1	Pollen tetrads contained loosely on a spatulate translator with basal corpusculum; filaments free.		(2)
+	Pollen granular, united into pollinia attached to a retinaculum through a caudicle; filaments connate into a gynostegium.		(7)
2 (1)	Corolla tube well developed; corona lobes free from stamens.		(3)
+	Corolla tube very short so that stamens are inserted very close to corona.		(4)
3 (2)	Flower buds conical-ovoid, apex obtuse; corona inserted at throat of corolla tube, lobes obovate, apex apiculate; pollen in 2 masses in each anther locule		1 Gymnanthera
+	Flower buds cylindric-lanceolate, apex caudate-lanceolate; corona inserted at middle of corolla tube, lobes ovate or linear, apex obtuse; pollen in a single mass in each anther locule		2 Cryptolepis
4 (2)	Corona lobes ovate, shorter than anthers		6 Stelmocrypton
+	Corona lobes subulate or threadlike, longer than anthers.		(5)
5 (4)	Corona lobes 3-fid, central segment threadlike, lateral segments broad, flaplike; anthers abaxially pilose		5 Periploca
+	Corona lobes entire; anthers glabrous.		(6)
6 (5)	Follicles not winged, densely tomentose; interpetiolar line inconspicuous; inflorescences solitary at nodes, obconical, top rounded to flat; cymules racemelike		3 Streptocaulon
+	Follicles with ca. 20 prominent papery wings, glabrous; interpetiolar line conspicuous, lobed; inflorescences normally paired at nodes, conical with well-defined main rachis, lax, top pointed; cymules forked		4 Myriopteron
7 (1)	Pollinaria each with 4 pollinia, fixed on a very small, sessile, pale retinaculum.		(8)
+	Pollinaria each with 2 pollinia, fixed on a stipitate, dark reddish retinaculum.		(11)
8 (7)	Anthers without a membranous apical appendage.		(9)
+	Anthers with a membranous apical appendage.		(10)
9 (8)	Corona deeply 5-lobed, lobes erect, acuminate or acute at apex, usually longer than stamens; inflorescences, and often rest of plant, with dark brown pilose hairs		7 Toxocarpus
+	Corona shallowly 5-lobed, lobes revolute, rounded at apex, as long as stamens; plant glabrous to pale puberulent		8 Goniostemma
10 (8)	Corolla lobes villous inside; corona lobes triangular		9 Genianthus
+	Corolla lobes glabrous inside; corona lobes falcate		10 Secamone
11 (7)	Plants always growing on trees or rock surfaces, often by means of adventitious roots; inflorescences flowering over long period and eventually developing a cylindric rachis covered with close-set pedicel scars; leaves mostly fleshy, rarely leathery to membranous.		(12)
+	Plants usually rooted in the ground; inflorescences various, rarely developing cylindric rachis covered with close-set pedicel scars; leaves membranous to leathery.		(14)
12 (11)	Leaves cuneate, apex truncate to shallowly retuse; corolla lobes overlapping to left; stigma head long beaked, longer than anther appendages		24 Micholitzia
+	Leaves linear to orbicular or obovate, apex rounded to long acuminate, very rarely truncate to retuse; corolla lobes valvate; stigma head discoid, 5-angled, shorter than anther appendages.		(13)
13 (12)	Corolla rotate or reflexed, conspicuous; corona lobes fleshy, stellately spreading, glossy when dried		25 Hoya
+	Corolla ovoid-urceolate, minute and inconspicuous; corona lobes not very fleshy, erect, not glossy when dried		26 Dischidia
14 (11)	Anthers without apical appendages or, if appendages present, inconspicuous and lacking membranous margin; pollinia with prominent translucent margin.		(15)
+	Anthers with apical appendages, these with conspicuous membranous margin; pollinia without prominent translucent margin.		(18)
15 (14)	Corolla tubular with a swollen base and funnelform limb, lobes erect, usually coherent at apex		44 Ceropegia
+	Corolla shortly campanulate to subrotate, lobes stellately spreading or incurved.		(16)
16 (15)	Corona apparently represented by 5 denticulate scales inserted on corolla tube alternating with corolla lobes, no corona associated with gynostegium; plant always growing in close association with flowing water		41 Pentasachme
+	Corolla tube without scales or appendages, corona inserted at base of gynostegium or on anthers; plants growing in relatively dry situations.		(17)
17 (16)	Erect herbs with tuberous rootstock; latex clear or translucent; corona apparently double: outer lobes erect, usually 2-toothed or lobed, inner lobes incumbent over anthers		43 Brachystelma
+	Twining, often robust, herbs; latex white; corona simple, with lobes flat on corolla, apex acute or rounded, inner lobes very short and inconspicuous		42 Heterostemma
18 (14)	Corona double: an outer whorl inserted at base of corolla and an inner whorl inserted on gynostegium or back of anthers.		(19)
+	Corona single, inserted on corolla tube, gynostegium, or back of anthers, sometimes very reduced to virtually absent.		(20)
19 (18)	Stems slender and herbaceous when young; leaves well developed, persistent; corolla bowl-shaped, 2-3 cm in diam.		11 Oxystelma
+	Stems succulent; leaves reduced to scales, short lived so plant is often leafless; corolla rotate or nearly so, deeply lobed, less than 1 cm in diam.		12 Sarcostemma
20 (18)	Erect herbs, shrubs, or small trees, always with self-supporting stems.		(21)
+	Climbing or prostrate herbs.		(25)
21 (20)	Corona lobes inserted on backs of anthers; pollinia erect or horizontal		39 Tylophora
+	Corona lobes inserted at base of gynostegium; pollinia pendulous.		(22)
22 (21)	Plants slender herbs, sometimes tending to twine at tip; corona membranous and cupular to cylindric, or if deeply 5-lobed, lobes always joined laterally at base, fleshy, simple except sometimes for adaxial appendage		18 Cynanchum
+	Plants robust herbs to small trees; corona of 5 free, fleshy, often elaborate lobes.		(23)
23 (22)	Leaves ovate to obovate, often oblong, 7- 30 × 3-15 cm, with cordate to amplexicaul base; corona lobes each with an upcurved dorsal spur at base		13 Calotropis
+	Leaves lanceolate, 5-15 × 0.5-4 cm, with cuneate to tapering base; corona lobes without spur at base.		(24)
24 (23)	Flowers erect; corolla red or purple; corona bright red or yellow; follicles smooth, 1-1.5 cm thick		14 Asclepias
+	Flowers pendent; corolla whitish; corona purplish; follicles with soft spines or bristles, 2.5-5 cm thick		15 Gomphocarpus
25 (20)	Corona lobes absent or reduced to separate scales at base of gynostegium, corolla tube sometimes with apparent corona.		(26)
+	Corona lobes well developed or corona forming a continuous ring around base of gynostegium.		(30)
26 (25)	Sepals leaflike, ca. 26 × 8 mm; corolla tube ca. 5 cm		32 Jasminanthes
+	Sepals up to 7 mm; corolla tube up to 1 cm.		(27)
27 (26)	Corolla tube with 5 longitudinal ridges sometimes produced into fleshy lobes and/or with lines of stiff hairs along each side		29 Gymnema
+	Corolla tube without fleshy lobes or lines of hairs.		(28)
28 (27)	Corolla lobes shorter than tube; stigma head club-shaped, exserted beyond anther appendages		17 Adelostemma
+	Corolla lobes as long as or longer than tube; stigma head rounded or conical, not exserted beyond anther appendages.		(29)
29 (28)	Corolla campanulate; corona lobes opposite anthers; pollinia erect		30 Gongronema
+	Corolla very shallowly bowl-shaped, almost rotate; corona lobes alternate with anthers; pollinia pendulous		22 Sichuania
30 (25)	Apex of corolla lobes abruptly narrowed into a long tail; anthers thread-like at apex; stems with very conspicuous long reddish brown hairs; inflorescences racemelike with fleshy rachis obviously thicker than peduncle		27 Dolichopetalum
+	Apex of corolla lobes obtuse or acuminate; anthers rounded at apex; stems without conspicuous reddish brown hairs; inflorescences various but never with fleshy rachis.		(31)
31 (30)	Corona inserted around base of gynostegium; pollinia nearly always pendulous (horizontal in Tylophora).		(32)
+	Corona lobes inserted on backs of anthers or gynostegium; pollinia erect or horizontal.		(38)
32 (31)	Stigma head elongated or beaked, exserted well beyond anther appendages		16 Metaplexis
+	Stigma head disclike, lower than membranous anther appendages.		(33)
33 (32)	Flowers 2-4 cm in diam.; fruit thick walled.		(34)
+	Flowers 0.4-1.2(-2) cm in diam.; fruit thin walled.		(36)
34 (33)	Leaf blade pinnately veined, base rounded to cuneate, axils often with reduced stipulelike leaves		23 Graphistemma
+	Leaf blade palmately to pedately 3-5-veined, base cordate, reduced stipulelike leaves absent.		(35)
35 (34)	Corolla tube campanulate; corona lobes linear-subulate, erect, longer than gynostegium; calyx glandular inside		20 Raphistemma
+	Corolla subrotate; corona forming a low, entire or undulate, fleshy ring around base of gynostegium; calyx not glandular inside		21 Holostemma
36 (33)	Corona much shorter than anthers, ringlike or shallowly cupular, entire, undulate, or deeply 5-notched, without adaxial appendages; corolla often urceolate or campanulate; leaves linear to narrowly elliptic, adaxially often with minute, raised pale dots		19 Biondia
+	Corona well developed, deeply lobed and fleshy and/or with adaxial appendages, sometimes cupular to tubular and membranous, tube apex and throat often with 5-10 teeth, sometimes threadlike, rarely shorter than anthers and then membranous; corolla usually deeply divided, tube usually very shallow, rarely campanulate and then stems erect; leaves very variable in form, adaxially never with raised pale dots.		(37)
37 (36)	Corona lobes circular to almost square, laterally contiguous to form a cup, with narrow inflexed tips; pollinia horizontal		39 Tylophora
+	Corona not as above; pollinia pendulous		18 Cynanchum
38 (31)	Corolla lobes strongly inflexed in bud, oblong, obviously curved to right at anthesis		40 Lygisma
+	Corolla lobes not inflexed in bud, ovate, straight.		(39)
39 (38)	Corolla salverform, urceolate, or campanulate.		(40)
+	Corolla rotate to shallowly bowl-shaped.		(43)
40 (39)	Corona inconspicuous to virtually absent; corolla 1.4-8.5 cm, salverform, inside of tube with 5 longitudinal lines of hairs		32 Jasminanthes
+	Corona conspicuous; corolla usually less than 1.4 cm, if more and salverform then inside of tube uniformly hairy or glabrous.		(41)
41 (40)	Corona lobes with inner appendages often longer than lobe proper and/or lobed or toothed, smooth toward base; corolla always salverform		31 Telosma
+	Corona lobes simple at tips, often ridged or grooved toward base; corolla campanulate to urceolate, rarely almost salverform (Marsdeniastenantha).		(42)
42 (41)	Corona lobes with back produced into a conspicuous longitudinal wing; corolla lobes with thickenings at base		34 Dischidanthus
+	Corona lobes with backs convex or shallowly ridged; corolla lobes without any thickening at base		33 Marsdenia
43 (39)	Corona lobes flattened on back, membranous		28 Cosmostigma
+	Corona lobes fleshy, hooked, spurred, horned, falcate, or turgid, or processes stellately spreading or erect.		(44)
44 (43)	Outer angle of corona lobes produced into curved, stellately spreading, acute, relatively slender horn		36 Belostemma
+	Outer angle of corona lobes rounded or 2-ribbed, if spreading then swollen and rounded.		(45)
45 (44)	Corona lobes as high as anthers and with interior angle forming an acute tooth incumbent on top of the anthers; inflorescences long pedunculate umbel-like clusters of cymules; follicles often with longitudinal or transverse ridges or wings		35 Dregea
+	Corona lobes shorter than anthers, tip incumbent on lower part of anther or on filament; inflorescences with a conspicuously elongated, often branched rachis, rarely condensed and umbel-like and then short pedunculate; follicles always smooth.		(46)
46 (45)	Corona lobes each with a pair of longitudinal wings on back		38 Pentastelma
+	Corona lobes ovoid, rounded on back.		(47)
47 (46)	Inflorescence rachis fleshy, bracts ovate, ca. 1 mm; corolla lobes ca. 4 mm wide; follicles with a thick, fibrous mesocarp		37 Merrillanthus
+	Inflorescence rachis slender, bracts linear-lanceolate, 1.5-2 mm; corolla lobes 1-3 mm wide; follicles with a thin mesocarp		39 Tylophora