Carex saxatilis L.
Sp. Pl. I: 976. 1753.
Nomenclatural section used by Flora of North America project subgenus Carex, sect. Vesicariae Carey
Carex miliaris Michx.
Carex saxatilis var. miliaris (Michx.) L.H. Bailey
Carex physocarpa Presl
Carex vesicaria var. physocarpa (Presl) Kükenthal
Carex compacta R. Br. ex Dewey
Carex ambusta Boott
Carex miliaris var. obtusa L. Bailey
Carex miliaris var. major L. Bailey
Carex miliaris f. longepedunculata Lepage Carex pulla Good.
Carex rotundata Wahlenb. var. elatior Lange
Carex miliaris var. ungavensis Raymond
Plants caespitose. Plants more than 15 cm high (usually); (7–)15–30(–90) cm high. Roots pallid-brown. Ground level or underground stems horizontal; rhizomatous; compact. Scales present. Aerial stems erect; not filiform (0.4–1.7(-2.1) mm in diameter above the uppermost leaf); triangular in cross section; glabrous, or scabrous (scaberulous near the inflorescence). Leaves mostly basal, or distributed along the stems (in the lower third, 3–9 per fertile stem). Sheaths collar present (tightly enveloping the stem, hyaline ventrally, mouth truncate or concave); breaking down into fibres; brown, or reddish. Ligules present; 0.4–6.6(–10) mm long (as wide as long, to slightly longer than wide, obtuse to the apex). Blades somewhat curled; linear; glabrous (sometimes scaberulous on the margins).
Flowering stems about as high as the leaves, or conspicuously taller than the leaves. Leaf or reduced bract closely associated with the base of the inflorescence present; conspicuous and leaf-like; similar in length to the inflorescence, or shorter than the apex of the inflorescence (lower leaves on the stem often extend beyond the inflorescence); (0.6–)1.5–12(–19) cm long (0.2 –2.9(-4.2) mm wide); sheathless. Inflorescence spicate; 2.5–14(–20) cm long; 5–45 mm wide. Pedicels scabrous (on ridges). Inflorescence multispicate; 2–3(–6) spikes; lateral spikes borne on pedicels. Individual spike(s) erect. 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, or as long as the perigynium in fruit; black, or pale grey; with margins, and sometimes mid-vein paler in colour than the adjacent area of the scale; acute; ovate; 1.9–4.3(–5) mm long; 0.9–2.1 mm wide; glabrous. Perianth absent. Anthers 1.1–3.4(–4.1) mm long. Styles slender, extending beyond the beak. Stigmas per style 2. Fruit surrounded by a perigynium. Perigynia fused to the apex except for a small aperture through which the style protrudes; broadly ovate; 2.2–4.8(–5.5) mm long; 1.1–3 mm wide; contracted at the base into a stipe-like structure (0–0.3(-0.4)mm long); erect or ascending (forming an angle 25–75° with the spike axis); golden brown, or brown, or green; surface glossy; glabrous; tuberculate (slightly); faintly nerved (with few nerves); apices beaked with a short beak (0.2–0.8 mm); apex oblique, becoming slightly bidentate. Achenes not filling the upper part of the perigynia; lenticular.
Chromosome information. 2n = 80.
Distribution. Circumpolar. Arctic. Range in the Canadian Arctic Archipelago wide-spread. Common. Arctic Islands: Baffin, Ellesmere, Axel Heiberg, Banks, Victoria, Southampton, Coats.
Ecology and habitat. Substrate wet meadows, hummocks, around the margins of ponds, marshes, along streams, river terraces, tundra, sea shore (in bogs or on beaches); aquatic, or imperfectly drained, or dry; calcareous; rock, gravel, sand, silt, clay; with low organic content, or with high organic content. In drier places, C. saxatilis can be found in grassy meadows; in wetter areas, it is reported with Dryas and mosses. It can occur in higher altitudes where it grows near mountain streams.
Taxon as an environmental indicator. Carex saxatilis occurs in a wide variety of open moist habitats. It is often found as a dominant in open cyperoid wetlands where it is commonly associated with other species of Carex as well as Eriophorum and Equisetum. Carex saxatilis also occurs in roadside ditches, Sphagnum bogs, sandy beaches, openings in spruce muskeg, seasonally wet ponds, wet gravel, mud flats, and standing water along the shorelines of lakes ponds, and slow moving streams. In more southerly habitats C. saxatilis is almost always associated with shoreline habitats and is absent from surrounding graminoid wetlands. This sedge may not compete well with more robust, temperate species and in these southerly stations may be reliant on water level fluctuations to eliminate competing vegetation.
Notes. Ford and Ball (1992) in a study of the circumpolar short-beaked taxa of Carex sect. Vesicariae using numerical analyses of macromorphological characters found that within the C. saxatilis complex, plants from western North America (C. physocarpa) tend to be robust individuals with long peduncles on the pistillate spikes, wide leaves, and large perigynia. These characters and others decrease in size eastward across the North American continent with intermediate plants usually referred to as C. saxatilis and small plants referred to as C. miliaris. This east/west cline is confounded by large amounts of variation within small geographic areas and phenotypic plasticity. Eurasian material is less variable than that from North America and is included within the range of variation found in North America. Ford and Ball (1992) concluded that a single distigmatic species, C. saxatilis should be recognized. They noted that anatomically C. saxatilis is indistinguishable from C. membranacea and presented evidence to suggest that this similarity is the result of homoplasy or stasis in anatomical characters rather than an indication of a close evolutionary relationship.
Ford and Ball (1992) stated that C. saxatilis occurs throughout arctic and boreal areas of Eurasia. It is most variable in North America and this may account for the proliferation of names on this continent. While much of the variation in North America occurs on a local scale or is due to phenotypic plasticity there is an underlying trend for plants to be largest in the west with a decrease in size eastwards across the North American continent. The establishment of clinal variation in northern latitudes is often explained by the splitting of a species range into isolated populations during the Late Pleistocene; remigration during the Holocene; followed by the secondary contact of these populations, which have become variously differentiated during their period of isolation (Barton and Charlesworth 1984; Prentice 1986). The persistence of the present day morphologic pattern could be explained by the existence of a selective gradient across North America, which is obscured by localized divergence and plasticity. Alternatively, the weak morphocline currently exhibited by C. saxatilis could be a relict of a more distinct assemblage of taxonomic entities that have decayed through introgression and localized divergence.
Illustrations. • Plants in habitat. Dominant plant in foreground. Nunavut, Baffin Island, Iqaluit. Susan Aiken 97–037, CAN. • Plants in habitat. Plants growing between rocks. Nunavut, Baffin Island, Iqaluit. Susan Aiken 97–037, CAN. Scale bar in cm. • Close-up of inflorescence. Terminal staminate spike at anthesis. Perigynia with two stigmas. • Close-up of inflorescence. Terminal spike staminate, middle spike, staminate at the apex, pistillate at the base. Lowest spike pistillate. Note the perigynia are brown. • 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).
