Flora of the Canadian Arctic Archipelago
English: Purple rockcress,
French: Braya glabre.
Brassicaceae (Cruciferae), Draba family.
Vegetative morphology. Plants (1.2–)3.5–17(–23) cm high; perennial herbs; caespitose. Taproot present. Ground level or underground stems vertical. Caudex present. Aerial stems a small transition zone between taproot and basal leaves, or branching from a tap at or near ground level into two or more branches; erect, or ascending, or decumbent, or prostrate. Aerial stem trichomes appressed, or spreading. Leaves mainly basal, or basal in a rosette; patent, or erect; alternate; dying annually and non-persistent. Petioles present, or absent; 0–40 mm long; winged, or not winged; glabrous, or hairy; pilose. Petiole hairs longer than the diameter of the petiole; spreading. Leaf blade bases attenuate. Blades (4–)8–60(–79) mm long, (0.3–)0.6–4 mm wide, spreading (somewhat fleshy, green to deep purple), linear or spatulate (broadly to oblanceolate), appearing single-veined or with inconspicuous veins. Blade adaxial surface glabrous or glabrescent or hairy, hairs pubescent or pilose, hairs simple or branched (bifid or trifid), hairs sparse, hairs white, or translucent. Blade abaxial surface glabrous or glabrescent or hairy, hairs pilose, hairs sparse or moderately dense, hairs white, hairs curved (or forked), hairs appressed or spreading. Blade margins entire or dentate, glabrous or with non-glandular hairs or with glandular hairs, with 1–2 teeth on each side of the blade; apices obtuse (often with a tuft of long simple trichomes).
Reproductive morphology. Flowering stems with leaves (occasionally, but then only one leaf), or without leaves (or with a single leaf or leafy bract subtending the lowermost flower or fruit, often purple or purple tinged). Flowering stems hairy. Flowering stems pilose. Flowering stem hairs simple, or branched; white or translucent. Inflorescences head-like (in flower), or racemose, or head-like (in fruit); dense, or diffuse; elongating as the fruit matures. Pedicels present; with non-glandular hairs. Flowers per inflorescence (3–)4–8(–10); small. Sepals conventional; 4; free; (0.7–)1–2 mm long; (1.6–)1.9–3.7 mm wide; green, or purple. Calyx hairy (usually), or glabrous (occasionally). Calyx hairs pilose; white or translucent. Calyx margins ciliate (sometimes, as a tuft of hairs at the tip). Petals conventional; free; 4; white, or purple; obovate, or spatulate; unlobed; (2.1–)2.4–4.5(–4.7) mm long; (0.75–)1–3(–3.2) mm wide. Stamens 6; stamen filaments markedly unequal in length; stamen filaments glabrous. Anthers yellow; sub-globose; 0.4–0.6 mm long. Ovary superior; carpels 2; syncarpous. Ovaries oblong; hairy; pilose. Ovary hairs very dense; white; spreading; straight, or wavy, or branched (2-forked). Styles 2; completely fused; thick and short; 0.5–1.5 mm long. Stigmas per ovary 1. Placentation parietal. Ovules per ovary (10–)16–20. Fruit stalked; stalk 2–5(–8) mm long; dry; a silique; ellipsoid to ovoid, or oblong, or lanceolate (terete, somewhat torulose or not at all, often curved); purple and green at maturity, or purple; (3–)5–13(–15) mm long; (0.8–)1.1–3(–3.6) mm wide (3.5–8.3 times longer than broad); hairy (hairs simple, bifucate, or occasionally trifurcate); surface venation ribbed (longitudinally with faint veins); not distinctly flattened; dehiscent; shedding the outer walls to expose a thin inner wall, with the seeds attached at the margins on either side. Styles persisting in fruit (0.35–)0.5–1.6(–2) mm long. Seeds (10–)16–20; 1.1–1.4 mm long; brown, or yellowish; surfaces smooth, rugose (at 40×).
Chromosome information. 2n = 56.
Ploidy levels recorded 8x.
Ecology and habitat. Substrates: lakeshores, seashores, barrens, flood plains (scree slopes); calcareous. Barren calcareous soils and gravels on lake and sea shores, gravel bars, scree slopes, solifluction lobes, and disturbed sites.
North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago widespread. Common. Arctic (the 'glabella' entity is Low Arctic to alpine, as is also parts of the 'purpurascens' entity (the 'henryae' part), Elven (personal communication, 2005)). Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry islands (Bathurst, Mackenzie King, Melville, Prince Patrick), Cornwallis, Banks, Victoria, Prince of Wales, Somerset, King William, Southampton.
Northern hemisphere distribution. Circumpolar. Northern Fennoscandian, Svalbard Franz Joseph Land, Polar Ural Novaya Zemlya, Taimyr Severnaya Zemlya, AnabarOlenyok, Kharaulakh, YanaKolyma, West Chukotka, Wrangel Island, South Chukotka, East Chukotka, West Alaska, North Alaska Yukon, Central Canada, Labrador Hudson Bay, Ellesmere Land Peary Land, West Greenland, East Greenland.
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..