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..
Cyperus flavescens L. Sp. PI. 46. 1753.
Annual, culms very slender, tufted, leafy below, 3'-12' tall, mostly longer than the leaves. Leaves 1"- 1 1/2" wide, smooth, the longer usually exceeding the inflorescence; clusters terminal and sessile or on 1-4 short rays; spikelets in 3's-6's, linear, subacute, yellow, many-flowered, flat, 4"-9" long, 1 1/2"-2" broad; scales ovate, obtuse, 1-nerved, appressed, twice as long as the orbicular-ovate black obtuse lenticular shining achene; stamens 3; style deeply 2-cleft, its branches slightly exserted; superficial cells of the achene oblong.
In marshy ground, New York to Michigan, Florida, Mexico and Costa Rica. Also in the Old World, in Bermuda, Cuba and Dominica. Reported from Maine. Aug.-Oct.
Annual, culms tufted, slender, 2'-15' tall. Leaves about 1" wide, those of the involucre usually 3, the longer much exceeding the spikelets; clusters sessile and terminal, or at the ends of 1-3 rays; spikelets 4"-9" long, linear-oblong, acute, flat, many-flowered; scales ovate, green, brown, or with brown margins, obtuse, i-nerved, appressed, membranous, dull; stamens 2 or 3; style 2-cleft, its branches much exserted; achene lenticular, oblong, subacute, gray, not shining, one-half as long as the scale, its superficial cells quadrate, about as long as wide.
In marshy places, New Brunswick to Minnesota, south to South Carolina and Kansas. Cypress-grass. Galingale or Galangal. Aug.-Oct
Similar to the preceding species, culms slender, tufted, 4'-15' tall. Umbel usually simple; spikelets linear or linear-oblong, acutish, 4"-10" long; scales green or dark brown or with brown margins, appressed, firm, subcoriaceous, shining, obtuse; stamens mostly 3; style 2-cleft, scarcely exserted; achene oblong or oblong-obovate, lenticular, somewhat pointed, dull, its superficial cells quadrate.
In wet soil, especially along streams and ponds, Maine to southern Ontario and Michigan, south to Missouri, North Carolina and Kansas. Aug.-Oct.
Cyperus filicinus Vahl, Enum. 2: 332. 1806.
C. Nuttallii Eddy; Spreng. Neue Entd. 1: 240. 1820.
Annual, culms slender, tufted, 4'-i8' tall, equalling or often longer than the leaves. Leaves of the involucre 3-5, spreading, the larger often 5' long; umbel simple or slightly compound, 3-7-rayed; spikelets rather loosely clustered, linear, very acute, flat, spreading, 1/2-1 1/2' long, 1"-1 1/2" wide; scales yellowish-brown with a green keel, oblong, acute, rather loosely spreading at maturity; stamens 2; style 2-cleft, its branches somewhat exserted; achene lenticular, narrowly obovate, obtuse or truncate, dull, light brown, one-third to one-half as long as the sqale, its superficial cells quadrate.
Salt marshes, Maine to Mississippi. Also in Bermuda. Aug.-Oct.