74. Carex tribuloides Wahlenb.

Pl. 48 a–g; Map 190

Plants with short, inconspicuous rhizomes, forming tufts or clumps. Vegetative stems abundant at flowering time, conspicuous and nearly as long as the flowering stems, the leaves well spaced along the apical half, occasionally becoming prostrate and rooting at the nodes. Flowering stems 30–110 cm long, usually somewhat longer than the leaves. Leaves with well-developed blades mostly 4–10 per flowering stem. Leaf blades 2–25 cm long, 3–7 mm wide, green to yellowish green. Leaf sheaths not extended past the insertion point of the leaf blade, the ventral side green nearly to the tip, the tip concave, the ligule longer than wide and U-shaped. Inflorescence straight or rarely (in depauperate specimens) somewhat nodding, the 4–15 spikes densely overlapping along the axis, the lowermost 1–3 spikes sometimes more loosely spaced. Spikes 6–16 mm long, 4–10 mm wide, the pistillate portion circular to ovate or obovate in outline, rounded at the tip, with numerous perigynia with appressed to ascending (rarely somewhat spreading) tips, at least the terminal spike narrowed to the short staminate portion, this often inconspicuous. Scales 1.9–3.8 mm long, shorter and narrower than, but not hidden by the perigynia, narrowly ovate, mostly sharply pointed, white to pale brown, with a green midrib. Perigynia 2.8–5.5 mm long, 0.9–1.6 mm wide, 2.5–3.5 times as long as wide, flat or nearly so on both sides, the main body 1.5–3.0 times as long as wide, lanceolate to oblanceolate, widest near the middle, the distance from the tip of the fruit to the tip of the perigynium 0.8–2.2 mm, narrowly winged, the wing tapered abruptly from about the middle of the main body and usually ending above the base, tapered gradually to a beak with toothed or roughened margins, the wing ending more or less at the tip of the beak, the ventral and dorsal surfaces lacking papillae, finely 3–7-nerved on the ventral surface and finely 5–9-nerved on the dorsal surface, green to pale brown or brown. Fruits 1.2–1.6 mm long, 0.5–0.8 mm wide, narrowly oblong-ovate in outline, light brown. 2n=70. May–June.

Common nearly throughout Missouri (eastern U.S. and adjacent Canada west to Minnesota and Texas; Mexico). Bottomland forest, swamps, bottomland prairies, banks of streams and spring branches, margins of lakes, ponds, and sinkhole ponds, acid and alkaline seeps, and fens; also moist pastures, railroads, roadsides, and moist disturbed areas.

Specimens with looser inflorescences of slightly smaller spikes and perigynia tending to be somewhat shorter (2.8–4.5 mm) and wider relative to their length (2.5–3.2 times) have been called var. sangamonensis Clokey (Mackenzie, 1931–1935; Reznicek, 1993). This variant tends to occur in the southern portion of the species’ range, including parts of Missouri. Its relationship to more typical C. tribuloides requires further study, but the two taxa do not appear to be easily separable in the state.

Several Missouri collections of C. tribuloides possess perigynia that are somewhat more spreading than is typical for the species. These specimens were referred to the related C. projecta Mack. by Steyermark (1963). True C. projecta occurs only to the north and east of Missouri, and differs from C. tribuloides in its more flexuous, slender inflorescences and spikes with fewer perigynia (15–30 vs. 30 or more). None of the Missouri specimens match Mackenzie’s concept of C. projecta, and he did not record the species from south of Iowa.