British ferns (Filicopsida)
Sporophyte. The rhizomes short; bearing scales. Plants with no clear distinction into fertile and sterile leaves (although those with sori tend to have narrower divisions).
Leaves aggregated terminally; to 20–75 cm long; compound; characteristically and complexly divided; bipinnate with more or less undivided pinnules (in that the basal pinna on each side consistently bears a basal pinnule near its base). Pinnae 1–5 on each side of the leaf. The leaves compound-pinnate, with long, narrow pinnae of which only the lowest on each side bears a single pinnule. Leaf blades in outline ovate-triangular. The longest pinnae 7–16 cm long (x 0.7–2 cm, oblong-linear and finely toothed, basally cuneate). The venation of the lamina open (occasionally dichotomising, to the margins).
The sporangia (sub-) marginal; aggregated in sori. The sori much elongated (linear along the lamina margins); seemingly remaining discrete at maturity; with only a false indusium derived exclusively from the lamina margin. The mature spores trilete.
Distribution and habitat. In very sheltered places on walls, old buildings and rock faces. Naturalized. Native to southern Europe, naturalized in central and southern England.
Vice-county records. Britain: West Cornwall, East Cornwall, South Devon, North Somerset, East Sussex, East Kent, West Kent, Surrey, Hertfordshire, Middlesex, Berkshire, Oxfordshire, Buckinghamshire, East Suffolk, West Norfolk, Cambridgeshire, Bedfordshire, Worcestershire, Warwickshire, Staffordshire, Shropshire, Leicestershire, Derbyshire, South-east Yorkshire, Dunbartonshire, Channel Islands. Ireland: Dublin.
Classification. Family Pteridaceae (Swale and Hassler); Pteridaceae (Stace). Order Pteridales (Swale and Hassler).
Illustrations. • P. cretica: habit. • P. cretica: sorus details.
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’.