Arthur Cronquist (1919) developed comprehensive system of classification of angiosperms which deals particularly with the grouping of families into orders and subclasses on worldwide basis. He presented the comprehensive version of his concepts of Classification in the Evolution and Classification of Flowering Plants (1968). The latest version of his system has appeared in 1981. He considered the pteridosperms (seed ferns) as probable ancestors of angiosperms. His system of classification is mainly based on the phylogenetic features of plant habits, leaves, stomatal apparatus, stem, nodes, flowers, pollination, pollen grains, placentation, ovules, and embryo.
Cronquist divided the angiosperms in two classes, Magnoliopsida and Liliopsida which are equivalent to traditional Dicotyledons and Monocotyledons. These were further subdivided into eleven sub-classes, six in the Magnoliopsida (Magnoliidae, Hamamelidae, Caryophyllidae, Dilleniidae, Rosidae and Asteridae) and five in the Liliopsida (Alismatidae, Arecidae, Commelinidae, Zingiberidae, and Liliidae). The Magnoliidae were considered as the basal complex and the remaining five sub-classes were derived from it separately. The Magnoliopsida consist 64 order, 318 families and about 165,000 species and the Liliopsida 19 orders, 65 families and about 50,000 species.