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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.

Jamesoniella undulifolia - Marsh Flapwort

Range & Status

Widespread but local in Europe, from the former Czechoslovakia north to Fennoscandia; also E. Asia, Greenland and N. America. ' Curiously rare' in Britain, with modern records from Cornwall northwards to Argyll.

Regional Distribution

Recorded in 1882 near Madron, but there are no modern records from W. Cornwall. Recent records are from five sites in E. Cornwall (SX06, SX17, SX27). However, the locality at Redhill Marsh (SX1671) was flooded by creation of the Colliford Lake reservoir and another population in the valley between Red Moor and Helman Tor (SX0661) has apparently been lost due to overgrazing by horses.

Habitat & Ecology

Grows amongst Sphagnum in wet, minerotrophic mires. Its ecology in Cornwall appears very similar to that revealed by a detailed study in France (Hugonnot et al ., 2003) which showed that it favours mature or ageing hummocks of S. capillifolium (Ehrh.) Hedw. It is a dioicous species in which perianths occur fairly often but capsules are very rare in Britain.


Likely to be at risk from any changes affecting the Sphagnum -rich mires in which it grows, such as those due to hydrological changes or excessive trampling by horses, cattle or sheep. All three of the populations that survive in Cornwall are very small and appear highly vulnerable.


One of the Cornish sites is protected as a SSSI, but the raised bog involved has tended to dry out and its surface has been over-grazed. Another site is now a nature reserve, but the species probably no longer occurs there following overgrazing by horses in the past. Listed as Endangered in the UK Red-list (Church et al ., 2001), as Endangered on the IUCN Red List, and placed on Schedule 8 of the Wildlife and Countryside Act 1981, as amended. This species is listed on the UK BAP Priority Species list (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.