Oxytropis nigrescens (Pall.) Fisch. subsp. arctobia (Bunge) Hultén
Fabaceae (Leguminosae), pea family.
Arkiv för Botanik, Andra Serien 7: 80. 1968
Oxytropis arctobia Bunge, Mem. Acad. Petersb., ser. 7, 22, 1: 114.
1871.
Oxytropis. nigrescens (Pall.) Fisch. var. uniflora
(Hook.) Barneby (1952), Proc. Calif. Acad. Sci., ser. 4, 27: 209. 1952.
Type: ?Nunavut: Barrow River, E. coast Melville Peninsula, lat. 67°21'N, on Parry's Second Voyage. Isotypes GH, NY.
Vegetative morphology. Plants perennial herbs; 1–5 cm high; cushion-like, velvety-grey and up to 30 cm in diameter, with leaves or prostrate branches. Taproot present. Caudex present (much branched). Aerial stems erect; densely hairy (not easily visible between the appressed leaves). Leaves distributed along the stems (that are very compact); alternate; compound; marcescent. Stipules present; sheathing (base of petiole expanded, stipules surrounding the stem); white (or pale grey from numerous hairs, stipule margins ciliate, sometimes with clavate processes). Petioles 5–15 mm long (not very obvious). Blades 50–80 mm long; 3–6 mm wide. Blades veins pinnate. Blades adaxial surface hairy. Blades adaxial surface hairs pubescent, or short-silky; simple, unbranched; dense; white and translucent. Blades abaxial surface hairy. Blades abaxial surface hairs very dense. Blades abaxial surface villous, or hairs short-silky. Blades abaxial surface hairs white, or translucent hairs; straight, or wavy; appressed, or spreading. Leaflet arrangement pinnate. Leaflets (3–)5–9(–13); 3–4.5 mm long (often conduplicate, i.e. margins rolled inwards, and with dense grey hairs).
Reproductive morphology. Flowering stems present. Flowering stems without leaves; hairy. Flowers solitary, or in inflorescences (of two flowers, often numerous on the plant cushion). Inflorescence 0.1–0.2 cm long (when applicable). Flowers per inflorescence 2 (when applicable); medium-sized, 5–15 mm in diameter or length; zygomorphic. Floral scales hairy all over (pilose). Calyx sepals 5; fused. Calyx green, or brown, or black (because of black hairs); tubular; 5-lobed; hairy (with numerous black hairs). Petals both free and fused; 5; purple (at the tips of the petals, fading to light brown); with contrasting markings (yellow insect guide lines along veins and towards the base of the petals); unlobed (4 petals), or shallowly lobed (banner petal); 8–12 mm long. Corolla papilionaceous. Corolla keel with a pointed tip. Stamens 10; filaments all equal in length (slightly unequal). Nectaries present. Gynoecia superior. Carpels monomerous. Stigmas per style 1. Ovules 15–25. Fruit sessile. Fruit with calyx persisting; dry; a legume (sessile within the calyx); ellipsoid, or elongate-cylindrical; dehiscent. Fruit (15–)25–30 mm long; 6–9 mm wide; black; hairy. Legume unilocular. Styles may persist until dehiscence but are not modified. Seeds 10–20; 1.2–1.6 mm long (i.e., the longest dimension); brown; with surfaces smooth.
Chromosome information. 2n = 16. 16 (2x). - Gillett et al. (1999 onwards, secondary ref.).
Distribution. Low arctic (endemic to the central Canadian arctic from Banks Island to Baffin Island, also on Melville Peninsula and the south coast of Baffin, Southampton and adjacent islands in Hudson Bay). Range in the Canadian Arctic Archipelago limited. Arctic Islands: Baffin, Parry Islands (Eglinton), Banks, Victoria, King William, Southampton (Elginton Island and Boothia Peninsula).
Ecology and habitat. Substrates: hummocks (uncommonly), river terraces, ridges (very often); moderately well drained areas; calcareous; gravel (limestone), silt, clay; with high organic content (locally). Habitats: At anthesis this species is strikingly handsome when the firm grey cushions of large individuals may be covered with several hundred flowers. In fruit the legumes are large and black and show up against the ashy-grey foliage, which otherwise tends to blend in with the grey gravel on which it grows.
Taxon as an environmental indicator. Polunin (1940) reported the northernmost record as Baffin Island, Arctic Bay, 73°05'N. Since that time, it has been collected further north, on Eglinton Island, Kuc, 8 July 1968, 75°48'N.
Notes. Polunin (1940) noted that there is a specimen of this species
in the Gray Herbarium among a collection that has often been referred to as
coming from Melville Island, but actually was made far to the south-east during
Parry’s second voyage. He indicated that the Arctic Bay material differs
from all other specimens that he had examined in having seeds that are light
brown instead of almost black when ripe, and having the insides of the pods
essentially glabrous instead of flocculent-pubescent. The pubescence on the
outside also tends to be less dense and spreading. On these characters he
recognized O. arctobia var. hyperarctica Polunin. This taxon has
not been widely taken up.
Prevost and Bal Arya (1994) studied the early
stages of nodulation in roots of what they called O. arctobia induced by
the arctic rhizobial strain N31.
Illustrations. • Herbarium specimen. Flowering specimen originally with blue petals that have faded to yellowish, and with blackish sepals. Note leaflets less than 0.5 cm long. Nunavut, Victoria Island, Cambridge Bay, 27 July, 1949, A.E. Porsild, 17206. CAN 128009. • Herbarium specimen. Fruiting specimen with hairy pods to 2 cm long, the remains of petals and blackish calyx lobes. Note finely divided pale grey-green leaves. Nunavut, Victoria Island, Cambridge Bay, 20 July, 1962, S. Stephens, 1091. CAN 273711. • Herbarium specimen. Holotype specimen of Oxytropis arctobia Bunge var. hyparctica. Polunin Bot. Can. E. Arctic, p. 293. Nunavut, Baffin Island, Arctic Bay, 8–11 Sept 1936, N. Polunin, 2583. CAN 76863. • Habitat. Plants growing on south facing rocky sandy barren. N.W.T., Banks Island, Aulavik National Park near Shoran Lake 73°30'73 N; 120°21'.13 W. 1 July, 1999, Aiken, no voucher. • Plants in habitat. Plants growing on south facing rocky sandy barren. N.W.T., Banks Island, Aulavik National Park near Shoran Lake 73°30'73 N; 120°21'.13 W. 1 July, 1999, Aiken. No voucher. • Plant with flowers in bud. Note the very black sepals and the first sign of petal colour. The "black" is the result of hairs on the sepals that appear to aid in warming the developing flower. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Aiken, SA99–015, CAN. • Flowers in bud. The "black" is the result of hairs on the sepals that appear to aid in warming the developing flower. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Aiken, SA99–015, CAN. • Plants with buds. Plant with closed and opening buds growing on south facing rocky sandy barren. Note the very black sepals, and almost all of the flowers pointing in the same direction towards the sun. N.W.T., Banks Island, Aulavik National Park near Shoran Lake 73°30'73 N; 120°21'.13 W. 1 July, 1999, Aiken 99–011, CAN. • Plant coming into flower. Plant coming into flower. Note the two colored standard or banner petal, and sepals covered with black hairs. These possibly aid in warming the developing flower. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Susan Aiken, SA99–015, CAN. Scale bar in cm. • Plant coming into flower. Note the two colored standard or banner petal, and sepals covered with black hairs. These possibly aid in warming the developing flower. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Aiken, SA99–015, CAN. • Close-up of flower. Flower with contrasting markings on the standard or banner petal. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Aiken, SA99–015, CAN. • Plant in habitat. Plant covered with a mass of flowers, growing with Dryas on south facing rocky sandy barren N.W.T., Banks Island, Aulavik National Park, confluence of Thomsen and Muskox Rives. 13 July, 1999, Aiken 99–062, CAN. Scale bar in cm. • Plant habit. Flowers fading to blue and returning to more or less prostrate on the ground after being erect. N.W.T., Banks Island in Aulavik National Park, beside Muskox River. 9 July, 1999. Aiken, 99–062, CAN. • Plant with seed pods. Previous season's seed pods lying on the tundra. Flowers in bud. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Susan Aiken. SA99–015, CAN. Scale bar in cm. • Close-up of seed pods. Previous season's seed pods lying on the tundra. N.W.T., Banks Island in Aulavik National Park, near Green Cabin, June 29, 1999. Aiken. SA99–015, CAN. • Arctic island distribution.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
