Systematically relevant characters of the Radula sporophyte (Radulaceae: Hepaticae)

Structural diversity exhibited by the sporophytic generation of Radida species exceeds expectations based upon the variation observed in the morphology and anatomy of the gametophytic generation, and is unprecedented in comparison with any other genus of Hepaticae. The sporopyte presents itself as a wealthy source of potentially informative characters in line with observed diversity. Surprising is the occurrence of both one and two phase patterns of capsule development, of both linear and spiral patterns of capsule dehiscence, and of a wealth of different capsule wall architectural types within the genus. Spores are variable in both size and ornamentation among the species studied, this with the repeated occurrence of various 'spore-types' in different species suggests this is a character of significance, despite the fact that comparatively little is known of the ecological significance of spore ornamentation. Elaters are also a source of useful definitive characters, with different shapes, types of elater bands, and ornamentation being observed. A total of 12 sporophyte and spore derived characters are here identified as potentially informative, of which only 4 have been utilised by previous workers. Sporophyte derived characters appear to have the potential to resolve conflicts, discrepancies and inadequacies of the current infrageneric classification, and may present a picture of infrageneric relationships quite different to that currently accepted based on gametophytic characters.