*bachelor's button*

(Bot.) A plant with flowers shaped like buttons; especially, several species of Ranunculus, and the cornflower (Centaurea cyanus) and globe amaranth (Gomphrena). [ 1913 Webster ]

☞ Bachelor's buttons, a name given to several flowers “from their similitude to the jagged cloathe buttons, anciently worne in this kingdom, ” according to Johnson's Gerarde, p. 472 (1633); but by other writers ascribed to “a habit of country fellows to carry them in their pockets to divine their success with their sweethearts.” Dr. Prior. [ 1913 Webster ]