| | 1. Fruit beak generally erect to erect-appressed, generally < 0.5 mm, generally << or = body; stamens generally 10 |
| M. minimus |
| | 1' Fruit beak ± ascending, 0.3–2 mm, generally > body; stamens generally 5 |
| |
| | 2. In fruit, inflorescence < leaves, peduncle < 1 cm; sepal spur < 1 mm |
| M. sessilis |
| | 2' In fruit, inflorescence > leaves, peduncle generally > 1 cm; sepal spur 1–3 mm |
| |
| | 3. Fruit body ± compressed laterally, longer than wide, keel not in a depression; Klamath Ranges, Cascade Range, Sierra Nevada (except Tehachapi Mountain Area), Sacramento Valley, San Bernardino Mountains, Modoc Plateau |
| M. apetalus |
| | 3' Fruit body not compressed, ± as long as wide, keel in a depression; eastern Desert Mountains |
| M. cupulatus
|