Diagram showing the parts of a mature flower; here the perianth is separated into sepals and petals.
The term perianth (sometimes called perigonium) has two similar but separate meanings in botany:
In flowering plants, the perianth consists of the calyx (all sepals) and the corolla (all petals) of the flower. These may be described as being either dichlamydeous in which the two components are clearly separate, or homochlamydeous, in which they are indistinguishable. When in two whorls, it is described as biseriate. When the corolla consists of separate petals the term apotepalous is used, or polypetalous where many petals. In contrast the petals may be united to form a tubular corolla (gamopetalous or sympetalous).