Cornish Biodiversity Network  -  Supporting Wildlife Recording

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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 huebeneriana - Violet Crystalwort

Range & Status

Reliably known in Europe from S. Scandinavia southwards to the W. Mediterranean, in N. Africa and Asia. Populations in N. America are treated as a different subspecies. Occurs in Britain at widely scattered localities in England and Wales from E. Cornwall and Sussex northwards to the Clyde Isles.

Regional Distribution

One locality known, in a pool beside Tamar Lake Reservoir (SS21) where it was found in 1968 and 1972.

Habitat & Ecology

A colonist of base-poor mud exposed by falling water levels at the edge of large ponds, lakes and reservoirs. It is a monoicous species in which sporophytes are abundant, maturing mainly in late summer and autumn.


The species depends on periodic exposure of mud at the edge of water bodies, its spores persisting in the mud through years when water levels remain high. The only Cornish site now has high water levels maintained continuously ' for operational reasons' , so the plant is unlikely to reappear.


Listed as Vulnerable in the UK Red-list (Church et al ., 2001) and as Vulnerable under the IUCN Red List. Surveys over the past decade have shown that it has strong populations surviving in Wales and N. England, but few persisting in S. England. The Plantlife International website has a detailed Species Dossier that can be downloaded.


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.