Preissia quadrata Narrow Mushroom-headed Liverwort

A dioicous, thallose liverwort which grows on calcium-rich substrates in fens, dune slacks and on walls and other stone structures. It bears a supeficial resemblance to Reboulia hemisphaerica, and is sometimes confused with it, but it is darker green, has more conspicuous air pores and it has a peppery taste. It is a Boreo-arctic montane species with a distinctly western and northern distribution in Britain and is represented in south and north Wales but is rare in, or absent from, much of mid and west Wales. It has undergone a significant decline in Britain, particularly in the lowlands and has been lost from many fenland habitats in England and dune slack habitats in Wales. It occurs in some Gower dune slacks but it is more frequently found growing on morter on stone bridges and walls in Neath Port Talbot. Sporophytes are occasional.