		(2)
2 (1)	Shrubs; leaf blade abaxial surfaces densely lepidote; pistillate petals 5, ovate, pale green; styles 3, usually unbranched, rarely 2-fid.		1 Croton alabamensis
+	Herbs, subshrubs, or shrubs; if shrubs, leaf blade abaxial surfaces mainly stellate-hairy or stellate-tomentose, seldom stellate-lepidote; pistillate petals 0, rudimentary, or, if 5 (sometimes in C. humilis and C. soliman), linear or subulate, white; styles 2–3, 2-fid to multifid, or 1, unbranched		(3)
3 (2)	Ovaries 1-locular; styles unbranched; leaves mostly clustered near inflorescences; annual herbs.		26 Croton setigerus
+	Ovaries 2–3-locular; styles 2-fid or multifid; leaves clustered near inflorescences or not; annual or perennial herbs, subshrubs, or shrubs		(4)
4 (3)	Leaf blade abaxial surfaces densely lepidote or stellate-lepidote, often silvery		(5)
+	Leaf blade abaxial surfaces usually stellate-hairy, if stellate-lepidote not markedly silvery		(10)
5 (4)	Inflorescences bisexual; staminate petals 5; columella 3-angled (not markedly 3-winged) or absent (when fruit an achene); annual or perennial herbs or subshrubs		(6)
+	Inflorescences usually unisexual (sometimes bisexual in C. punctatus); staminate petals 0; columella 3-winged; subshrubs or shrubs		(7)
6 (5)	Leaf blades on proximal parts of stems oval to narrowly obovate, on distal parts oblong to lanceolate-oblong or broadly elliptic, apex obtuse to rounded, adaxial surface sparsely lepidote or glabrate; inflorescences racemes; ovaries 3-locular; fruits capsules; staminate sepals 5 mm, petals 5 mm, pedicels 1–5 mm; pistillate sepals connate for 1/2+ length.		3 Croton argyranthemus
+	Leaf blades lanceolate-linear to ovate-lanceolate, apex acute, adaxial surface sparsely stellate-hairy; inflorescences spikes; ovaries 1-locular; fruits achenes; staminate sepals 1 mm, petals 0.6–1 mm, pedicels 0–1 mm; pistillate sepals distinct.		20 Croton michauxii
7 (5)	Plants monoecious (sometimes appearing dioecious); leaf blades more than 1/2 as wide as long, petioles 1/2 to as long as leaf blade; Atlantic and Gulf coasts.		24 Croton punctatus (in part)
+	Plants dioecious; leaf blades usually less than 1/2 as wide as long, petioles usually less than 1/2 as long as leaf blade; c Texas to California		(8)
8 (7)	Subshrubs, 2–5(–9) dm; petioles 0.2–0.8(–2) cm; New Mexico, Texas.		9 Croton dioicus
+	Shrubs, 4–11 dm; petioles 1–4(–4.5) cm; Arizona, California, Nevada, Utah		(9)
9 (8)	Pedicels of pistillate flowers less than or equal to 1 mm (1–3 mm in fruit); seeds 4–5.5 × 3.5–5.5 mm; Arizona, California, Nevada, Utah.		4 Croton californicus (in part)
+	Pedicels of pistillate flowers 1–2 mm (4–7 mm in fruit); seeds 6.5–7 × 2–3 mm; sw Arizona, se California.		31 Croton wigginsii (in part)
10 (4)	Annual herbs		(11)
+	Shrubs or perennial herbs		(21)
11 (10)	Plants dioecious; inflorescences unisexual; staminate petals 0; capsules verrucose, columella 3-winged		(12)
+	Plants monoecious; inflorescences bisexual or unisexual; staminate petals 3–5; capsules smooth, columella not markedly 3-winged (usually 3-angled or apex with 3 lobes)		(13)
12 (11)	Plants 5–15 dm; leaf blade abaxial surfaces densely stellate-tomentose; capsules 8–9 mm; s Texas.		22 Croton parksii
+	Plants 2–7(–9) dm; leaf blade abaxial surfaces densely appressed stellate-hairy; capsules 5–8 mm; widespread in s and c United States, mostly not s Texas.		30 Croton texensis
13 (11)	Leaf blade abaxial surfaces appearing brown-dotted, some stellate hairs with dark brown centers; stamens 3–5; styles 2, 2-fid, terminal segments 4; ovaries 2-locular, only 1 fertile.		21 Croton monanthogynus
+	Leaf blade abaxial surfaces not appearing brown-dotted, no stellate hairs with brown centers; stamens 7–16; styles 3, 2-fid or multifid, terminal segments 6–18(–24); ovaries 3-locular		(14)
14 (13)	Pistillate sepal margins laciniate.		2 Croton argenteus
+	Pistillate sepal margins entire		(15)
15 (14)	Inflorescences 4–7 cm; staminate flowers 15–25, sepals 3 mm, petals 3–3.5 mm, stamens 14–16; pistillate flowers 8–15.		8 Croton coryi
+	Inflorescences 0.5–4 cm; staminate flowers 1–15, sepals 0.8–2 mm, petals 0.8–1.5 mm, stamens 7–13; pistillate flowers 1–8		(16)
16 (15)	Pistillate sepals 5–6; styles 2-fid, terminal segments 6; herbs 1–5 dm		(17)
+	Pistillate sepals 6–9; styles multifid, terminal segments 12–18(–24); herbs 3–20 dm		(18)
17 (16)	Pistillate sepals unequal, 3 outer 5–7 mm, 2 inner 1–2 mm.		16 Croton leucophyllus
+	Pistillate sepals equal, 3 mm.		18 Croton lindheimerianus
18 (16)	Leaf blades 0.2–0.8 cm wide, if wider then pistillate sepal apices recurved; staminate sepals and petals 0.8–1 mm; styles 2–3 mm		(19)
+	Leaf blades 1–5 cm wide, pistillate sepal apices straight or slightly incurved; staminate sepals 1–2 mm, petals 1–1.5 mm; styles 3–4 mm		(20)
19 (18)	Leaf blades ovate to lanceolate-elliptic, 3–8(–15) × 1–4 cm; pistillate sepals 7–10(–15 in fruit) mm, apices recurved.		5 Croton capitatus
+	Leaf blades lanceolate to oblong, 2–5.5 × 0.2–0.8 cm; pistillate sepals 5–6 mm, apices incurved.		10 Croton elliottii
20 (18)	Pistillate sepals whitish appressed-tomentose; styles each appearing 4-fid.		13 Croton heptalon
+	Pistillate sepals yellowish woolly-tomentose; styles each 2 times 2-fid.		17 Croton lindheimeri
21 (10)	Staminate petals 0; columella 3-winged		(22)
+	Staminate petals (4–)5(–6); columella apex with 3 rounded, inflated lobes or 3 sharp projections		(24)
22 (21)	Plants monoecious or sometimes apparently dioecious; leaf blades much less than 2 times as long as wide, petioles 1/2 to equal blade length; beaches and coastal dunes, Atlantic and Gulf coasts.		24 Croton punctatus (in part)
+	Plants strictly dioecious; leaf blades more than 2 times as long as wide, petioles usually less than 1/2 blade length; dunes and sandy areas, inland as well as coastal, Arizona, California, Nevada, Utah		(23)
23 (22)	Pedicels of pistillate flowers to 1 mm, 1–3 mm in fruit; seeds 4–5.5 × 3.5–5.5 mm; various habitats, Arizona, California, Nevada, Utah.		4 Croton californicus (in part)
+	Pedicels of pistillate flowers 1–2 mm, 4–7 mm in fruit; seeds 6.5–7 × 2–3 mm; dunes of se-most California and sw Arizona.		31 Croton wigginsii (in part)
24 (21)	Perennial herbs; columella apex with 3 sharp projections.		23 Croton pottsii
+	Shrubs; columella apex with 3 rounded, inflated lobes		(25)
25 (24)	Petioles mostly 1/4–7/10+ leaf blade length, if shorter (C. fruticulosus) then leaf blade margins finely serrulate and staminate sepals 0.8–1.2 mm; leaf blades usually ovate to lanceolate or oblong, margins entire, minutely glandular-denticulate, or serrulate, abaxial surfaces stellate-hairy or glabrous; staminate petal abaxial surfaces glabrous except margins often villous or ciliate; seeds shiny; styles 2- or 4-fid, terminal segments 6 or 12		(26)
+	Petioles mostly 1/10–1/4 leaf blade length, if longer (C. incanus) then leaf blade surfaces stellate-tomentose, staminate petal abaxial surfaces villous, and seeds dull; leaf blades usually obovate, elliptic, oblong, or linear, sometimes lanceolate or ovate, margins entire or minutely denticulate, abaxial surfaces stellate-hispid, stellate-tomentose, or stellate-hairy; staminate sepals 1.5–2.5 mm; staminate petal abaxial surfaces villous, glabrate, or glabrous except base sometimes villous and margins ciliate or tomentose; seeds shiny or dull; styles 2-fid, terminal segments 6		(30)
26 (25)	Styles 2-fid, terminal segments 6; petioles mostly 1/8–1/2 leaf blade length; stamens 9–16; stipules not glandular-ciliate; petioles not stipitate-glandular at apices (C. sonorae glandular-ciliate on leaf blade margins)		(27)
+	Styles 4-fid, terminal segments 12; petioles 3/8–7/10+ leaf blade length; stamens 15–35; stipules glandular-ciliate or not; petioles stipitate-glandular or without glands at apices		(28)
27 (26)	Staminate pedicels 2.5–4 mm, pistillate 0–0.5 mm; seeds 4–5 mm; leaf blades 2–8 cm, adaxial surfaces puberulent, margins serrulate, often slightly undulate.		11 Croton fruticulosus
+	Staminate pedicels 1–1.5 mm, pistillate 1–4 mm; seeds 6–7 mm; leaf blades 0.8–4 cm, adaxial surfaces glabrate, margins entire, not undulate.		28 Croton sonorae
28 (26)	Stipules and leaf blade margins glandular-ciliate; petioles stipitate-glandular at apices.		6 Croton ciliatoglandulifer
+	Stipules not glandular-ciliate (may be small clusters of stipitate glands or have short-stipitate glandular processes); leaf blade margins not glandular-ciliate (sometimes glandular-denticulate or with glandular-capitate processes); petioles without glands at apices		(29)
29 (28)	Leaf blade abaxial surfaces densely stellate-hairy; staminate sepals 3–4 mm, petals 3–4 mm; pistillate sepals 4 mm, petals 1 mm; seeds 3–4 × 2.5–3 mm.		14 Croton humilis
+	Leaf blade abaxial surfaces glabrous or sparsely stellate-hairy (usually along margins); staminate sepals 0.8–1 mm, petals 1–1.3 mm; pistillate sepals 5–6 mm, petals 0 or 2.5–3.5 mm; seeds 4–5 × 3–4 mm.		27 Croton soliman
30 (25)	Leaf blade adaxial surfaces glabrous or minutely stellate-puberulent; plants dioecious		(31)
+	Leaf blade adaxial surfaces stellate-tomentose or stellate-hairy; plants monoecious or dioecious		(32)
31 (30)	Leaf blades narrowly obovate, oblong, elliptic, or lanceolate, mostly less than 3.5 times as long as wide, petioles 1–1.5 cm; Texas.		7 Croton cortesianus
+	Leaf blades linear to narrowly oblong, mostly more than 4 times as long as wide, petioles 0.3–1 cm; se Florida.		19 Croton linearis
32 (30)	Shrubs 10–20 dm, much-branched distally; stipules linear-subulate, 2–3 mm; stems stellate-velutinous.		15 Croton incanus
+	Shrubs 1–5 dm, much-branched proximally; stipules papilliform, 0.1–0.5 mm; stems coarsely stellate-tomentose		(33)
33 (32)	Plants dioecious; stipules each 1 glandular papilla, 0.1 mm; capsules 5.5–6 mm wide; seeds 3.6–4.7 mm.		25 Croton sancti-lazari
+	Plants monoecious; stipules each 5–10 glandular papillae, 0.2–0.5 mm; capsules 6–8 mm wide; seeds 5.5–7 mm.		29 Croton suaveolens