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

Kobresia Willd.

Cyperaceae, Sedge family.

Published in Sp. Pl. 4, 1: 205. 1805.

Vegetative morphology. Plants 3–40 cm high; perennial herbs; caespitose; in dense single compact tufts. Only fibrous roots present. Roots pallid-brown, or black. Ground level or underground stems absent. Aerial stems erect; filiform, or not filiform. Leaves mainly basal; alternate; dying annually and non-persistent, or marcescent. Petioles absent. Sheaths present; persisting; forming a conspicuous build-up at the base of the plant; greyish brown, or reddish orange; sheath collars absent. Ligules present; 0.1–0.4 mm long. Leaves grass-like. Blades 20–200 mm long, 0.2–2 mm wide. Leaves filiform. Blades straight, linear, circular in cross section or folded or channelled, veins parallel, midvein similar in size to other veins in the leaf. Blade adaxial surface glabrous (sometimes scabrous along the margins, or even with sparse cilia that are not much shorter than those in Carex nardina). Blade abaxial surface glabrous. Blade margins entire, glabrous; apices acuminate.

Reproductive morphology. Plants monoecious. Flowering stems circular or oval in cross section. Flowering stems about as high as the leaves, or conspicuously taller than the leaves; with leaves, or without leaves. Leaf or reduced bract subtending the base of the inflorescence absent. Inflorescences spicate; linear, or oblong, or ovate; 0.8–3 cm long; 2–10 mm wide. Inflorescence unispicate, or multispicate. Inflorescence 2–9 spikes, or 10–12 spikes, or 13–20 spikes. Individual spike(s) erect, or ascending. Terminal spike staminate at the apex (lateral "spikelets" have male flowers above and female flowers below). Floral scales orange-brown; with margins and sometimes midvein paler in colour than the adjacent area of the scale, or with margins paler than body of the scale; lanceolate, or obovate; 2–6.5 mm long; 1–3 mm wide; glabrous; apex acute. Flowers bisexual. Staminate flowers inconspicuous. Perianth represented by a perigynium. Petals modified as bristles or perigynia. Stamens 3. Anthers 1–3 mm long. Ovary carpels 3; syncarpous. Perigynia sessile. Styles 3; long and thick. Stigmas per ovary 3. Placentation basal. Ovules per ovary 1. Fruit surrounded by a perigynium. Perigynia open on one side (a larger sterile scale enclosing sterile scales, a pistillate flower and one or more staminate flowers); lanceolate, or broadly ovate; 1.9–5.5 mm long; 0.8–1.8 mm wide; erect or ascending; brown; membranous; surface dull; glabrous; faintly veined, or appearing veinless; apices without a beak. Fruit sessile; dry; an achene; ellipsoid, or obovate; yellowish, or golden brown, or straw-coloured; 0.6–3.2 mm long; 0.7–1.4 mm wide; glabrous; indehiscent. Achenes trigonous (usually); not filling the upper part of the perigynia. Seeds 1.

Ecology and habitat. Substrates: hummocks, around the margins of ponds, marshes, river terraces, lakeshores, tundra, slopes, ridges, cliffs, seashores, dry meadows; imperfectly drained moist areas, seepage slopes, solifluction slopes, dry; rocks, gravel, sand, clay, till; with low organic content, with high organic content, peat; calcareous, or circum-neutral.

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, or limited. Common, rare. Arctic, Low Arctic, alpine. Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry islands, Banks, Victoria, Somerset, Southampton.

Northern hemisphere distribution. Circumpolar, or circumboreal, or amphi-Beringian, or Siberian. Northern Iceland, Northern Fennoscandian, Svalbard – Franz Joseph Land, Polar Ural – Novaya 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. Ivanova (1939) discussed the genus Kobresia, its morphology and its systematics.

The inflorescences of Kobresia cannot be clearly divided into primary and secondary inflorescences as in most other genera of Cyperaceae. The proximal part of the inflorescence is usually composed of bisexual spikelets arranged on a simple axis or a compact panicle. Distally there is a transition first to spikelets consisting only of a pistillate flower, then to staminate flowers subtended by a scale. In species with compound inflorescences, this transition may also occur on the inflorescence branches. For convenience, the structures subtended by a scale are all considered to be spikelets even though staminate flowers are considered to be a simple flower and not a reduced staminate inflorescence. Ball (in Ball et al. 2002), provided the following key.

1. Perigynia 3.5–5.5 mm; scales 3.5–5 mm, midvein fading towards the tip...Kobresia sibirica

1. Perigynia 2–3.5 mm; scales 2–3.5 mm, midvein distinct almost to the tip

2. Inflorescences usually compound (2-)3–8 mm wide; basal sheaths

persistent, dull, usually with remains of blades attached... Kobresia simpliciuscula

2. Inflorescence simple, 2–3 mm wide; basal sheaths persistent, somewhat glossy, bladeless...Kobresia myosuroides.

Illustrations. • Open perigynium. Members of the genus Kobresia have spikelets comprised of an ovary subtended by an open perigynium (left and top arrows), and floral bracts (right arrows). Achene has a long style that branches into three stigmas.


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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