Woodsia ilvensis (L.) R. Br.
Rusty cliff fern, woodsie de l'île d'Elbe.
Polypodiaceae, fern family.
Trans. Linn. Soc. London, 11: 173. 1813.
Acrostichum ilvense L. Sp. Pl.: 1071. 1753.
Type: Linnaean Herbarium 1245.13 (LINN) lectotype, selected by Jonsell and Jarvis, Nordic J. Bot. 14: 149. 1994.
Vegetative morphology. Plants perennial herbs; 5–15(–20) cm high; caespitose (loosely clustered); with erect to ascending unbranched stems arising close together, from a cluster of persistent petiole bases. Roots black. Ground-level or under-ground stems horizontal; stoloniferous; compact. Leaves present and green; leaves in a basal tuft; leaves alternate; leaves compound; leaves existing for a single season or less, or marcescent. Petioles (10–)15–30(–50) mm long; hairy (usually brown or dark purple, articulate above the base at a swollen node, relatively brittle and easily shattered); hairs more than the diameter of the petiole. Blades 45–150(–200) mm long; 12–25(–35) mm wide. Blades circinate when young (narrowly lanceolate fronds); with inconspicuous veins. Blades adaxial surface hairy (the blades narrowly lanceolate, usually two-pinnate towards the base, lacking glands). Blades adaxial surface hairs long-silky. Blades abaxial surface hairy. Blades abaxial surface hairs very dense (along the midrib, a mixture of multicellular hairs and linear-lanceolate scales). Blade margins entire. Conspicuous hydathodes present (as whitish enlarged slits near the tips of the veins), or absent (not visible). Leaf apices acute. Leaflet arrangement pinnate (pinnae ovate-lanceolate to deltate, longer than wide, abruptly tapered to a rounded or broadly acute apex; pinnules entire or crenate, rarely shallowly lobed; margins thin with multicellular hairs).
Reproductive morphology. Sporangia in sori on the under-surface of the leaves. Sori with a distinct indusium. Indusia of narrow hair-like segments, one row of cells many times longer than wide, and longer than the sporangia.
Chromosome information. 2n = 78–82. Britton (1953 Canada); Löve and Löve (1961c Iceland, 1976); Sorsa (1961, 1962 Finland); Taylor and Lang (1963 western Canada, 2n = 80–82); Cody and Mulligan (1982 Canada); Ma (1985 2n = 78); Ma and Wang (1986 China 2n = 78); Wagner (1987); Jonsell (2000 Sweden, secondary reference). Several more southern counts. Ploidy levels recorded 2x.
Distribution. Northern hemisphere distribution: circumpolar; Greenland, Canada, United States, Eurasia. Yukon, Continental Northwest Territories, Nunavut Islands, Continental Nunavut, Northern Québec. Low arctic. Arctic Islands: Baffin (and Nottingham Island).
Ecology and habitat. Substrates: cliffs.
Notes. Although generally separable, shade forms and possibly high latitude forms of W. ilvensis with reduced numbers of scales and hairs are occasionally misidentified as W. alpina. The morphological distinctions between these species are further blurred, at least in the south, by natural hybridization, which produces the intermediate triploid known as W. glacilis. Some of the best characters for distinguishing these taxa are spore size and morphology. Spores average less than 46 microns in W. ilvensis, more than 46 microns W. alpina, and are malformed and abortive in the hybrid. F.S. Wagner (1987).
Illustrations. • Plants in environment. Plants less than 15 cm high growing in rocky terrain. CMN Photo Library image S78–724. Photograph by Mildred and Raymond D. Wood. • Close-up of plant. Plants growing among rocks which is characteristic of cliff ferns. CMN Photo Library S84–5615. • Arctic Island Distribution.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
