Fimbristylis dichotoma |
Fimbristylis |
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fork fimbry |
fimbristyle, fimbry |
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Habit | Plants perennial, cespitose, (10–) 20–80 cm, base thickened, not bulbous; rhizomes absent. | Herbs, annual or perennial, usually cespitose, rhizomatous or not. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Culms | sometimes solitary, scapose, stiff or flaccid, terete, compressed, or 3–5-angled, coarse or fine. |
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Leaves | 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. |
basal, distichous or polystichous; sheaths open apically, shorter than blade, with broad scarious margins; ligule absent at junction with blade or, if present, of erect short hairs, transverse, continuous or interrupted; blades flat or variously folded, terete, or sulcate, not prominently keeled on abaxial surface, the widest not more than 2 mm wide. |
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Inflorescences | anthelae compound, dense or open, ascending-branched, longer than broad; scapes slender, 1 mm wide, slightly compressed distally; proximalmost involucral bract exceeding anthela. |
simple or compound anthelae, rarely capitate; spikelets 1–80+, rarely single; involucral bracts 2–5, spreading or rarely erect, scalelike or leaflike. |
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Spikelets | 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. |
mainly ovoid to lanceoloid or cylindric, sometimes compressed; scales 8–100+, spirally arranged, each subtending flower or proximal 1–2 empty. |
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Flowers | stamens 1–2; styles 2-fid, flat, fimbriate. |
bisexual; perianth absent; stamens 1–3; styles flattened or subterete, 2–3-fid, base enlarged, deciduous. |
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Achenes | 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. |
biconvex or trigonous, reticulate-honeycombed. |
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2n | = 20, 30. |
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Fimbristylis dichotoma |
Fimbristylis |
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Phenology | Fruiting summer–fall, into winter southward. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Moist, usually sandy waste areas, roadsides, low fields, and savannas | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 0–200 m (to 2000 m, tropics) (0–700 ft (to 6600 ft, tropics)) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
AL; FL; GA; LA; MS; NC; SC; TX; Mexico; Central America; South America; Atlantic Islands; Pacific Islands; Indian Ocean Islands; West Indies; Africa; Eurasia; Bermuda; Australia [Introduced in North America]
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Worldwide; mostly subtropical and tropical; mostly in sunny; moist to wet places |
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Discussion | 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.) |
Species well over 100 (16 in the flora). Culms terminate in scapes; scapes are variously elongate, slender, shallowly to strongly ribbed, overtopping leaves. Leaf blades are mostly linear, compressed or thickened, rarely onefacial. Involucral bracteal blades (more common than scales in Fimbristylis) are linear to setaceous, abbreviated or exceeding inflorescence. Spikelet scales are erect or ascending, rarely nearly distichous; proximal scales sterile, usually bladed, larger than fertile scales; fertile scales mostly uniform, carinate or convex, thin, medially with thicker, longitudinally ribbed band, margins entire; ribs converging apically, often short or longexcurrent. Flowers are protandrous, on short rachilla joint; filaments flattened; anthers bilocular, two- to four-sporangiate; ovary two- to three-carpellate; styles disarticulating at very base, flat, fimbriate, or slender, angular, smooth or papillose. Achenes are tumid, obscurely threeribbed, with faces and angles variously sculpted. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 23, p. 125. | FNA vol. 23, p. 121. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Cyperaceae > Fimbristylis | Cyperaceae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | Scirpus dichotomus, F. annua var. diphylla, F. brizoides, F. diphylla subsp. diffusa, F. glauca, F. polymorpha, Scirpus diphyllus | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (Linnaeus) Vahl: Enum. Pl. 2: 287. (1805) | Vahl: Enum. Pl. 2: 285. (1805) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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