British ferns (Filicopsida)


L. Watson and M. J. Dallwitz

Onoclea sensibilis L.

“Sensitive Fern”.

Sporophyte. The rhizomes creeping; bearing scales. Plants bearing markedly different fertile and sterile leaves (the fertile leaves much smaller, non-green, with very narrow pinnae).

Leaves distributed along the rhizomes; to 30–100 cm long; compound (at least basally); simply divided (the sterile leaves fully pinnate only at the base and deeply lobed above), or simply divided to complexly divided (the fertile leaves); once pinnate, with conspicuously divided pinnae to bipinnate with more or less undivided pinnules (the fertile leaves being bipinnate or nearly so). The petioles longer than the blades; vascularised via a single strand. Leaf blades in outline ovate-triangular. The longest pinnae of the sterile leaves the lowermost. The venation of the lamina reticulate.

The sporangia marginal; aggregated in sori. The sori sub-orbicular (in compact groups, protected by the incurved lamina margin); remaining discrete at maturity; protected by true and false indusia combined. The false indusia continuous along the blade segments (protecting the rows of sori). Paraphyses absent. The mature spores monolete; without a perispore.

Distribution and habitat. In shady places. Naturalized. Native to eastern North America and eastern Asia, naturalized in CW and SW Scotland, W Wales, NW and S England, and Jersey.

Vice-county records. Britain: West Cornwall, South Devon, South Somerset, North Somerset, Dorset, South Hampshire, North Hampshire, East Sussex, West Kent, Surrey, South Essex, North Essex, Hertfordshire, Middlesex, Berkshire, Buckinghamshire, Worcestershire, Warwickshire, Staffordshire, Shropshire, Cardiganshire, Flintshire, Nottinghamshire, South Lancashire, West Lancashire, South-east Yorkshire, North-east Yorkshire, Mid-west Yorkshire, South Northumberland, Westmorland, Cumberland, Isle of Man, Kirkcudbrightshire, Renfrewshire, Lanarkshire, Mid Perthshire, East Perthshire, Banffshire, Dunbartonshire, Channel Islands.

Classification. Family Polypodiaceae (C.T.W.); Onocleaceae (Swale and Hassler); Woodsiaceae (Stace). Order Athyriales (Swale and Hassler).

Illustrations. • Onoclea sensibilis (K. Sytsma, photo).

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.’.