An individual unit of the *calyx
. It is usually green and often hairy but in some species, e.g. marsh marigold (Caltha palustris), the sepals are brightly coloured and assume the function of *petals
. In such plants the petals may be absent, as they are in marsh marigold, or reduced, as in the Christmas rose (Helleborus niger), where they form small tubular nectaries. Sepals are supplied by several vascular bundles and are thought to be modified leaves.