1	Capsules: dehiscence circumscissile.		(2)
+	Capsules indehiscent.		(14)
2 (1)	Styles ± subulate (tapering from base to stigma).		(3)
+	Styles filiform (not tapered; sometimes slightly subulate in C. dentatasquamata).		(5)
3 (2)	Flowers: calyx and receptacle fleshy, corollas membranous; corolla lobes without hornlike appendages; capsules 4–7 × 4–6 mm		30 Cuscuta mitriformis
+	Flowers membranous; corolla lobes each with a hornlike appendage; capsules 1.8–2.5 × 1–2.5 mm.		(4)
4 (3)	Pedicels 0.2–0.6 mm; calyx lobes oblong, obovate, ovate, or spatulate, apex acute to obtuse, each exceeded by a hornlike appendage; seeds 0.7–1.1 × 0.7–0.9 mm		7 Cuscuta boldinghii
+	Pedicels 1.5–6 mm; calyx lobes oblong-obovate or orbiculate, apex ± truncate, each not exceeded by a hornlike appendage; seeds 0.9–1.4 × 0.8–1.3 mm		19 Cuscuta erosa
5 (2)	Calyces divided 1/4 length; seeds 1		5 Cuscuta americana
+	Calyces divided 1/3–3/4 length or ± to base; seeds (1 or)2–4.		(6)
6 (5)	Infrastaminal scales usually 1/4–1/2 corolla tube length (1/2 to equaling in C. odontolepis).		(7)
+	Infrastaminal scales equaling or longer than corolla tube.		(10)
7 (6)	Inflorescences dense, paniculiform-glomerulate; calyx lobe bases over­lapping; capsules 2.9–4 × 3–3.2 mm; seeds 1–1.2 × 0.6–0.8 mm		34 Cuscuta odontolepis
+	Inflorescences loose, racemiform or umbelliform; calyx lobe bases not overlapping; capsules 1.3–2.2 × (0.7–)1.5–2.3 mm; seeds 0.6–0.9(–1.1) × 0.3–0.8 mm.		(8)
8 (7)	Flowers 5-merous; calyx lobe midveins carinate; corolla lobes erect		46 Cuscuta tuberculata
+	Flowers (3 or)4-merous; calyx lobe midveins not carinate, sometimes with multicellular protuberances; corolla lobes spreading to reflexed.		(9)
9 (8)	Calyces 1/3–1/2 corolla tube length; infrastaminal scales 1/2 corolla tube length		28 Cuscuta leptantha
+	Calyces equaling corolla tube length; infrastaminal scales 1/4–1/3 corolla tube length		29 Cuscuta liliputana
10 (6)	Pedicels 2–10 mm; calyx lobe midveins not carinate, without multicellular protuberances.		(11)
+	Pedicels 0.3–2 mm; calyx lobe midveins carinate and/or with multicellular protuberances.		(12)
11 (10)	Flowers 4–5.5(–6) mm; calyx lobe apices acuminate		27 Cuscuta legitima
+	Flowers 2–3 mm; calyx lobe apices obtuse to acute		47 Cuscuta umbellata
12 (10)	Calyx lobe bases overlapping, apices obtuse or rounded; corolla lobe apices rounded to obtuse		12 Cuscuta chinensis
+	Calyx lobe bases not overlapping, apices acute; corolla lobe apices acute.		(13)
13 (12)	Flowers 2–2.6 mm, membranous; calyces straw yellow; infra­staminal scales oblong or rounded, distal 1/2 fimbriate; capsules 1.5–2.5 × 1–1.8 mm		6 Cuscuta azteca
+	Flowers 2.6–3.8 mm, fleshy; calyces reddish brown; infrastaminal scales truncate or distally irregularly denticulate or 3–7-fimbriate; capsules 3–4 × 1.8–2.9 mm		16 Cuscuta dentatasquamata
14 (1)	Bracts at bases of flower clusters, pedicels, and/or flowers (or on pedicels) 2–11; calyces divided to base or nearly so.		(15)
+	Bracts at bases of flower clusters 1(–3), at bases of pedicels and/or flowers (0 or)1(–3); calyces divided 2/5–2/3 length.		(18)
15 (14)	Pedicels 2–5 mm; inflorescences loose, paniculiform		15 Cuscuta cuspidata
+	Pedicels 0–1 mm; inflorescences glomerulate, ropelike, or spiciform.		(16)
16 (15)	Inflorescences dense, ropelike, spiraling around and closely appressed to host stem, individual flower clusters not discernible; bracts narrowly triangular to lanceolate, apex recurved		21 Cuscuta glomerata
+	Inflorescences dense to loose, glomerulate or spiciform, not ropelike, individual flower clusters discernible; bracts ovate-orbiculate to ovate-triangular, apex erect.		(17)
17 (16)	Calyx lobes orbiculate, apices rounded; corolla lobe apices obtuse; seeds 1.9–2.5 × 1.7–2.3 mm		13 Cuscuta compacta
+	Calyx lobes ovate, apices acute to cuspidate; corolla lobe apices usually acute, sometimes cuspidate; seeds 1.5–1.7 × 1.1–1.3 mm		42 Cuscuta squamata
18 (14)	Infrastaminal scales absent.		(19)
+	Infrastaminal scales present.		(22)
19 (18)	Corolla lobes ovate-triangular, 1/3–1/2 tube length, apices inflexed		26 Cuscuta jepsonii
+	Corolla lobes narrowly lanceolate to lanceolate, shorter than, equaling, or longer than tube, apices straight.		(20)
20 (19)	Styles 0.5–1(–1.5) mm; anthers 0.2–0.5 mm; capsules surrounded by, not completely enclosed by, withered corolla (capsule top visible)		33 Cuscuta occidentalis
+	Styles 1.2–3 mm; anthers 0.6–1.1 mm; capsules surrounded by, sometimes also capped by, withered corolla (capsule top not or barely visible).		(21)
21 (20)	Calyces 1/4–1/2 corolla tube length; corolla lobes shorter than or equaling tube; stamen filaments 0.3–0.6 mm		8 Cuscuta brachycalyx
+	Calyces 3/4 to equaling corolla tube length; corolla lobes equaling or longer than tube; stamen filaments 0.6–1.1 mm		9 Cuscuta californica
22 (18)	Infrastaminal scales relatively poorly developed, apically irregularly denticulate, or 2-fid with 1–3 fimbriae on each side of filament attachment, or 2-fid with denticulate wings.		(23)
+	Infrastaminal scales well developed, notably fimbriate.		(26)
23 (22)	Calyx lobes each with a hornlike appendage 0.5–0.7 mm		49 Cuscuta warneri
+	Calyx lobes without hornlike appendages.		(24)
24 (23)	Calyx lobe apices obtuse to rounded		38 Cuscuta polygonorum (in part)
+	Calyx lobe apices acute to long-attenuate.		(25)
25 (24)	Flowers fleshy; corolla lobe apices acute, inflexed; styles 0.7–1.8 mm, usually equaling, sometimes longer than, ovary; capsules not translucent, interstylar aperture relatively large; 50–1200 m, not California, Oregon, Washington		14 Cuscuta coryli
+	Flowers membranous; corolla lobe apices lance-attenuate, straight; styles 0.3–0.7 mm, 1/4 ovary length; capsules translucent, interstylar aperture relatively small; 1500–2600 m, California, Oregon, Washington		45 Cuscuta suksdorfii
26 (22)	Calyx and corolla lobe apices dissimilar: calyx lobe apices obtuse, rounded, or subacute; corolla lobe apices usually acuminate, acute, or subacute, sometimes cuspidate, mucronate, or truncate, usually inflexed (± cucullate in C. draconella).		(27)
+	Calyx and corolla lobe apices similar: calyx lobe apices either: 1) usually acuminate, acute, long-attenuate, and rarely cuspidate (C. subinclusa) or subacute, or 2) usually obtuse to rounded; corolla lobe apices acuminate, acute, long-attenuate, cuspidate (C. pacifica and C. salina), obtuse, or rounded, usually straight, rarely inflexed (C. indecora) or recurved (C. howelliana).		(35)
27 (26)	Calyces 1/2–3/4 corolla tube length; corolla lobes 1/2 tube length		43 Cuscuta suaveolens
+	Calyces usually equaling corolla tube length, sometimes shorter (C. runyonii); corolla lobes equaling or longer than tube.		(28)
28 (27)	Flowers (3 or)4(or 5)-merous.		(29)
+	Flowers (4 or)5-merous.		(30)
29 (28)	Calyces angled, lobe bases overlapping, midvein ± carinate; capsules globose to ovoid; seeds 1 or 2		23 Cuscuta harperi
+	Calyces not angled, lobe bases not overlapping, midvein not carinate; capsules depressed-globose; seeds 3 or 4		38 Cuscuta polygonorum (in part)
30 (28)	Calyx lobe midveins with multicellular protuberances.		(31)
+	Calyx lobe midveins without multicellular protuberances.		(32)
31 (30)	Calyces ± angled, lobe bases overlapping		18 Cuscuta draconella
+	Calyces not angled, lobe bases not overlapping		40 Cuscuta runyonii
32 (32)	Calyces angled, lobes broadly ovate to rhombic, bases auriculate, overlapping; flowers 1.4–2.5 mm; corolla tubes 0.7–1.2 mm; anthers 0.2–0.3 mm 36. Cuscuta pentagona		(32)
+	Calyces not angled, lobes ovate-triangular to triangular, not auricu­late, bases overlapping or not; flowers 1.9–4.6(–5) mm; corolla tubes 1.1–2.5 mm; anthers (0.3–)0.4–0.7 mm.		(33)
33 (32)	Calyx lobe bases overlapping; capsules to 1/3 enveloped by withered corolla		10 Cuscuta campestris
+	Calyx lobe bases not or slightly overlapping; capsules 1/2+ enveloped by withered corolla.		(34)
34 (33)	Perianths papillate (sometimes not obvious in calyx); corollas drying reddish brown to yellow, tube cam­panulate, later globose, saccate between lines of stamen attachments; infrastaminal scales equaling or longer than corolla tube		20 Cuscuta glabrior
+	Perianths not papillate; corollas drying creamy white, tube narrowly campanulate to cylindro-campanulate, not saccate between lines of stamen attachments; infra­staminal scales 3/4–4/5 corolla tube length		37 Cuscuta plattensis
35 (26)	Calyx lobe apices obtuse to rounded; corolla lobe apices obtuse to rounded.		(36)
+	Calyx lobe apices usually acuminate, acute, or long-attenuate, rarely cuspidate (C. subinclusa); corolla lobe apices usually acuminate, acute, or long-attenuate, sometimes cuspidate (C. pacifica and C. salina).		(41)
36 (35)	Calyces straw yellow, reticulate, shiny, lobe margins denticulate; seeds 1, globose to globose-ovoid		17 Cuscuta denticulata
+	Calyces yellow-brown or brownish, not or finely reticulate, or not or slightly shiny, lobe margins usually entire, sometimes serrulate; seeds (1 or)2–4, ± angled, ellipsoid, obcompressed, oblong, obovoid, ovoid, or subglobose.		(37)
37 (36)	Flowers (3 or)4(or 5)-merous		11 Cuscuta cephalanthi
+	Flowers (4 or)5-merous.		(38)
38 (37)	Calyces equaling corolla tube length; capsules depressed-globose, not raised or thickened around interstylar aperture		32 Cuscuta obtusiflora
+	Calyces usually 1/3–1/2 corolla tube length, sometimes equaling corolla tube (C. gronovii var. latiflora); capsules conic-globose, ovoid, or subobpyri­form, raised and thickened around interstylar aperture.		(39)
39 (38)	Flowers 4–6(–7) mm; capsules broadly ovoid (with stout beak 1–1.5 mm)		39 Cuscuta rostrata
+	Flowers 2–4(–4.4) mm; capsules conic-globose, ovoid, or subob­pyriform (rarely apically narrowed into a neck to 1 mm).		(40)
40 (39)	Infrastaminal scales equaling corolla tube; styles (0.6–)1.2–2.2 mm; capsules 2.5–4.5(–5.2) mm		22 Cuscuta gronovii
+	Infrastaminal scales (1/3)–1/2 corolla tube length; styles 0.3–0.9 mm; capsules 3.5–6.5(–7) mm		48 Cuscuta umbrosa
41 (35)	Flowers fleshy; corolla lobe apices inflexed		25 Cuscuta indecora
+	Flowers membranous or base of perianth and receptacle fleshy (C. nevadensis); corolla lobe apices usually straight, rarely recurved (C. howelliana).		(42)
42 (41)	Flowers 5–7(–9) mm; calyces 1/2 corolla tube length; corolla lobes 1/4–1/3 tube length; anthers 0.8–2 mm		44 Cuscuta subinclusa
+	Flowers (2.5–)2.8–5(–6) mm; calyces equaling or longer than corolla tube; corolla lobes equaling or longer than tube; anthers 0.3–0.8 mm.		(43)
43 (42)	Infrastaminal scales equaling corolla tube; embryo bases globose-enlarged		31 Cuscuta nevadensis
+	Infrastaminal scales 1/2–2/3(–4/5) corolla tube length; embryo bases not globose-enlarged.		(44)
44 (43)	Flowers embedded in inflorescence of host, 4(or 5)-merous; calyx lobe apices acuminate to long-attenuate; capsules depressed-globose to globose		24 Cuscuta howelliana
+	Flowers not embedded in inflorescence of host, 5-merous; calyx lobe apices acuminate to acute; capsules ellipsoid-ovoid or ovoid.		(45)
45 (44)	Inflorescences subglomerulate to umbelliform; pedicels 0.5–2 mm; flowers 3.5–6 mm; corolla tubes campanulate, lobes broadly ovate to rhombic-ovate; infrastaminal scales 1/2–3/4 corolla tube length; coastal salt marshes and tidal flats, coastal interdune depressions and grasslands		35 Cuscuta pacifica
+	Inflorescences corymbiform; pedicels (0.5–)1–5 mm; flowers 2.5–4.5 mm; corolla tubes ± cylindric-campanulate to obconic, lobes lance-oblong to lance-ovate; infrastaminal scales 4/5 corolla tube length; inland salt flats		41 Cuscuta salina