British ferns (Filicopsida)

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L. Watson and M. J. Dallwitz

Osmunda regalis L.

“Royal Fern”.

Sporophyte. The rhizomes short, stout (massive); erect (emergent, so that emature plants may exhibit a small trunk of 30 cm or more); hairy, or naked (? - “not scaly”). Plants bearing markedly different fertile and sterile leaves.

Leaves aggregated terminally; to (30–)60–250(–400) cm long; complexly divided; bipinnate with more or less undivided pinnules, or bipinnate with more or less undivided pinnules to bipinnate with conspicuously divided pinnules (the pinnules of sterile leaves sometimes with a rounded lobe on the lower side at the base). Pinnae (5–)7–15(–17) on each side of the leaf (the 2–3 basal pairs fertile in the fertile leaves). The fertile leaves bipinnate with several pinnae, the lower (proximal) pinnae bearing normal green pinnules, but those of the upper (distal) pinnae non-laminate, more or less linear, and densely covered with sporangia. The petioles hairy when young, soon glabrous; vascularised via a single strand (this horseshoe shaped at the base, becoming half-moon shaped acroptally). The longest pinnae the lowermost to near the base of the blade (the sterile ones markedly decreasing in length acropetally). The venation of the lamina open (branching by repeated dichotomies, and reaching the margin).

Eusporangiate. The sporangia short-stalked and relatively massive, in non-indusiate, ill-defined clusters densely covering the fertile pinnules, brown; in the absence of laminae on the fertile pinnae, usually described as marginal; exposed; not aggregated into sori. The sporangial wall of several cell layers. The sporangia with an ‘annulus’ represented by a group of thick-walled cells on one side; dehiscing by a slit running across the apex from the lateral annulus.

Distribution and habitat. Helophytic to mesophytic. On peaty soil in fens, bogs, wet woods and heaths, and naturalized in ditches and hedgerows. Recorded throughout the British Isles and common in parts of western Britain and western Ireland, but absent from large areas of eastern Britain.

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, East Norfolk, West Norfolk, Bedfordshire, Northamptonshire, 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, Berwickshire, East Lothian, Midlothian, Fifeshire, Stirlingshire, West Perthshire, Mid Perthshire, Kincardineshire, 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 Sutherland, West Sutherland, Caithness, Outer Hebrides, 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 Osmundaceae (C.T.W.); Osmundaceae (Swale and Hassler); Osmundaceae (Stace). Order Osmundales (Swale and Hassler).

Illustrations. • Osmunda regalis: Eng. Bot. 1838 (1886). • Osmunda regalis: Sowerby and Johnson (1859). • Osmunda regalis: habit and vernation. • Osmunda regalis: details. Osmunda regalis: fertile pinna, ts near base of petiole, and sporangium showing the annulus. • Osmunda regalis (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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