(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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Hieracium L.
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PlaceOfPublication
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Sp. P1. 799. 1753
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Note
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TYPE: H. murorum L.
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Description
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Perennial herbs; stems mostly with long hairs, often also with short hairs, dendritic hairs, glandular hairs, or bristles; sap milky. Leaves often in a basal rosette, cauline leaves present or not, obovate or oblanceolate, entire, dentate or undulate, petiolate or not, sometimes clasping the stem. Inflorescence scapose, paniculate, or rarely of a solitary sessile head; peduncles or pedicels often pubescent, sometimes subtended by narrow bracts. Heads ligulate; involucral bracts in 2-several, graded, imbricate series, the innermost often subequal, nearly valvate; receptacle flat or slightly convex, naked; florets all perfect, all fertile, the corollas yellow (Panama), white, orange or purplish, the ligule short or long, 5-dentate, the tube sometimes apically pubescent, the anthers appendaged, with sagittate or auriculate bases, the style branches slender, papillose, sometimes dark. Achene cylindrical or fusiform, often prominently ribbed or sulcate; pappus of numerous, mostly tawny bristles in 1 series. Pollen echinolophate, usually 3-colporate. Base chromosome number x = 9.
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Habit
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herbs
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Distribution
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Hieracium comprises more than 1000 apomictic "species" in Europe and perhaps a dozen sexual species in the New World north of Colombia.
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Note
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In Panama, species of Hieracium may be recognized by their stout, long, tawny hairs and their inconspicuous, ligulate corollas.
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Common
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Hawkweed Hierba del Gavilan
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Reference
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Robinson, B. L. & J. M. Greenman. 1904. Revision of the Mexican and Central American species of Hieracium. Proc. Amer. Acad. Arts 40: 14-24. Zahn, K. H. 1923. Compositae-Hieraceum. In A. Engler (editor), Das Pflanzen- reich IV. 280 (Heft. 79): 1100-1108, 1115-1124.
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Key
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a. Leaves narrow, mostly less than 2 cm wide, more than 7 times as long as wide, the minute teeth conspicuous; achenes columnar to the apex; upland plants. b. Involucral bracts puberulent with small, whitish, eglandular hairs, a few dark, glandular hairs sometimes present, the margins mostly herbaceous; inflorescence much-branched, many-headed; leaves cauline and basal ...... 1. H. absissum bb. Involucral bracts with copious long, black, often glandular hairs, the margin hyaline at both sides and tips; inflorescence crowded, little-branched, few-headed; leaves mostly basal ...... 3. H. irasuense aa. Leaves spatulate, often more than 2 cm wide, mostly less than 7 times as long as wide, the teeth, if present, inconspicuous; achenes tapering in the upper half; lowland plants ...... 2. H. gronovii
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