| Maximowiczia lindheimeri var. tenuisecta (A. Gray) Cogn., 1881 |
| Maximowiczia sonorae S. Watson, 1889 |
| Maximowiczia sonorae var. peninsularis I.M. Johnst., 1924 |
| Megarrhiza Torr. & A. Gray, 1860 |
| Megarrhiza californica Torr., 1876 |
| Megarrhiza guadalupensis S. Watson, 1876 |
| Mellonia Gasp., 1847 |
| Melo Mill., 1754 |
| Melopepo Mill., 1754 |
| Melothria L., 1753 |
| Melothria angustifolia Cogn., 1895 |
| Melothria costensis C. Jeffrey, 1978 |
| Melothria donnell-smithii Cogn., 1891 |
| Melothria donnell-smithii var. hirtella Cogn., 1891 |
| Melothria donnell-smithii var. rotundifolia Cogn., 1891 |
| Melothria fluminensis Gardner, 1842 |
| Melothria guadalupensis (Spreng.) Cogn., 1881 |
| Melothria heteroloba Pittier, 1940 |
| Melothria pendula L., 1753 |
| Melothria pringlei (S. Watson) Mart. Crov., 1954 |