| 1 | Leaves deeply 3-lobed |
| 1' | Leaves not deeply lobed, margin entire, toothed or only slightly lobed. |
| 2 | Leaf-margin irregularly toothed (Taiwan) |
| 2' | Leaf-margin entire or slightly lobed. |
| 3 | Leaves very narrow, 0.4-2 cm broad (Australia) |
| 3' | Leaves broader. |
| 4 | Leaves hairy (sometimes sparsely) beneath. |
| 4' | Leaves glabrous beneath. |
| 5 | Leaves sagittate to hastate (China, Vietnam) |
| 5' | Leaves ± ovate. |
| 6 | Leaves puberulous above, tomentellous or rather densely puberulous beneath (SE. Asia, S. China, Hongkong, Hainan) |
| 6' | Leaves glabrous above. |
| 7 | Fine reticulation not or scarcely visible on both surfaces, which dry minutely wrinkled; uncinate hairs absent from main nerves beneath |
| 7' | Fine reticulation raised on both surfaces; some uncinate hairs present on main nerves beneath |
| 8 | Leaves narrowly elliptic to elliptic. |
| 8' | Leaves ± ovate, rotund or triangular. |
| 9 | Leaf-base sagittate |
| 9' | Leaf-base rounded or subtruncate |
| 10 | Inflorescences appearing when plant is leafless. |
| 10' | Inflorescences appearing together with leaves. |
| 11 | Stems strongly tuberculate (tubercles may be little-developed on young stems). Leaves lacking hollow domatia in basal nerve-axils. Petals usually 3. Endocarp 11-13 mm long |
| 11' | Stems not tuberculate; petals 6. |
| 12 | Leaves with a pair of hollow domatia on lower surface in basal nerve-axils. Petals usually 6. Endocarp 7-9 mm long |
| 12' | Leaves with glandular patches on lower surface in basal nerve-axils, ± triangular with sides straight or sometimes concave towards base. Endocarp shortly pointed at both ends (Australia) |
| 13 | Leaves 18-28 by 11-23 cm, thinly coriaceous, lacking domatia or glandular patches in basal nerve-axils. Endocarp 1.7-2.4 cm long, surface very smooth, whitish |
| 13' | Leaves smaller and thinner, sometimes with domatia or glandular patches in basal nerve-axils. Endocarps not as above. |
| 14 | Leaves drying matt and minutely wrinkled, fine reticulation not or scarcely visible on either surface, main nerves usually impressed on upper surface. Petals unguiculate, apically subreniform and markedly thickened. Endocarp thinly crustaceous, broadly elliptic in outline, 7-8 mm long, surface smooth or obscurely tuberculate |
| 14' | Characters not combined as above. |
| 15 | Inflorescences with lateral branches, at least towards base. Leaves with very fine, raised reticulation, glandular patches present in basal nerve-axils. Flower-pedicels 5-10 mm. Endocarps 10-12 mm long, strongly tuberculate |
| 15' | Inflorescences unbranched. |
| 16 | Flowers in sessile clusters; inflorescences sometimes zigzag. Endocarps 3.5-4.5 cm long. |
| 16' | Flowers pedicellate; inflorescences always straight. Endocarps up to 2.5 cm long. |
| 17 | Sepals subequal |
| 17' | Sepals unequal, the outer 3 much smaller than the inner 3 |
| 18 | Leaves with a pair of domatia in basal nerve-axils. Endocarp 2-2.5 cm long, the surface bearing scattered spinules |
| 18' | Leaves with glandular patches or domatia (rarely neither) in basal nerve-axils. Endocarp 6-8 mm long, pointed at both ends. |
| 19 | Leaves with domatia usually present in basal nerve-axils (replaced by glandular patches in New Guinea). Flower-pedicels 8-12 mm. Outer sepals much smaller than inner sepals |
| 19' | Leaves with glandular patches in basal nerve-axils. Flower-pedicels 1-5 mm. |
| 20 | Male inflorescences 4-7 cm long; male flower-pedicels 1-2.5 mm. Drupes borne on a ± subglobose or shortly 3-branched carpophore, 1.5-2 mm long (Australia) |
| 20' | Male inflorescences (5—)7—15 cm long; male flower-pedicels 4-5 mm. Drupes borne on a columnar carpophore, 4-5 mm long |
