Fimbristylis dichotoma
Fimbristylis perpusilla
fork fimbry
Harper's 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.
polystichous, spreading to ascending, mostly excurved, exceeding or exceeded by culms;
sheaths entire, backs glabrous;
ligule absent;
blades setaceous-filiform, to 0.5 mm wide, flat to involute, sparsely scabrid-ciliate.
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, open, nearly as broad as long, ascending-branching, umbelliform, of 3–10 cormose spikelets;
scapes filiform, 0.5–0.6 mm thick;
proximalmost involucral bracts setaceous-bladed, 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.
pale green to light brown, ovoid to globose or short-cylindric, 2–5 mm;
fertile scales lance-linear to oblong-linear, 1.5 mm, glabrous, midrib strongly excurrent, erect to excurved cusp.
stamens 1–2;
styles 2-fid, flat, fimbriate.
stamens 1;
styles 2-fid, slender, glabrous.
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 brown with iridescent tints, curved-cylindric, 0.4–0.6 mm, finely reticulate, in 12 vertical rows of narrowly rectangular, horizontal cells.
= 20, 30.
= 10.
Fimbristylis dichotoma
Fimbristylis perpusilla
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.
The nearest relative of this ephemeral is Fimbristylis dipsacea, a similarly diminutive Eurasian and South American annual with broader, more spreadingcusped spikelets and oddly compound-papillate fruit.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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