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(Last Modified On 6/20/2013)
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(Last Modified On 6/20/2013)
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Genus
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Sonchus L.
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PlaceOfPublication
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Sp. P1. 793. 1753
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Note
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TYPE: S. oleraceus L.
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Description
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Robust herbs (Panama) or trees; stems, often hollow, glabrous or pubescent, often with gland-tipped bristles; rootstock fibrous or stout, sometimes divided, sometimes creeping; sap milky, bitter. Leaves alternate, in a basal rosette or cauline, dentate to dissected, often incised, the teeth with callose or spinose tips, often glabrous, basally auriculate or not. Inflorescence mostly paniculate, some- times scapose but not solitary; peduncles glabrous to pilose, sometimes with gland-tipped bristles; pedicels often subtended by foliaceous bracts. Heads ligulate, mostly about as broad as long, slightly broader after anthesis; involucre of numerous similar bracts in several graded series, imbricate or the innermost series sometimes valvate, narrow and acute, often basally swollen in fruit; receptacle flat or convex, mamillose, 'naked; florets numerous, all ligulate, all perfect, all fertile, the corolla yellow, rarely white, with 5 acute teeth, the tube apically pilose, the outer series sometimes pinkish dorsally, exceeding the involucre, the inner series smaller, the anthers 5, connate, with deltoid appendages, basally sagittate, the style apically pubescent, the branches narrow, puberulent, sometimes dark. Achenes mostly alike but sometimes the outermost series lighter and differing in texture, cylindrical or compressed, sometimes flat, oblong, ellipsoidal or lachrymiform, beakless, sulcate or ribbed, rugose or smooth; pappus of strigulo'se, silky, white bristles or of numerous, persistent, capillary hairs and fewer, stouter, deciduious bristles. Pollen echinolophate, mostly 3-colporate, with a tendency to extra lacunae at the poles. Base chromosome numbers x = 7, 8, 9.
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Note
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Sonchus is an Old World genus of about 50 species centered in Europe and Africa. About 4 species are now widespread and 2 of these are naturalized in Panama. Robust, yellow-headed weeds with stout rootstocks, they may become troublesome weeds. Not known to be toxic, they are unpalatable to cattle and have reputed medicinal value in some countries.
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Common
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Sow thistles Cerraja
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Reference
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Boulos, L. 1960. The genus Sonchus, a general systematic treatment. Bot. Not. 113: 400-420.
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Key
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a. Leaves incised, the apical segment truncate, the auricles clasping the stem pointed, the margins not decidedly prickly to the touch; achene compressed but not flat, rugose with ribs on the sides ...... 2. S. oleraceus aa. Leaves dentate, if incised then lacking a conspicuous apical segment, the auricles clasping the stem rounded (dentate), the margins prickly; achene flat, smooth, with narrow sulci on the sides ...... 1. S. asper
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