The family of the Ranunculaceae, although a large one (ca. 1200 species) occurring almost throughout the world, is generally regarded as a very natural one. The only genera with a recently more or less disputed position are Circaeaster, Glaucidiutn, Hydrastis, Kingdonia, and Paeonia. The others may at present all be considered to be ‘true’ Ranunculaceae. Various botanists have studied the delimitation of these genera, their affinity and phylogenetic links. Their ideas are often widely divergent. There is no need to go into the subject here, but some opinions on the place in the system of Caltha may be reviewed.