The genus Caltha comprises approximately 12-16 species growing in wet, marshy places in arctic and North and South temperate regions. The genus in classed in the tribe Helleboreae of the Ranunculaceae. A. de Candolle (1818) subdivided the genus into two sections: Psychrophila and Populago, the distinguishing features being that in the former the calyx is persistent, the auricles of the leaf laminae having upturned to erect appendages, whereas in the latter the calyx is deciduous and the leaves are cordate to reniform. In the section Psychrophila he placed two species of the Southern Hemisphere, the other section including all the species of the Northern Hemisphere. The peculiar leaf characters of the species of the Southern Hemisphere (5-8) are highly distinctive. Not only the morphological characters of some species of the genus vary considerably, but also in terms of cytology differentiation within the genus and even within species occurs. Therefore, various authors differ in that opinion with regard to the taxonomic treatment of the many forms.