a subclass of dicotyledonous plants. The flowers either lack perianths or have simple perianths (Monochlamydeae). The flowers of some species have double perianths with unfused petals (Choripetalae). The subclass was first established in 1892 by the German botanist A. Engler as an initial, primitive group of dicotyledons, presumably going back to the beginnings of the phylogenetic system. Engler’s definition is no longer widely accepted, since the simple flower structure of Archichlamydeae is a secondary feature, which developed mainly as a result of adaptation for wind pollination.