This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Bog sedges, perennial by rootstocks, the culms erect, triangular or nearly terete, the leaves linear, or 1 or 2 of the upper ones reduced to bladeless sheaths. Spikelets terminal, solitary, capitate or umbelled, subtended by a 1-several-leaved involucre, or naked. Scales spirally imbricated. Flowers perfect. Perianth of 6 or apparently numerous, smooth soft bristles, which are white or brown, straight or crisped, and exserted much beyond the scales at maturity. Stamens 1-3. Style 3-cleft. Achene 3-angled, oblong, ellipsoid or obovoid. [Greek, signifying wool-bearing, referring to the soft bristles.]
Spikelet solitary; involucral leaf short or none.
Bristles 6, simple, white, crisped.
Bristles 6, each 4-6-cleft, thus appearing numerous.
Scales with very narrow pale margins.
Scales with broad pale margins.
Plants tufted, not stoloniferous.
Upper sheath inflated; culm rough at the top.
Upper sheath not inflated; culm smooth.
Spikelets several, involucrate by 1 or several leaves.
Leaves triangular-channeled throughout.
Blade of the upper stem-leaf not longer than the sheath.
Blade of the upper stem-leaf much longer than the sheath.
Leaves flat, at least below the middle.
Scales with a prominent midvein; stamens 3.
Midvein not prominent at the tip of the scale.
Midvein prominent to the tip of the scale.
Scales striate-nerved; stamen 1.