Easily confused with : Parsley Fern but that has only one groove on the upper-surface of the mid-rib rather than the two of Black Spleenwort.
Western Black Spleenwort (Asplenium onopteris) grows only in Ireland, again on limestone ricks. It has more delicate and narrower yellowish-green leaves with the secondary leaflets narrowly pointed throughout their length. It has longer stalks with the reddish-brown coloration extending to the mid-ribs.
Occupies niches in walls, rocks, and hedge-banks. Most common in the West of the UK.
There seems to be a quite pronounced variation in the fronds of Black Spleenwort, even on other websites, many looking un-like the drawings in Blamey, Fitter and Fitters 'Wildflowers of Britain and Ireland' book, and this includes the specimen shown here. It could be that myself (and several other websites) have identified these wrongly, or it could be that the differences reflect real variations in appearance, your Author knows not. If anyone does, do please get in touch.
However, the numerous recorded hybrids of Black Spleenwort cannot account for this apparent variability because they are all very rare and none occur anywhere near the North West of England, and nearly all of the once few locations are now devoid of any hybrids.
Hybridizes with :
Forked Spleenwort (Asplenium septentrionale) to produce Asplenium × contrei only ever found in one hectad in North Wales, not been seen since 1999.
Hart's-tongue (Asplenium scolopendrium) to produce Asplenium × jacksonii only found in one or two hectads in Cornwall and an island SW of Penzance.
Irish Spleenwort (Asplenium onopteris) to produce Asplenium × ticinense only found in one or two hectads in Southern Ireland.
Lanceolate Spleenwort (Asplenium obovatum) to produce Asplenium × sarniense which has once to be found in Ireland in one hectad , but now only in one or two islands south west of Penzance.