18. Section Ovales (Kunth) H. Christ

Plants monoecious, mostly with short-creeping rhizomes, forming loose to dense tufts or clumps. Vegetative stems present, variously short or elongate, sometimes reduced to basal clusters of leaves or nearly so. Flowering stems erect, mostly longer than the leaves, sharply to bluntly trigonous, unwinged, firm, glabrous, smooth or roughened on the angles near the tip, green or light brown to dark brown at the base. Leaves basal and on the basal half of the stems, glabrous, the basal leaves reduced to nearly bladeless sheaths, the brown remains of the lowermost leaves persisting through the following year. Leaf blades flat or somewhat folded near the base, the margins minutely roughened or toothed. Leaf sheaths green or sometimes pale green to white with green lines near the tip, the ventral side firm or papery, green, white, or yellowish white, not cross-wrinkled or red-spotted, the lowermost sheath bases green or light brown to dark brown. Inflorescences with 2–15 spikes, these sessile or very short-stalked, widely or closely spaced on the axis, the bracts inconspicuous, scalelike, the lowermost sometimes with an elongate awn, shorter than the spikes, lacking a sheath. Spikes with a broad pistillate region toward the tip and a much narrower staminate region toward the base, this inconspicuous or prominent, occasionally the lowermost spikes entirely pistillate, elliptic to obovate or nearly circular in outline, the base and tip appearing rounded or pointed, with numerous densely spaced perigynia, these ascending or spreading at maturity, sometimes radiating in all directions. Staminate and pistillate scales similar, the staminate scales usually slightly longer than the pistillate ones. Perigynia thin-walled, flat to somewhat concave ventrally, flat to somewhat rounded dorsally, ovate to narrowly elliptic-lanceolate in outline, tapered to a flattened beak with minute teeth along the margins and 2 narrow teeth at the tip, the base rounded or tapered, the sides mostly strongly winged, glabrous. Styles withering during fruit development, jointed to the main body of the fruit, which is not or minutely beaked at maturity. Stigmas 2. Fruits biconvex and somewhat flattened in cross-section, shiny. About 85 species, North America to South America, Hawaii, Europe, Asia; introduced in New Zealand.

Section Ovales is among the most easily recognized groups of Missouri sedges, but the species within the section can be very difficult to determine. The section is one of the largest and most difficult taxonomically in North America. To help with determinations of specimens of Ovales, collectors should note characteristics of the vegetative stems, which can be important in distinguishing closely related species. When examining spikes, it is important to locate the most mature, best developed perigynia in a sample, as these facilitate interpretation of subtle characters of perigynium shape, size, and texture.