Fimbristylis vahlii

Plants annual, cespitose, delicate, 4-15 cm, bases soft; rhizomes absent. Leaves polystichous, mostly spreading or excurved, often exceeding culms; sheaths entire, abaxially smooth or sparsely hirtellous; ligule absent; blades filiform, to 0.5 mm wide, somewhat involute, abaxially glabrous or ascending-strigillose. Inflorescences terminal; spikelets sessile or subsessile in single capitate leafy-involucrate cluster; scapes filiform; involucral bracts leafy, setaceous, greatly overtopping inflorescence. Spikelets greenish, cylindric to lanceoloid-cylindric, 5-10 mm; fertile scales narrowly ovate to lanceolate, 1-1.5 mm, acute, glabrous, midrib strong, excurrent as cusp. Flowers: stamens 1; styles 2-fid, slender, bulbous-based, smooth or papillate. Achenes pale, tumidly obovoid, 0.5-0.7 mm, cancellate, pits horizontally rectangular in 5-7 vertical rows per side. 2n = 20.

Fruiting summer-fall. Moist to wet, alluvial or mineralized banks, shores, fluctuating pond and lake edges, often a 'drawdown' plant around stock tanks and reservoirs; 0-500 m; Ala., Ariz., Ark., Calif., Fla., Ga., Ill., Kans., Ky., La., Miss., Mo., Nebr., Okla., S.C., Tenn., Tex.; Mexico; Central America; South America.

Diminutive, tufted annual to 1.5 dm; lvs slender, spreading- recurved, less than 1 mm wide, often stiffly short-hairy; ligule wanting; scapes slender, wiry, subterete; spikelets 5-10 mm, linear-elliptic to lance-ovoid, 3-8 in a dense terminal cluster subtended by several long, slender invol bracts; scales lance-ovate or lance-oblong, glabrous, with an often slightly spreading mucro; stamen 1; anther less than 0.5 mm; style bifid, much longer than the achene, smooth or merely papillate; achene lenticular, thick, obovate, 0.5-0.7 mm, rather coarsely cellular-reticulate in vertical rows; 2n=20. Weedy in fine soil in moist places; trop. Amer., n. irregularly to N.J., Ky., Ill., and Kans

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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