British ferns (Filicopsida)
Allosorus crispus (L.) Röhl.
Sporophyte. The rhizomes short, creeping to ascending; bearing scales. Plants bearing markedly different fertile and sterile leaves (the sorus-bearing segments of the fertile leaves narrower than those of the sterile leaves).
Leaves densely distributed along the rhizomes (the outer ones sterile); to 5–30 cm long (the sterile leaves 5–15 cm, the fertile ones 10–30 cm); complexly divided; once pinnate, with conspicuously divided pinnae to bipinnate with more or less undivided pinnules (the pinnae of sterile leaves being usually 2-pinnatisect, and the pinnules pinnately lobed or toothed), or bipinnate with conspicuously divided pinnules to 4-pinnate (the fertile leaves more complexly divided). Pinnae 3–4 on each side of the leaf (in fertile leaves), or 3–7 on each side of the leaf (in sterile leaves). The petioles about as long as the blades to longer than the blades (up to 3 times as long, with a few brownish scales at the base). The venation of the lamina open.
The sporangia marginal to superficial; protected; initially aggregated in sori. The sori elongated (borne along the apical part of the veins, at first oblong); becoming confluent when mature (to form continuous longitudinal bands); with only a false indusium derived exclusively from the lamina margin. The false indusia continuous along the blade segments. Paraphyses absent. The mature spores trilete; without a perispore.
Distribution and habitat. On acid substrates. Montane, in rocky places on acid soils. Locally common in Wales, Scotland, England south to SW Yorkshire, local in Devon and in central and northern Ireland.
Vice-county records. Britain: South Devon, North Devon, South Somerset, Worcestershire, Shropshire, Glamorgan, Breconshire, Radnorshire, Carmarthenshire, Pembrokeshire, Cardiganshire, Montgomeryshire, Merionethshire, Caernarvonshire, Denbighshire, Derbyshire, Cheshire, South Lancashire, West Lancashire, North-east Yorkshire, South-west Yorkshire, Mid-west Yorkshire, North-west Yorkshire, Durham, South Northumberland, North Northumberland, Westmorland, Cumberland, Isle of Man, Dumfriesshire, Kirkcudbrightshire, Wigtownshire, Ayrshire, Renfrewshire, Lanarkshire, Peeblesshire, Selkirkshire, Roxburghshire, Berwickshire, Midlothian, Fifeshire, Stirlingshire, West Perthshire, Mid Perthshire, East Perthshire, Angus, Kincardineshire, South Aberdeenshire, North Aberdeenshire, Banffshire, Moray, East Inverness-shire, West Inverness-shire, Argyll Main, Dunbartonshire, Clyde Isles, Kintyre, South Ebudes, Mid Ebudes, North Ebudes, West Ross, East Ross, East Sutherland, West Sutherland, Outer Hebrides. Ireland: West Galway, Wicklow, Longford, Leitrim, Cavan, Louth, Fermanagh, West Donegal, Tyrone, Armagh, Down, Antrim, Londonderry.
Classification. Family Polypodiaceae (C.T.W.); Notholaenaceae (Swale and Hassler); Adiantaceae (Stace). Order Pteridales (Swale and Hassler).
Illustrations. • C. crispa: Eng. Bot. 1844 (1886). • C. crispa: Sowerby and Johnson (1859). • Cryptogramma crispa (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’.