Evolution of Isoetalean Lycopsids

The recognition of numerous similarities between Isoetes L. and extinct arborescent lycopsids historically led to one of the best Known phylogenetic lineages in vascular plant evolution. The lycopsid reduction series proposed the derivation of the extant guillwort Isoetes from the Carboniferous lepidodendrids through a progressive reduction in both stems and stigmarian rooting systems. New information gained in the past decade demonstrates that the history of this group is more complex than the linear reduction sequence suggests (...)