angiosperm

noun

(Gr. aggeion: vessel, bowl, container; sperma: seed) Any flowering plant, i.e. a seed-bearing plant whose ovules, and hence seeds, develop within an enclosed ovary. Angiosperms comprise a vast phylum (or division) of diverse leafy green plants (Anthophyta or Angiospermophyta; about 240 000 species) in which the seeds are formed within an ovary, which becomes the fruit. They are thought to have evolved from the cone-bearing gymnosperms at the end of the Jurassic period (about 135 million years ago), rapidly radiating and becoming the dominant plants in the mid-Cretaceous (about 100 million years ago). They include many trees and shrubs but most are herbaceous. The 300 families are grouped into two classes: the monocotyledons and dicotyledons. Cf. gymnosperm.