Rothwell, G. W. (Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701) and M. T. Dunn (Department of Biological Sciences, Cameron University, Lawton, OK 73505). A century of seed ferns: Introduction to the symposium. J. Torrey Bot. Soc. 133: 4–6. 2006.—More than one hundred years have now elapsed since the reconstruction of Lyginopteris oldhamia documented the existence of the previously unrecognized major group of extinct seed plants that we now call seed ferns (Oliver and Scott 1904). This recognition by Oliver and Scott (1904) may well have been the single most important element ushering in a new era of botanical inquiry by placing fossils at the center of plant phylogenetic studies. Originally envisaged as an evolutionary link between ferns and modern seed plants, seed ferns are united by the combination of large and often highly dissected leaves, and seeds that are borne on the leaves (Stewart and Rothwell 1993, Taylor and Taylor 1993).