Carex atrofusca Schk.
Riedgr. 1: 106. 1801.
Nomenclatural section used by Flora of North America project subgenus Carex, sect. Aulocystis Dumortier
Carex ustulata Wahlenb.
Plants caespitose (loosely). Plants more than 15 cm high (usually); (6–)15–30 cm high. Roots pallid-brown. Ground level or underground stems horizontal, or not developed horizontally or vertically; compact. Scales present. Aerial stems decumbent; triangular in cross section; glabrous. Leaves mostly basal. Sheaths brown. Ligules present. Blades straight; linear; flat, or revolute (glaucous); glabrous. Blades adaxial surface glabrous.
Flowering stems conspicuously taller than the leaves. Leaf or reduced bract closely associated with the base of the inflorescence present; reduced, or scale-like (often bristle pointed); shorter than the apex of the inflorescence; 1–2(–2.5) cm long; with sheath shorter than the blade. Inflorescence spicate; 2–3.5 cm long; 20–30 mm wide. Pedicels smooth (capillary). Inflorescence multispicate; 2–4 spikes; lateral spikes borne on pedicels. Individual spike(s) erect (drawf specimens), or pendent. Terminal spike wholly staminate, or staminate at the apex (club-shaped, rarely two spikes with staminate flowers). Cladoprophyll present at the base of the peduncle of lateral spikes. Staminate flowers conspicuous (usually). Floral scales as long as the perigynium in fruit; black; with margins, and sometimes mid-vein paler in colour than the adjacent area of the scale; ovate, or lanceolate (bristle-tipped); 3.5–4.5 mm long; 0.7–1 mm wide; glabrous. Perianth absent. Anthers 1.5–3.5 mm long. Styles slender, not extending beyond the beak. Stigmas per style 3. Fruit surrounded by a perigynium. Perigynia fused to the apex except for a small aperture through which the style protrudes; broadly ovate; 3–4.5 mm long; 2–2.5(–3) mm wide; sessile; erect or ascending; black; surface dull; glabrous; appearing nerveless; not keeled (scaberulous towards the apex); apices beaked with a long beak; apex deeply bidentate. Achenes not filling the upper part of the perigynia; trigonous.
Chromosome information. 2n = 38 and 40.
Distribution. Circumpolar. Arctic. Range in the Canadian Arctic Archipelago wide-spread. Common. Arctic Islands: Baffin, Devon, Ellesmere, Banks, Victoria, Southampton, and Coats.
Ecology and habitat. Substrate wet meadows, hummocks (mossy), marshes, along streams, river terraces, lake shores, tundra; imperfectly drained, or on seepage slopes; calcareous; gravel, sand, silt, till (often on till plains); with high organic content, or peat (occasionally). Typically sparse or uncommon; found with other sedges such as C. membranaceae and C. aquatilis var. stans. It can occur in areas extensively grazed by musk oxen.
Notes. Polunin (1940) noted that this species may be mistaken for a marsh form of Carex fuliginosa and that specimens of the two are sometimes mounted together, although in the field they have practically no resemblance to one another.
In a study of scale-dependent correlations of Arctic vegetation and snow cover in southeastern Victoria Island, Schaefer and Messier (1995) found that C. atrofusca exhibited positive associations with various measures of snow cover. It is thought that snow cover may reduce the rate of desiccation, protect plants from abrasion, and insulate from low temperatures.
Specimens with two staminate spikes CAN 23127, CAN 483451. Specimen with a subterminal spike, with both staminate and pistillate flowers, CAN 483450.
Variety major is considered to be no more than larger plants from more favourable environments (P. Ball personal communication April 1998.
Illustrations. • Plants in habitat. Gravelly meadow. Nunavut, Baffin Island, Iqaluit, July 24, 1982, J.M. Gillett 19023, CAN. • Close-up plants. Plants showing several drooping spikes on each inflorescence. Apex, Baffin Island, Nunavut, 28 Aug. 1997, S.G. Aiken 97–063, CAN. Scale bar in cm. • Close-up inflorescence. Inflorescences with lighter brown, terminal male spikes and dark brown female spikes. Plant collected beside seepage runoff near Apex, Baffin Island, Nunavut, 28 Aug. 1997, S.G. Aiken 97–063, CAN. • Close-up of Inflorescence. Herbarium specimen showing inflorescence with uppermost spike at anthesis not drooping in this drawf plant. Lower spikes pistillate: perigynia with long beaks. • Close-up of Inflorescence. Mature spike with perigynia sessile or almost sessile on the rachis. • Arctic Island distribution.
Cite this publication as: Aiken, S.G., Boles, R.L., and Dallwitz, M.J. 1999 onwards. ‘Cyperaceae of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval.’ Version: 6th November 2000. http://http://www.mun.ca/biology/delta/arcticf/. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
