Status in Britain: Red Data Book
Other: WCA Schedule 8; European RDB; Biodiversity Key Species

A species found on rocks and trees in the flood zone of rocky rivers. A fairly robust plant with shoots having a cylindrical appearance, and often curved. The leaves are ovate with a nerve running about three-quarters their length. Cells are rounded. This is a rare species in Britain, and in Wales is only known from a section of the River Teifi. It is specially protected by inclusion on Schedule 8 of the Wildlife and Countryside Act