[++] Teeth of the perigynium strongly reflexed.
2. C. subulàta, Michx. Green, very slender but erect, 6´–2° high; leaves narrow, somewhat shorter than the culm; bracts leafy, sheathing; pistillate spikes 2–4, scattered, 2–6-flowered; perigynium deflexed.—Deep sphagnum swamps, R. I. to E. Penn., and southward; very local.
[++][++] Teeth erect or spreading.
[=] Whole plant yellowish; perigynium little or not at all inflated.
3. C. Michauxiàna, Boeckl. Slender but stiff and erect, 1–2° high; leaves narrow and firm, shorter than the culm; spikes 2–3, the lowest usually remote and short-peduncled, the remainder aggregated and sessile; staminate spike small, wholly sessile; perigynium not inflated, erect or spreading, twice longer than the blunt scale. (C. rostrata, Michx.)—Bogs and lake-borders, mountains of N. H. and N. Y., and westward to L. Superior; local.
4. C. folliculàta, L. Stout, 2–3° high; leaves very broad and flat, lax; pistillate spikes 3–4, scattered, all but the uppermost prominently peduncled; staminate spike short-peduncled; perigynium larger, inflated, the scale awned and nearly as long.—Cold swamps, New Eng. to N. J. and Penn., and west to Mich.; rather local.
[=][=] Plant green; perigynium much inflated.
5. C. intuméscens, Rudge. Slender, 18–30´ high; leaves narrow, pistillate spikes two, loosely 1–8-flowered, the perigynium erect-spreading, not prominently many-nerved.—Wet pastures and swamps; common.
6. C. Gràyii, Carey. Larger and stouter; leaves broad and flat, 3–4´´ wide; pistillate spikes 1 or 2, the lowest often peduncled, perfectly globular and compactly 12–30-flowered, the perigynium spreading or deflexed and prominently many-nerved.—Meadows and copses, Vt. to Ill., and south to Ga.; rare eastward.—In var. hispídula, Gray, the perigynium is sparsely hispidulous.
7. C. lupulìna, Muhl. Very stout and leafy; leaves rather broad and loose; pistillate spikes 2–6, approximate at the top of the culm, all closely sessile or the lower sometimes short-peduncled, oblong or short-cylindrical, very heavy and densely flowered; staminate spike small and sessile; perigynium large and rather soft, erect or but slightly spreading, giving the spike a hop-like aspect (whence the name). (C. lurida, Bailey.)—Swamps and wet pastures; frequent.