1Upper surface of leaves very finely and closely striate. Inflorescences racemose on leafless stems, usually ferrugineous-tomentose
1'Upper surface of leaves not striate.
2Leaves triplinerved, the Maln basal pair of nerves extending almost to the leaf-apex.
2'Leaves not triplinerved.
3Woody climber. Sepals and petals marked with reddish lines or spots. Inflorescence a panicle or raceme
3'Erect shrub or small tree. Sepals and petals not marked with lines or spots. Inflorescence a cyme or short raceme of cymes 22.
4Inner 3 sepals connate in a fleshy tubular calyx, minute outer sepals free. Stamens c. 18-24, connate in a conical cluster
4'Sepals free or if connate then calyx of one whorl only.
5Petals thick and fleshy, much larger than sepals. Inflorescences pseudoracemose. Leaves peltate or sub-peltate
5'Petals smaller than sepals or absent.
6Sepals 7-12, spirally arranged, not in distinct whorls. Stamens 9-40, free or connate. Inflorescences cymose or thyrsoid
6'Sepals in one or more distinct whorls.
7Connective prolonged into a flattened tongue. Stamens 9, the outer 6 joined at base, the inner 3 free. Inflorescences fasciculate on old stems
7'Stamens without a prolonged connective.
8Stamens united or at least partly connate at the base, or only the inner 3 stamens connate.
8'Stamens all free.
9Stamens completely united in a peltate or clavate synandrium, the anthers in a horizontal ring.
9'Stamens with the filaments ± connate or only the inner stamens connate.
10Inflorescences composed of umbelliform cymes or disciform capitula. Leaves peltate 25. Stephania b. Inflorescences cymose, thyrsoid or pseudoracemose. Leaves peltate or not.
11Inflorescence a peduncled, corymbose cyme. Sepals 4. Petals connate in a cup. Leaves peltate
11'Inflorescences thyrsoid or pseudoracemose, or if cymose then sepals 6 in 2 whorls and petals 6.
12Sepals 4(-5), free or connate. Petals 4, free or connate. Inflorescences thyrsoid or pseudoracemose. Leaves sometimes peltate
12'Sepals 6, free in 2 whorls. Petals 6, free. Inflorescences thyrsoid or cymose. Leaves not peltate
13Inflorescence a raceme of peduncled balls of flowers. Stamens 6, the outer 3 free, the inner 3 joined. Leaves tomentellous (often whitish) below
13'Inflorescence a panicle, cyme or fascicle.
14Lower surface of leaves with domatia in axils of main nerves. Leaves palmately nerved at base. Inflorescence a panicle. Anthers in a globose cluster.
14'Leaves lacking domatia, penninerved or subpalmately nerved at base. Inflorescence a cyme or fascicle. Stamens 6-18 with the filaments ± joined
15Flowers pedicellate. Anthers 30-35 in a stalked cluster
15'Flowers sessile or subsessile. Anthers 9-12 in a sessile cluster
16Petals absent. Stamens with thick filaments, a prominent collar evident below the anther. Inflorescence a lax panicle. Wood yellow
16'Petals present. Stamens without a prominent collar below the anther. Wood not yellow.
17Inner 3 sepals valvate.
17'Inner 3 sepals imbricate.
18Sepals glabrous or subglabrous. Inflorescence a pseudoraceme. Petiole rugulose
18'Sepals tomentellous to densely pilose. Petiole not rugulose.
19Inflorescence a cyme or lax pseudopanicle
19'Inflorescence narrowly thyrsoid, the branches subspicate
20Main basal nerves and their main outer lateral branches extending to the leaf-margin.
20'Main basal nerves and their main outer lateral branches breaking up or anastomosing well with-in the leaf-margin.
21Inflorescences on old leafless stems, long racemes of cymes
21'Inflorescences axillary.
22Anthers dehiscing with longitudinal latrorse slits, the cells parallel and close together. Leaves usually broadly and shallowly crenate
22'Anthers dehiscing with transverse ± introrse slits, the cells separated abaxially by the thickened connective. Leaves usually entire or subentire
23Inflorescence a large panicle up to c. 50 cm long with lateral branches up to 15 cm, borne on old leafless stems. Stamens with flattened elliptic filaments broader than the anthers
23'Inflorescences much smaller and narrower, pseudoracemose, pseudospicate, narrowly thyrsoid or narrowly pseudopaniculate, axillary or on leafless stems. Stamens with filaments not broader than the anthers.
24Petals bifid. Inflorescence a cyme or a raceme of cymes 22.
24'Petals entire.
25Inflorescences yellowish tomentose to pubescent, always axillary and pseudoracemose. Leaf-base rounded to truncate or very obtuse (rarely subcordate)
25'Inflorescences glabrous, puberulous or hispidulous, axillary or on leafless stems, various in form. Leaf-base often cordate