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 castaneus Sm.

English: Chestnut rush,

French: Jonc marron,

Inuktitut: Iviit, ivisuka, ivitsuskaka.

Juncaceae, Rush family.

Published in Fl. Brit. 1: 383. 1800.

Type: Described from Scotland.

Vegetative morphology. Plants 10–30(–50) cm high; perennial herbs; not caespitose. Only fibrous roots present. Ground level or underground stems horizontal; rhizomatous (slender); elongate, or compact. Aerial stems erect (coarse, 2–3 mm wide); not filiform. Leaves present; mainly basal (when plants are growing in clumps), or distributed along the stems (more easily seen in isolated stems; cataphylls 1–2); alternate; dying annually and non-persistent. Petioles absent. Sheaths present; with the margins not fused. Ligules absent. Leaves grass-like. Blades 30–100(–250) mm long, 1–4 mm wide, straight, linear, without auricles (distally, rounded proximally, a contrast with other Juncus taxa), channelled or convolute (pressing flat), veins parallel. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blade margins glabrous; apices acuminate.

Reproductive morphology. Flowering stems circular or oval in cross section. Flowering stems with leaves. Leaf or reduced bract subtending the base of the inflorescence present; conspicuous and leaf-like (1–6 cm long); exceeding the inflorescence (conspicuously so). Flower orientation flowers side by side in a horizontal plane. Inflorescences cymose, or head-like (in 1–3 cymose heads, each with 2–10 flowers); terminal; dense; 1–6 cm long. Pedicels absent. Bisexual spike(s) with empty bracts at the base (leafy and green, longer than the inflorescence). Floral bracts 10–20 mm long (usually surpassing the inflorescence; bracteoles absent); apices entire. Flowers per inflorescence 3–10 (in clusters 0.8–1.2 cm in diameter); medium-sized. Sepals conventional (brown tepals); 3; free; 4.5–6.5 mm wide; brown; scarious. Calyx glabrous. Petals conventional (brown tepals); free; same length as the calyx (or slightly shorter); 3; brown (or occasionally paler); lanceolate; unlobed; 4.5–6.5 mm long. Stamens 6. Anthers 1.2–1.5 mm long. Ovary superior; carpels 3; syncarpous. Styles 3; free; 1–1.3 mm long. Stigmas per ovary 3. Ovules per ovary 20–40. Fruit sessile; with calyx persisting; dry; a capsule; elongate-cylindrical (with an acute top); black, or brown (reddish and shiny, three locular, narrowly oblong); 5–8 mm long; 2–3 mm wide; not distinctly flattened; dehiscent. Seeds 25–35; 2–3.5 mm long (including tails 0.8–1.1 mm long at both ends, lanceolate, 1–3 mm wide); brown (pallid); surfaces smooth.

Chromosome information. 2n = 60. Jørgensen et al. (1958, Greenland); Löve and Ritchie (1966, northern Canada); Löve (1970a); Zhukova (1980, southern Chukotka); Löve (1981d, northern Canada).

A chromosome count of 2n = 40 from Iceland (Löve and Löve 1956, possibly also Sørensen and Westergaard, in Löve and Löve 1956) was not included by Löve and Löve (1975), and it is discounted until there is further evidence

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Ecology and habitat. Substrates: wet meadows, around the margins of ponds (and swales), marshes, along streams, river terraces; aquatic (occasionally), imperfectly drained moist areas, seepage slopes; rocks (on beach cobble), gravel, sand, silt, clay; with low organic content, with high organic content, peat (occasionally); calcareous. A plant of moist areas, typically growing in sedge wet meadows, along streams and rivers, and around the margins of ponds.

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, Low Arctic. Arctic islands: Baffin, Devon, Ellesmere, Parry islands, Victoria, Southampton (and Mill Island).

Northern hemisphere distribution. Circumpolar, or circumboreal. 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. Brooks and Clemants (2000) fully synonymised the 'leucochlamys' entity (Juncus castaneus Sm. subsp. leucochlamys (Zinger ex V. Krecz.) Hultén) with J. castaneus. Hultén first accepted them as species [Hultén 1943: 428] but later changed his opinion to subspecies after investigation of more material (Hultén 1967). Elven et al. (2003) followed Hultén's later viewpoint, because the taxa had been observed to intergrade in Alaska. They noted that there are plants from eastern Canada (e.g., from southern Baffin Island: Iqaluit) very different from Eurasiatic J. castaneus s.s. (Elven, after visiting the island in 1999).

Hultén (1968) noted that J. castaneus var. pallidus has pale perianth bracts and capsules, and often has few-flowered heads. It occurs in scattered localities. Polunin (1940) considered this a well-marked colour phase, which occurs only in the south.

Since Porsild (1957) new records have been collected on Ellesmere Island.

Illustrations. • Habitat: Iqaluit. Plants growing beside a drainage ditch. Nunavut, Baffin Island, Iqaluit. 15 July, 2002. Aiken. No Voucher. • Habitat: Dorset. Plants forming a dense stand in a runoff ditch beside a road. Nunavut, Baffin Island, Cape Dorset. 2 August, 2005. Aiken. No voucher. • Sheath to leaf blade. Front and side views of the transition between the leaf blade and sheath showing glabrous leaf blade margins and no evidence of a ligule or collar. Nunavut, Baffin Island, Iqaluit. July, 2004. Photographed by LeBlanc. No voucher. • Close-up of Inflorescence. Inflorescence with a long subtending leaf-like bract that extends well beyond the flowers. Note the small yellow anthers and the three pale yellow twisted stigmas. Nunavut, Baffin Island, Iqaluit. July, 2005. Photographed by Kathy Thornhill. Aiken 05–074. CAN 586946. • Close-up of inflorescence. Capsules with pointed tops. Nunavut, Baffin Island, Iqaluit. 27 August, 1997. Aiken 97–050. • Close-up of inflorescence. Inflorescence of three flowers, borne in the axil of a leaf-like bract that is longer than the inflorescence. Drawing by Mrs. S. Bergh and Mrs. L. Barstad based on the collection Svalbard, Nordenski÷ld Land, Longyeardalen, s°sida. 27 July, 1924. J. Lid. O-200115. With permission of the Botanical Museum University of Oslo, Norway. • 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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