Mannia californica (Gottsche ex Underw.) L.C.Wheeler (Aytoniaceae, Marchantiales) in Ardèche (France), new to Europe

Mannia californica (Gottsche ex Underw.) L.C. Wheeler is reported as new to Europe from Ardèche department, France. The French collections are briefly described and compared with other European species of the genus Mannia, notably M. fragrans and M. androgyna. The French populations occur in clefts on calcareous cliffs in well preserved canyons. The plants are scarce at each locality but freely produce spores. The known populations do not seem to be under extreme threat at present but should urgently receive statutory protection.