The Probert Encyclopaedia of Nature

PERIANTH

In botany, the perianth is the outer floral envelope - calyx and corolla - which surrounds and to some extent protects the essential organs of generation in a flower. As a rule it consists of an outer layer of greenish parts called sepals, and an inner layer of brightly coloured parts called petals; but sometimes one or other of these layers is missing, and sometimes though they are both present, they are indistinguishable from each other. Many plants, especially trees, contain no trace of a perianth in their flowers, and these are usually wind propagated.
Research Perianth