Trifolium polymorphum has been used in a broad sense by Zohary and Heller in their 1984 monograph to include a wide range of both geographical and morphological variation. We have determined, in a morphometric study, that the broad circumscription encompasses several species, which have distinct morphological and geographical ranges. One species has an unusual disjunct distribution between northern Chile and south-central United States. The Chilean portion has traditionally been called Trifolium polymorphum, while the North American portion has been called Trifolium amphianthum by many authors. There is no morphological hiatus between these portions, and we believe that they represent a species in its native range and an introduction in the North American range. The correct name for this entity, as well as evidence that it is introduced into North America, are presented.

Key words: Fabaceae, North America, South America, Trifolium amphianthum, Trifolium polymorphum