MAIDENHAIR SPLEENWORT : Asplenium trichomanes
This is a very attractive small fern. It has long fronds made up of short, round leaflets paired from a central black stem. The examples shown below grow from a stane dyke with sufficient earth and dampness to sustain it. It can also be be found growing in tufts on rocks, old walls and mossy branches.
It spreads by means of spores, so new 'crowns' establish themselves naturally.
Growing happily from the smallest of cracks.
EPBS / BRITISH PTERIDOLOGICAL SOCIETY : https://ebps.org.uk/ferns/identification/key-to-common-british-native-ferns/common-native-ferns/