8. Carex eburnea Boott

Pl. 31 i–n; Map 124

Plants monoecious, with slender, long-creeping rhizomes, forming dense tufts, clumps, or colonies, glabrous. Vegetative growth consisting of tufts of basal leaves at the tips of rhizome branches, sometimes appearing as short, very slender, leafy stems (these actually false stems consisting of a series of overlapping leaf sheaths). Flowering stems 10–30 cm long, very slender, erect or arched outward. Leaves basal or nearly so, mostly shorter than the stems, light green, glabrous. Leaf blades 4–25 cm long, 0.3–0.5 mm wide, the margins and midrib smooth, the margins inrolled. Leaf sheaths with the tip deeply concave, the ligule short and broadly V-shaped, the lowermost sheath bases usually tinged light brown. Spikes 3–5 per stem, the lowermost bract reduced to a tubular sheath, the blade absent or short-triangular. Terminal spike staminate, 4–8 mm long, sessile or short-stalked, linear, the staminate scales 3–5 mm long, oblanceolate, yellowish white. Lateral spikes 2–4, pistillate, densely to loosely spaced near the tip of the axis, long-stalked, ascending and mostly overtopping the staminate spike, 3–6 mm long, broadly oblong to ovate or lanceolate in outline, with 2–6 densely to loosely spaced perigynia, the pistillate scales 1.2–1.8 mm long, ovate to broadly ovate, rounded or bluntly pointed at the tip, white to pale yellow, sometimes faintly brownish tinged, the midrib green. Perigynia 1.5–2.0 mm long, usually with 2 prominent, longitudinal ribs on opposite sides, otherwise usually finely few-nerved, trigonous, green or sometimes olive green to light brown, tapered abruptly to a short beak at the tip, glabrous, the beak 0.2 mm long, not flattened, with short, soft, inconspicuous teeth at the tip. Styles withering during fruit development, jointed to the main body of the fruit, which is beakless or short-beaked at maturity. Stigmas 3. Fruits 1.2–1.8 mm long, elliptic in outline, trigonous, brown. 2n=54. April–August.

Common, mostly in the Ozark and Ozark Border Divisions, and locally north of the Missouri River in eastern Missouri (eastern U.S. west to Montana, North Dakota, and Arkansas; Canada, Alaska). Under Juniperus on glades, along dry to seepy ledges of bluffs, and in loose talus, almost always on calcareous substrates.

This attractive sedge, with its hairlike stems and leaves, occupies two different types of habitats in Missouri. Steyermark (1963) noted that it characteristically occurs in tufts along ledges and talus areas, often on limestone bluffs. However, at the time that Steyermark was compiling distributional data, the species was not known from dolomite and limestone glades, where it is commonly found today, almost always growing in dense colonies under cedar trees. Evidently, the spread of C. eburnea onto glade habitats occurred as a result of the well-documented increase in Juniperus on these glades during the past 50–60 years.