88. Carex aggregata Mack.

Pl. 55 f–k; Map 204

C. sparganioides Muhl. ex Willd. var. aggregata (Mack.) Gleason

Plants with poorly developed rhizomes, forming tufts or clumps. Flowering stems 20–100 cm long, shorter than to longer than the leaves. Leaf blades 2–50 cm long, 3–6 mm wide, light green. Leaf sheaths loose and somewhat baggy around the stem, the ventral side relatively firm and usually without cross-wrinkles, usually remaining intact at maturity, somewhat thickened and yellow to brown at the tip, the dorsal side white with green veins or mottled green and white, also with scattered, short, dark green or brown cross-lines (these actually darkened cross-walls of the cells, clearly visible with magnification), the ligule shorter than to about as long as wide and U-shaped. Inflorescence compact, narrowly ovate to narrowly oblong in outline, dense, the 5–10 spikes overlapping on the axis, the lowermost bracts 2–8(–30) mm long, much shorter than the inflorescence, hairlike with the base somewhat broadened. Spikes 7–13 mm long, 8–13 mm wide, with 5–15 mostly ascending to spreading perigynia, the scales 2.0–3.5 mm long, 2/3 as long to about as long as the perigynia, ovate, the tip sharply pointed and sometimes short-awned. Perigynia 3.2–4.6 mm long, 1.9–2.8 mm wide, up to 2 times as long as wide, ovate in outline, widest just below the middle, the tip with a beak 1/3–1/2 as long as the main body with minutely toothed or roughened margins, the base rounded, the basal portion not thickened with corky to spongy tissue (rarely slightly thickened), usually green at maturity, the ventral surface nerveless, the dorsal surface nerveless or with 2–5 faint nerves. Stigmas long, slender, straight or sometimes loosely coiled. Fruits 1.8–2.1 mm long, broadly elliptic-ovate to nearly circular in outline. May–June.

Scattered nearly throughout Missouri, but apparently absent from the Mississippi Lowlands Division (northeastern U.S. and adjacent Canada west to South Dakota and Kansas). Bottomland forests, mesic upland forests, bottomland prairies, and banks of streams; also in pastures and moist, disturbed areas.

Steyermark (1963) discussed the presence of a few Missouri collections with leaf sheaths somewhat intermediate between C. aggregata and C. sparganioides, and he noted that further studies might result in the combining of these two taxa. Some authors (Gleason and Cronquist, 1991) have treated them as varieties of C. sparganioides. However, the difference in inflorescence density and the occasionally compound inflorescences of C. sparganioides, along with its generally wider leaves, shorter pistillate scales, and shorter teeth on the perigynium beaks, correlate with the leaf sheath characters to separate virtually all of the Missouri specimens into two well-defined taxa. Thus the two are recognized as separate species in the present treatment.