1999 Volume 86 Pages 71-87
Verdoornia Schust., a monotype of New Zealand, differs from all other investigated Metzgeriales in the stout, short archegonia with virtually no differentiation of a narrowed neck, and no basal constriction. It is one of a small group of primitive endemics in which there is little or no aggregation of gametangia into gynoecia and androecia; it is, equally, one of a small group of genera with exceedingly large, clavate slime papillae, secreting massive amounts of mucilage.
The implications of these three distinctive features are analyzed. They, with the peculiar large “idioblasts” in thallus cells ― structures that seem quite different from normal oil-bodies, suggest the genus is highly isolated. It seems likely that it, and several other isolated genera currently assigned to the Metzgeriales, will need to be segregated from that heterogeneous order.
The heterogeneity of the Metzgeriales s. amplo, together with the evident stenotypy and wide phylogenetic distances between most genera, suggest that the group is a very old one. It is inferred that, hence, evolution of a thallus occurred very early ― perhaps prior to evolution of leafy gametophytes, perhaps from a radial, simple, leafless gametophyte.