Flora of the Canadian Arctic Archipelago
Asteraceae (Compositae), Daisy family.
Published in Fl. Dan. 13, 39: 6. 1840.
Type: Described from Greenland.
Vegetative morphology. Plants 4–12(–30) cm high (CAN 273748); perennial herbs; with milky juice. Taproot present. Caudex present. Aerial stems a small transition zone between taproot and basal leaves. Leaves mainly basal, or basal in a rosette; patent (usually), or erect; alternate; dying annually and non-persistent. Petioles present, or absent; 0–30 mm long; not winged; glabrous. Leaf blades simple. Leaf blade bases attenuate. Blades 15–35 mm long, 2.5–8(–13) mm wide (leaves to 13 mm, conspicuously wide, bright green (CAN 500038)), oblanceolate or obovate, flat, veins pinnate. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blades lobed (shallowly, triangularly lobed) or not lobed. Blade margins entire (or sub-entire) or crenate or dentate or runcinate (in occasional robust plants; often variable on the same plant), glabrous; degree of incision 5–55%; apices acute (often decumbent).
Reproductive morphology. Flowering stems without leaves. Inflorescences solitary heads. Flowering heads 10–20 mm deep; 8–18 mm wide (remaining closed during anthesis; Porsild (1957)); with only ligulate florets. Pedicels absent. Involucral bracts present. Number of rows 2–3. Outer involucral bracts mostly green (to bluish black and prunose); lying adjacent to the flowers, or spreading to erect; lanceolate (broadly), or ovate; 3–5 mm high; 1.8–2.5 mm wide; glabrous. Inner involucral bracts lanceolate (broadly); 12–14 mm high; 2.5–3 mm wide; margins wide, scarious for at least one quarter of the bract, or narrow and scarious, less than one quarter of the bract (usually; rather variable); apex sometimes callused, but without a prominent horn. Flowers per inflorescence 35–50; bilaterally symmetrical (zygomorphic). Sepals represented by a pappus. Pappus with a single row of hairs; yellowish, or whitish. Ligulate florets pappus 4–6(–7) mm long. Petals conventional; fused; longer than the calyx; 5; yellow (a pale lemon yellow: sometimes drying with a pinkish tinge to the petals, but without the pink-grey stripe seen in T. hyparcticum); with contrasting markings (outer ligules with a grey, violet or purple stripe), or without contrasting markings (inner flowers). Corolla flat, strap-like. Ray florets limb 1–2 mm wide. Ligulate florets limb 35–50 mm long; 8–9 mm wide. Stamens 5. Anthers yellow; 3.5–4 mm long. Ovary inferior; carpels 2; syncarpous. Styles 1. Stigmas per ovary 2. Placentation basal. Ovules per ovary 1. Fruit sessile; with calyx persisting; dry; cypselas; obovate; black (or greyish); 3.3–4.5 mm long (cone about 1 mm long); 0.9–1.1 mm wide; surface appearing veinless (but with deep longitudinal grooves); indehiscent. Cypselas beak stout, shorter or similar in length to the body; surface spinulose (usually over the entire surface); surface throughout (usually), or in upper half. Seeds 1.
Chromosome information. 2n = 24.
2n (3x) = 24. Mosquin and Hayley (1966, northern Canada), Johnson and Packer (1968, northwestern Alaska); Zhukova (1968, northeastern Asia); Zhukova et al. (1973, northeastern Asia); Petrovsky and Zhukova (1981, Wrangel Island); Zhukova and Petrovsky (1987b, north and northeastern Asia);
2n (4x) = 32 and 2n (5x) = 40. Mosquin and Hayley (1966, northern Canada).
Ploidy levels recorded 3x, 4x, and 5x.
Ecology and habitat. Substrates: slopes, flood plains; dry, moderately well-drained areas; rocks (talus), gravel (and stony areas), sand, clay (shale); with low organic content, with high organic content; calcareous. Silty, hummocky Jesse till (CAN 593650); gravel embankment; moist turfy places on rocky scree (CAN 223355); on owl perches (CAN 128188); raised low-centre polygons (CAN 526804); exposed muddy gravel (CAN 261600); dry alkaline clay flat (CAN 219932).
North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut, Labrador (?). Range in the Canadian Arctic Archipelago widespread. Common. Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry islands (Bathurst and Prince Patrick), Banks, Victoria, Prince of Wales, Somerset.
Northern hemisphere distribution. Circumpolar (with a gap in northern Europe and northwestern Siberia). Taimyr Severnaya Zemlya, Kharaulakh, Wrangel Island, East Chukotka, West Alaska, North Alaska Yukon, Central Canada, Labrador Hudson Bay, Ellesmere Land Peary Land, West Greenland, East Greenland.
General notes. Leaves sub-entire to runcinate on the same plant. There are no horns on the bracts, but the tips are sometimes calloused. The flowering heads are relatively small and do not spread flat at anthesis. The cypselas are mottled grey to dark grey or black, with prominent vertical grooves and spinulose from top to bottom, similar to the illustration in Dahlstedt (1905, p. 25; see image library).
Illustrations. • Dandelions in the grass. Yellow dandelions in grassy tundra dominated by Festuca baffinensis and Astragalus alpinus. N.W.T., Melville Island, Ibbett Bay. July, 1985. Aiken. No voucher. • Close-up of plant. On a ridgetop along side the Thomsen River. Note lemon yellow flowers and linear, almost entire leaves. N.W.T., Banks Island, Aulavik National Park. 19 July, 2002. Photograph by James McCormick. • Close-up of plant. Lemon yellow flowers with deeper colour on the tips of the petals and sub-entire leaves. Nunavut, Ellesmere Island, Tanquary Fiord. Lynn Gillespie 6469 and Laurie Consaul. CAN. • Side view of flowers. Plant with entire to sub-entire leaves, involucral bracts that lack horns, lemon yellow petals, and erect flowering heads. Note the head going to seed has recurved towards the ground. Nunavut, Ellesmere Island, Tanquary Fiord. Lynn Gillespie 6469 and Laurie Consaul. CAN. • Close-up of plant. Lemon yellow flowers with deeper colour on the tips of the petals and sub-entire leaves. Nunavut, Ellesmere Island, Tanquary Fiord. Lynn Gillespie 6469 and Laurie Consaul. CAN. • Close-up of fruiting heads. Plant with bright red flowering stems that were erect but have since curved so that the flowering heads that now have maturing fruits are closed and lying on the ground. Note involucral bracts without horns or calloses, and sub-entire leaves. Nunavut, Ellesmere Island, Tanquary Fiord. Lynn Gillespie 6469 and Laurie Consaul. CAN. • Line drawings. Illustration from the type description by Dahlstedt (1905). Note the entire to sub-entire or slightly runcinate leaves, the slightly modified tips to the inner involucral bracts and the fruit that is uniformly spinulose from the top to the bottom. • 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..