asplenium onopteris

Asplenium onopteris is known as the Irish spleenwort or western black spleenwort. It is difficult to identify compared with the black spleenwort, Asplenium adiantum-nigrum. The main difference is that A. onopteris is diploid and is one of the two parents of the tetraploid A. adiantum-nigrum (the other being the diploid A. cuneifolium). Armed with a microscope, the most consistent observable difference between A. onopteris and A. adiantum-nigrum is that A. onopteris spores have a mean diameter of ...