Fimbristylis dichotoma
Fimbristylis brevivaginata
fork fimbry
glade 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 polystichous, spreading to ascending, 1/2 as long as culms;
sheaths contracted, abruptly dilated, margins fimbriate-ciliate distally;
ligule present, complete;
blades narrowly linear, 1.5–2.5 mm wide, flat to shallowly involute, margin intermittently scabrid-ciliate, abaxial surface usually 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 simple, of 2–7(–9) spikelets, ascending-branched, slightly mostly longer than broad, scapes slender, 1 mm wide, to very compressed distally;, proximalmost involucral bract shorter than 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.
red-brown, narrowly ovoid to lanceoloid or cylindric, 5–15 mm, fertile scales broadly ovate, 4.5–5 mm, glabrous to puberulent, midrib excurrent as cusp or mucro.
stamens 1–2;
styles 2-fid, flat, fimbriate.
stamens 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.
dark brown to greenish brown, obovoid-lenticular, 1.2–1.5 mm, faces each 11–13-ribbed, cancellate, ribs connected by vertical rows of transversely rectangular pits.
= 20, 30.
Fimbristylis dichotoma
Fimbristylis brevivaginata
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.)
Of conservation concern.
Fimbristylis brevivaginata, with its slender, distally compressed scapes and its complete, transverse ligule of short hairs, bears a strong resemblance to Fimbristylis caroliniana, yet it also has bulbous culm bases that produce short, strongly tapering, bulbousbased rhizomes, reminiscent of some F. puberula races. It is very infrequent, known to occupy fewer than ten of the hundreds of sandy rock outcrops in the Georgia Piedmont and Alabama Cumberland Plateau.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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