This figure is taken from Pearson (1995).  The phylogeny was produced by comparisons between morphological characters and informed by molecular data.  Pearson illustrates the seed plants as coming from the archaeopterid "ferns".  From there, the cycad-seedferns gave rise to two major groups: one that culminated in the conifers and flowering plants and the other that culminated in the gnetophytes.  Compare this with Pryer et al. (2001) and Tudge (2000).