Caltha

Caltha, from the Greek kalathos, a cup, the name of a small genus of marsh plants, belonging to the buttercup family, of which the one British species, C. palustris, the marsh marigold, is the best known. They are natives of cold and temperate regions, and are characterised by having regular, cup-shaped flowers made up of five roundish petaloid sepals (golden-yellow in C. palustris), no petals, indefinite stamens, and a ring of follicles. The yellow perianth, with no green sepals, at once distinguishes them from the buttercups.