Flora of the Canadian Arctic Archipelago

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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

Juncus biglumis L.

English: Two-flowered bog rush,

French: Jonc à deux glumes,

Inuktitut: Iviit, ivisuka, ivitsuskaka.

Juncaceae, Rush family.

Published in Sp. Pl. 328. 1753.

Vegetative morphology. Plants 3–20(–30) cm high; perennial herbs; caespitose (loosely). Only fibrous roots present. Ground level or underground stems horizontal; rhizomatous; compact (forming small rather compact tufts of producing leafy, non-flowering shoots and stiffly erect culms with terminal inflorescences of 1–3 flowers borne one above the other, sepals dark brown, capsules with a conspicuous notch on the top). Aerial stems erect (usually longer than the leaves). Leaves mainly basal (cataphylls 2–3); alternate; dying annually and non-persistent. Petioles absent. Sheaths present; with the margins not fused (loose). Ligules absent. Leaves grass-like. Blades 10–80 mm long, 0.4–1.5 mm wide, straight, linear, with sheath auricles (rounded to 0.5 mm) or without auricles, circular in cross section (hollow and pressing flat), veins parallel, septate nodulose (imperfectly). Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blade margins glabrous; apices acuminate.

Reproductive morphology. Flowering stems circular or oval in cross section (with a hollow centre). Flowering stems without leaves in the upper half. Leaf or reduced bract subtending the base of the inflorescence present; conspicuous and leaf-like, or reduced, or scale-like (0.5–3 cm long); exceeding the inflorescence (slightly). Flowers in inflorescences (very rarely solitary). Flower orientation two (or three) flowers side by side on one top of the other. Inflorescences head-like (flowers tend to be one on top of the other, the upper one flowering first; a contrast to J. triglumis); terminal; dense; 0.5–1 cm long. Pedicels absent. Bisexual spike(s) with empty bracts at the base. Floral bracts apices entire. Flowers per inflorescence (1–)2–3(–4); small. Sepals conventional (brown tepals); 3; free; 2.5–4 mm wide; brown; scarious. Calyx glabrous. Petals conventional (brown tepals); free; same length as the calyx; 3; brown (to blackish, and scarious); lanceolate; unlobed; (2.5–)3–3.5(–4) mm long. Stamens 6. Anthers 0.4–0.7 mm long. Ovary superior; carpels 3; syncarpous. Styles 3; free; 0.3–0.4 mm long (deciduous). Stigmas per ovary 3. Ovules per ovary 20–30. Fruit sessile; with calyx persisting; dry; a capsule; obovate (with a distinct hollow notch at the apex when mature; this contrasts with J. albescens); black, or brown (pale with dark purplish valve margins, pseudo-3-locular, oblate to narrowly ovoid); 3–4(–5.5) mm long; 1.5–2.5 mm wide; not distinctly flattened; dehiscent. Seeds 10–30; 0.8–1.2 mm long (ellipsoid, with attenuating membranous structures, "short tails" at both ends); brown (yellowish tan); surfaces smooth.

Chromosome information. 2n = 60. Knaben and Engelskjøn (1967, northern Norway);

2n = 100. Johnson and Packer (1968, northwestern Alaska); Krogulevich (1971, southern and northern Siberia); Packer and McPherson (1974, northern Alaska; Zhukova (1967, northeastern Asia as 2n = more than 100);

2n = 120. Holmen (1952, Greenland); Löve and Löve (1956, Iceland), Löve (1981d, northern Canada); Engelskjøn and Knaben (1971, southern Norway); Löve et al. (1971, western North America);

2n = 130 ± 10, Mosquin and Hayley (1966, northern Canada, 'corrected' by Löve and Löve, 1975, to 2n = about 120!).

Ecology and habitat. Substrates: wet meadows, snow patches, around the margins of ponds, depressions of low-centre polygons, marshes, along streams, river terraces (and deltas), tundra, slopes (wet), ridges (along beaches, also in intervening swales), seashores; aquatic (ponds and streambeds), imperfectly drained moist areas, seepage slopes; gravel (rarely), sand, silt, clay (rarely), till, moss; with low organic content, with high organic content, peat (occasionally); acidic, or calcareous (usually). A plant of wet places, usually in sand or silt. Juncus biglumis typically inhabits wet sedge grass meadows, seepage areas, and creek and river flats. It occurs in various stages of colonisation: in bare mud or sand, and also in more developed vegetation, including thick moss carpets and peat.

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. Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, and Parry islands (Melville and Bathurst), Cornwallis, Banks, Victoria, Prince of Wales, King William, and Southampton (as well as Air Force, Eglinton, Lougheed, Meighen, Stephansson and Winter Islands).

Northern hemisphere distribution. Circumpolar, or circumboreal (arctic-alpine). Northern Iceland, Northern Fennoscandian, Kanin–Pechora, Svalbard – Franz Joseph Land, Polar Ural – Novaya Zemlya, Yamal–Gydan, Taimyr – Severnaya Zemlya, Anabar–Olenyok, Kharaulakh, Yana–Kolyma, 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.

General notes. Polunin (1940) noted that this is "one of the most characteristic of all arctic phanerogams [and varies] little in any features that are of true taxonomic importance. However, in size and robustness it is liable to show great extremes in different habitats almost anywhere within the [eastern Canadian Arctic], varying from 2 to 30 cm in height, with the culms sometimes stout and sometimes very slender. It is also variable in the length and prominence of the "spathe" [leaf associated with the inflorescence] that subtends the flowers, this being generally longer in plants growing under favourable conditions, but often varying considerably on different culms coming from the same tuft." (p. 146).

A specimen from Ward Hunt Island, 83°N, at the northern edge of its range, has leaves longer than the flowering stems CAN (234211).

Danvind and Nilsson (1997) used J. biglumis in a study testing the hypothesis that diaspore buoyancy is an important factor in determining the distribution range of riparian plants. The authors measured the floating capacity of fruits and seeds from 17 alpine vascular plant species during one year along the free-flowing Vindelu River in northern Sweden. Minimum, median, mean, and maximum floating times of fruits and seeds were related to the downstream distribution of plants. The distances from the alpine headwater region to the most downstream occurrence of plants, and to the cessation of a more continuous distribution, were evaluated. The variation in downstream limits of plants could not be statistically explained by variation in seed buoyancy between species, indicating that floating ability of seeds is not important for plant distribution patterns.

Elven et al. (2003) noted that there might be some interesting unexplored variation in this common arctic-alpine species. Both the two main ploidy levels are known from Scandinavia. Most Scandinavian plants seem to differ morphologically from the majority of plants in the Arctic, in size (smaller), and in some other details.

Illustrations. • General view of habitat: Ogac. Tiny plants less than 5 cm high (beside white markers) at edge of evaporating snowmelt pond. Nunavut, Baffin Island, Ogac Lake. 13 July, 2004. Aiken and LeBlanc 04–081. CAN 586553. • Habitat. Tiny plants less than 5 cm high growing in black muck of a snow melt pond. Nunavut, Baffin Island, Ogac Lake. 13 July, 2004. Aiken and LeBlanc 04–081. CAN 586553. • Close-up of plants. Close-up of plants from the previous location (dug up for photography of base). Note loosely tufted habit and flowering inflorescences with two flowers, one above the other. Nunavut, Baffin Island, Ogac Lake. 13 July, 2004. Aiken and LeBlanc 04–081. CAN 586553. • Close-up of young inflorescence. Spicate inflorescence with a subtending bract just longer than the two flowers. The flowers are arranged one above the other, as opposed to Juncus triglumis in which they are side by side. Note the brown tepals of the flowers. July, 2004. Aiken and LeBlanc 04–081. CAN. • Side view of inflorescence. Two-flowered inflorescence. A. Young pinkish stigmas beginning to expand. B. Much older spent stigmas that are turning brown. C. Anthers of the first whorl of three stamens becoming exposed. July, 2004. Aiken and LeBlanc 04–081. CAN 586553. • Fruiting inflorescence. Capsule is notched at the top. Note also the leafy bract that is longer than the capsules. • 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.

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