1	Inflorescences very congested, bracts and bracteoles leaflike, hiding rachis and flowers; calyx twice as long as corolla; apex of corolla lobes incised		1 Marsdenia incisa
+	Inflorescences relatively lax, bracts and bracteoles small and not hiding rachis and flowers; calyx much shorter than corolla; apex of corolla lobes entire.		(2)
2 (1)	Stigma head produced into long, threadlike to cylindric beak exserted from anther appendages.		(3)
+	Stigma head depressed, hemispherical or short conical, not long beaked.		(7)
3 (2)	Corona lobes as long as anthers; stems short yellowish tomentose.		(4)
+	Corona lobes shorter than anthers; stems glabrous to minutely puberulent or pubescent along two lines.		(5)
4 (3)	Corolla tube uniformly pilose inside; follicles densely tomentose		10 Marsdenia oreophila
+	Corolla throat with a dense reflexed pubescence, interior of tube glabrous toward base; follicles glabrous		11 Marsdenia officinalis
5 (3)	Corolla tube longer than lobes; peduncle 1.5-3 cm		7 Marsdenia yunnanensis
+	Corolla tube shorter than lobes; peduncle 2.5-6 cm.		(6)
6 (5)	Corolla ca. 12 mm; pollinia reniform		8 Marsdenia griffithii
+	Corolla 5-6 mm; pollinia slender		9 Marsdenia formosana
7 (2)	Corolla tube not longer than lobes.		(8)
+	Corolla tube longer than lobes.		(15)
8 (7)	Corolla lobes 9-12 mm.		(9)
+	Corolla lobes 3-7 mm.		(10)
9 (8)	Leaf blade 5.5-10 cm wide; inflorescences 7-15 cm; corolla interior pubescent; sepals ca. 8 × 6 mm		14 Marsdenia koi
+	Leaf blade 2-3 cm wide; inflorescences 4-4.5 cm; corolla glabrous; sepals 3-4 × 2-2.5 mm		12 Marsdenia medogensis
10 (8)	Base of leaf blade rounded to truncate; inflorescences unbranched.		(11)
+	Base of leaf blade cordate; inflorescences usually obviously branched.		(13)
11 (10)	Plants tomentose; corolla yellowish white, 6-8 mm; back of corona lobes rounded		19 Marsdenia tenii
+	Plants glabrous; corolla violet or purple, 10-15 mm; back of corona lobes winged or with a hooklike spur at base.		(12)
12 (11)	Peduncle to 10 cm; corona lobes as long as anthers, dorsiventrally compressed, with a hooklike dorsal spur at base		2 Marsdenia longipes
+	Peduncle to 3 cm; corona lobes reaching base of anthers, laterally compressed without spur at base		3 Marsdenia brachyloba
13 (10)	Corolla very densely hairy outside; corona lobes exserted from corolla tube, apex 2(-4)-toothed		5 Marsdenia tenacissima
+	Corolla glabrous outside; corona lobes included within corolla tube, apex entire.		(14)
14 (13)	Peduncle to 16 cm; corolla interior pilose; corona lobes shorter than corolla tube		15 Marsdenia hainanensis
+	Peduncle ca. 1.5 cm; corolla interior glabrous; corona lobes longer than corolla tube		13 Marsdenia yuei
15 (7)	Leaf blade palmately 3(-5)-veined at base, base deeply cordate; corona lobes with a hooklike spur at base of back.		(16)
+	Leaf blade pinnately veined; corona lobes flattened or slightly curved at base of back, without a spur.		(17)
16 (15)	Branches, petiole, abaxial leaf surface, and outside of corolla densely pubescent to tomentose; corolla lobes ca. 2 × 1 mm		4 Marsdenia cavaleriei
+	Branches, leaves, and corolla glabrous; corolla lobes 3-4 × 1.5-2 mm		6 Marsdenia stenantha
17 (15)	Corona lobes as long as or longer than anther appendages.		(18)
+	Corona lobes shorter than anther appendages.		(21)
18 (17)	Leaf blade elliptic-oblong or oblong-lanceolate; inflorescences ca. 7 mm; peduncle ca. 0.2 cm; corolla ca. 1.5 mm		20 Marsdenia pseudotinctoria
+	Leaf blade ovate to oblong or ovate-triangular; inflorescences more than 3 cm; peduncle 1-5 cm; corolla 3.5-13 mm.		(19)
19 (18)	Leaf blade 1-2.5 × ca. 1 cm, papillate abaxially; petiole 0.5-1 cm; corolla tube sparsely retrorse pubescent inside; corona ringlike, as high as anthers and with undulating margin		21 Marsdenia pulchella
+	Leaf blade 5-13 × ca. 2.7 cm, not papillate; petiole 1-4 cm; corolla tube with a ring of hairs or densely pubescent at throat; corona of separate subulate to ovate lobes.		(20)
20 (19)	Corolla urceolate, 3.5-4(-6) mm; leaf blade papery, often blue when dry		22 Marsdenia tinctoria
+	Corolla subcampanulate, ca. 9 mm; leaf blade membranous, not blue when dry		23 Marsdenia glomerata
21 (17)	Corolla tube interior uniformly hairy; inflorescences branched; corolla throat densely long hairy; leaves without blue pigment.		(22)
+	Corolla tube interior with hairs restricted to lines or patches; inflorescences unbranched; corolla throat with a thin ring of hairs only; leaves often with blue pigment when dried.		(24)
22 (21)	Leaf blade broadly ovate to suborbicular, approximately as long as wide		16 Marsdenia tomentosa
+	Leaf blade ovate-cordate to oblong, distinctly longer than wide.		(23)
23 (22)	Stems and undersides of leaves finely yellowish tomentose; corolla lobes hairy on both sides		17 Marsdenia sinensis
+	Stems and leaves sparsely hairy when young, glabrescent; corolla lobes glabrous, contrasting sharply with prominently hairy throat		18 Marsdenia lachnostoma
24 (21)	Leaf blade abaxially tomentose; inflorescence rachis 3-7 cm, clearly spiral		24 Marsdenia schneideri
+	Leaf blade abaxially glabrous to puberulent; inflorescence rachis mostly less than 1 cm, if longer then rachis straight.		(25)
25 (24)	Corolla urceolate		25 Marsdenia glabra
+	Corolla campanulate		22 Marsdenia tinctoria