| 1 | Midrib above either not visible, hidden in a narrow groove, or rarely visible as a very slender and sharp sunken line |
| 1' | Midrib above clearly visible, but sometimes covered with hairs |
| 2 | Nerves 12-30 per side. Calyx connate for ⅓. Petals not clawed. Disc annular or slightly cup-shaped. Stipe of fruit 0-6(-15) mm high |
| 2' | Nerves 6-15 per side. Calyx connate for ½-⅔. Petals clawed. Disc cup-shaped. Stipe of fruit 10-25 mm high |
| 3 | Inflorescences axillary, pseudoterminal, and ramiflorous. Calyx connate for ¼. Petals 0-2. Disc not interrupted, c. 1.5 mm in diam., puberulous. Stipe of fruit 1.5-6(-15) mm high; endocarp pubescent to densely woolly |
| 3' | Inflorescences ramiflorous (rarely also axillary). Calyx connate for ⅓. Petals (|3-)5. Disc often interrupted, 0.75-1 mm in diam., glabrous or locally puberulous. Fruit not (or hardly) stipitate; endocarp glabrous |
| 4 | Midrib above more or less hairy in at least some leaflets |
| 4' | Midrib above always glabrous, rarely subglabrous (see M. reticulatus) |
| 5 | Petiolules 4-18(-25) mm long. Cymules stalked, short sericeous. Calyx connate lor ⅓-⅔. Petals (0) 1-5. Filaments hairy. Fruits outside glabrous |
| 5' | Petiolules 2-5 mm long. Cymules almost sessile, long-hairy. Calyx connate for ⅓. Petals absent. Filaments glabrous. Fruit outside densely ferrugineous |
| 6 | Inflorescences ramiflorous (rarely also axillary). |
| 6' | Inflorescences axillary and pseudoterminal. |
| 7 | Inflorescence branches more than 11 cm long, branching. Fruit without a stipe or stipe at most 3 mm high |
| 7' | Inflorescence branches less than 11 cm long, branching or not. Fruit stipe at least 4 mm high |
| 8 | Fruits not stipitate or stipe at most 1 mm high. Calyx outside sparsely pubescent, inside puberulous near the base, often as a row of short hairs. Disc often irregularly deeply lobed to interrupted. Arillode without pseudo-funicle. |
| 8' | Fruit stipe 1-3 mm high. Calyx outside glabrous, inside glabrous or with a few hairs. Disc slightly lobed. Arillode with short pseudo-funicle |
| 9 | Inflorescence axes up to 10 cm long, not or very sparsely branched. Calyx hardly connate. Petals (2-)5. Filaments sparsely hairy or glabrous |
| 9' | Inflorescence axes up to 5 cm long, branching. Calyx connate for ½-¾. Petals absent. Filaments glabrous |
| 10 | Midrib above prominent, angular to rounded. Calyx connate for ⅓ (if connate for more than ¼, then petals absent and filaments glabrous). Petals well-developed but not clawed, or reduced to absent. Disc annular, 1—2(—3) mm in diam. Filaments hairy or glabrous |
| 10' | Midrib above a prominulous to flattened slender line only. Calyx connate for ⅓- ⅔. Petals 1-5, well developed, clawed. Disc cup-shaped, 0.5-1 mm in diam. Fila ments ± hairy |
| 11 | Leaflets (1 or) 2-6 per side; midrib above angular (to locally to rarely completely rounded); reticulation usually coarse. Calyx outside ± puberulous all over, hardly connate (rarely for ¼). Petals 0-5. Filaments usually puberulous at least at the base (to glabrous); anthers glabrous or ± hairy |
| 11' | Leaflets 1-3 (or 4) per side; midrib above rounded, locally (to completely) angular; reticulation usually fine and dense. Calyx outside ± hairy in the lower half only, connate for ¼-⅓. Petals 0 (rarely up to 3 in Peninsular Malaysia). Filaments glabrous; anthers glabrous |
