The ferns are a group of vascular plants that differ from the seed plants in that they reproduce sexually via spores rather than seeds. Based upon recent molecular data the ferns are now also considered to include the horsetails (Equisetum) & whisk ferns (Psilotum).
February 7, 2017 - The higher order classification of ferns has been reorganized to correspond with:
PPG I (2016), A community-derived classification for extant lycophytes and ferns. Jnl of Sytematics Evolution, 54: 563–603. doi:10.1111/jse.12229