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Arnica is a genus of perennial, herbaceous plants in the sunflower family (Asteraceae). The genus name ''Arnica'' may be derived from the Greek ''arni,'' "lamb", in reference to the soft, hairy leaves. This circumboreal and montane (subalpine) genus occurs mostly in the temperate regions of western North America, with a few species native to the Arctic regions of northern Eurasia and North America.''〔(Altervista Flora Italiana, Arnica, ''Arnica montana'' L. ) includes photos and European distribution maps〕 ''Arnica'' used to be included in the tribe Senecioneae because it has a flower or pappus of fine bristles. This was soon questioned and Nordenstam (1977) placed it tentatively in tribe Heliantheae s.l. This arrangement also became uncertain because of the sesquiterpene lactone chemistry in certain species. Recently Arnica was placed in an unresolved clade together with Madiinae, Eupatorieae, Heliantheae s.s. and Pectidinae. Several species, such as ''Arnica montana'' and ''A. chamissonis'', contain helenalin, a sesquiterpene lactone that is a major ingredient in anti-inflammatory preparations (used mostly for bruises). ''Arnica'' species are used as food plants by the larvae of some Lepidoptera species including Bucculatrix arnicella. ''Arnica'' is also known by the names Mountain Tobacco and, somewhat confusingly, Leopard's bane and Wolfsbane—two names that it shares with the entirely unrelated genus ''Aconitum''. ==Characteristics== ''Arnica'' plants have a deep-rooted, erect stem that is usually unbranched. Their downy opposite leaves are borne towards the apex of the stem. The ovoid, leathery basal leaves are arranged in a rosette.〔(Flora of North America, ''Arnica'' Linnaeus )〕 They show large yellow or orange flowers, 6–8 cm wide with 10–15 cm long ray florets and numerous disc florets. The phyllaries (a bract under the flowerhead) has long spreading hairs. Each phyllary is associated with a ray floret. Species of ''Arnica'', with an involucre (a circle of bracts arranged surrounding the flower head) arranged in two rows, have only their outer phyllaries associated with ray florets. The flowers have a slight aromatic smell. If taken in the wrong dose it can be very dangerous.〔 The seedlike fruit has a pappus of plumose, white or pale tan bristles. The entire plant has a strong and distinct pine-sage odor when the leaves of mature plants are rubbed or bruised.〔 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「arnica」の詳細全文を読む スポンサード リンク
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