FLORA OF ICELAND elements: Dryopteris expansa, Northern Buckler-fern, Dílaburkni

Dryopteris expansa; The Northern Buckler-fern is a large bipinnate, near to tripinnate fern having sori/sporangia on the bottom-side of the leaflets. On every leaflet are in two longitudal rows about 10 sori. However, on the first lobe and sometimes on other lobes as well, there are about 4 sori in two lateral rows. This shows that the first lobe is well on its way to become a leaflet by itself (making the whole leaf tripinnate). The similar Male-fern (Dryopteris filix-mas) does not have this feature.
It is most common in the north-western fjord region of Iceland. Elsewhere, it can be found in certain northern, western and south-western regions. It grows in cracks/hollows of lava fields and in taller shrub vegetations (birches).
It can easily be confused with the Male-fern and the Lady-fern. It differs frond the Male fern by the more incised leaflets (at the base tripinnate). The Dryopteris species (Male- & Buckler-fern) differ from the Athyrium species (Lady-ferns) by having the sporangia next to the main leaf-veins where on the Athyria's they are placed on top of the veins.
It is a member of the Dryopteridaceae - shield fern / wood fern family. The Icelandic name for this species is Dílaburkni.