Carex subimpressa Clokey, Rhodora 21: 84. 1919
Carex lanuginosa X impressa Clokey, Torreya 16: 199. 1916. (Type from Macon County, Illinois.)
Loosely cespitose and stoloniferous, forming beds, the stolons long, horizontal, rather slender, tough, scaly, the culms 3-6 dm. high, erect, shorter than the leaves, aphyllopodic, sharply triangular, more or less roughened above, purplish-tinged at base; sterile shoots conspicuous, elongate, the leaves largely bunched near the top ; leaves with well-developed blades 3-5 to a fertile culm, not clustered at base, strongly septate-nodulose, the blades flat or somewhat channeled toward base, the margins somewhat revolute, thin but firm, dull-green, 1.5-4 dm. long, 3-6 mm. wide, long-attenuate, roughened toward apex; the sheaths tight, glabrous, deeply concave and dull-brownish at mouth, the lower at least breaking and becoming filamentose, the ligule wider than long; staminate spikes usually 3, contiguous or somewhat separated, narrowly linear, slender, 2.5-5 cm. long, 3 mm. wide, the scales oblanceolate, short-awned to acuminate, not ciliate, dull-reddish with lighter center and narrow dull-white margins, or in age straw-colored; pistillate spikes usually 2, separated, erect, short-peduncled, or the upper sessile or nearly so, oblong-cylindric, 2.5-7.5 cm. long, 8-12 mm. wide, closely flowered, or sometimes more loosely toward base, the perigynia 25-75, spreading-ascending in several to many rows; bracts leaf -like, the lowest short-sheathing, exceeding culm; scales lanceolate to ovate-lanceolate, rough-awned, the center green, strongly 3-nerved, the margins dull-hyaline, more or less strongly purplish-tinged, narrower and usually shorter than the perigynia; perigynia ovoid, 5 mm. long, 2.5 mm. wide, suborbicular in cross-section, somewhat inflated, coriaceous, many-ribbed, the ribs mostly hidden by the short dense pubescence, dull-green or grayish-green, rounded at base, sessile, contracted into a slender, somewhat flattened, bidentate beak about half as long as the body, the teeth 0.5 mm. long, slender, stiff, ascending, hispidulous within; achenes orbicular-obovoid, 1.75 mm. long, 1.5 mm. wide, triangular with concave sides below and prominent angles, loosely enveloped in lower half of perigynium-body, yellowish, substipitate, abruptly contracted into and continuous with the long, slender, strongly flexuous style; stigmas 3, slender, dark-colored, rather long.
Type locality (of C. lanuginosa X impressa, on which C. subimpressa is based): Cowford bridge, Macon County, Illinois (Clokey 2338).
Distribution: Swampy open woodlands, Indiana and Illinois. (Specimens examined from Indiana and Illinois.)