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(Last Modified On 6/6/2013)
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(Last Modified On 6/6/2013)
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Genus
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Aster L.
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PlaceOfPublication
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Sp. PI. 872. 1753
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Note
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TYPE: A. anellus L.
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Synonym
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Leucosyris E. L. Greene, Fl. Francisc. 384. 1891. TYPE: L. carnosa (A. Gray) E. L. Greene.
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Description
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Annual or perennial, mostly erect herbs, sometimes spreading by rhizomes; the stems often much branched, occasionally woody. Leaves alternate, mostly entire or nearly so and well spaced along the stems, usually becoming smaller upward, rarely reduced to thorns or scales, basal leaves when present often different and wider than those of the stem. Inflorescence mostly open-paniculate, occasionally racemose. Heads radiate, many flowered; involucral bracts in a few series, imbricate, mostly herbaceous at least near the tips, lanceolate or oblong with hyaline or scarious margins and sometimes subulate tips; receptacle slightly convex, naked; ray florets uniseriate or occasionally biseriate, the corollas exceeding the style and pappus, never yellow, apically dentate or entire, the style branches linear with margins generally thickened or papillose; disc florets perfect, the corollas mostly yellowish with a campanulate, 5-dentate limb, the anthers basally obtuse with ovate or oblong terminal appendages, the style branches oblong to subulate, dorsally papillose-pilose. Achenes somewhat flattened with 2-5 conspicuous nerves, glabrous or variously pubescent; the pappus in 1 or, less often, 2 series of fine, strigulose, white or buff bristles.
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Habit
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herbs
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Note
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The genus Aster may be recognized by its solitary radiate heads with manifest ligules, by the flattened, laterally nerved achenes, and by the strigulose pappus. It is distinct from other genera in the usually broadened tips of the herbaceous portion of the involucral bracts. The sole Panamanian species is distinct from other members of the genus in its striking vegetative morphology, and it may warrant separation from Aster. At the same time, the structure of the involucral bracts and absence of pubescence argue against recognizing it as a member of the segregate genus Leucosyris. When considered in the broad sense, this genus comprises 300 to 500 widely dissimilar species. Many workers consider that Aster will eventually be broken into many taxonomically acceptable segregate genera, but an overall consideration of the group is preferable to piecemeal fragmentation into heterodox units.
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Distribution
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In its full array the genus is nearly cosmopolitan in distribution with the greatest number of species in temperate regions. The type species is from southern Europe.
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