| 1 | Leaves paripinnate, without pseudogemmula or its scar |
| 1' | Leaves imparipinnate or pseudogemmulate |
| 2 | Inflorescences borne on leaves. — New Guinea |
| 2' | Inflorescences axillary, supra-axillary, ramiflorous or borne on bosses on bole. |
| 3 | Leaves ± densely pubescent, petiolules 3–6 mm long |
| 3' | Leaves sparsely hairy to glabrous, petiolules (5–)10–23 mm long |
| 4 | Inflorescences borne on long-lived bosses on bole. — Borneo |
| 4' | Inflorescences otherwise |
| 5 | Leaflets strongly asymmetric, petals 5 or 6, red, anthers 8–10 (limestone) |
| 5' | Leaflets not so, petals (3) 4 (5), white, anthers 6–9 (mountains) |
| 6 | Pseudopedicel c. 10 mm long, calyx with conspicuous annular thickening, petals 6-10 in 2 whorls — Malay Peninsula |
| 6' | Pseudopedicel, if present, much smaller |
| 7 | Calyx (10–)13–20(–23) mm long. — Borneo, Philippines |
| 7' | Calyx smaller 9 |
| 8 | Leaflets ± densely fulvescent abaxially, inflorescence to 30 cm, petals 9–14, anthers 15–20, stylehead discoid, seeds sarcotestal |
| 8' | Leaflets not so, inflorescence to 220 cm, petals 6–10, anthers 16–30, stylehead capitate, seeds arillate |
| 9 | Leaves imparipinnate |
| 9' | Leaves pseudogemmulate |
| 10 | Leaflets subglabrous abaxially — Sumatra, ?Java |
| 10' | Leaflets golden- to brown-pubescent, pilose or strigose adaxially |
| 11 | Anthers 3–5, corolla clavate in bud. — Malay Peninsula, Riau Arch |
| 11' | Anthers 6 or more |
| 12 | Petals 16 mm long. — Borneo |
| 12' | Petals 20 mm or longer |
| 13 | Leaflets rugose, surface strongly reticulate-areolate abaxially, shiny and glabrous adaxially save brown-tomentose midrib; seed sarcotestal. — Malay Peninsula |
| 13' | Leaflets smooth, abaxial surface not strongly reticulate-areolate; seeds arillate or unknown. — Borneo |
| 14 | Leaves strigose with ‘tinkling’ hairs, petals glabrous |
| 14' | Leaves appressed hirsute abaxially, glabrous or sparsely pubescent on veins adaxially, petals densely pubescent without. |
| 15 | Petals 26–37 mm long, pachycaul treelets with irritant fruit hairs |
| 15' | Petals smaller, fruit unarmed |
| 16 | Anther connective glabrous, seeds sarcotestal. — Malay Peninsula |
| 16' | Anther connective hairy, seeds arillate. — Borneo |
| 17 | One or more petals narrower than and enclosed by the others |
| 17' | Petals ± the same width or, at least, none completely enclosed by the others |
| 18 | Petals c. 8 mm long. — Sumatra |
| 18' | Petals 14 mm or longer |
| 19 | Costae c. 5–8 on each side of midrib, leaves to 38 cm. — Malay Peninsula |
| 19' | Costae c. 15 on each side of midrib, leaves to 150 cm. — Borneo, Celebes |
| 20 | Tube not conspicuously lobed or strongly crenulate (if unclear, follow the alternative) |
| 20' | Tube conspicuously lobed |
| 21 | Calyx 5–6.5 mm. — Celebes, New Guinea |
| 21' | Calyx up to 4 mm tall |
| 22 | Calyx 5–6.5 mm, shallowly cupulate. — Papua New Guinea |
| 22' | Calyx 5 mm, cylindrical-cupulate. — Celebes |
| 23 | Tube villous or sericeous without |
| 23' | Tube ± glabrous or at most sparsely hairy in middle or distal half without |
| 24 | Anthers 8. — Philippines |
| 24' | Anthers (3) 4–6 |
| 25 | Petals 5. — Sumatra |
| 25' | Petals (3) 4 |
| 26 | Petals glabrous, leaflets tomentose abaxially. — Celebes |
| 26' | Petals ± hirsute without 27 |
| 27 | Petals (3) 4, 7 mm long, ovary 4-locular. — New Guinea |
| 27' | Petals 4, much longer 28 |
| 28 | Ovary bilocular, seeds 2, arillate |
| 28' | Ovary 5-locular, seeds exarillate |
| 29 | Inflorescence villous, to 80 cm, calyx 1.5–2 mm long, anthers 8 or 9, petiolules c. 12 mm. — New Britain |
| 29' | Not this combination of characters |
| 30 | Flowerbuds less than 1.5 mm diam. — New Guinea |
| 30' | Flowers larger |
| 31 | Leaves with conspicuous venation on both sides (dry), coriaceous, glabrescent; petals c. 13.5 mm long, fruit rostrate |
| 31' | Leaves different, fruit not rostrate |
| 32 | Petals c. 12 mm long, flowers crowded towards distal end of inflorescence, fruit spherical |
| 32' | Petals up to 10 mm long, or, if slightly longer, then the tube villous within and the leaves pilose abaxially |
| 33 | Flowerbuds 9–10 mm, anthers 4–6 (7), style to 0.15 mm |
| 33' | Flowerbuds c. 11.5 mm, anthers 6–8, style 0.25 mm diam.. |
| 34 | Inflorescence borne on supra-axillary branch resembling supra-axillary inflorescence; petiolules fulvous tomentose, disk 1 mm |
| 34' | Inflorescences different; disk absent . |
| 35 | Inflorescences borne on supra-axillary branch resembling supra-axillary inflorescence; petiolules fulvous tomentose . |
| 35' | Inflorescences different. |
| 36 | Hairs simple. |
| 36' | Hairs stellate, disk present, seeds sarcotestal. — Borneo eastwards. |
| 37 | Corolla aestivation imbricate. |
| 37' | Corolla aestivation valvate, seeds sarcotestal |
| 38 | Costae 15–22 on each side of leaflet midrib, flowerbuds clavate, anthers 3–5, pachycaul treelet. — Malay Peninsula, Riau |
| 38' | Not this combination of characters |
| 39 | Ovary 4-locular, seeds (3) 4. |
| 39' | Ovary 2-locular, seeds 2. |
| 40 | Disk obscure. |
| 40' | Disk prominent, subtubular to 1 mm. |
| 41 | Calyx 4-5-lobed, petals 5 or 6, anthers scarcely locellate . |
| 41' | Calyx margin entire, petals (3) 4 (5), anthers locellate |
| 42 | Disk present. |
| 42' | Disk absent |
| 43 | Venation very prominent on both sides (dried), seeds 3 cm diam. — Borneo |
| 43' | Venation and seeds different |
| 44 | Petals 18 mm long. — Philippines |
| 44' | Petals shorter . |
| 45 | Tube crenate, anthers hairy . |
| 45' | Tube lobes long-triangular, anthers glabrous . |
| 46 | Disk present |
| 46' | Disk absent |
| 47 | Twigs subglabrous 48 |
| 47' | Twigs fawn pubescent. |
| 48 | Petals 13–19 by 2 mm, tube lobes ± truncate, flowers in panicles, fruit 4.5 cm or more . |
| 48' | Petals 8–12(–19) mm, tube lobes ± laciniate, flowers in panicles only if flowers small; fruit to 2.1 cm diam . |
| 49 | Petals 16 mm long. — Philippines . |
| 49' | Petals 9–13 mm long |
| 50 | Flowers 11–12 mm long. — Borneo, Celebes |
| 50' | Flowers less than 8 mm long . |
| 51 | Inflorescence velutinous, style glabrous. — New Guinea |
| 51' | Inflorescence subglabrous, style densely hairy |
