Mercurialis perennis
Because of the ecology of the area was designated as a biological Site of Special Scientific Interest in 1952. The ground flora is indicative of the calcareous nature of the site, with dog's mercury ("Mercurialis perennis") being locally dominant. Many of the associated species are characteristic of ancient woodland. Wood anemone ("Anemone nemorosa") and common bluebell ("Hyacinthoides non-scripta") are both locally abundant. The valley of the main gorge is humid and provides ideal conditions for fungi and ferns. It contains a substantial assemblage of bryophytes with over 120 species recorded including the nationally rare "Bryum canariense" and the very rare "Amblystegiella confervoides".