A protective structure in some flowering plants and bryophytes. In flowering plants it consists of a ring of bracts arising beneath the flower cluster of those species with a capitulum (i.e. members of the dandelion family) or an umbel (i.e. members of the carrot family). In mosses and liverworts the involucre is a projection of tissue from the thallus that arches over the developing archegonium.
Subjects: Biological Sciences.