Carex rariflora (Wahlenb.) Sm.
Engl. Bot. tab. 2516. 1813.
Nomenclatural section used by Flora of North America project subgenus Carex, sect. Limosae (O.F. Lang) Kükenthal
Carex rariflora f. erecta Polunin
Carex rariflora (Wahlenb.) Sm.
Carex rariflora var. androgyna Porsild = Carex stygia Holm, non Fries
Carex limosa var. rariflora Wahlenb.
Plants not caespitose (stems sometimes loosely clustered). Plants less than 15 cm high, or more than 15 cm high; (8–)10–20(–25) cm high. Roots tomentose, thick furry and yellow; typical of sect. Limosae. Roots pallid-brown. Ground level or underground stems horizontal; stoloniferous; elongate, or compact. Scales present (on stolons). Aerial stems erect; filiform (0.5–0.8 mm in diameter); triangular in cross section; glabrous (glaucous). Leaves mostly basal. Sheaths brown, or reddish. Ligules present. Blades straight; linear; flat, or folded (loosely); scabrous (coarsely ciliate to serrulate on margins).
Flowering stems conspicuously taller than the leaves. Leaf or reduced bract closely associated with the base of the inflorescence present; reduced, or scale-like; shorter than the apex of the inflorescence (terminating in a short blade); (0.5–)1–3 cm long; with sheath longer than the blade, or with sheath shorter than the blade. Inflorescence spicate; linear, or oblong; 2.5–3(–4) cm long; 10–20 mm wide. Pedicels smooth (and capillary). Inflorescence multispicate; 2–4 spikes; lateral spikes borne on pedicels (spikes with 3–8 flowers). Individual spike(s) erect (terminal staminate spike), or pendent (pistillate spikes). Terminal spike wholly staminate. Cladoprophyll present at the base of the peduncle of lateral spikes. Staminate flowers conspicuous. Floral scales shorter than the perigynium in fruit; brown, or black; with margins the same colour as the body of the scale (midvein conspicuously pale); cuspidate, or acute; ovate; 3.5–4.5 mm long; 2.8–3.2 mm wide (broader than the perigynia); glabrous. Perianth absent. Anthers 2–2.5 mm long. Styles thick and short. 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; 3.2–3.6 mm long; 1.5–1.8 mm wide; sessile; erect or ascending; green (pale); surface dull; glabrous; papillose; faintly nerved; with 2 keels; apices merely conical or rounded. Achenes filling the perigynia; trigonous (when mature).
Chromosome information. 2n = 50 and 52.
Distribution. Circumpolar. Low arctic. Common. Arctic Islands: Baffin, Southampton, Coats, and Victoria (new records since Porsild (1957).
Ecology and habitat. Substrate wet meadows, hummocks, around the margins of ponds, marshes (occasionally), along streams (often braided), tundra, sea shore (on sand in swales); imperfectly drained, or on seepage slopes; calcareous; sand, till, moss; with high organic content, or peat (rarely). This species occurs on alkaline till plains. In wet meadows, it is typically found with Carex, Salix and Petasites frigidus. In wet hummocky tundra common associates are Ledum, Empetrum, Vaccinium and Eriophorum.
Notes. Polunin (1940) noted that this species varies considerably in the length of the pedicels, even the lowest of which may be so short (less than 1 cm long) and rigid as to hold the spike erect instead of pendulous, and so constitute f. erecta Polunin. The species also varies in the colour of the scales which except along the midrib are generally of such a dark brown as to appear jet-black in the field; but they can be of almost any shade to quite a pale brown. This occurrence of forms with light-coloured scales in species that normally have them dark is almost general in this and closely related groups.
In a study of geographic patterns of genetic diversity for C. rariflora sampled from the east coast of James Bay, interior Nouveau-Quebec and the northern Yukon Territory, Vellend and Waterway (1997) found that within-population diversity was low overall, and that the degree of population differentiation was high. Particularly low levels of genetic variation at James Bay are attributed to founder events following post glacial colonization. Higher genetic variation in the northern Yukon is attributed to the presence of glacial refugia during the Pleistocene.
Illustrations. • Plants in habitat. Sedge meadow. Nunavut, Baffin Island, Iqaluit. Susan Aiken 97–031, CAN. Scale bar in cm. • Close-up of plants. Plants with horizontal stems growing in a silty substrate. Nunavut, Baffin Island, Iqaluit. Susan Aiken 97–031, CAN. • Close-up of inflorescence. Terminal spike staminate and lateral spike pistillate; perigynia apex merely conical. Note the contrast in color between the floral scales and the perigynia. Nunavut, Baffin Island, Iqaluit. Susan Aiken 97–031, CAN. • 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).
