British ferns (Filicopsida)
Sporophyte. The rhizomes stout; creeping to erect (the long, underground rhizomes becoming erect towards their apices); bearing scales. Plants bearing markedly different fertile and sterile leaves (the sterile leaves Dryopteris-like, the fertile ones brown, much smaller, and featherlike, with very narrow pinnae).
Leaves aggregated terminally; to 20–60 cm long (fertile), or 60–150 cm long (sterile); compound; simply divided to complexly divided (the fertile leaves), or complexly divided (the sterile ones); once pinnate, with conspicuously divided pinnae to bipinnate with more or less undivided pinnules (the sterile leaves once pinnate with deeply lobed pinnae, or just bipinnate). The petioles shorter than the blades (those of the sterile leaves less than half as long); vascularised via a single strand (representing a single leaf trace arising from the lower angle of the leaf gap). Leaf blades in outline more or less oblanceolate (long-attenuate to the base). The longest pinnae around the middle of the blade to above the middle of the blade. The pinnae gradually reducing in length to the very short basal ones. The venation of the lamina open.
The sporangia marginal; initially aggregated in sori. The sori sub-orbicular (in one or two contiguous rows along the pinna, covered by the tightly inrolled, firm lamina margins); becoming confluent when mature, or remaining discrete at maturity; protected by true and false indusia combined (the true indusia very fragile and soon obsolete). The false indusia continuous along the blade segments (protecting the rows of sori).
Distribution and habitat. In shady places. Naturalized. Mainland-European, commonly cultivated, and naturalized in southern and central Scotland, Westmoreland, Salop, and Northern Ireland.
Vice-county records. Britain: West Cornwall, South Somerset, North Somerset, Dorset, South Hampshire, West Sussex, Surrey, Middlesex, East Suffolk, East Norfolk, West Norfolk, East Gloucestershire, Worcestershire, Warwickshire, Staffordshire, Shropshire, Glamorgan, Carmarthenshire, Cardiganshire, Derbyshire, South Lancashire, Mid-west Yorkshire, South Northumberland, Westmorland, Isle of Man, Dumfriesshire, Kirkcudbrightshire, Peeblesshire, Selkirkshire, Roxburghshire, Berwickshire, Midlothian, West Lothian, Fifeshire, West Perthshire, Mid Perthshire, East Perthshire, Argyll Main, Dunbartonshire, Kintyre, North Ebudes. Ireland: West Mayo, Tyrone, Armagh, Antrim, Londonderry.
Classification. Family Polypodiaceae (C.T.W.); Onocleaceae (Swale and Hassler); Woodsiaceae (Stace). Order Athyriales (Swale and Hassler).
Illustrations. • Matteuccia struthiopteris (D. Lubin, photo).
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’.