| Malacothrix foliosa subsp. foliosa A. Gray ex Lyon, 1886 |
| Malacothrix glabrata (A. Gray ex D.C. Eaton) A. Gray, 1884 |
| Malacothrix insularis Greene, 1885 |
| Malacothrix platyphylla A. Gray, 1874 |
| Malacothrix similis W.S. Davis & P.H. Raven, 1962 |
| Malacothrix sonorae W.S. Davis & P.H. Raven, 1962 |
| Malacothrix stebbinsii W.S. Davis & P.H. Raven, 1962 |
| Malacothrix xanti A. Gray, 1874 |
| Mallinoa J.M. Coult., 1895 |
| Mallinoa corymbosa J.M. Coult., 1895 |
| Malperia S. Watson, 1889 |
| Malperia tenuis S. Watson, 1889 |
| Margacola Buckley, 1861 |
| Marshalljohnstonia Henrickson, 1976 |
| Marshalljohnstonia gypsophila Henrickson, 1977 |
| Maruta (Cass.) Gray, 1821 |
| Maruta cotula (L.) DC., 1837 |
| Maruta foetida Cass., 1823 |
| Matamoria La Llave & Lex., 1824 |
| Matamoria spicata La Llave, 1824 |