British ferns (Filicopsida)
W. hyperboria (Lilj.) R. Br.
Sporophyte. The rhizomes short, more or less erect; bearing scales (sparsely scaly above).
Leaves aggregated terminally; to 4–15 cm long; dying in the autumn; complexly divided; once pinnate, with conspicuously divided pinnae, or bipinnate with more or less undivided pinnules (the pinnae deeply lobed to pinnatifid). Pinnae about 7–15 on each side of the leaf. The petioles shorter than the blades (from about a quarter to two thirds as long, pubescent, sparsely clothed with short scales); jointed and ultimately abscising in the mid-region; vascularised via a single strand. The longest pinnae about a third of the distance from the base of the blade, or around the middle of the blade (the lowest pinna scarcely shorter to considerably so); 0.5–1.2 cm long. The largest pinnae triangular-ovate, 1–1.5 times as long as broad and the rachis and the undersides of the pinnae scale-less or with only short scales of about 1mm long, and few hairs. The venation of the lamina open.
The sporangia superficial; aggregated in sori. The sori sub-orbicular (borne on the vein endings, near the margins of the lobes); remaining discrete at maturity; with a true indusium. The indusia consisting mainly of hairs; resembling that of W. ilvensis (q.v.). The mature spores monolete; without a perispore.
Distribution and habitat. On base-rich substrates. In similar places to W. ilvensis (q.v.), but on more basic rocks, from 580 to 920 m. Very local, in Caerns and central Scotland, decreasing.
Vice-county records. Britain: Caernarvonshire, West Perthshire, Mid Perthshire, Angus, South Aberdeenshire, West Inverness-shire, Argyll Main, North Ebudes, West Ross.
Classification. Family Polypodiaceae (C.T.W.); Woodsiaceae (Swale and Hassler); Woodsiaceae (Stace). Order Athyriales (Swale and Hassler).
Illustrations. • W. alpina: as W. hyperborea, Eng. Bot. 1863 (1886). • W. alpina: Sowerby and Johnson (1859). • Gymnocarpium spp. and Woodsia spp. (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’.