| 1 | Petiole 3-5 mm long, stipular scar present for nearly its whole length. Leaves glabrous, 4.5-6.5 by 2-3 cm. Tepals 6 |
| 1' | Petiole longer than 5 mm. The other characters different or the tepals more than 6. |
| 2 | Young twigs glabrous. Terminal buds hairy at the apex only. Carpels 1-4. Stipules free from the 15-35 mm long petiole. Leaves glabrous, 9-35 cm long |
| 2' | Young twigs hairy, at least directly under the terminal bud. Carpels 8 or more. |
| 3 | Stipules adnate to the petiole for one third or more than one third of its length. |
| 3' | Stipules free from petiole or adnate to its base only (in M. salicifolia sometimes up to one third). |
| 4 | Leaves 8-12 by 2.5-3.5 cm. Petiole 6-16 mm |
| 4' | Leaves 10-35 by 4-11 cm. Petiole 14-50 mm. |
| 5 | Tepals 15, from light yellow to orange, 20-45 mm long. Carpels c. 30, fertile. Leaves 10-30 cm |
| 5' | Tepals c. 12, white, 30-55 mm long. Carpels c. 10, sterile. Leaves 15-35 cm |
| 6 | Leaves 15-35 by 5.5-11 cm. Petiole 15-50 mm. Tepals c. 12, white, 30-55 mm. Carpels sterile, c. 10 |
| 6' | Leaves 4-16 by 2.3-6 cm. Petiole 5-20 mm. Tepals white to yellow, 10-40 mm. Carpels fertile. |
| 7 | Brachyblast 10-17 mm. Outer tepals 3, membranous, inner tepals 6, coriaceous. Twigs and stipules puberulous to nearly glabrous. Leaves glabrous beneath, 6-16 by 3-6 cm. Carpels c. 10 |
| 7' | Brachyblast 3-7 mm. All the tepals the same, 9-17. Twigs and stipules pubescent or puberulous. Leaves glabrous or hairy beneath, 4-13 by 1.5-4 cm. Carpels 8-16 or c. 30. |
| 8 | Tepals 20-40 mm. Leaves 9-13 by 2.3-4 cm, often glaucous beneath. Carpels c. 30 |
| 8' | Tepals 10-15 mm. Leaves 4-12 by 1.5-3.5 cm, not glaucous beneath. Carpels 8—c. 16 |
