Double Fertilization in Ephedra, a Nonflowering Seed Plant: Its Bearing on the Origin of Angiosperms

• DOI: 10.1126/science.247.4945.951
• Publication Date: 2006-10-05T22:10:14Z
• Authors: William E. Friedman
• Keywords: Double fertilization; Autapomorphy

Double fertilization and the associated formation of endosperm have long been considered unique defining characters (autapomorphies) angiosperms. During normal in Ephedra nevadensis, a nonflowering seed plant, fusion second sperm nucleus with ventral canal occurs regularly within egg cytoplasm. The occurrence double assumes added significance light its critical phylogenetic position as basal member most closely related extant group plants (Gnetales) to Thus, angiosperms may represent an evolutionary homology.