Fimbristylis dichotoma
Fimbristylis tomentosa
fork fimbry
woolly 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.
nearly distichous, ascending, 1/2–3/4 length of culms;
sheath margins ciliolate, adaxial surface sparsely to copiously hirtellous distally;
ligule present, complete;
blades narrowly linear, 2–4(–5) mm wide, flat to shallowly involute, margins ciliate-scabrid, abaxial surface pilose-hirsute.
anthelae compound, dense or open, ascending-branched, longer than broad;
scapes slender, 1 mm wide, slightly compressed distally;
proximalmost involucral bract exceeding anthela.
anthelae compound, ascending-branched, longer than broad;
scapes distally oval or flattened, glabrous to pubescent;
longest involucral bract exceeding anthela.
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.
rusty brown, lanceoloid, 4–6 mm;
fertile scales broadly ovate to nearly orbiculate, 2–3 mm, broadly acute, midrib excurrent as mucro or cusp.
stamens 1–2;
styles 2-fid, flat, fimbriate.
stamens 2;
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.
pale to dark brown with pale umbo, lenticular-obpyriform, 1.7–2 mm, finely pitted, appearing nearly smooth, the pits in at least 20 narrow vertical rows per face.
= 20, 30.
= 10.
Fimbristylis dichotoma
Fimbristylis tomentosa
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 tomentosa apparently was introduced with early rice culture and is rapidly expanding its range.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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