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.]

About 15 species, in the northern hemisphere. Besides the following, 1 occurs in Alaska. Type species: Eriophorum vaginatum L. The specie's are called Cotton-grass or Cotton-rush.

Spikelet solitary; involucral leaf short or none.

Bristles 6, simple, white, crisped.

1.

E. alpinum.

Bristles 6, each 4-6-cleft, thus appearing numerous.

Plants stoloniferous.

Scales with very narrow pale margins.

2.

E. Scheuchzcii.

Scales with broad pale margins.

3.

E. Chamissonis.

Plants tufted, not stoloniferous.

Upper sheath inflated; culm rough at the top.

4.

E, callithrix.

Upper sheath not inflated; culm smooth.

5.

E. opacum.

Spikelets several, involucrate by 1 or several leaves.

Leaves triangular-channeled throughout.

Blade of the upper stem-leaf not longer than the sheath.

6.

E. gracile.

Blade of the upper stem-leaf much longer than the sheath.

7.

E.

tenellum.

Leaves flat, at least below the middle.

Scales with a prominent midvein; stamens 3.

Midvein not prominent at the tip of the scale.

8.

E.

angustifolium.

Midvein prominent to the tip of the scale.

9.

E.

viridicarinatum.

Scales striate-nerved; stamen 1.

10.

E.

virginicum.