British ferns (Filicopsida)
Dryopteris thelypteris (L.) A. Gray, Aspidium thelypteris (L.) Sw., etc.
Sporophyte. The rhizomes long, slender; creeping (below ground); bearing scales to naked (the few, small scales soon lost). Plants rather ambiguously bearing markedly different fertile and sterile leaves to with no clear distinction into fertile and sterile leaves (the sterile leaves often smaller, with relatively shorter petioles and broader segments).
Leaves usually distributed along the rhizomes (singly, or sometimes in sparse tufts), or aggregated terminally (rarely with a few-leaved crown); to 15–120(–150) cm long (the fertile leaves usually longer); dying in the autumn; compound; complexly divided; once pinnate, with conspicuously divided pinnae (the pinnae only shortly stalked). Pinnae about 15–25 on each side of the leaf. The petioles about as long as the blades to longer than the blades (in fertile leaves), or shorter than the blades to about as long as the blades (often relatively shorter in sterile leaves, slender, brittle, blackish at the base and with very few or no scales). Leaf blades in outline narrowly oblong to elliptic, or ovate, or lanceolate. The longest pinnae around the middle of the blade, or near the base of the blade to about a third of the distance from the base of the blade; about 5–9 cm long. The venation of the lamina open.
The sporangia superficial; exposed to protected; aggregated in sori. The sori sub-orbicular (very small, forming a row on either side of the segment, about midway between midrib and margin, though usually appearing closer to the margin because of reflexing); remaining discrete at maturity; with a true indusium, or naked and neither indusiate nor pseudo-indusiate (the indusia if present small and fugaceous). The indusia when present, reniform and attached at the indentation (small, thin, irregularly toothed).
Distribution and habitat. Helophytic. In marshes and fens, often abundant in carr or alderwood, usually shaded by taller vegetation. Scattered in Britain and Ireland, north to central Scotland, but decreasing and now frequent only in East Anglia.
Vice-county records. Britain: West Cornwall, East Cornwall, South Devon, North Devon, North Somerset, South Wiltshire, Dorset, Isle of Wight, South Hampshire, North Hampshire, West Sussex, East Sussex, East Kent, West Kent, Surrey, South Essex, North Essex, Berkshire, Oxfordshire, Buckinghamshire, East Suffolk, West Suffolk, East Norfolk, West Norfolk, Cambridgeshire, Bedfordshire, Huntingdonshire, Northamptonshire, Monmouthshire, Herefordshire, Warwickshire, Staffordshire, Shropshire, Glamorgan, Breconshire, Radnorshire, Carmarthenshire, Pembrokeshire, Caernarvonshire, Denbighshire, Flintshire, Anglesey, South Lincolnshire, North Lincolnshire, Nottinghamshire, Derbyshire, Cheshire, South-east Yorkshire, North-east Yorkshire, South-west Yorkshire, Mid-west Yorkshire, North-west Yorkshire, North Northumberland, Westmorland, Cumberland, Kirkcudbrightshire, Mid Perthshire, Angus, South Aberdeenshire, South Ebudes, Mid Ebudes. Ireland: South Kerry, North Kerry, West Cork, Mid Cork, Clare, North Tipperary, South-east Galway, North-east Galway, Offaly, Kildare, Wicklow, Meath, West Meath, Longford, Roscommon, East Mayo, West Mayo, Sligo, Leitrim, Cavan, Louth, Monaghan, Fermanagh, East Donegal, West Donegal, Tyrone, Armagh, Down, Antrim, Londonderry.
Classification. Family Polypodiaceae (C.T.W.); Thelypteridaceae (Swale and Hassler); Thelypteridaceae (Stace). Order Athyriales (Swale and Hassler).
Comments. The leaves not glandular, not lemon-scented when crushed; and by contrast with Phegopteris, the bases of the upper pinnae are not decurrent on the rachis.
Illustrations. • T. palustris: as Lastrea thelypteris, Eng. Bot. 1848 (1886). • T. palustris: Sowerby and Johnson (1859). • British Thelypteridaceae (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’.