British ferns (Filicopsida)
Unless indicated otherwise, the following attributes are implicit throughout the descriptions, except where the characters concerned are inapplicable.
Sporophyte. Plants rhizomatous. The rhizomes not becoming trunk-like as in tree ferns. Plants with no clear distinction into fertile and sterile leaves.
Leaves not rooting at their tips; circinnate; laminate; compound; not conspicuously bent near the junction of rachis and petiole; the leaves not as in Pteris (q.v.). The petioles not jointed. Leaf blades not thin and translucent; not lemon-scented when crushed; not covered underneath with rust-coloured scales. The lowermost pair of pinnae not conspicuously bent backwards away from the rest.
Homosporous; leptosporangiate. The sporangia tiny and delicate, stalked, all alike, borne in aggregates; protected. The sori not sunken. The sporangia not developing sequentially. The sporangial wall of only one cell layer; incorporating a conspicuous annulus of thick-walled cells. The sporangia with a vertical annulus; dehiscing horizontally by a transverse split.
Prothallus. Prothalli free-living; green and fleshy.
Distribution and habitat. Mesophytic. Native to the British Isles.
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’.