Cyperus
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Authority
Acevedo-Rodríguez, Pedro & collaborators. 1996. Flora of St. John, U.S. Virgin Islands. Mem. New York Bot. Gard. 78: 1-581.
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Family
Cyperaceae
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Scientific Name
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Description
Genus Description - Perennials or annuals; rhizomes when present short or stoloniferous, rarely elongate and creeping; culms 3-angled or sometimes cylindrical, smooth or scabrous. Leaves primarily basal; blades herbaceous or stiff, flat, pleated, inrolled, cylindrical, or crescentshaped, sometimes septate, the margins, ventral midvein, and dorsal lateral veins when present usually scabrous; sheaths rarely bladeless, eligulate or shortly ligulate, finely veined, sometimes septate, usually glabrous, the ventral band membranous. Inflorescence a simple or compound, terminal, umbel-like corymb, rarely congested or pseudolateral and headlike; involucral bracts leaflike, spreading, or the lowest erect and appearing as a continuation of the culm; rays unequal in length, glabrous, rarely scabrous, prophyllate at base, the lowermost each borne from the axil of a single involucral bract, the uppermost borne just below the base of the central spike, these frequently flexuous, becoming divergent to reflexed at maturity; spikes solitary or in umbels at ray tips, the central spike usually sessile or subsessile; spikelets ovate, ovate-lanceolate, or linear, many-flowered, flattened, subcylindrical or 4-angled, palmately, pinnately, or imbricately arranged on the rachis; scales 2-ranked, ovate, oblong-ovate, or elliptic, keeled or boat-shaped, sometimes 2-keeled, usually glabrous, the apex acute, obtuse, mucronulate, or cuspidate, the lowermost scale and subtending bract empty; rachilla winged from the persistent, decurrent base of the scale, or wingless, sometimes corky or thickened, disarticulating at base from the rachis, the whole spikelet falling entire, or disarticulating at the nodes, the internodes, scales, and achenes falling as 1-fruited segments, or rachilla persistent on the rachis, the scales and achenes deciduous. Flowers bisexual; bristles absent; stamens 1-3, the anthers oblong-elliptic, lanceolate, or linear, sometimes minutely appendaged at apex; styles 2- or 3-branched, slender, uniform, the branches minutely scaly, shorter than to exceeding the smooth unbranched portion. Achenes 3-angled or 2-sided, ovoid, obovoid, oblong-obovoid, ellipsoid, or narrowly ellipsoid, usually short-apiculate at apex, the surface puncticulate, reticulate, or smooth, sometimes transversely wrinkled; bristles absent.
Distribution and Ecology - A cosmopolitan genus with approximately 650 species, in temperate and tropical regions.