Fimbristylis schoenoides
Fimbristylis dichotoma
ditch fimbry
fork fimbry
polystichous, mostly spreading to ascending;
sheath margins entire;
ligule present, complete;
blades narrowly linear, to 1 mm wide, flat to shallowly involute, margins distantly scabrid, surface glabrous.
nearly distichous, spreading to ascending, 1/2 length of culms;
sheaths distally ciliate, backs mostly glabrous;
ligule line of short hairs;
blades narrowly linear, 2–3 mm wide, flat to broadly involute, scabridciliate, adaxially smooth or hirtellous.
spikelets 1, terminal or 2–3 in simple anthela longer than broad, laterals subsessile;
scapes narrowly linear, coarsely ribbed, distally compressed;
involucral bracts usually 1 per spikelet, exceeding or exceeded by it.
anthelae compound, dense or open, ascending-branched, longer than broad;
scapes slender, 1 mm wide, slightly compressed distally;
proximalmost involucral bract exceeding anthela.
yellowish, mostly turgidly ovoid, 5–8 mm;
fertile scales broadly ovate, 2–3 mm, apex obtuse, entire, midrib excurrent or not.
pale drab brown to chestnut brown, ovoid-lanceoloid, 4–8 mm;
fertile scales broadly oblong or ovate, 2 mm, acute to obtuse angled, glabrous, midrib reaching scale tip or excurrent, finely mucronate.
stamens 3, styles 2-fid, flattened, fimbriate.
stamens 1–2;
styles 2-fid, flat, fimbriate.
near white to pale brown, lenticular-obovoid to obpyriform, 2 mm, appearing smooth under 10–20X magnification, under higher power finely longitudinally ribbed, with fine, isodiametric pits in vertical lines.
white to brownish, lenticular, obovoid, 1–1.2 mm, cancellate, each face longitudinally with (5–)10–12 ribs, connected by vertical rows of horizontally rectangular pits.
= 10.
= 20, 30.
Fimbristylis schoenoides
Fimbristylis dichotoma
Fimbristylis schoenoides is an unusual Fimbristylis for us, with a smooth, “eleocharis-like” appearance. The plants are mostly low and spreading-culmed, glabrous annuals of Asian origin.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Fimbristylis dichotoma is found in temperate to tropical regions worldwide. It is one of the most widespread and weedy species of Fimbristylis, unquestionably with many races and forms. The two commonest forms in the United States often occur in mixed populations, one sort with inflorescence branches more ascending, inflorescence dense, habit lower, and leaves broader; the other sort usually taller, inflorescence more sparse, branches more widely spreading, and leaves more ascending and narrower. The abundance of such plants both in regions where rice originated and in regions where rice is, or was, introduced, indicates an Asian origin for such weeds.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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