Fimbristylis dichotoma
Fimbristylis castanea
fork fimbry
marsh fimbry
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.
erect or ascending, 1/2–2/3 plant height, bases of leaves hard, leathery, usually dark brown or castaneous;
sheaths distally bristly-ciliate, backs chestnut brown, glabrous;
ligule absent;
blades narrowly linear, 1–2(–3) mm wide or thick, mostly strongly involute or adaxially deeply sulcate, margins scabridulous, surfaces glabrous.
anthelae compound, dense or open, ascending-branched, longer than broad;
scapes slender, 1 mm wide, slightly compressed distally;
proximalmost involucral bract exceeding anthela.
anthelae mostly compound, ascending-branched, longer than broad;
scapes wandlike, narrowly linear, 1.5–2(–3) mm thick, distally round or slightly compressed;
proximalmost leafy involucral bract mostly shorter than anthela or equaling it, rarely slightly longer.
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.
chestnut brown to dull brown, ellipsoid, ovoid, or cylindric, 5–20 mm;
fertile scales broadly ovate to nearly orbiculate, 3.5–4.5 mm, apex rounded, sometimes ciliolate, midrib reaching tip or excurrent as short mucro.
stamens 1–2;
styles 2-fid, flat, fimbriate.
stamens 2–3;
styles 2-fid, flat, fimbriate.
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.
lustrous brown, lenticular-obovoid or obpyriform, 1.5–2 mm, appearing striate, with many fine, vertical lines of isodiametric pits.
= 20, 30.
= 20.
Fimbristylis dichotoma
Fimbristylis castanea
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.)
Fimbristylis castanea, commonly placed in synonymy of F. spadicea (Linnaeus) Vahl, a widespread salt marsh perennial of tropical America, is distinguishable by its relatively shorter spikelets, usually lower habit, and by its proportionately shorter involucral bracts. Fimbristylis spadicea is hardy with us only as a greenhouse plant.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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