comprising seed plants that produce an embryo with paired cotyledons and net-veined leaves; divided into six (not always well distinguished) subclasses (or superorders): Magnoliidae and Hamamelidae (considered primitive), Caryophyllidae (an early and distinctive offshoot), and three more or less advanced groups: Dilleniidae, Rosidae, Asteridae | a group of families of trees and shrubs and herbs having well-developed perianths and apocarpous ovaries and generally regarded as the most primitive extant flowering plants; contains 36 families including Magnoliaceae and Ranunculaceae; sometimes classified as a superorder |