Comprising seed plants that produce an embryo with a single cotyledon and parallel-veined leaves: includes grasses and lilies and palms and orchids; divided into four subclasses or superorders: Alismatidae; Arecidae; Commelinidae; and Liliidae. Synonyms: class Monocotyledonae, class Monocotyledones, Liliopsida, Monocotyledonae, Monocotyledones.
