Perianth poorly developed or lacking

• A group of chiefly woody plants considered among the most primitive of angiosperms
• Contains 23 families including the Betulaceae and Fagaceae (includes the Amentiferae)
• Sometimes classified as a superorder
• Flowers often unisexual and often in catkins and often wind pollinated

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Dicotyledonae \Dicotyledonae\ n. (Bot.) a class of plants comprising those seed plants that produce an embryo with two cotyledons and net-veined leaves; divided into six (not always well distinguished) subclasses (or superorders): Magnoliidae and Hamamelidae ...