The descriptive text, below the map, is from the Flora of Cornwall (1999), which was a Tetrad Atlas (the maps had 2km square dots or Tetrads). The map on this web page depicts the plant's distribution at the 1km square scale and shows the records made pre-2000 which were used in the 1999 Flora and those made since.
French, C.N., Murphy, R.J. & Atkinson, M. 1999. Flora of Cornwall. Wheal Seton Press, Camborne.