1	Erect herbs, sometimes uppermost parts tending to twine.		(2)
+	Twining climbers.		(23)
2 (1)	Corona tube cupular to tubular, at least as long as gynostegium, membranous, longitudinally pleated, white or near white.		(3)
+	Corona usually deeply lobed, lobes fleshy, tube (when present) usually much shorter than gynostegium (well developed in C. bicampanulatum), not longitudinally pleated nor grooved, variously colored.		(4)
3 (2)	Flowers produced after leaves are fully developed; corolla green-white; corona tube as high as gynostegium, marginal lobes linear-triangular; inner appendages well developed, as long as corona lobes; base of leaf blade cordate to truncate		2 Cynanchum anthonyanum
+	Flowers produced before leaves are fully developed; corolla purple; corona tube much higher than gynostegium, marginal lobes very short; inner appendages absent; base of leaf blade rounded to narrowly cuneate		3 Cynanchum purpureum
4 (2)	Leaf blade ovate, broadly ovate, ovate-oblong, or broadly elliptic.		(5)
+	Leaf blade linear to narrowly elliptic or lanceolate.		(14)
5 (4)	Leaves (at least lower on stem) amplexicaul; stems and leaves glabrous or nearly so; inflorescences pedunculate		31 Cynanchum amplexicaule
+	Leaves not amplexicaul; stems and leaves often hairy and/or inflorescences sessile.		(6)
6 (5)	Inner surface of corolla lobes and/or tube hairy.		(7)
+	Inner surface of corolla glabrous, rarely a few hairs inside tube.		(9)
7 (6)	Corolla lobes erect, slender but with a blunt apex; corolla glabrous except for conspicuously woolly tube		37 Cynanchum rockii
+	Corolla lobes rotate, ovate; corolla indumentum variable but never with a conspicuously woolly tube.		(8)
8 (7)	Stems flexuous; leaves glaucous, leathery; corona lobes broadly ovate, broader than long		33 Cynanchum canescens
+	Stems erect; leaves green, thin papery; corona lobes triangular-ovate, longer than broad		35 Cynanchum forrestii
9 (6)	Corolla campanulate, tube as long as lobes, lobes apparently erect; corona tube as long as anthers, adnate to anthers and corolla		36 Cynanchum bicampanulatum
+	Corolla reflexed to shallowly bowl-shaped with spreading lobes; corona tube much shorter than anthers, not adnate to corolla.		(10)
10 (9)	Corona lobes lanceolate, subacute, clearly higher than gynostegium, each lobe with a well-developed inner appendage incumbent on anther; leaf margin shallowly undulate		26 Cynanchum lysimachioides
+	Corona lobes rounded, not higher than gynostegium, inner appendages not incumbent on anther or absent; leaf margin not undulate.		(11)
11 (10)	Leaves uniformly densely pubescent on both surfaces; corolla deep purple; inflorescences mostly sessile		32 Cynanchum atratum
+	Leaves pubescent to puberulent on veins only at least on adaxial surface; corolla dull yellow or white; inflorescences pedunculate.		(12)
12 (11)	Corolla up to 1 cm in diam.; peduncles not longer than leaves		34 Cynanchum inamoenum
+	Corolla 1.2-1.8 cm in diam.; peduncles longer than upper leaves; stems sometimes tending to twine at tip, leaves sometimes whorled.		(13)
13 (12)	Corolla lobes ca. 3 mm wide; leaves abaxially puberulent on veins only		47 Cynanchum acuminatifolium
+	Corolla lobes 1.2-1.5 mm wide; leaves abaxially densely uniformly puberulent		48 Cynanchum pingshanicum
14 (4)	Most parts of plant densely puberulent, rarely leaves glabrous; corona with short but distinct tube and inflexed linear-oblong lobes		1 Cynanchum thesioides
+	At least some parts of plant sparsely pubescent to glabrous; corona divided to near base, with ill-defined tube and triangular-ovate, fleshy lobes.		(15)
15 (14)	Inflorescences strictly lateral, longer than leaves; leaves 1-2 mm wide; corolla lobes oblong-lanceolate; corona deeply 5-lobed		39 Cynanchum wangii
+	Inflorescences terminal and from upper nodes or, if strictly lateral, shorter than leaves; leaves 5-15 mm wide; corolla lobes ovate or ovate-oblong.		(16)
16 (15)	Peduncles 2.5-4 cm, often subterminal, longer than uppermost leaves; leaf blade with lateral veins ca. 8 pairs; corona lobes laterally compressed		38 Cynanchum paniculatum
+	Peduncles less than 2 cm, much shorter than leaves; leaf blade with lateral veins obscure or up to 6 pairs; corona lobes dorsiventrally compressed.		(17)
17 (16)	Leaves leathery, glabrous, glaucous.		(18)
+	Leaves membranous to thin papery, often hairy.		(19)
18 (17)	Stems glabrous; corolla dark red		40 Cynanchum mongolicum
+	Stems pubescent; corolla yellow		41 Cynanchum glaucescens
19 (17)	Corolla hairy inside; lateral leaf veins ca. 6 pairs.		(20)
+	Corolla glabrous; lateral leaf veins obscure or up to 4 pairs.		(21)
20 (19)	Leaves always paired, veins glabrous; inflorescences racemelike, slender		46 Cynanchum stauntonii
+	Leaves often whorled, veins puberulent; inflorescences umbel-like		43 Cynanchum hydrophilum
21 (19)	Corona lobes adnate dorsally to corolla; inflorescences raceme-like		42 Cynanchum stenophyllum
+	Corona lobes free from corolla; leaves often whorled; inflorescences umbel-like.		(22)
22 (21)	Stems glabrous; leaves 2-9 mm wide		45 Cynanchum riparium
+	Stems pubescent; leaves 7-15 mm wide		44 Cynanchum verticillatum
23 (1)	Fruit winged or setose.		(24)
+	Fruit not ornamented (not known for several species).		(25)
24 (23)	Fruit densely and conspicuously setose, not winged		15 Cynanchum corymbosum
+	Fruit smooth, longitudinally winged		19 Cynanchum callialatum
25 (23)	Corona without inner free-tipped appendages, interior sometimes with longitudinal folds or wings.		(26)
+	Corona with appendages inside, these free at apex.		(45)
26 (25)	Stems uniformly pubescent, sometimes densely so, basal part often not twining, erect.		(27)
+	Stems glabrescent or pubescent along 1 or 2 lines only.		(31)
27 (26)	Leaves linear to lanceolate, up to 2.3 cm wide, usually much less, adaxially with tiny pale dots		1 Cynanchum thesioides
+	Leaves narrowly elliptic to ovate, 2.5-10 cm wide, adaxially without dots.		(28)
28 (27)	Lower part of stem erect, only upper part twining.		(29)
+	Stems twining throughout.		(30)
29 (28)	Base of leaf blade rounded or subcordate; pedicel up to 5 mm		50 Cynanchum versicolor
+	Base of leaf blade cuneate; pedicel 1-2 cm		52 Cynanchum taihangense
30 (28)	Pedicel 15-22 mm; corolla lobes ovate; 5-5.5 × ca. 3 mm; sepals glabrous		53 Cynanchum linearisepalum
+	Pedicel 5-13 mm; corolla lobes oblong, ca. 10 × 2.5 mm; sepals pubescent		54 Cynanchum mooreanum
31 (26)	Corona fleshy, often deeply lobed; leaves concolorous, abaxial surface at most only slightly paler.		(32)
+	Corona membranous, cupular, often with marginal lobes shorter than tube; leaves often discolorous with abaxial surface much paler.		(36)
32 (31)	Leaf blade linear, 0.5-1 cm wide; corona shallowly lobed, shorter than anthers		49 Cynanchum biondioides
+	desc needed
33	Stems with basal part erect; leaf blade broadly elliptic to ovate, 4-15 cm wide, base cuneate		51 Cynanchum chekiangense
+	Stems always twining from base; leaf blade lanceolate or narrowly oblong, 1.5-5 cm wide, base shallowly cordate to rounded.		(34)
34 (33)	Corolla purple or purple-red		55 Cynanchum sublanceolatum
+	Corolla white or yellow-white.		(35)
35 (34)	Lateral leaf veins 4-6 pairs; corolla ca. 7 mm in diam., oblong, glabrous		56 Cynanchum fordii
+	Lateral leaf veins 7-10 pairs; corolla 12-15 mm in diam., lobes lanceolate, pubescent inside		57 Cynanchum volubile
36 (31)	Corolla lobes hairy; corona tube shorter than prominent lobes.		(37)
+	Corolla lobes glabrous; corona tube longer than lobes, lobes sometimes rounded teeth.		(39)
37 (36)	Corolla lobes ca. 10 mm; corona cupular, ca. 1 mm high, with 5 triangular marginal lobes to 3 mm high		16 Cynanchum megalanthum
+	Corolla lobes 2-5 mm; corona tube absent, lobes well developed, narrower at base.		(38)
38 (37)	Leaf blade ovate or ovate-cordate, apex cuspidate, basal lobes incurved and sometimes overlapping; peduncle ca. 1.5 cm; corona lobes shorter than gynostegium, truncate		22 Cynanchum wilfordii
+	Leaf blade ovate-lanceolate, apex acuminate, basal lobes not incurved; peduncle to 3.5 cm; inflorescences dense, with flowers overlapping when pressed; corona slightly longer than gynostegium, rounded		23 Cynanchum otophyllum
39 (36)	Corona ca. ½ as high as anthers; sepals reflexed at anthesis		10 Cynanchum brevicoronatum
+	Corona at least as high as anthers or only slightly shorter; sepals not reflexed.		(40)
40 (39)	Leaves linear-lanceolate, to 11 × 1.2 cm, base cuneate; corona ca. 2.5 mm high; inflorescences umbel-like		17 Cynanchum kingdonwardii
+	Leaves ovate-oblong, 2-8(-10) cm wide, base cordate; corona ca. 4 mm high; inflorescences racemelike, cymules arranged in regular spiral along rachis.		(41)
41 (40)	Stems pubescent along 1 line, hairs sometimes very sparse, or in 2 obscure lines immediately above node.		(42)
+	Stems pubescent along 2 lines.		(43)
42 (41)	Corolla ca. 3 mm; corona tube lower than anthers, marginal teeth prominent, almost acute		12 Cynanchum duclouxii
+	Corolla 3.5-5 mm; corona tube higher than anthers, marginal teeth low and rounded		14 Cynanchum kintungense
43 (41)	Corolla lobes erect		13 Cynanchum sinoracemosum
+	Corolla lobes rotate to strongly reflexed.		(44)
44 (43)	Inflorescences to 3.5 cm, subsessile		11 Cynanchum wallichii
+	Inflorescences 2.5-7 cm, peduncle 1-5 cm		15 Cynanchum corymbosum
45 (25)	Corona deeply 5-divided, lobes fleshy, tube much shorter than gynostegium to absent, lobes erect or ascending.		(46)
+	Corona distinctly cupular or cylindric, usually obviously membranous, sometimes plicate, tube as long as or longer than gynostegium and/or much longer than marginal lobes.		(52)
46 (45)	Peduncle much longer than pedicel.		(47)
+	Peduncle up to 3(-4) cm, up to 2 × as long as pedicel.		(49)
47 (46)	Corolla strongly reflexed		30 Cynanchum boudieri
+	Corolla rotate.		(48)
48 (47)	Corolla lobes 4.5-5 mm, minutely pubescent		28 Cynanchum officinale
+	Corolla lobes (4.5-)5.5-8(-10) mm, densely pilose or villous		29 Cynanchum auriculatum
49 (46)	Corolla glabrous; leaf blade hastate, hastate-oblong, or narrowly ovate-deltate.		(50)
+	Corolla adaxially puberulent; leaf blade broadly ovate to ovate-oblong.		(51)
50 (49)	Corona shorter than gynostegium, inner appendages ca. as long as lobes; leaf blade 7-14 × 3-8 cm		24 Cynanchum giraldii
+	Corona longer than gynostegium, inner appendages shorter than lobes; leaf blade 3-8 × 1-5 cm		27 Cynanchum bungei
51 (49)	Peduncle 1-2 mm, much shorter than pedicel; base of leaf blade auriculate; corolla purple		25 Cynanchum batangense
+	Peduncle 20-30 mm; about as long as pedicel, base of leaf blade shallowly cordate; corolla white		26 Cynanchum lysimachioides
52 (45)	Leaves pinnately veined, slightly fleshy.		(53)
+	Leaves palmately to pedately 5-7-veined at base, often with enlarged basal lobes.		(55)
53 (52)	Inflorescences simple, umbel-like; peduncle 1-7 mm; leaf base cordate		19 Cynanchum callialatum
+	Inflorescences racemelike, sometimes branched; peduncle 5-30 mm; leaf base rounded to cuneate.		(54)
54 (53)	Leaf blade 2.5-7 cm, apex acute or rounded, rarely subacuminate, blade often leathery		20 Cynanchum formosanum
+	Leaf blade 6-10 cm, apex long acuminate or caudate, blade membranous		21 Cynanchum kwangsiense
55 (52)	Corona lobes or teeth rounded to triangular, often shorter than corona tube, sometimes obsolete.		(56)
+	Corona lobes threadlike to acute triangular, as long as or longer than corona tube.		(59)
56 (55)	Corolla lobes ca. 10 mm		16 Cynanchum megalanthum
+	Corolla lobes up to 5 mm.		(57)
57 (56)	Corolla glabrous; corona appendages reduced to small teeth or ridges; leaf blade ovate-deltate, oblong-hastate, lanceolate, or linear-lanceolate, less than 1.5 cm wide		18 Cynanchum insulanum
+	Corolla hairy; corona appendages well developed, fleshy; leaf blade ovate or ovate-lanceolate, 2-4 cm wide.		(58)
58 (57)	Corona shorter than stigma head, lobes very short, rounded; corolla reflexed		9 Cynanchum decipiens
+	Corona longer than stigma head, lobes triangular, acute; corolla erect to rotate		8 Cynanchum longipedunculatum
59 (55)	Corona lobes longer than corolla; leaves lanceolate or oblong-lanceolate, basal sinus very deep, lobes mostly incurved to overlapping		4 Cynanchum heydei
+	Corona lobes shorter than corolla; leaves ovate, deltate-ovate, hastate, or hastate-cordate, basal sinus shallow or, if deep, lobes parallel or divergent.		(60)
60 (59)	Corolla pubescent inside, lobes lanceolate, 1.5-2 mm wide		5 Cynanchum szechuanense
+	Corolla glabrous inside, lobes oblong or oblong-lanceolate, 1-1.3 mm wide.		(61)
61 (60)	Corolla erect, purple inside; inner corona appendages included in corona tube; leaf blade hastate or hastate-cordate with enlarged basal lobes, apex long acuminate		6 Cynanchum acutum subsp. sibiricum
+	Corolla rigidly rotate to slightly reflexed, white; inner corona appendages nearly as long as main corona lobes; leaf blade broadly triangular-cordate; apex acute to short acuminate		7 Cynanchum chinense