British ferns (Filicopsida)

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L. Watson and M. J. Dallwitz

Ceterach officinarum DC.

“Rusty-back Fern”.

Asplenium ceterach L.

Sporophyte. The rhizomes short, more or less erect; bearing scales (these narrow and dark).

Leaves to 4–20 cm long; persistent; simple, or compound (often pinnate only near the base, the broad-based pinnae becoming decurrent on the rachis acropetally); conspicuously, pinnately lobed; simply divided. The petioles shorter than the blades (a quarter as long or less, scaly). Leaf blades in outline linear to oblong; leathery; covered underneath with rust-coloured scales. The longest pinnae or lobes up to 2 cm long. The venation of the lamina reticulate.

The sporangia superficial; exposed; initially aggregated in sori. The sori elongated (linear, about 2 mm long, borne along forks of the lateral veins of the lobes); becoming confluent when mature; naked and neither indusiate nor pseudo-indusiate (or the indusia rudimentary). Paraphyses absent. The mature spores monolete; with a perispore.

Distribution and habitat. On base-rich substrates. In base-rich rock crevices, and mortar cracks in walls. Common in SW Britain to NW England, scattered to E England and north to Easterness, also in Ireland and the Channel Islands.

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, Roxburghshire, Berwickshire, East Lothian, Midlothian, West Lothian, Fifeshire, Stirlingshire, West Perthshire, Mid Perthshire, East Perthshire, Angus, Kincardineshire, East Inverness-shire, West Inverness-shire, Argyll Main, Dunbartonshire, Clyde Isles, Kintyre, South Ebudes, Mid Ebudes, North Ebudes, Caithness, 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).

Illustrations. • C. officinarum: Eng. Bot. 1883 (1886). • C. officinarum: Sowerby and Johnson (1859). • Ceterach officinarum (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’.

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