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Published In: Primitiae Florae Holsaticae 56. 1780. (29 Mar 1780) (Prim. Fl. Holsat.) Name publication detail
 

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced

 

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48. Taraxacum F.H. Wigg. (dandelion)

Plants perennial herbs, with somewhat fleshy taproots. Latex white. Stems 1 to several, continuing to elongate as the heads mature, erect or ascending, unbranched, hollow, finely ridged or nearly smooth, glabrous or with patches of fine, white, cobwebby hairs, sometimes purplish-tinged or purplish-mottled. Leaves all basal (see discussion under T. erythrospermum), short- to long-petiolate. Leaf blades shallowly to deeply and irregularly pinnately lobed, sometimes nearly compound, narrowly oblanceolate to obovate or elliptic in outline, the lobes triangular with angled sinuses, irregularly toothed, glabrous or 1 or both surfaces sparsely to moderately pubescent along the veins with fine, irregularly curled, white, sometimes somewhat cobwebby hairs, sometimes pinkish- to purplish-tinged toward the base. Venation of 1 main vein and a network of anastomosing secondary and tertiary veins. Heads solitary at the stem tips. Involucre elongating somewhat as the fruits mature, somewhat urn-shaped to cup-shaped at flowering, the bracts in 1 inner series of 11–23 and 1 or 2 additional outer series of 11–17, usually glabrous, often purplish-tinged, especially toward the tip; those of the inner series similar in size and shape, sometimes more or less fused along the margins toward the base when young, lanceolate, with well-differentiated, thin, pale margins, the tip sharply pointed or minutely notched, ascending at flowering; those of the outer series less than to more than half as long as the inner series, ovate to narrowly ovate, mostly becoming reflexed as the heads first develop. Receptacle naked. Ligulate florets 40–120 or more per head. Corollas bright yellow, sometimes purplish- or grayish-brown-tinged on the outer surface. Pappus of numerous bristles, these smooth or microscopically barbed, white. Fruits with the body oblanceolate in outline, tapered to a slender beak usually more than twice as long as the body, not or only slightly flattened, with 4 or 5 rounded or flattened ribs, these sometimes with 1 or 2 shallow longitudinal grooves, smooth or appearing smooth or more commonly minutely pebbled or roughened, with several rows of prominent barbs toward the tip, glabrous, variously colored, the pappus attached to a relatively broad, expanded, disclike tip. About 60 to more than 2,000 species, North America, South America, Europe, Asia, introduced worldwide.

The taxonomy of the weedy dandelions is in a state of perpetual confusion. As in Hieracium, botanists working in the Old World centers of taxonomic diversity for the genus have described large numbers of apomictic polyploid races as microspecies, which has tended to confound application of species-level nomenclature to the introduced populations in North America. The two taxa present in Missouri have been assigned to two different sections, sect. Erythrosperma (H. Lindb.) Dahlst. and sect. Ruderalia Kirschner, H. Øllg. & Štěpánek, which are characterized by large numbers of weedy polyploid apomictic taxa within their native ranges. In fact, ecological and biochemical studies of nonnative populations in the northwestern United States have indicated that the two taxa present in Missouri may not be particularly distinct morphologically, biochemically, or ecologically (Taylor, 1987). Conversely, genetic studies (King and Schaal, 1990; King, 1993) have documented surprisingly high genetic diversity among North American dandelions, as well as intertaxon hybridization, due in part to low levels of outcrossing sexual reproduction in these predominantly apomictic plants (Valentine and Richards, 1967). The nomenclature and taxonomy of both of the Missouri dandelions remains controversial, with most recent authors provisionally relying on traditional names and circumscriptions for the species until the taxonomic situation with these complexes within their native ranges becomes stabilized. See further discussion below.

 

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1 Fruits dull brick red to reddish or purplish brown at maturity ... 1. T. ERYTHROSPERMUM 1 Taraxacum erythrospermum
+ Fruits olive-colored to greenish brown at maturity ... 2. T. OFFICINALE 2 Taraxacum officinale
 
 
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