| 1 | Leaf bud with minute, appressed hairs, 0.1-0.2(-0.3) mm or less. |
| 1' | Hairs more than 0.2 mm. |
| 2 | Lower leaf surface with (sub)persistent dense indumentum (hairs may be very small), old leaves sometimes glabrescent. Fruits with woolly scurfy hairs 0.1 mm. [Inflorescences with distinct peduncle (often short in female).]. |
| 2' | Lower leaf surface glabrous or early glabrescent or with scattered (not dense) minute hairs. Fruits with variable indumentum, glabrous, or glabrescent. |
| 3 | Buds (best to be seen in male flowers) ± angular in the upper part. Twigs 1.5-2.5 (-4) mm diam. Leaves (8-)10-22 cm long, lateral nerves 10-17 per side. [Fruits 5-9 cm long, often subsessile. Check also M. smythiesii.]. |
| 3' | Buds not angular. Twigs 2-8 mm diam. Leaves 15-40 cm long, with 16-33 lateral nerves per side. |
| 4 | Twigs (4-)5-8 mm diam. Leaves 16-40 cm long, drying dark brown; lateral nerves (20-)23-33 per side. Fruits 6-9 cm long. |
| 4' | Twigs 2-3 mm diam. Leaves 15-30 cm long, drying olivaceous; nerves 16-23 per side. Fruits 5-7 cm long. |
| 5 | Inflorescences pedunculate; perianth largely glabrous (except in M. gigantea and M. papyracea). Fruits glabrous, glabrescent, or with minute scattered hairs; in glabrescent fruits sometimes a minute indumentum remaining in sheltered places near the insertion of the pedicel. |
| 5' | Inflorescences a sessile brachyblast, or pedunculate; perianth pubescent. Fruits with persistent dense-scurfy indumentum, or partly glabrescent but with dense indumentum remaining in sheltered places. |
| 6 | Buds (especially in male flowers) sharply angular in the apical part. Twigs and leaves drying yellowish; lateral nerves 8—13(—15) per side. [Fruits drying dark brown or blackish, often with a green-yellowish exudate, 4.5-7.5 cm long, glabrescent, hairs minute, scattered, 0.1 mm.]. |
| 6' | Buds rounded. Twigs drying (yellowish) brown, leaves olivaceous or brown; lateral nerves 10-30 per side. |
| 7 | Lines of interarching of lateral nerves on lower leaf surface (of mature leaves) indistinct. |
| 7' | Lines of interarching raised and distinct. |
| 8 | Bracteole (in male flowers) subpersistent or late caducous. Leaf apex acute-acuminate; lower leaf surface not papillose. Fruits 3-6(-8) cm long, pericarp 3-10 mm thick. |
| 8' | Bracteole caducous. Apex of leaves of fertile twigs acute or blunt; lower leaf surface papillose. Fruits 5-8 cm long, pericarp 15-20 mm thick. |
| 9 | Leaves membranous, chartaceous, or subcoriaceous, 7-24 cm long. Peduncle in female to 1 cm long, 1-2 mm thick. Fruits 4-6(-8) cm long, pericarp 4-10 mm thick, late or early glabrescent. Male buds 4-6(-7) mm long. |
| 9' | Leaves thinly membranous, 7-14 cm long. Peduncle in female 1-2.5 cm long, 1.5 mm thick. Fruits 3-4 cm long, early glabrescent; pericarp 3-4 mm thick. Male buds 3 mm long. |
| 10 | Twigs 2-4 mm diam. Leaves about 3 times longer than broad, 10-30 by 4-9.5 cm, apex acute-acuminate, base rounded to acute; lateral nerves 14-20 per side; lower leaf surface papillose or not. Male buds 3-3.5 mm long. Female buds 2-2.5 mm long. Fruits 4-6 cm long. |
| 10' | Twigs 4-8 mm diam. Leaves large and comparatively broad, 16-44 by 8-14.5 (-18) cm, apex blunt or acute, not acute-acuminate, base ± rounded or subcordate; nerves (16-)20-28 per side; lower leaf surface papillose. Male buds 6-8 mm long. Female buds 6 mm long. Fruits 7-9 cm long. |
| 11 | Inflorescences (and infructescences) with a peduncle, and ± branched. |
| 11' | Inflorescences sessile, a short, scar-covered sessile brachyblast. [Leaves chartaceous or thinly coriaceous.]. |
| 12 | Leaves 16-40 cm long; lateral nerves 16-30 per side. Inflorescences large, widely paniculate, 6-18 cm long in male, (1.5—)5—9 cm in female. Fruits 6-8 cm long |
| 12' | Leaves 10-30 cm long; lateral nerves 13-20(-22) per side. Inflorescences 2-6 cm long in male, 1.5-2.5 cm long in female. Fruits (4.5-)5-7.5 cm long. [Male buds 3-4 mm long.]. |
| 13 | Twigs (4-)5-8 mm diam. Leaves: lateral nerves (20-)23-30 per side; lines of interarching ± distinct; papillae usually apparent. Male buds 5-7 mm long. |
| 13' | Twigs 2.5-5 mm diam. Leaves: lateral nerves 16-24 per side; lines of interarching ± indistinct; papillae not apparent. Male buds 4(-4.5) mm long |
| 14 | Twigs 5-10 mm diam. [Bark usually conspicuously cracking and flaking.] Leaf bud [and fruits] with very conspicuous villous hairs (1—)2—3 mm. [Inflorescences sessile.]. |
| 14' | Twigs 6 mm diam. or less. Leaf bud with hairs 1.5 mm or less. |
| 15 | Leaves pubescent below. Fruits 2.5-4.5 cm long. |
| 15' | Leaves glabrous below. Fruits 5 cm long or more. |
| 16 | Inflorescences (best to be seen in male specimens) branched and with distinct ± flattened main peduncle, with flowers in subumbels or spikes. Fruits 2.5-4.5 cm long. |
| 16' | Inflorescences (sub)sessile scar-covered short-shoots lasting several flowering seasons. Fruits densely pubescent, 2.5-3.5 cm long. [Leaf bud with hairs up to 0.5(-l) mm. — Inland species; not from limestone.]. |
| 17 | Twigs 3-5(-10) mni diam. Leaves (12—) 15—35 cm long; lateral nerves 15—19(—25) per side. Leaf bud with hairs to 1(—1.5) mm. Buds rounded towards apex. Fruits 2.5-4.5 cm long, densely shaggy pubescent with hairs 0.5-1 mm. — Mainly a coastal species, but sometimes inland in degraded forest. |
| 17' | Twigs 1.5-3.5 mm diam. Leaves 11-20 cm long; lateral nerves 10-18 per side. Leaf bud with appressed hairs 0.5-1 mm. Buds sharply angular towards apex. Fruits 3.5-4 cm long, glabrescent or with thin scattered pale brown appressed hairs to 0.5 mm. — W Sarawak, NE Kalimantan; mostly from limestone. |
| 18 | Twigs 2-3 mm diam. Leaves thinly coriaceous, base rounded or short acute; nerves not distinct above. Fruits 2.5-3.5 cm long, with scurfy hairs 0.2-0.3(-0.5) mm. |
| 18' | Twigs 3-4(-5) mm diam. Leaves coriaceous, base rounded or emarginate, sometimes short-acute; nerves distinct above. Fruits 2.5-3.5 cm long, with woolly hairs 0.5-1 mm. |
| 19 | Male flowers: androecium ± sessile, with a collar of conspicuous hairs at base, sterile apex ± pubescent. |
| 19' | Androecium with distinct androphore, sterile apex without hairs. One collection, see note 3 under. |
| 20 | Lower leaf surface concolorous with upper surface, not papillose. Fruits glabrous (early glabrescent). |
| 20' | Lower leaf surface distinctly papillose, generally paler than upper leaf surface. Fruits either with persistent indumentum, late glabrescent, or early glabrescent in M. gi-gantea. |
| 21 | Leaves membranous, up to 24 cm long, base attenuate. Twigs up to 4 mm diam., smooth or striate, the bark of the twigs lower down cracking or not; leaf bud slender, 7-12 by 1-2 mm. Fruits to 8 cm long, pericarp 5-10 mm thick. — Stout forms, mainly from NE Borneo. |
| 21' | Leaves chartaceous, 15-35 cm long, base broadly rounded. Twigs (4-)5-6 mm diam., bark early conspicuously cracking; leaf bud stout, 10-15 by 4-6 mm. Fruits 7.5-9.5 cm long, pericarp 15-20 mm thick. — NE Borneo. |
| 22 | Twigs 1.5—2.5(—3) mm diam. Leaves 7—12(—15) cm long, chartaceous, apex acute, blunt, or rounded; lateral nerves 10—15(—18) per side. Fruits 5-8 cm long, (late) glabrescent, hairs scurfy, 0.2 mm. |
| 22' | Twigs 3-6 mm diam. Leaves 14-35 cm long, coriaceous, the apex acute-acuminate; lateral nerves 13-22 per side. Fruits (5-)6-7 cm long, with conspicuous persistent shaggy hairs 1-2 mm. |
