| General Information |
| Distribution | Open, usually sandy sites, primarily disturbed habitats, from North Dakota south to Kansas, Oklahoma, and Texas east to the Atlantic coast, introduced in California and in many parts of the world. It is puzzling that O. laciniata has been collected only once in Mexico, adjacent to Texas. We see no reason that the range should terminate abruptly as shown on the map, and expect that, if sought out, it will be found to occur more widely, at least in Tamaulipas.In the Hawaiian Islands,
naturalized on
Kure, Midway, Maui, Hawai`i.
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Habit
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Erect to procumbent annual or short-lived perennial herbs, usually forming rosettes; stems 5-50 cm long, green or flushed with red, simple to much-branched, sparsely to moderately strigillose and villous or only strigillose, in the region of the inflorescence often also glandular-puberulent.
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Leaves
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Leaves alternate, in a rosette and cauline, all leaves and bracts green, strigillose and villous, often also glandular-puberulent, rosette leaves 4-15 cm long, 1-3 cm wide, linear-oblanceolate to narrowly oblanceolate, occasionally lanceolate, deeply lobed to dentate, cauline leaves 2-10 cm long, 0.5-3.5 cm wide, narrowly oblanceolate to oblanceolate or narrowly oblong to narrowly elliptic, narrowly cuneate at base, bracts 2-7 cm long, 0.8-3 cm wide, spreading, narrowly oblong to narrowly ovate, flat, obtuse to narrowly cuneate at base.
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Flowers
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Inflorescence lax, usually with lateral branches. One flower per spike opening each day near sunset, floral tube 12-35 mm long, ca. 1 mm in diameter, yellowish often flushed with red, densely to sparsely villous and glandular-puberulent, sometimes also strigillose, mature buds 2.5-5 mm in diameter at the base, narrowly oblong to narrowly ovoid, the older buds curved upward, sepals 5-15 mm long, green to yellowish, often flushed with red and with a marginal red stripe, rarely flecked with red, sepal tips 0.3-3 mm long, usually spreading in bud, strigillose to villous, petals 5-22 mm long, 7-20 mm wide, yellow to pale yellow, very broadly obovate, truncate to emarginate, staminal filaments 3-14 mm long, anthers 2-6 mm long, shedding pollen directly on the stigma at anthesis, pollen ca. 50% fertile, style 20-50 mm long, the exserted part 3-14 mm long, stigma surrounded by the anthers at anthesis, lobes 2.5-5 mm long, ovary 10-23 mm long, ca. 1.5 mm in diameter, strigillose or also villous, sometimes with a few glandular hairs.
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Fruit
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Capsule dehiscent 20-50 mm long, 2-4 mm in diameter, cylindrical, subterete, dehiscent nearly throughout capsule length, sessile.
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Seeds
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Seeds numerous, in 2 rows per locule, 0.9-1.8 mm long, 0.4-0.9 mm in diameter, ellipsoid to suborbicular, brown to dark brown, the surface reticulate and regularly pitted. Autogamous, permanent structural heterozygote.
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Chromosomes
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Chromosome number: n = 7 (ring of 14* chromosomes at meiotic metaphase I).
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Notes
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FNA
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