| | 1. Bractlets subtending calyx lanceolate to ovate; flowers generally conspicuous |
| |
| | 2. Petals 10–12 mm; stem generally trailing or ascending, 2–6 dm |
| 2 M. nicaeensis |
| | 2' Petals 12–30 mm; stem erect, 10–30 dm |
| 2 M. sylvestris |
| | 1' Bractlets subtending calyx narrowly linear to lanceolate; flowers generally inconspicuous |
| |
| | 3. Fruit segments smooth or weakly ridged on back, margins round |
| M. neglecta |
| | 3' Fruit segments wrinkled and net-veined on back, margins angled or winged |
| |
| | 4. Petals 12–30 mm, generally bright purple or pink |
| 2 M. sylvestris |
| | 4' Petals 4–12 mm, pale pink or lilac |
| |
| | 5. Calyx somewhat enlarged in fruit, lobes spreading or arching over fruit, scarcely net-veined; petal claw generally hairy; margins of fruit segment angled not winged |
| 2 M. nicaeensis |
| | 5' Calyx much enlarged in fruit, lobes spreading, net-veined; petal claw glabrous; margins of fruit segment winged |
| M. parviflora
|