1	"Colleters absent from base of lamina"	2
1	"Colleters present at base of lamina"	5
2	"Lamina narrowly-elliptic to ovate, apex apiculate"	"Vincetoxicum carnosum"
2	"Lamina linear-lanceolate, apex acute"	3
3	"Leaves mostly 10-20 mm long, upright herb; pedicels 1.5-2.5 mm long"	"Vincetoxicum brachystelmoides"
3	"Leaves 20-90mm long, twining vines; pedicels 3-15 mm long"	4
4	"Flowers 6-14 mm diameter; pedicels 7-15 mm long"	"Vincetoxicum lineare"
4	"Flowers 6-7 mm diameter; pedicels 3-5 mm long"	"Vincetoxicum forsteri"
5	"Latex in stems and leaves yellow"	6
5	"Latex in stems and leaves white or clear"	7
6	"Plants erect, with dense yellowish indumentum; leaf lamina lanceolate to lanceolate-ovate"	"Vincetoxicum erectum"
6	"Plants twining, glabrous or with sparse colourless indumentum; leaf lamina ovate to elliptic"	"Vincetoxicum polyanthum"
7	"Latex in stems and leaves white"	8
7	"Latex in stems and leaves clear"	10
8	"Leaves with dense yellow indumentum when young; corolla lobes less than 3 mm long"	"Vincetoxicum cinerascens"
8	"Leaves glabrous or with scattered colourless indumentum; corolla lobes more than 3 mm long"	9
9	"Corolla green or brown; colleters 2"	"Vincetoxicum williamsii"
9	"Corolla cream; colleters 3 or 4"	"Vincetoxicum ovatum"
10	"Leaf lamina purplish below; colleters 7 or 8"	"Vincetoxicum coloratum"
10	"Leaf lamina not purplish below; colleters 2–5"	11
11	"Corolla lobes twisted in bud and at anthesis, lanceolate, attenuate"	"Vincetoxicum paniculatum"
11	"Corolla lobes not twisted, not lanceolate, acute"	12
12	"Corolla lobes 5–6.5 mm long"	13
12	"Corolla lobes 2–4 mm long"	14
13	"Leaf lamina with indumentum; corolla lobes 6–6.5 mm long; staminal corona c. 1.5 mm diameter; corolla red"	"Vincetoxicum grandiflorum"
13	"Leaf lamina glabrous; corolla lobes 5 mm long; staminal corona c. 2.5 mm diameter; corolla pink"	"Vincetoxicum rupicola"
14	"Staminal corona 1–1.5 mm diameter"	"Vincetoxicum flexuosum"
14	"Staminal corona 2–3 mm diameter"	"Vincetoxicum woollsii"