As the result of molecular analysis, the Treubiales and Haplomitriales (Haplomitriopsida) are now recognized as sister to all other liverworts and the Blasiales are sister to the Marchantiidae in a monophyletic Marchantiopsida.
According to a recent synthesis (Crandall-Stotler & Stotler, 2000), the phylum Marchantiophyta (liverworts) is divided into three classes, the small early divergent Haplomitriopsida, Marchantiopsida (complex thalloids) and Jungermanniopsida (simple thalloid and leafy).
Whereas the Jungermanniopsida exhibit extreme quadrilobing, the Marchantiopsida are characterized by a gradation in quadripolarity and a diversity of spindle types and patterns of meiosis.
Next we describe features of meiosis in examples from the two major liverwort classes, the Marchantiopsida and Jungermanniopsida.
2007), the Marchantiopsida radiated to give rise to forms with elaborate elevated gametangiophores and reduced forms with receptacles hidden within the thallus, reduced sporophytes and loss of elaters.