Stace (2010) pg 39/ Rose (1989) pg 230/ BSBI Distribution: http://www.bsbimaps.org.uk/atlas/map_page.php?spid=1544.2
This plant is very noticable and found throughout the stable dunes of Blakeney Point, often in clumps of both living and dead ferns:
It is identifiable as a fern due to the characteristic “fronds” and the sporangia on the underside of the pinnae (Rose 1989). As a member of the Polypodiaceae, this plant has scaly, extended rhizomes and leaves borne singly along these rhizomes. The leaves coil spirally when young.
The leaves (including petioles) of P.vulgare are 25cm, narrowly with 12 to 30 pinnae on either side (Stace 2010). The whole leaf shape is oblong and the margin has deeply pinnafied lobes (Stace 2010).
Upperside:
Another characeteristic of the Polypodiaceae family are that sori (asexual fructification/group of sporangia) are borne on the side veins of the underside pinnae and have no indusium (membranous flap covering sori). In the case of Polypodium vulgare, the sori are circular rather than elliptical in P. interjectum or P.cambricum. Also there are no hairs between the sporangia (Rose 1989).
Underside:
Plants of Blakeney Point 