British ferns (Filicopsida)


L. Watson and M. J. Dallwitz

Cystopteris montana (Lam.) Desv.

“Mountain Bladder-fern”.

Sporophyte. The rhizomes long and slender; long and rather creeping (about 2 mm in diameter, blackish); bearing scales (when young, these few, scattered, ovate).

Leaves distributed along the rhizomes (distant); to 10–30(–45) cm long; dying in the autumn; circinnate; complexly divided; bipinnate with conspicuously divided pinnules to tripinnate with undivided ultimate pinnules. Pinnae 4–13 on each side of the leaf (? - “up to 13”). The petioles longer than the blades (with a few ovate-lanceolate scales mainly near the base, dark brown at the base and paler above). Leaf blades in outline ovate-triangular. The longest pinnae the lowermost; 2.5–7 cm long. The adjacent pinnae approximated but not strongly overlapping to distant from one another and not at all overlapping. The venation of the lamina open.

The sporangia superficial; protected; aggregated in sori. The sori sub-orbicular (each on a receptacle with a vascular strand from the vein, widely separated, borne singly or in two short rows, one on either side of the midrib of ultimate segments); remaining discrete at maturity; with a true indusium. The indusia not reniform but flap-like from the base of the sorus, vaulted at first, later reflexed; whitish, ovate-orbicular, acute or sub-obtuse, irregularly toothed. The mature spores without a perispore.

Distribution and habitat. On base-rich substrates. Shady, wet, basic rock ledges, gullies and scree above 700 m. Local in central Scotland, formerly in Westmoreland.

Vice-county records. Britain: Westmorland, Stirlingshire, Mid Perthshire, East Perthshire, Angus, South Aberdeenshire, East Inverness-shire, West Inverness-shire, Argyll Main, South Ebudes.

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

Illustrations. • C. montana: Eng. Bot. 1868 (1886). • C. montana: Sowerby and Johnson (1859). • Cystopteris species (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.’.