British ferns (Filicopsida)


L. Watson and M. J. Dallwitz

Polystichum munitum (Kaulf.) C. Presl

“Western Sword-fern”.

Sporophyte. The rhizomes stout; ascending; bearing scales. Plants with no clear distinction into fertile and sterile leaves.

Leaves aggregated terminally; to tough, 30–120(–180) cm long; persistent; circinnate; compound; simply divided (simply pinnate, the 5–15cm, unequal-sided pinnae much narrower than those of P. lonchitis, alternating on the rachis, narrowly elongate pinnae with with no free pinnule at the base, only a basal deltoid lobe on the upper side, otherwise only shortly toothed with bristle-tipped serrations). The petioles much shorter than the blades; vascularised by several discrete strands (derived via several leaf traces). Leaf blades in outline lanceolate; leathery. The longest pinnae near the base of the blade to around the middle of the blade (the lowest pinnae scarcely shorter than the longest ones). The pinnae not decreasing markedly in length basipetaly, the basal pinnae not or scarcely shorter than the longest pair. The venation of the lamina open.

The sporangia superficial; aggregated in sori. The sori sub-orbicular (in a row down each side of the midrib of the pinna, nearer the midrib than the margin, and a double row down its basal lobe, with the vein upon which the sorus is borne not or only shortly continued beyond it); remaining discrete at maturity; with a true indusium. The indusia peltate (umbrella-like and fringed). Paraphyses absent. The mature spores monolete; with a perispore.

Distribution and habitat. On neutral substrates and on acid substrates (in its native habitats, seems to favour well-drained acidic soils rich in humus). Naturalized (a garden escape from western North America, where it contributes understorey in moist coniferous forest at low elevations). On a shady laneside bank in Surrey.

Vice-county records. Britain: East Cornwall, Surrey. Ireland: Wicklow.

Classification. Family Polypodiaceae (C.T.W.); Dryopteridaceae (Swale and Hassler); Dryopteridaceae (Stace). Order Dryopteridales (Swale and Hassler).

Illustrations. • Polystichum munitum (J. Dwyer, 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.’.