| 1 | Leaves simple |
| 1' | Leaves compound |
| 2 | Underside of leaves with a closed felt of thin, curly hairs, apart from straight, stouter hairs on nerves and veins |
| 2' | Not a closed felt on underside of the leaves, leaf surface visible between the hairs |
| 3 | Stipules and bracts entire or with few minute teeth |
| 3' | Stipules and bracts distinctly toothed to deeply incised |
| 4 | Inflorescence richly and widely branched. Sepals at anthesis 5-6 mm long |
| 4' | Inflorescence a compact, few-flowered raceme. Sepals c. 12 mm long |
| 5 | Flowerbuds globular |
| 5' | Flowerbuds ovoid, pointed |
| 6 | Leaves ± ovate, at least 1.4 times as long as wide, not or very shallowly lobed. Dioecious |
| 6' | Leaves suborbicular to broadly ovate in outline, ± as long as wide, deeply 5- to 7-lobed. Flowers bisexual |
| 7 | Inflorescence a simple, compact raceme |
| 7' | Inflorescence elaborately branched |
| 8 | Leaves bullate above, surface distinctly raised between the veins |
| 8' | Leaves flat above, nerves (and veins) sometimes slightly impressed but leaf surface between the veins not distinctly raised |
| 9 | Outer sepals shortly toothed, teeth up to 1.5 mm long. Anthers glabrous |
| 9' | Outer sepals with longer lobes or teeth. Anthers hairy on top |
| 10 | Outer sepals with 5 or more lobes on each side, lobes up to 7 mm long |
| 10' | Outer sepals with 1-3 teeth on each side, teeth up to 3 mm long |
| 11 | Leaves (broadly) ovate, length/width up to 2(-2.5), not or shallowly lobed, if distinctly lobed (var. angulosus), the basal lobes overlapping. Stipules early falling, 4-12 mm wide, on each side with 4-10 lobes. Ovaries and fruits glabrous |
| 11' | Leaves broadly ovate, length/width less than 1.5, distinctly 3-lobed, base cordate but lobes not touching. Stipules rather persistent, up to 2 mm wide, with 2 or 3 lobes on each side. Ovaries and fruits glabrous or hairy |
| 12 | Creeping plants with solitary, terminal flowers, rarely 1 or 2 axillary flowers under the terminal one. Leaves reniform, often wider than long. Hypanthium and outside of sepals with needle-shaped prickles |
| 12' | Erect, climbing, or straggling shrubs with flowers in inflorescences. Leaves usually distinctly longer than wide. Hypanthium and sepals unarmed |
| 13 | Stipules serrate to dentate |
| 13' | Stipules deeply digitately divided |
| 14 | Anthers basifixed |
| 14' | Anthers dorsifixed or dorso-versatile |
| 15 | Underside of leaves with scattered hairs only |
| 15' | Underside of leaves densely hairy |
| 16 | Ovaries hairy |
| 16' | Ovaries glabrous, on hairy or glabrous torus |
| 17 | Leaves distinctly cordate at base |
| 17' | Leaves with rounded, subtruncate or very shallowly cordate base |
| 18 | Leaves less than 1.5 times as long as wide, petiole 1.5 cm or longer, nerves terminating in the margin. Flowers unisexual (?) |
| 18' | Leaves normally more than 1.5 times as long as wide, petiole rarely longer than 1 cm, nerves not reaching the margin. Flowers bisexual |
| 19 | Petals 5 |
| 19' | Petals 0 or 1 |
| 20 | Leaves suborbicular to broadly ovate in outline, about as long as wide, deeply 5-7-lobed. Stipules and bracts divided into thin thead-like lobes. |
| 20' | Leaves longer than wide, not or hardly lobed. Stipules and bracts toothed or dissected but not with thin, thread-like lobes |
| 21 | Inflorescences laxly paniculate, up to 35 cm long, compound racemes with up to 20 racemes of each up to 30 flowers |
| 21' | Inflorescences rarely longer than 10 cm, racemes of 3- to 1-flowered cymes, the upper ones often congested |
| 22 | Flowers large, sepals 10-12 mm long |
| 22' | Flowers smaller, sepals 6-8 mm long |
| 23 | Leaves 1-1.3 times as long as wide. Glandular hairs on outside of hypanthium and sepals, outer sepals on each margin with 3-6 distinct teeth of up to 1 mm long |
| 23' | Leaves 1.4 or more times as long as wide. Outside of hypanthium and sepals without glandular hairs, outer sepals entire or with 1 or 2 minute teeth on each margin |
| 24 | Leaves pinnate with more than 3 leaflets, or bipinnate |
| 24' | Leaves 3-foliolate or pedately/palmately 5-foliolate |
| 25 | Needle-shaped spines on stems, leaves and also on hypanthium 1 to 5 spines alternating with the sepals |
| 25' | Prickles not needle-shaped |
| 26 | Leaves bipinnate, 3-pinnate at base, simply pinnate at apex |
| 26' | Leaves simply pinnate |
| 27 | Leaflets 1-4 by 0.5-2 cm, with 7—12(—18) teeth on each side, upper surface glabrous or hairy between the nerves, lower surface glabrous or hairy on midrib and veins |
| 27' | Leaflets 0.5-1.5 by 0.5-1 cm, with 4-6(-7) teeth on each side, both surfaces glabrous or almost so |
| 28 | Stems and leaves with up to 5 mm long gland-tipped hairs. |
| 28' | No long gland-tipped hairs present |
| 29 | Leaves almost glabrous |
| 29' | Leaves hairy, at least on underside |
| 30 | Leaflets biserrate, with long-tapering apex. Pistils down to the base of the torus, ovaries with shortly stalked glands |
| 30' | Leaflets serrate, apex acute to long-pointed. Base of torus without pistils. Ovaries without glands |
| 31 | Leaflets below with a dense, woolly, silvery-white felt all over and with straight hairs on the nerves. Flowers small: sepals 4-7 mm long, petals 3.5-5 mm long, pink. Ovaries and fruits densely hairy |
| 31' | Leaflets below long-hairy but without woolly felt. Flowers large: sepals 7-15 mm or longer, petals 8-17 mm long, white. Ovaries with stalked glands and apically with some hairs |
| 32 | Leaves 5-foliolate, the uppermost ones and/or the first leaves on a branch sometimes only 3-foliolate |
| 32' | Leaves 3-foliolate, the upper ones sometimes unifoliolate |
| 33 | Leaflets with 18 or (many) more pairs of nerves. Unarmed or prickles very rare |
| 33' | Leaflets with 6-17 pairs of nerves. Armed |
| 34 | Normally 30-40 pairs of nerves. Stipules 2-4 cm long. Sepals sericeous outside, the covered parts woolly. Petals 4-5 mm long, distinctly shorter than sepals |
| 34' | Normally 16-26 pairs of nerves. Stipules 0.5-1 cm long. Sepals with few hairs outside, covered parts woolly. Petals 9-12 mm long, ± as long as sepals |
| 35 | Prickles rather few. Stipules long persistent, 4-12 mm long. Inflorescences monochasial or dichasial |
| 35' | Prickles rather many. Stipules absent or fugacious, 3-7 mm long. Inflorescences racemose, racemes solitary or in bundles |
| 36 | Terminal leaflets 4.5-12 by 2-7 cm, with 9-14 pairs of nerves. Racemes with 10-25 flowers, solitary or in bundles. Filaments glabrous. Ovaries glabrous or hairy, not glandular |
| 36' | Terminal leaflets 3-5 by 2-3 cm, with 6-8 pairs of nerves. Racemes with 2-7 flowers, solitary. Filaments long-hairy. Ovaries hairy and dorsally with many yellow glands |
| 37 | Stems unarmed or almost so |
| 37' | Stems armed |
| 38 | Leaflets with more than 16 pairs of nerves |
| 38' | Leaflets with fewer than 10 pairs of nerves |
| 39 | Inflorescence a large, terminal thyrse with up to 20 rich-flowered laterals under the terminal flower |
| 39' | Inflorescence much poorer, with under the terminal flower only 1-4 axillary cymes of up to 4 flowers |
| 40 | Hypanthium outside with up to 5 mm long bristles or spine-like hairs, otherwisehairy or not |
| 40' | Hypanthium outside without bristles or spines, with or without short hairs and/or few short prickles |
| 41 | Stipules deeply divided. Petals red. Ovaries hairy. |
| 41' | Stipules entire, serrate, or with some short teeth. Petals white |
| 42 | Hypanthium outside with straight prickles and with capitate spines, otherwise glabrous. Ovaries glabrous. Fruits red |
| 42' | Hypanthium outside hairy and with straight bristles |
| 43 | Stipules 10-18 by 3-15 mm. Inflorescences poor, usually less than 8 flowers. Ovaries glabrous. Fruits orange to red |
| 43' | Stipules up to 10 by 0.5 mm. Inflorescences rich, up to 150 flowers or more. Ovaries hairy. Fruits yellow to orange |
| 44 | Flowers solitary and terminal or in poor racemes of 2-5 flowers |
| 44' | Inflorescences richer, thyrsoid or racemose |
| 45 | Underside of leaflets woolly all over |
| 45' | Underside of leaflets glabrous or with hairs on midrib and larger nerves only. |
| 46 | Axillary racemes, almost always simple, rarely partly with cymes instead of flowers, racemes solitary or in bundles of up to 4. Flowers (always?) unisexual |
| 46' | Under the terminal flower up to 6 lateral cymes or dichasia in the axils of bracts or leaves. Flowers bisexual |
| 49 | Terminal leaflets 3-10 by 2-7 cm. Flowers small: sepals 2.5-4 mm, petals 4-8 mm long |
| 49' | Terminal leaflets 10-15 by 8-12 cm. Flowers larger: sepals 6-7 mm, petals 10-17 mm long |
| 47 | Stipules deeply divided |
| 47' | Stipules entire or with 1 or 2 small teeth |
| 48 | Petals longer than sepals, early falling. Stamens and pistils both more than 150 7. R. acuminatissimus b. Petals shorter than sepals, long-persistent Stamens up to 45, pistils up to 25 |
