| 1 | Leaves membranous, usually irregularly whitish blotched. Perianth 2-lobed; ovary glabrous. Fruits globose, 1.5-2 cm diam., glabrous; pericarp 1-2 mm thick; seeds globose. — Riverine or marshy, mostly near the coast |
| 1' | Leaves variable, usually not whitish blotched. Fruits subglobose or ellipsoid; seeds ellipsoid. — Coastal or not |
| 2 | Perianth 3-lobed. [Ovary and fruits glabrous.] |
| 2' | Perianth 2-lobed |
| 3 | Leaf bud and inflorescences with hairs 0.2-0.6 mm long. Pedicel articulated. [Fruits 2(-2.5) cm long.] — Philippines (Mindanao, Palawan) |
| 3' | Leaf bud and inflorescences with hairs 0.1-0.2 mm long. Pedicel not articulated |
| 4 | Fruits 3.5-7 cm long; (dry) pericarp (4—)8—15 mm thick. Leaves ± membranous, olivaceous-brown, midrib glabrous above; leaves sometimes with whitish blotches as in H. irya. — Philippines, Sulawesi |
| 4' | Fruits 4 cm long, (dry) pericarp 3.5-8 mm thick. Leaves membranous to thinly coriaceous, brown; midrib towards the base pubescent above in younger leaves. — C Sulawesi |
| 5 | Twigs 4-14(-20) mm diam. Leaves 20-45 cm long, petiole 2-7 mm long. Leaf bud and inflorescences with hairs 0.3-1 (-1.5) mm long. Buds 3.5-5 mm long, glabrous; ovary glabrous. Fruits 3.5-5.5 cm long, glabrous |
| 5' | Twigs more slender. Leaves smaller, petiole comparatively longer. Leaf bud and inflorescences with hairs up to 0.2 mm long. Buds 3(-3.5) mm long or less. Fruits up to 3 cm long (in H. lancifolia to 3.5 cm long) |
| 6 | Leaves ± chartaceous, oblong-lanceolate to lanceolate. Buds cleft c. 1/4; ovary pubescent. Fruits often ± pear-shaped, 2.5-3.5 cm long, early glabrescent; (dry) pericarp 4-8 mm thick. — Sulawesi |
| 6' | Leaves of different consistency, generally broader, oblong to oblong-lanceolate. Buds cleft c. 1/3 or more. Fruits 1-3 cm long |
| 7 | Ovary and fruits pubescent; hairs on the fruits may be inconspicuous and only remaining at the very base near the insertion of the pedicel (lens!); pericarp thick or thin |
| 7' | Ovary and fruits glabrous; pericarp 1-2 mm thick. [Female flowers and fruits not known in H. aruana and H. samarensis.] |
| 8 | Flower buds 2.5-3 mm long, cleft 1/3-1/2. Fruits (1.6-) 1.8-3 cm long; pericarp 2-3 mm thick |
| 8' | Female flowers not known. Fruits smaller, pericarp thinner |
| 9 | Fruits 1.5-1.6 cm long, short-ellipsoid. [Male buds transversely ellipsoid, cleft 2/3-4/5. Leaves 8-30 cm long, membranous or chartaceous; nerves flat, inconspicuous. Twigs terete, not ridged.] — Moluccas (Talaud Is.), possibly Sulawesi. |
| 9' | Fruits smaller, 1.1-1.3 cm long |
| 10 | Fruits subglobose. Twigs ± flattened, usually lined or low-ridged. Leaves 12-25 cm long, membranous; nerves flat, inconspicuous. Male buds ± pear-shaped, cleft to c. 2/3. — Moluccas |
| 10' | Fruits short-ellipsoid. Twigs terete, not lined. Leaves 5-14 cm long, chartaceous, nerves inconspicuous on both surfaces. Male buds ± obtriangular, cleft about halfway. — Philippines (Luzon) |
| 11 | Twigs angular or ridged. [Species distinctive only in male flowering specimens.] |
| 11' | Twigs (sub)terete or sometimes faintly angular, or shallowly lined |
| 12 | SW New Guinea, possibly Aru and Tanimbar Is. [Female flowers and fruits not known.] |
| 12' | Moluccas (Seram, Banda, Dammar I., possibly Ternate) |
| 12'' | Philippines. [Ovary glabrous or almost so.] |
| 13 | Bark of twigs pale, grey-brown, contrasting with the blackish petioles. [Fruits blackish on drying, 1.5-2 cm long.] — Moluccas |
| 13' | Twigs brown, in colour not contrasting with the petioles |
| 14 | Fruits ± globose to subellipsoid, 0.9-1.2 cm long (to 2 cm in New Guinea); blackish on drying. — Aru Is., New Guinea |
| 14' | Fruits 1.1-1.6 cm long (fruits not known in H. samarensis) |
| 15 | Philippines (Samar) |
| 15' | Moluccas, Sulawesi |
| 16 | Fruits ellipsoid, 1.5 cm long; blackish on drying. — Moluccas (Morotai, Obi Is.) |
| 16' | Fruits subglobose or ellipsoid, l.l-1.6(-2) cm long, brown on drying. — Sulawesi (Kabaena Is.), Moluccas (Seram) |
