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(Last Modified On 5/29/2013)
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(Last Modified On 5/29/2013)
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Genus
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Centaurium Hill
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PlaceOfPublication
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Brit. Herb. 62. 1756.
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Synonym
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Erythraea Neck., Elem. Bot. 2: 10. 1790.
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Description
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Herbs, annual, biennial, or perennial, often with a basal rosette of leaves; stems erect to procumbent at the base, terete to angulate, often branched. Leaves sessile to subsessile, occasionally amplexicaul. Inflorescences of loose cymes, corymbiform or capituliform with a usually sessile central flower, or the cymes unpaired and spicate, or in reduced dichasia, or the flowers solitary. Flowers with 2 opposite bracts, 4- to 6-merous; calyx tubular at the base, the lobes cari- nate; corolla contorted, dextrorse, usually pink, sometimes yellow or white, the tube cylindrical, shorter to longer than the lobes, the lobes spreading to ascend- ing at anthesis; stamens with the filaments filiform, inserted on the corolla tube, the anthers introrse, subbasifixed and spirally twisting at maturity; ovary sessile, elongate, 1-celled, the placentae often intruded, the style filiform, exserted, the stigmas bilamellate. Capsules elongate, surrounded by the marcescent calyx and corolla, septicidally 2-valvate; seeds minute, variously shaped, the testa finely reticulate. Pollen grains in monads, radially symmetrical, isopolar, subprolate to prolate, the amb rounded-triangular, 24-29 x 18-23 ,u, 3-colporate, the colpi relatively long with tapering, ? acute ends, the colpus membrane smooth or finely granular, the ora usually lolongate with lateral extensions, the diameter of apocolpia 6-7 ,u; exine 3 ,u thick; sexine thicker than nexine, striate, striate- reticulate, rarely reticulate, the lirae (muri) 0.6-0.8 microns wide, parallel or not, crisscrossed (C. quitense, C. strictum).
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Distribution
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A genus of approximately 40 species in temperate and tropical regions of the Old and New World with 2 species reported from Panama.
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Key
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a. Calyx lobes equal to the tube; lower leaves narrowly obovate; flowers 8-15 mm long; corolla lobes 5-6 mm long; stigma shallowly bilobate ...... 1. C. strictum aa. Calyx lobes longer than the tube; lower leaves narrowly ovate to elliptic; flowers 6-9 mm long, corolla lobes 2-4 mm long; stigma distinctly bilobate ...... 2. C. quitense
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