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Cornish Red Data (2009)

The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.

Riccia nigrella - Black Crystalwort

Range & Status

Mainly a Mediterranean species in Europe, extending northwards along the Atlantic coast to Wales. Also occurs in SW. Asia, N. Africa, Macaronesia, N. America and Australia. In Britain, modern records are only from Wales (two sites) and W. Cornwall.

Regional Distribution

Restricted to the Lizard (SW61, SW71), where known by modern records from at least seven sites.

Habitat & Ecology

Grows on rather bare, shallow soil on cliffs, cliff tops, rocky slopes, banks and paths, in sites that are moist in winter but dry in summer (when the plant apparently disappears). In Cornwall it is known only from sites near the coast. It is a monoicous species in which sporophytes are frequent, maturing from December to May.


Plenty of suitable habitat apparently remains around its old sites, but there have been few records of it in the past decade. It is potentially susceptible to shading from taller plants or from increased use of paths by walkers.


Nearly all of its Cornish sites are in SSSI. The species is listed as Vulnerable in the UK Red-list (Church et al. , 2001) and was added to the UK BAP in 2007.

Click here to see Dr. David Holyoak's Bryophyte Flora for this species


I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.

The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.

Cornish Biodiversity Network. 2017.