RECOGNITION OF FRULLANIA CONGESTA: A CASE STUDY TO PRESENT A SPECIES CONCEPT AND A SYNTHESIS OF SIGNIFICANT TAXONOMIC CHARACTERS FOR THE LARGE LIVERWORT GENUS FRULLANIA (FRULLANIACEAE)

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  Frullania Raddi is a large and complex liverwort genus, with a worldwide distribution, consisting of over 1000 binomials. Historically, many critical morphological and anatomical features have constantly been neglected or overlooked and this has resulted in considerable taxonomic confusion for a number of species. An assessment of Frullania congesta Gottsche, Lindenb. & Nees is used as a case study to discuss species concepts. A synthesis of significant taxonomic characters is provided in an effort to help refine species boundaries within the genus, and to provide an aid in future monographic and regional studies. We stress the importance of examining a suite of morphological and chemical characters that are significant in Frullania systematics for determining satisfactory species boundaries; the study of live material and the ecology is also essential. Salient morphological features include those associated with the initial branching appendages, cell wall anatomy, oil bodies, position of gynoecia, and ornamentation of the spore surface. Lectotypification of F. congesta and F. dissitifolia Steph. are also provided.