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..
Culm stiff, smooth, obtusely triangular above, nearly terete below, 1°-2° tall or less, all the sheaths blade-bearing. Leaves flat, at least below the middle, roughish-margined, 1 1/2"-4" wide, tapering to a triangular channeled rigid tip, the upper shorter than or rarely overtopping the culm, those of the involucre 2-4, often black at the base, the longer commonly equalling or exceeding the inflorescence; spikelets 2-12, ovoid, or oblong, clustered in a terminal umbel; rays filiform, smooth; scales ovate-lanceolate, acute or acuminate, purple-green or brown, the midvein not extending to the tip; bristles numerous, bright white, about 1' long, 4-5 times as long as the scale; achene obovoid, obtuse, light brown.
In bogs, Newfoundland to Alaska, Maine, Illinois, Colorado and Oregon. Also in Europe and Asia. E. polystachyon L. is confined to the Old World. June-Aug.
9. Eriophorum viridicarinatum (Engelm.)
E. latifolium viridicarinatum Engelm. Am. Journ. Sci.
46: 103. 1844. Eriophorum polystachyon latifolium A. Gray, Man.
529. 1848. Not E. latifolium Hoppe.
Similar to the preceding species but with thinner green, grass-like leaves, which are flat, except at the tip, 1"-3," wide, the upper one 6' long or less, those of the involucre not black at the base; spikelets usually more numerous, sometimes as many as 30, the rays finely hairy, elongated or sometimes very short; scales ovate-lanceolate, the midvein extending to the tip, sometimes slightly excurrent; achene oblong-obovoid; bristles white or yellowish-white.
In wet meadows and bogs, Newfoundland to British Columbia, New York, Georgia, Ohio and Michigan.
Eriophorum virginicum L. Sp. PI. 53. 1753.
E. virginicum album A. Gray, Man. Ed. 5, 566. 1867.
Culm stiff, rather slender, obtusely triangular above, terete below, smooth, 1 1/2°-4° tall, rather leafy. Leaves narrowly linear, flat, 1"-2 1/2" wide, rough-margined, somewhat channeled toward the apex, the upper often overtopping the culm, those of the involucre 2-4, spreading or deflected, 2'-6' long, 1 or 2 of them much longer than the spikelets; spikelets several or numerous in a dense terminal capitate cluster usually broader than high, erect or the outer ones spreading; scales ovate, acute, brown with a green center, about 5-nerved; bristles numerous, dingy brown, rarely white, about 3 times as long as the scale; achene linear-oblong, acute, apiculate, light brown.
In bogs, Newfoundland to Manitoba, south to Florida and Nebraska. June-Sept.