|
''Senecio eboracensis'', the York groundsel or York radiate groundsel, is a self-pollinating hybrid species of ragwort and one of only six new plants to be discovered in either the United Kingdom or North America in the last 100 years. It was discovered in 1979 in York, England growing next to a parking lot and formally described in 2003. Like many of the Senecio genus it can be found growing in urban habitats, such as disturbed earth and pavement cracks and this particular species only in York and between a railway and a parking lot.〔 ==Description== York radiate groundsel is a deciduous annual plant that sets its seed within the 3 months〔 that it takes this plant to mature from germination to the upwards of high adult plant. With pretty yellow daisy-like flowers from its Sicilian parent (''S. squalidus'') but also with the less-promiscuous habits of its native parent (''S. vulgaris''); this member of the Senecio genus is morphologically distinct from related species.〔 :Leaves and stems ''S. eboraccensis'' have large many lobed leaves divided into slender segments, the clefts not reaching the midrib. The stems are mostly erect to ascending with an occasional horizontal base section up to with 'adventitious roots' at base. The upper and lower leaves petiolate and lobes appearing at quarter whole leaf lengths along the midrib. The upper leaves are generally more deeply lobed and in lobed pairs. Leaves on plants grown in fertile soils or in greenhouses can be much more luxurious and more highly dissected (or more finely divided into slender segments) up to x with lobes appearing at fifth whole leaf lengths along the midrib. The plants tip is usually acute with a very small tooth. Leaf edges throughout are dentate or sometimes divided into lobes.〔 :Flowers ''York groundsel'' has showy flower-heads especially when compared to its Common ragwort parent. The flower-head, found at the tips of the plants (apical) appearing in clusters (an inflorescence) usually consists of three to seven florets in a grouped corymb; at first dense and leafy but eventually less dense with peduncles 5 to 20 millimeters (0.2 to 0.8 in) which get longer when fruiting (up to 25 mm (1 in)). The flower-head is broadly cylindrical 10×4 millimeters (0.4×0.16 in), becoming slightly bell shaped) when the bright yellow ray florets open. Involucral bracts sparse (4-8), elongated (3.5–4 mm), usually without black tips. The floret ligules are narrow and long 5 to 7 millimeters (0.2 to 0.24 in) long and 1.5 millimeters (0.06 in) wide), occasionally becoming revolute. Like other Senecios, the 10-30 papilla occur stigmatically into pericarp; each usually with four-pored pollen, the grains in polar view 30-35 micrometers when fully expanded.〔 :Seeds The umbrella-like achenes can be 2.5 to 3.5 millimeters (0.1 to 0.15 in) long, are straight and shallowly grooved; with hairless smooth ribs while the grooves are covered with hairs. Silky white pappus which readily detach from the fruit when ripe.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Senecio eboracensis」の詳細全文を読む スポンサード リンク
|