On the south side of the road bridge over the river Line I found a small plant of black spleenwort fern (Asplenium adiantum-nigrum). This is a pioneer species that often colonises bare, open rocky places though in this area it seems mainly confined to walls.
I particularly like a rather strange piece of writing on this. Talking of scree slopes, C. N. Page (1997) in The Ferns of Britain and Ireland says “In such sites where also semi-exposed but south facing, warm and sunny, some of the largest and oldest clumps of A. adiantum-nigrum can occur, each marking an island of least mobility, with bare unstable portions sliding all around it. Such microcosms of pioneering vegetation are probably mostly initiated by the fern, and thereafter only gradually accumulate a humus content largely from mosses and the fern’s own frond decay, bound only within the zone of the fibrous roots of the fern. Into these eventually also typically establish a few other wind-pruned vascular associates, typically including scattered miniature shrubs of Gorse (Ulex europaeus), wind-blasted Wood Sage (Teucrium scorodonia) and tightly-leaved shoots of low-profiled English Stonecrop (Sedum anglicum) or compact and clinging Ivy (Hedera helix).”