| | 1. Leaves opposite, not much reduced upwards |
| |
| | 2. Perennial with stolon-like stems bearing pink bulblets; petals 5–9 mm, >> sepals |
| M. chamissoi |
| | 2' Annual; stems often matted; petals 1–2 mm, ± = sepals |
| M. fontana |
| | 1' Leaves all alternate, reduced upwards or not |
| |
| | 3. Perennial; basal leaves on short, caudex-like stem; petals 7–15 mm — flower-stem with axillary, easily detached, fleshy bulblets |
| M. parvifolia |
| | 3' Annual; leaves cauline, gradually reduced upwards; petals < 6.5 mm |
| |
| | 4. Leaves petioled; blades wide, base truncate or wedge-shaped; seeds with projecting fleshy appendage 0.2– 0.4 mm |
| M. diffusa |
| | 4' Leaves ± linear; seed appendage 0 or minute, not projecting |
| |
| | 5. Sepals 3–7 mm; stem 5–25 cm; lower stem leaves 2–10 cm; seeds 1.4–2.5 mm |
| M. linearis |
| | 5' Sepals < 2.5 mm; stem 1–9 cm; lower stem leaves 0.5–4.5 cm; seeds 0.7–1.2 mm |
| |
| | 6. Inflorescences both terminal and from axils of stem leaves; plants tufted, not matted or rooting at nodes |
| M. dichotoma |
| | 6' Inflorescences lateral, each from membranous bract opposite a stem leaf; plants moss-like, matted, rooting at nodes |
| M. howellii
|