British ferns (Filicopsida)
Sporophyte. The rhizomes rather stout (fleshy); creeping (on or below the surface); bearing scales (densely clothed with reddish-brown, lanceolate scales).
Leaves distributed along the rhizomes; to 10–30(–45) cm long; persistent; simple, or compound; when not truly pinnate, conspicuously, pinnately lobed (and deeply pinnatifid); when truly pinnate, simply divided (once pinnate, the pinnae broad-based). The petioles shorter than the blades to about as long as the blades (from about a third as long, erect, naked); jointed and ultimately abscising at the point of attachment to the rhizome. Leaf blades in outline usually narrowly oblong lanceolate (mostly 2–4 times as long as wide, the lobes or pinnae 12–30 on either side and becoming shorter towards base and apex, the longest of them about one third to halfway from the base and (2.0-)4.0–7.0(-9.0) cm long, more or less entire or toothed, apically rounded or tapered). The venation of the lamina reticulate, or open.
The sporangia superficial; exposed; aggregated in sori. The sori when young, mostly elongated (broadly elliptic); remaining discrete at maturity; not sunken; naked and neither indusiate nor pseudo-indusiate. Paraphyses absent. The annuli (4–)7–9(–13) celled. The mature spores monolete; with a perispore.
Distribution and habitat. On base-rich substrates. In similar places to P. vulgare, but more calcicole and with a stronger preference for shade. With a similar distribution to P. vulgare (q.v.), but commoner in the South rare in the North, present in Channel Isles and absent from Orkney and Shetland.
Vice-county records. Britain: West Cornwall, East Cornwall, South Devon, North Devon, South Somerset, North Somerset, North Wiltshire, South Wiltshire, Dorset, Isle of Wight, South Hampshire, North Hampshire, West Sussex, East Sussex, East Kent, West Kent, Surrey, South Essex, North Essex, Hertfordshire, Middlesex, Berkshire, Oxfordshire, Buckinghamshire, East Suffolk, West Suffolk, East Norfolk, West Norfolk, Cambridgeshire, Bedfordshire, Huntingdonshire, Northamptonshire, East Gloucestershire, West Gloucestershire, Monmouthshire, Herefordshire, Worcestershire, Warwickshire, Staffordshire, Shropshire, Glamorgan, Breconshire, Radnorshire, Carmarthenshire, Pembrokeshire, Cardiganshire, Montgomeryshire, Merionethshire, Caernarvonshire, Denbighshire, Flintshire, Anglesey, South Lincolnshire, North Lincolnshire, Leicestershire, Nottinghamshire, Derbyshire, Cheshire, South Lancashire, West Lancashire, South-east Yorkshire, 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, Roxburghshire, Berwickshire, East Lothian, Midlothian, West Lothian, Fifeshire, Stirlingshire, West Perthshire, Mid Perthshire, East Perthshire, Angus, South Aberdeenshire, 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, Caithness, Outer Hebrides, Channel Islands. Ireland: South Kerry, North Kerry, West Cork, Mid Cork, East Cork, Waterford, South Tipperary, Limerick, Clare, North Tipperary, Kilkenny, Wexford, Carlow, Leix, South-east Galway, West Galway, North-east Galway, Offaly, Kildare, Wicklow, Dublin, 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.); Polypodiaceae (Swale and Hassler); Polypodiaceae (Stace). Order Polypodiales (Swale and Hassler).
P. x mantoniae Rothm. & U. Schneid. = P. vulgare x P. interjectum (the commonest, sterile hybrid); P. x shivasiae Rothm., also sterile, = P. interjectum x P. cambricum.
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’.