British ferns (Filicopsida)
Sporophyte. The rhizomes short, creeping to erect; bearing scales (when young, the scales dark, narrow). Plants with no clear distinction into fertile and sterile leaves.
Leaves aggregated terminally; to 5–20(–40) cm long; persistent; circinnate; compound; simply divided (the pinnae crenate or crenate-dentate distally). Pinnae 15–40 on each side of the leaf. The petioles much shorter than the blades (only about a quarter as long, or less, blackish with a narrow brownish wing); vascularised via a single strand (representing fusion of a pair of leaf traces). The petioles and rachides blackish, both with very narrow brownish wings. Leaf blades in outline linear; herbaceous (not leathery). The longest pinnae around the middle of the blade (the pinnae more or less equal in length for some distance around the middle); 3–7(–10) cm long. The venation of the lamina open.
The sporangia superficial; protected; aggregated in sori. The sori linear elongated (1–2 mm long, several borne obliquely on each side of the pinna, midway between its midrib and the margin, mainly along the upper branches of the veins but sometimes extending below the fork); remaining discrete at maturity; with a true indusium. The indusia attached on one side along a vein; whitish, entire or nearly so. Paraphyses absent. The mature spores monolete; with a perispore.
Distribution and habitat. On base-rich substrates, on neutral substrates, and on acid substrates. Non-calcareous (subsp. trichomanes), calcareous or neutral (subsp. quadrivalvens) and limestone (subsp. pachyrachis) rocks and walls. Represented by at least one sub-species almost everywhere in the British Isles, with subsp. quadrivalvens the commonest.
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, Peeblesshire, Selkirkshire, Roxburghshire, Berwickshire, East Lothian, Midlothian, West Lothian, 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, Caithness, Outer Hebrides, Orkney islands, Shetland, 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.); Aspleniaceae (Swale and Hassler); Aspleniaceae (Stace). Order Aspleniales (Swale and Hassler).
X Asplenophyllitis confluens (Moore ex Lowe) Alston is a sterile hybrid of this species with Phyllitis scolopendrium. A. x alternifolium Wulfen = A. trichomanes x A. septentrionale.
Illustrations. • A. trichomanes: Eng. Bot. 1878 (1886). • A. trichomanes: Sowerby and Johnson (1859). • A. x clermontiae (A. trichomanes x A. ruta-muraria): Eng. Bot. 1879 (1886). • A. x alternifolium (A. trichomanes x A. septentrionale): as A. germanicum, Eng. Bot. 1881 (1886). • 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’.