British ferns (Filicopsida)
Sporophyte. The rhizomes short, ascending to erect; bearing scales (densely so, the blackish scales subulate). Plants with no clear distinction into fertile and sterile leaves.
Leaves aggregated terminally; to 6–40(–100) cm long; persistent; circinnate; compound; simply divided, or simply divided to complexly divided (the pinnae irregularly crenate, asymmetric, more developed on their upper side, which may bear a small lobe); sometimes approaching once pinnate, with conspicuously divided pinnae. Pinnae 8–20 on each side of the leaf (? - up to 20). The petioles shorter than the blades (about a third to half as long, brown, scaly at the extreme base); vascularised via a single strand (representing fusion of a pair of leaf traces). Leaf blades in outline oblong, or lanceolate (or oblong-lanceolate); leathery. The longest pinnae about a third of the distance from the base of the blade to around the middle of the blade; (1–)1.5–4 cm long. The venation of the lamina open.
The sporangia superficial; protected; aggregated in sori. The sori linear elongated (3–5 mm long, borne along the upper forks of the secondary veins of the pinna, two to several arranged obliquely on each side, about midway between the midrib and the margin); remaining discrete at maturity; with a true indusium. The indusia attached on one side along a vein; brownish, entire. Paraphyses absent. The mature spores monolete; with a perispore.
Distribution and habitat. Walls, cliffs and rock crevices close to the sea, often sea-sprayed. Frequent around the coasts of the British Isles, except for eastern and southern England from S Hampshire to E Yorkshire (though formerly in E Sussex).
Vice-county records. Britain: West Cornwall, East Cornwall, South Devon, North Devon, South Somerset, North Somerset, Dorset, Isle of Wight, East Sussex, East Kent, Monmouthshire, Herefordshire, Glamorgan, Carmarthenshire, Pembrokeshire, Cardiganshire, Merionethshire, Caernarvonshire, Anglesey, Derbyshire, Cheshire, South Lancashire, West Lancashire, South-east Yorkshire, North-east Yorkshire, Durham, South Northumberland, North Northumberland, Westmorland, Cumberland, Isle of Man, Kirkcudbrightshire, Wigtownshire, Ayrshire, Renfrewshire, Berwickshire, East Lothian, Fifeshire, Angus, Kincardineshire, South Aberdeenshire, North Aberdeenshire, Banffshire, Moray, West Inverness-shire, Argyll Main, Clyde Isles, Kintyre, South Ebudes, Mid Ebudes, North Ebudes, West Ross, East Ross, East Sutherland, West Sutherland, Caithness, Outer Hebrides, Orkney islands, Shetland, Channel Islands. Ireland: South Kerry, North Kerry, West Cork, Mid Cork, East Cork, Waterford, Limerick, Clare, Kilkenny, Wexford, West Galway, Wicklow, Dublin, West Mayo, Sligo, Leitrim, Louth, Fermanagh, East Donegal, West Donegal, Down, Antrim, Londonderry.
Classification. Family Polypodiaceae (C.T.W.); Aspleniaceae (Swale and Hassler); Aspleniaceae (Stace). Order Aspleniales (Swale and Hassler).
Illustrations. • A. marinum: Eng. Bot. 1876 (1886). • A. marinum: Sowerby and Johnson (1859). • 9 British Aspleniaceae (inter alia).
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2004 onwards. British ferns (Filicopsida). Version: 4th January 2012. http://delta-intkey.com’.