Key 1

1	Plants parasitic, leafless, with haustoria; flowers in clusters or short racemes; corolla inside usually with 5 fimbriate scales opposite sepals		20 Cuscuta
+	Plants not parasitic, with green leaves; flowers and corolla not as above (scales present in Lepistemon but flowers in ± umbellate cymes).		(2)
2 (1)	Pollen pantoporate, finely spiny.		(3)
+	Pollen grains with various aperture types, never finely spiny.		(7)
3 (2)	Fruit dehiscing by 4 (or more) valves, sometimes tardily so.		(4)
+	Fruit indehiscent, or at length eroding or irregularly breaking open.		(5)
4 (3)	Corolla urceolate; filaments dilated basally into a concave scale, scales arched over ovary		16 Lepistemon
+	Corolla campanulate, funnelform, or salverform; filaments basally pubescent or glandular, not forming scales		15 Ipomoea
5 (3)	Calyx greatly enlarged, completely enclosing fruit; leaves (and often sepals and corolla lobes) with minute blackish glandular dots abaxially; fruit wall at length eroding between septa, lantern-shaped		19 Stictocardia
+	Calyx enlarged, either reflexed from fruit or not fully enclosing it; leaves (and sepals and corolla lobes) without blackish dots; fruit an indehiscent or irregularly shattering berry.		(6)
6 (5)	Flowers few to many in cymes or capitula; corolla mostly membranous or transparent, limb spreading to recurved, subentire, 5-lobed to deeply 5-parted; twining or trailing herbs, scandent shrubs, or lianas; sepals usually reflexed from fruit, often colored adaxially		18 Argyreia
+	Flowers solitary, nodding; corolla waxy, limb erect, subentire or shallowly 5-dentate; slender woody twiners (in China); sepals ± enclosing fruit		17 Blinkworthia
7 (2)	Ovary deeply 2-lobed; styles 2, gynobasic		1 Dichondra
+	Ovary not deeply 2-lobed; styles, if present, terminal.		(8)
8 (7)	Styles absent; stigma 1, ± conical, 5-10-ridged; corolla deeply 5-lobed, each lobe 2-lobulate apically		4 Erycibe
+	Styles present, sometimes very short; neither stigma nor corolla as above.		(9)
9 (8)	Outer 2 or 3 or all 5 sepals much enlarged in fruit and falling off with fruit as a dispersal unit; fruit indehiscent; seeds 1.		(10)
+	Sepals enlarged in fruit or not, remaining attached to pedicel when fruit dehisces; fruit dehiscent by valves or breaking irregularly; seeds usually 4 (or less by abortion).		(12)
10 (9)	Herbaceous twiners; corolla glabrous outside or lobes with a minute apical tuft of hairs; all 5 sepals ± equally elongated in fruit or inner sepals slightly less so		7 Dinetus
+	Woody climbers; corolla pubescent outside on midpetaline bands; outer 2 or 3 sepals greatly elongated in fruit, inner sepals much less so.		(11)
11 (10)	Flowers mostly less than 8 mm, white, in ± crowded panicles; bracteoles minute, scalelike; fruiting sepals with a single midvein and reticulate secondary veins		5 Poranopsis
+	Flowers 10-35(-50) mm, blue, violet, or white, in racemes or few-branched panicles; bracteoles sepal-like, forming a secondary calyx (calycle) immediately below calyx; fruiting sepals with 7, 9, or 11 parallel longitudinal veins		6 Tridynamia
12 (9)	Styles 2, free or united basally.		(13)
+	Style 1, entire or with 2 minute branches concealed by stigmas.		(14)
13 (12)	Plants erect or sprawling, never twining; bracts tiny, not enlarged in fruit; styles 2-cleft; stigmas terete, filiform or slightly clavate		2 Evolvulus
+	Plants climbing; 1 bract greatly enlarged, winglike in fruit; styles entire; stigmas peltate or reniform, rather deeply lobed		3 Neuropeltis
14 (12)	Stigmas ± globular; calyx enlarged in fruit, often enclosing it.		(15)
+	Stigmas elliptic, ovate-oblong, oblong, ovate, or linear, usually ± flattened; calyx not enlarged in fruit or outer 3 sepals somewhat enlarged, inner sepals less so.		(17)
15 (14)	Herbs prostrate; leaves linear, oblong-linear, lanceolate-elliptic, or oblanceolate to spatulate, base hastate, ± clasping stem; inner 3 sepals tapering into slender points apically; pollen pantoporate		13 Xenostegia
+	Herbs twining or woody climbers (sometimes prostrate); leaves variously shaped, usually wider, bases rarely clasping (except some Merremia hirta); inner sepals tapering into slender points apically; pollen colpate or rugate.		(16)
16 (15)	Stems terete or striate, not winged; fruit a 4-valved capsule or shattering irregularly		12 Merremia
+	Stems (and often petioles, peduncles) winged; fruit with a thickened circumscissile lid that separates from ± papery and tardily shattering endocarp		14 Operculina
17 (14)	Bracts or bracteoles prominent, sepal-like or leaflike, persistent in fruit.		(18)
+	Bracts inconspicuous, scalelike, linear or subulate, deciduous or persistent in fruit.		(19)
18 (17)	Corolla pale yellow or whitish, center purple; bracts oblong-lanceolate, attached visibly below calyx; capsule pilose		8 Hewittia
+	Corolla pinkish, lavender, or white, center often paler; bracteoles sepal-like, broadly ovate or elliptic, attached just below and closely enclosing calyx; capsule glabrous		10 Calystegia
19 (17)	Stigmas linear or clavate; hairs 2-armed or simple; pollen ellipsoid, 3-colpate		11 Convolvulus
+	Stigmas elliptic or oblong; hairs stellate (3- or more armed); pollen globose, usually 5-zonocolpate		9 Jacquemontia