Before leaving the California poppy (Eschscholzia califormica), I might as well point out another interesting trait.
The outer parts of a flower (calyx) are usually composed of leaflike parts called sepals that protect the bud as it develops and before it opens. The sepals, commonly green in color, generally surround the base of the unfurled petals.
The sepals of California poppy fuse together completely and form a hood or cap over the bud. This dunce-cap covering, called a calyptra, is attached to the flower receptacle (the expanded part of the flower stalk that bears the reproductive organs). As the petals expand the calyptra (plural, calyptrae) parts from the receptacle (abscission) and is pushed off the plant. There are no sepals on a California poppy flower.
Bryophytes (mosses and liverworts) and root tips also have calyptrae. Both the bryophyte and root calyptrae are protective, as is the California poppy calyptra, but are different types of plant structures.