What is (a) An inner appendage to a petal or a corolla, often forming a special cup, as in the daffodil and jonquil. (b) Any crownlike appendage at the top of an organ called?

corona — (Bot.) (a) An inner appendage to a petal or a corolla, often forming a special cup, as in the daffodil and jonquil. (b) Any crownlike appendage at the top of an organ. (Webster's 1913.)