Tepal

A tepal is one of the outer parts of a flower (collectively the perianth) when these parts cannot easily be divided into two kinds, sepals and petals. This may be because the parts of the perianth are undifferentiated (i.e. of very similar appearance), as in Magnolia, or because, although it is possible to distinguish an outer whorl of sepals from an inner whorl of petals, the sepals and petals have similar appearance to one another (as in Lilium). The term was first proposed by Augustin Pyramus de Candolle in 1827. (De Candolle used the term perigonium or perigone for the tepals collectively; today this term is used as a synonym for "perianth".)

Undifferentiated tepals are believed to be the ancestral condition in flowering plants. For example, Amborella, which is thought to have separated earliest in the evolution of flowering plants, has flowers with undifferentiated tepals. Distinct petals and sepals would therefore have arisen by differentiation, probably in response to animal pollination. In typical modern flowers, the outer or enclosing whorl of organs forms sepals, specialised for protection of the flower bud as it develops, while the inner whorl forms petals, which attract pollinators.