In this, the ninth and final article in the series on southern African Marchantiales, a taxonomic account is given of the genus Marchantia which is locally represented by five species. Two of the three subgenera that are recognized, namely subgenus Marchantia (with two species, M. polymorpha subsp. ruderalis and M. berteroana), as well as subgenus Chlamidium (Corda) Bischl. which is divided into three sections, namely Paleaceae (with M. paleacea subsp. paleacea), Chlamidium (with M. pappeana subsp. pappeana) and Papillatae (with M. debilis) are treated. The third subgenus, Protomarchantia Schust., is absent from the region. Corrections need to be made to the Marchantia species given in Magill & Schelpe's (1979) checklist and in Arnold & De Wet (1993). Descriptions and illustrations of the taxa together with distribution maps, their ecology and a key to the subgenera and species are provided. Only traditional taxonomic methods were employed and this treatment closely follows that of Bischler-Causse (1993a), the recognized world authority on the group. All southern African specimens held al BOL and PRE, as well as a few from other herbaria have been studied and some new collections have been added. it is shown that M. polymorpha subsp. ruderalis has been introduced, as it is only known from local nurseries. The presence here of M. paleacea subsp. paleacea is confirmed, although it is rare. Otherwise little that is new could be added to the exhaustive studies by Bischler-Causse (1993a).
