Polystichum lonchitis; The Holly fern is a fern that has leaves which are only subdivided in single leaflets. It has spore-forming organs (sori) on the underside of the leaflets which are covered by kidney-shaped membrane, typical for the Dryopteridaceae family (see the photo). It superficially resembles the Hard fern (Blechnum spicant). The latter has distinctly different fertile fronds (leaves) in comparison to the non-fertile fronds (the fertile = spore-forming fronds have much narrower leaflets). Another difference between the holly fern and the hard fern is that the hard fern leaflets have dentated edges, while the hard fern leaflets have smooth edges. The holly fern is more common and can be found in a broad band around the west, north and east coast. The hard fern is rarer occurring only in certain regions of the north, northwest and west coast and a few local spots elsewhere. The Icelandic name for this species is Skjaldburkni.