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..
Low annual sedges, with slender tufted culms leafy at the base, and terete many-flowered spikelets in a terminal head, subtended by a i-several-leaved involucre. Scales firm, spirally imbricated all around, all fertile or several of the lower ones empty, at length deciduous. Flowers perfect, with a small hyaline scale on each side; bristles none. Stamens 1-2; anthers 4-celled. Style 2-3-cleft, deciduous, its base not swollen. Achene plano-convex or 3-angled. [Greek, alluding to the thick sepals in some species.]
About 15 species, widely distributed in warm and tropical regions. Type species: Hypaelytrum argenteum Vahl.
Annual, glabrous, roots fibrous, culms tufted, grooved, compressed, smooth, longer than the narrowly linear somewhat channeled leaves, 3'-10' tall. Leaves of the involucre 2-4, the larger 1'-5' long; spikelets ovoid-oblong, obtuse, 21"-3" long, 1" in diameter, 2-6 together in a terminal capitate cluster; scales rhombic or lanceolate, acute at the apex, curved, the sides nearly white, or flecked with reddish-brown spots, the midvein green; exterior sepal convolute around the achene, nerved, hyaline; stamen 1; achene oblong, yellowish, contracted at the base.
In wet or moist soil, Virginia to Florida. Near Philadelphia probably adventive. Cuba, Panama. July-Sept.
Low tufted mostly annual sedges, with erect or spreading, almost filiform culms and leaves, and terete small terminal capitate or solitary spikelets subtended by a 1-3-leaved involucre. Scales spirally imbricated all around, deciduous, all subtending perfect flowers, a single hyaline inner scale between the flower and the rachis of the spikelet; bristles none. Stamen 1. Style 2-cleft, deciduous, not swollen at the base. Achene oblong, turgid or lenticular. [Greek, in allusion to the single inner scale.]
About 5 species, natives of temperate and tropical regions. Besides the following, another occurs in the western United States. Type species: Hemicarpha Isolepis Nees.
Scales with a short tip or mucronate.
Scales abruptly narrowed into an awn about as long as the body.
Scirpus microvillus Vahl, Enum. 2: 254. 1806.
H. Drummomlii Nees, in Mart. Fl. Bras. 21: 61. 1842.
H. micrantha Pax in E. & P. Nat. Pflf. 22: 105. 1887.
Annual, glabrous, culms densely tufted, compressed, grooved, diffuse or ascending, 1'-5' long, mostly longer than the setaceous smooth leaves. Spikelets ovoid, many-flowered, obtuse, about 1" long, capitate in 2's-4's or solitary; involucral leaves, or one of them, usually much exceeding the spikelets; scales brown, obovate, with a short blunt tip; achene obovate to oblong, obtuse, mu-cronulate, little compressed, light brown, its surface minutely cellular-reticulated.
'In moist, sandy soil. New Hampshire to Ontario, Washington, Florida, Texas, Mexico and South America. July-Sept.
H. micrantha aristulata Coville, Bull. Torr. Club 21:
36. 1894. H. aristulata Smyth, Trans. Kans. Acad. Sci. 16: 163.
1899. H. intermedia Piper; Piper & Beattie, Fl. Pal. Reg. 36:
Similar to the preceding species; culms 8' high or less, longer than the setaceous leaves; involucral leaves 1-3, sometimes nearly 1' long. Spikelets ovoid, 2"-4" long; scales rhombic-obovate, brown, rather abruptly contracted into a subulate spreading or somewhat recurved awn about as long as the body; inner scale larger than that of H. micrantha; style short; achene narrowly obovate, black.
Wet, sandy soil, Kansas to Wyoming, Colorado and Texas; California and Washington.
H. occidentalis A. Gray, a species of California and Oregon, with larger subglobose heads and lanceolate scales, is erroneously recorded from western Ontario.