Flora of the Canadian Arctic Archipelago


S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Astragalus eucosmus B.L. Rob.

English: Elegant milk-vetch,

French: Astragale élégant.

Fabaceae (Leguminosae), Pea family.

Published in Rhodora 10: 33. 1908.

Type: North America: "Prairis of the Rocky Mountains", leg. Drummond, as Phaca elegans Hooker. Holotype: K.

Synonymy. Phaca elegans Hooker, Fl. Bor. Amer. 1: 144. 1831.

Astragalus elegans (Hooker) Sheldon., Minn. Bot. Stud. 1: 154. 1894, non Bunge 1869.

Atelophragma elegans (Hooker) Rydberg, Bull. Torrey Bot. Club 32: 660. 1905.

Astragalus oroboides var. americanus A. Gray, Proc. Amer. Acad. 6: 204. 1864 (non A. americanus (Hooker) Jones, 1898).

Atelophragma atratum Rydberg, N. Amer. Fl. 24: 372. 1929. "Type collected August 22, 1896, on Herschel Island, Yukon, Alvin Seale". Holotype: DS. Non Astragalus atratus S.Wats., 1871.

Vegetative morphology. Plants 10–30 cm high; perennial herbs; not caespitose. Taproot present. Well developed on older plants. Ground level or underground stems vertical. Caudex present (branching and subligneous in older plants). Aerial stems decumbent (to ascending with slender branches). Aerial stem trichomes appressed. Leaves distributed along the stems; alternate; dying annually and non-persistent (leaf blades), or marcescent (petioles). Stipules present; persisting for 2 or more years; 5–6 mm long; 3–4 mm wide; not sheathing; brown, or green; hairy (sparsely so); pilose (sparse and around the margins); apex acute. Petioles 5–15(–20) mm long; hairy (glabrescent); pilose. Petiole hairs shorter than the diameter of the petiole; appressed; straight; smooth (flattened, whitish, approaching strigose). Leaf blades compound. Leaves not grass-like. Blades 25–40 mm long, 15–25 mm wide, spreading, appearing single-veined. Blade adaxial surface glabrous. Blade abaxial surface glabrous (seen at 10×) or hairy (densely hairy, with white or black hairs), hairs short-silky or strigose, hairs sparse or moderately dense, hairs white, hairs straight, hairs appressed. Blade apices acute, or obtuse, or rounded (very variable, sometimes approaching truncate). Leaflet arrangement pinnate (odd-pinnate). Leaflets 8–17; 5–12 mm long; 1–4 mm wide; linear, or oblong, or ovate (lateral veins often obscure); veins conspicuous (midvein, lateral veins often obscure).

Reproductive morphology. Flowering stems two or more per plant; about as high as the leaves, or conspicuously taller than the leaves; without leaves. Flowering stems hairy. Flowering stems strigose. Flowering stem hairs simple; white or translucent and black. Inflorescences racemose; terminal; dense (in flower); oblong, or globose or sub-globose; 1.5–5 cm long (dense in bud in the Arctic islands but elongating to as much as 19 cm further south); 10–15(–20) mm wide; elongating as the fruit matures. Bisexual spike(s) with empty bracts at the base (stipule-like). Flowers per inflorescence 6–16; medium-sized; bilaterally symmetrical (zygomorphic). Sepals conventional; 5; fused; 4–5 mm wide; brown, or black (because of black hairs). Calyx tubular, or funnel-form; 5-lobed; hairy (densely). Calyx hairs strigose; black and white or translucent. Calyx teeth equal or nearly so; 0.9–1.1 mm long. Petals conventional; both free and fused; 5; purple (dark); with contrasting markings (veins prominent); unlobed (4 petals), or slightly lobed or undulating (banner petal); 6.5–7.5 mm long. Corolla papilionaceous; keel blunt. Stamens 10; stamen filaments all equal in length (slightly unequal). Anther filaments 9 fused into a tube, plus 1 free. Anthers yellow; 0.3–0.4 mm long. Nectaries present. Ovary superior; carpels 1; monomerous (stipitate). Stipes 0–0.4 mm long (in fruit). Stigmas per ovary 1. Ovules per ovary 3–8. Fruit stalked (on a short stalk and hanging downwards); with calyx persisting; dry; a legume; spherical (almost), or ellipsoid, or ovoid (or cuneate after pressing; not inflated); black, or brown; 5–13 mm long; 2.5–5.5 mm wide; hairy (with white and black hairs); not distinctly flattened; dehiscent; splitting to the base into separate segments. Legume nearly 2-locular by intrusion of placenta; valves straight. Styles persisting but not modified. Seeds 3–8; 1–2 mm long (i.e., the longest dimension); yellowish; surfaces smooth.

Chromosome information. 2n = 32.

2n (4x) = 32. Ledingham (1957, 1960); Ledingham and Fahselt (1964, Alaska); Johnson and Packer (1968, northwestern Alaska); Dawe and Murray, in Löve (1979, Alaska); Löve and Löve (1982a, central Canada).

Ploidy levels recorded 4x.

Taxon as an environmental indicator. Plants vary in height from 10 cm tall in severe environments to 30 cm tall under ideal growing conditions. The northernmost record that Polunin (1940) found was Great Bear Lake approx. 66°N. Since 1940, this species has been collected further north, in the Mackenzie Delta, 68°55'N. On the Arctic islands, this species grows north to Iqaluit, 63°45'N.

Ecology and habitat. Substrates: river terraces, slopes, ridges, seashores; moderately well-drained areas; gravel, sand, till; calcareous (growing in sand, gravel, and with grasses at Iqaluit. Plants grow as sand binders on the beach at Apex. In continental North America, plants of this species often grow among willows on sand and gravel bars in rivers and by sheltered lake shores). Plants flower and fruit abundantly.

North American distribution. Alaska, Yukon, continental Northwest Territories, Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago limited. Rare (known from Apex, Iqaluit, and Kimmirut). Low Arctic. Arctic islands: Baffin.

Northern hemisphere distribution. North American. West Alaska, North Alaska – Yukon, Central Canada, Labrador – Hudson Bay.

General notes. Barneby (1964) recognised this taxon as being in section Oroboidei. A similar species, A. robbinsii (Oakes) Gray, grows in central and southern Yukon and southern Alaska. Barneby (1964) considered the elegant milk-vetch A. eucosmus to be closely related to A. robbinsii, differing chiefly in the sessile pod. The leaflets tend to be narrower and the flowers are often smaller, but neither of these features is diagnostic of A. eucosmus, and fruits, at least half-formed, are often necessary for identification. Despite its great range, A. eucosmus is only moderately variable, much less so than a glance at the synonymy might suggest. Normally an erect plant of moderate stature, it is susceptible to dwarfing in open montane and far northern environments, where the stems become diffuse or weakly ascending as well as shorter, and the raceme tends to become shorter and more compact in fruit. The raceme of A. eucosmus ordinarily elongates rapidly during anthesis, the axis becoming about 3.5–19 cm long in fruit, with pods well spaced along its length. Instances of shorter fruit are correlated with short diffuse stems and an unfavourable habitat, mostly on exposed seashores at high latitudes in eastern Canada and Baffin.

Elven et al (2005) noted that "Scoggan (1978) synonymised A. sealei with A. eucosmus f. eucosmus (one of four formae). Gillett et al. (1999) also fully included A. sealei in A. eucosmus. Hultén (1968b and elsewhere) treated the entities 'eucosmus' and 'sealei' as subspecies but commented on the similarity between 'sealei' and the Eurasian A. norvegicus. Yurtsev (in Elven et al. 2003) treated all three entities as species. Murray and Elven [personal communication, 2005] compared material of all three taxa and share[d] Yurtsev's opinion. [They found] the diploid amphi-Beringian A. sealei morphologically more similar to the diploid Eurasian A. norvegicus than to the tetraploid North American A. eucosmus to which it usually has been assigned as a subspecies. An alternative might be to assign 'sealei' as a subspecies to A. norvegicus, but we are not aware of such a combination."

Illustrations. • Habitat: Baffin Island, Iqaluit. Plants growing on rocky ridge. Nunavut, Baffin Island, Iqaluit. 26 July, 1982. J.M. Gillett 19055. CAN. • Leaves and young inflorescence. Compound leaves very hairy on the abaxial surface, less hairy on the abaxial suface. Nunavut, Baffin Island, Iqaluit. July, 2005. Photograph by Kathy Thornhill. No voucher. • Close-up of young inflorescence. Inflorescence in the early stages of flowering with flowers spreading at right angles to the flowering stem. Flowers with purple petals and silver-grey, hairy sepals. Nunavut, Baffin Island, Iqaluit. 26 July, 1982. J.M. Gillett 19055. CAN. • Close-up of fruiting stem. Ovoid, hairy fruiting pods developing. Nunavut, Baffin Island, Iqaluit. Aiken 02–064. • Aboveground and belowground. Plant with extensive development of an underground caudex and branching root system. Nunavut, Baffin Island, Iqaluit. CAN 518182. • Close-up of stipules. A pair of almost glabrous green stipules on either side of the leaf base. The stipules are free for almost their entire length. Nunavut, Iqaluit. CAN 518327. • Contrasting sizes. Left, relatively large leaflets; centre, relatively small flowers; right, ovate, subglobose fruits. Nunavut, Iqaluit. CAN 518327. • Close-up of young leaf. Leaves glabrescent. Left, young leaf that is covered with strigose hairs; right, mature leaflets that are almost glabrous. Nunavut, Iqaluit. CAN 518327. • 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.