M. scandens, as treated in the Fl. Madagasc. (Humbert, 1960), represented a widespread, complex and problematic group of plants. More recently, Holmes (1982), refered most of the African and Malagasy material of this group to M. capensis, while restricting M. scandens mainly to plants occuring in the USA. We provisionally follow Holmes, who also noted the presence of a second Afro-Malagasy sp, M. chenopodioides, but we note that there are a number of taxa originally described as Malagasy endemics that were reduced to synonymy by Humbert and by Holmes that merit re-examination.