| 1 | Leaves pinnate |
| 1' | Leaves ternate or palmate |
| 2 | Flowering stems as long as or distinctly longer than the leaves. Stamens usually 10 or more (often 5 in P. parvula) |
| 2' | Flowering stems shorter than the leaves. Stamens usually in one whorl of 4 to 6 (10-15 in P. gorokana) |
| 3 | Leaflets densely silky hairy below, leaf surface not visible between the hairs. |
| 3' | Leaves glabrous to hairy, but not densely silky, leaf surface visible |
| 4 | Stems, petioles, and rachis patently hairy. Flowering stems procumbent |
| 4' | Stems, petioles, and rachis appressed hairy |
| 5 | Ovaries hairy |
| 5' | Ovaries glabrous |
| 6 | Epicalyx leaves entire or practically so. Leaflets crowded, stiff |
| 6' | Epicalyx leaves pinnatifid to pinnatisect. Leaflets distant, not stiff 13. P. papuana 7a. Lateral leaflets entire or some with one incision, apical leaflet bifid. |
| 6'' | Leaflets incised |
| 7 | Leaflets pseudodigitate (pinnately incised but with a minimally short midrib |
| 7' | Leaflets pinnatisect to pinnatipartite |
| 8 | Upper leaflets normally shorter than 10 mm, leaf not more than 10 cm long. Stamens as many as petals or twice that number, rarely more (-20) |
| 8' | Upper leaflets 10-30 mm, leaf 9-35 cm long. Stamens 4 times the number of petals or more |
| 9 | Leaflets digitate, incisions going to the very base |
| 9' | Leaflets entire, bipartite, or pinnately incised |
| 10 | Leaflets pinnatisect to pinnatipartite |
| 10' | Leaflets undivided or bipartite to the very base |
| 11 | Epicalyx leaves entire or apically shallowly notched |
| 11' | At least part of the epicalyx leaves pinnatifid to pinnatipartite, or 3 -4-partite. 15 13a. Leaflets densely silky hairy below, leaf surface not visible between the hairs. 14 b. Leaflets with long hairs below but not densely silky, leaf surface visible |
| 12 | Leaflets 8-13 pairs |
| 12' | Leaflets 1-5 (-8) pairs |
| 13 | Leaves 5-foliolate. Flowers in dichasial, terminal inflorescences |
| 13' | Leaves trifoliolate. Flowers solitary, opposite normal leaves on prostrate stems |
