THE PHYLOGENETIC RELATIONSHIP OF OPHIOGLOSSACEAE

Summary The systematic position of Ophioglossaceae was examined using available evidence from recent anatomical and morphological studies. Although the Ophioglossaceae are free‐sporing vascular plants like the Filicopsida, and are therefore commonly placed in that group, the character correlation of eustelic or sympodial primary vascular system of stem, the presence of vascular cambium, periderm, circular bordered‐pitted tracheids, the anatomy of axillary branching, solitary sporangia, and also noncircinate vernation indicate a relationship of the family with the progymnosperm‐seed plant line. It is suggested that the Ophioglossaceae are living progymnosperms and, among extant seed plants, the family is most closely related to Cycadopsida, both having large, fernlike leaves. It is pointed out that the Ophioglossaceae resemble glossopterid gymnosperms in the three‐dimensional structure of their leaves with epiphyllous sporophores.