In botanical usage, the term "plantain" is used only for true plantains, while other starchy cultivars used for cooking are called "cooking bananas". All modern true plantains have three sets of chromosomes (i.e. they are triploid). Many are hybrids derived from the cross of two wild species, "Musa acuminata" and "Musa balbisiana". The currently accepted scientific name for all such crosses is "Musa" × "paradisiaca". Using Simmonds and Shepherds' 1955 genome-based nomenclature system, cultivars which are cooked often belong to the AAB Group, although some (e.g. the East African Highland bananas) belong to the AAA Group, and others (e.g. Saba bananas) belong to the ABB Group.