co·rol·la /kəˈrɑlə, ˈro-/
花冠
Co·rol·la n. Bot. The inner envelope of a flower; the part which surrounds the organs of fructification, consisting of one or more leaves, called petals. It is usually distinguished from the calyx by the fineness of its texture and the gayness of its colors. See the Note under Blossom.
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corolla
n : (botany) the whorl of petals of a flower that collectively
form an inner floral envelope or layer of the perianth;
"we cultivate the flower for its corolla"