117. Carex sterilis Willd.

Pl. 62 a–g; Map 233

Plants dioecious or less commonly monoecious. Flowering stems 10–70 cm long, sharply trigonous and roughened on the angles toward the tip. Leaf blades 25 cm long, 1.0–2.6 mm wide. Inflorescences with 3–8 spikes. Terminal spike mostly all staminate (4–14 mm long, 1.2–2.6 mm wide, with 6–30 flowers) or all pistillate (3–13 mm long, 4.5–7.0 mm wide, with 5–25 perigynia), less commonly either mostly staminate with few, scattered perigynia, or mostly pistillate with few, basal staminate flowers and with the staminate portion 0.5–1.0 mm long. Lateral spikes similar to the terminal one. Staminate scales 2.2–3.3 mm long, ovate, pointed at the tip, brown with a green midrib and lighter margins. Pistillate scales 1.8–2.9 mm long, ovate, pointed at the tip, brown with a green midrib and lighter margins. Perigynia 2.1–3.8 mm long, 1.2–2.2 mm wide, tapering evenly or concavely from the main body to the beak, not forming a shoulder, the beak densely and irregularly toothed along the margins, mostly without spaces visible between the teeth, the ventral surface with 5–12 strong nerves or less commonly nerveless or nearly so, the dorsal surface with 5–12 strong nerves, brown to reddish brown at maturity (turning dark brown when overripe). Fruits 1.0–1.7 mm long. April–June.

Uncommon in the eastern portion of the Ozark Division (northeastern U.S. west to Minnesota and Missouri). Fens.

Dioecious and mostly staminate individuals of C. sterilis are separated easily from other Missouri species of section Stellulatae. However, monoecious plants with spikes containing mostly perigynia can be difficult to separate from C. interior, which is common at every Missouri station for C. sterilis. In addition to the key characters, C. sterilis is distinct in having more stiffly erect stems and anthers mostly 1.2–2.2 mm long (vs. mostly 0.6–1.6 mm). The species was first reported for Missouri by Orzell (1983) and Orzell and Bridges (1989). For discussion of a putative hybrid between these two species, see the treatment of C. interior.