Nowell's limestone moss  (Zygodon gracilis)

Information supplied by English Nature:

http://www.englishnature.org.uk/

Endemic: A species or taxonomic group that is only found in one particular country or geographic area.
Ex-situ: Measures to conserve a species or habitat that occur outside of the natural range of the species. E.g. in zoos or botanical gardens.
Spores: Microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.