Flora of the Canadian Arctic Archipelago
English: Alpine rockcress,
French: Arabette alpine.
Brassicaceae (Cruciferae), Draba family.
Published in Sp. Pl. 664. 1753.
Type: Described from mountains in Switzerland and northern Scandinacia, selected by Jonsell in Jarvis et al., Regnum Veget. 127: 20. 1993. Lectotype: BM. Clifford Herbarium: 335, Arabis No. 1.
Vegetative morphology. Plants 7–15 cm high; perennial herbs; caespitose. Only fibrous roots present. Ground level or underground stems absent. Caudex present (short). Aerial stems erect, or decumbent. Leaves mainly basal; alternate; dying annually and non-persistent. Petioles absent. Leaf blades simple. Leaf blade bases cordate. Leaves not grass-like. Blades (15–)20–40(–60) mm long, (5–)7–12(–15) mm wide, ovate, flat, veins pinnate. Blade adaxial surface dull, without sessile glands, hairy, hairs stellate (2- or 3-forked), hairs sparse, hairs white, or translucent. Blade abaxial surface dull, hairy, hairs pubescent. Blades not lobed. Blade margins dentate (coarsely dentate to sub-entire), with non-glandular hairs, with teeth all around the blade. Hydathodes present but inconspicuous (at the tips of the leaf dentations). Blade apices acute.
Reproductive morphology. Flowering stems conspicuously taller than the leaves; with leaves. Inflorescences racemose (with relatively large showy flowers in crowded racemes); elongating as the fruit matures. Pedicels present; glabrous. Flowers per inflorescence 5–20; small, or medium-sized; radially symmetrical (actinomorphic). Sepals conventional; 4; free; 0.9–1.1 mm long; 2.5–3(–3.2) mm wide; green, or yellow (cream), or purple; herbaceous. Calyx hairy. Calyx hairs a few forked hairs on the apex; non-glandular; white or translucent. Petals conventional; free; longer than the calyx; 4; white; ovate; unlobed; (7–)7.5–8.5 mm long; 1.6–2 mm wide. Stamens 6; stamen filaments markedly unequal in length; stamen filaments glabrous. Anthers yellow; 0.5–0.7 mm long. Ovary superior; carpels 2; syncarpous. Ovaries glabrous. Styles 1; thick and short; 0.1–0.3 mm long. Stigmas per ovary 1. Placentation parietal. Ovules per ovary 10–16. Fruit stalk 5–8 mm long; dry; a silique (straight or slightly curved); elongate-cylindrical; yellowish, or purple; 24–48 mm long; 1–2 mm wide; glabrous; dehiscent; shedding the outer walls to expose a thin inner wall, with the seeds attached at the margins on either side. Styles remaining straight; persisting in fruit 0.25–0.75 mm long (stocky). Seeds 10–16; 1–1.2 mm long (+0.2–0.3 mm, "halo" of material that becomes mucilaginous when wet); brown (body), or yellowish (mucilaginous "halo"); surfaces smooth and winged (orbicular, narrowly winged all around, i.e., the "halo").
Chromosome information. 2n = 16.
2n (2x) = 16. Böcher (1938a, Greenland?); Rollins (1941, eastern Canada); Böcher and Larsen (1950); Löve and Löve (1956, Iceland; 1982, Arctic Canada); Jørgensen et al. (1958, Greenland); Sokolovskaya and Strelkova (1960, 1962, northern Russia); Hedberg (1962b); Mulligan (1964, Canada); Dalgaard (1988, western Greenland). Mulligan (2003, citing counts by Knowlton, and Cinq-Mars et al. 1960). Numerous more southern counts.
Ploidy levels recorded 2x.
Ecology and habitat. Substrates: snow patches, along streams, river terraces, ridges, barrens, flood plains; imperfectly drained moist areas, dry, moderately well-drained areas; gravel, sand; with low organic content; acidic, or circum-neutral. Elven (personal communication, 2005) described this species as commonly growing in circumneutral or acidic situations rather than in calcareous ones. The most common habitats, in my opinion, is snow-bank environments, banks of creeks and rivers, and generally on at least seasonally wet gravel and sand, sometimes in the damp, lower parts of long snow-covered scree.
The other entities of the group (the European petraea, the NE European to N Siberian septentrionalis, and the broadly amphi-Beringian umbrosa) occur in similar habitats.
North American distribution. Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago limited. Uncommon. Low Arctic (rather oceanic). Arctic islands: Baffin, Southampton.
Northern hemisphere distribution. Amphi-Atlantic. Northern Iceland, Northern Fennoscandian, KaninPechora, Svalbard Franz Joseph Land, Polar Ural Novaya Zemlya, Taimyr Severnaya Zemlya, Central Canada, Labrador Hudson Bay, West Greenland, East Greenland.
General notes. See Al-Shehbaz et al. (1999), Novon 9: 296–307, for their concept of Arabis and Arabidopsis.
Illustrations. • Habitat: Baffin Island. Plant growing between the markers on a talus slope. 10 July, 2004. Nunavut, Baffin Island, Ogac Lake. Aiken and LeBlanc 04–041. CAN 586510. • Close-up of plant. Plant growing between the markers on a talus slope. 10 July, 2004. Nunavut, Baffin Island, Ogac Lake. Aiken and LeBlanc 04–041. CAN 586510. • Close-up of leaves. Simple leaves with no petiole, dentate margins, and hairy adaxial blade surfaces. Aiken and LeBlanc 04–041. CAN 586510. • Close-up of leaves. Simple leaves with no petiole, dentate margins, and adaxial blade surfaces covered with stellate hairs. Aiken and LeBlanc 04–041. CAN 586510. • Surface view of flowers. Note characteristic Brassicaceae flowers with 4 petals, a whorl of 4 anthers that ripen first and a second whorl of two anthers that ripen later. Aiken and LeBlanc 04–041. CAN 586510. • Previous season's fruit. Remains of previous season's fruit showing the silique in this species is many times longer than wide, and seeds attached to the central partition. Aiken and LeBlanc 04–041. CAN 586510. • Arctic Island Distribution.
This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.
Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.
Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa..