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Thistle is the common name of a group of flowering plants characterized by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the plant against herbivorous animals, discouraging them from feeding on the plant. Typically, an involucre with a clasping shape of a cup or urn subtends each of a thistle's flowerheads. The term thistle is sometimes taken to mean exactly those plants in the tribe Cynareae (synonym: Cardueae),〔(【引用サイトリンク】 work = Tree of Life webproject )〕 especially the genera ''Carduus'', ''Cirsium'', and ''Onopordum''.〔(【引用サイトリンク】 thistle )〕 However, plants outside this tribe are sometimes called thistles, and if this is done thistles would form a polyphyletic group. Thistle is the floral emblem of Scotland, as well as the emblem of the Encyclopaedia Britannica. ==Taxonomy== Genera in the Asteraceae with the word thistle often used in their common names include: *''Carduus'' – musk thistle and others *''Carlina'' – carline thistle *''Carthamus'' – distaff thistle *''Centaurea'' – star thistle *''Cicerbita'' – sow thistle *''Cirsium'' – common thistle, field thistle and others *''Cnicus'' – blessed thistle *''Cynara'' – artichoke, cardoon *''Echinops'' – globe thistle *''Notobasis'' – Syrian thistle *''Onopordum'' – cotton thistle, also known as Scots or Scotch thistle *''Scolymus'' – golden thistle or oyster thistle *''Silybum'' – milk thistle *''Sonchus'' – sow thistle Plants in families other than Asteraceae which are sometimes called thistle include: *''Kali'' – Russian thistle, Tartar thistle, or tumbleweed, plants formerly classified in the genus ''Salsola'' (family Chenopodiaceae) *''Argemone mexicana'' – flowering thistle, Mexican prickly poppy 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「Thistle」の詳細全文を読む スポンサード リンク
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