sepal, a modified leaf, part of the outermost of the four groups of flower parts. The sepals of a flower are collectively called the calyx and act as a protective covering of the inner flower parts in the bud. Sepals are usually green, but in some flowers (e.g., the lily and the orchid) they are the same color as the petals and may be confused with them. In some groups of plants (e.g., the marsh marigold and the anemone) they are absent. The small green leaflike structures at the base of the flower head in the aster family are not true sepals but bracts; the sepals are modified into a circle of tiny white hairs on the ovary (the pappus; see aster). The sepals are sometimes fused into a tube around the base of the petals, as in the mint family.
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