A taxonomic assessment of the initial branching appendages in the liverwort genus Frullania Raddi

The liverwort genus Frullania is large and complex with over 1000 described taxa and the subgeneric boundaries, in particular, remain largely unresolv ed. Previous studies have alluded to the potential significance of the init ial appendages borne on Frullania-type branches. However, the use of initia l branching appendages has almost routinely been ignored or overlooked in F rullania systematics. Here, we have assessed and examined in detail the ini tial appendages for over 2000 lateral branches for 60 taxa representing 9 s ubgenera, which was expanded to a total of 100 species from twelve subgener a after surveying relevant literature. Characters investigated include: num ber of segments or lobes, position of insertion, orientation, symmetry, dep th of incision, and features associated with size, shape, and the apex of t he lobe or segment. Key criteria that are taxonomically informative both at a species and subgeneric level include: the presence or absence of saccate appendages, the number of saccate appendages, and the number of lobes or s egments at the first branch underleaf and first branch leaf. We have also d eveloped a novel means of classifying this otherwise complicated suite of c haracters. On the basis of these characters we recognise 13 discrete catego ries and easily recognisable names have been applied to each of these categ ories. A key and descriptions are provided. Speculation is also made regard ing possible phylogenetic relationships between taxa based on characters as sociated with the initial branching appendages.