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. 2: 1071. 1753.
Plants caespitose (loosely clustered); with erect to ascending unbranched stems arising close together, from a cluster of persistent petiole bases; less than 15 cm high (usually); 5–15(–20) cm high. Roots black. Ground-level or under-ground stems horizontal; stoloniferous; compact. Leaves mostly basal; alternate; compound. Petioles 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; circinate when young (narrowly lanceolate fronds); with inconspicuous veins; adaxial surface hairy (the blades narrowly lanceolate, usually two-pinnate towards the base, lacking glands). Blades abaxial surface hairy; hairs very dense (along the midrib, a mixture of multicellular hairs and linear-lanceolate scales). Leaf margins entire. Conspicuous hydathodes present (as whitish enlarged slits near the tips of the veins), or absent (not visible). Plants reproducing by spores borne in sporangia. 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 = 82.
Distribution. Circumpolar. Low arctic. Greenland, Canada, United States, Eurasia. Arctic Islands: Baffin (two records from south-east Baffin Island mapped in Porsild and Cody, 1980. Records not at CAN).
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 terain. 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.C. LeBlanc, and M.J. Dallwitz 2000 onwards. Pteridophytes of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval.’ Version: 23rd February 2001. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000) , and Aiken, Dallwitz et al. (1999) should also be cited (see References).
