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Taraxacum
''Taraxacum'' is a large genus of flowering plants in the family Asteraceae and consists of species commonly known as dandelion. They are native to Eurasia and North America, and two species, ''T. officinale'' and ''T. erythrospermum'', are found as commonplace wild flowers worldwide.〔(【引用サイトリンク】url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=132314 )〕 Both species are edible in their entirety.〔(【引用サイトリンク】 Wild About Dandelions )〕 The common name dandelion ( , from French ''dent-de-lion'', meaning "lion's tooth") is given to members of the genus. Like other members of the Asteraceae family, they have very small flowers collected together into a composite flower head. Each single flower in a head is called a floret. Many ''Taraxacum'' species produce seeds asexually by apomixis, where the seeds are produced without pollination, resulting in offspring that are genetically identical to the parent plant.
==Description==
The species of ''Taraxacum'' are tap-rooted, perennial, herbaceous plants, native to temperate areas of the Northern Hemisphere. The genus contains many species which usually (or in the case of triploids, obligately) reproduce by apomixis, resulting in many local populations and endemism. In the British Isles alone, 234 microspecies are recognised in 9 loosely defined sections, of which 40 are "probably endemic".
In general, the leaves are 5–25 cm long or longer, simple, lobed, and form a basal rosette above the central taproot. The flower heads are yellow to orange coloured, and are open in the daytime, but closed at night. The heads are borne singly on a hollow stem (scape) that is usually leafless and rises 1–10 cm or more〔 above the leaves. Stems and leaves exude a white, milky latex when broken. A rosette may produce several flowering stems at a time. The flower heads are 2–5 cm in diameter and consist entirely of ray florets. The flower heads mature into spherical seed heads called blowballs or clocks (in both British and American English)〔("Blowball" ) entry, Collins Dictionary〕〔("Blowball" ), InfoPlease Dictionary〕〔("Clock" ) entry, American Heritage Dictionary〕 containing many single-seeded fruits called achenes. Each achene is attached to a pappus of fine hairs, which enable wind-aided dispersal over long distances.
The flower head is surrounded by bracts (sometimes mistakenly called sepals) in two series. The inner bracts are erect until the seeds mature, then flex downward to allow the seeds to disperse. The outer bracts are often reflexed downward, but remain appressed in plants of the sections ''Palustria'' and ''Spectabilia''. Some species drop the parachute from the achenes; the hair-like parachutes are called pappus, and they are modified sepals. Between the pappus and the achene is a stalk called a beak, which elongates as the fruit matures. The beak breaks off from the achene quite easily, separating the seed from the parachute.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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