Arnica chamissonis
 
Leafy Arnica

Flower Head Side

Duck Mountain Provincial Park
26-July-2009

Note that the key to the genera in Budd's Flora requires involucral bracts usually one series, not or scarcely imbricated.  In fact, the Flora of Alberta is more accurate when it states that the bracts are in 1-2 series in this genus.

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Chamissonis: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 
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stem leaves numerous, in 4-8 pairs; NOT [stem leaves less numerous, in 1-3 pairs] (BF)

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cauline leaves mostly 5-10 pairs; NOT [cauline leaves mostly 2-4 pairs, not including those (in any) of the basal cluster] (FOA)

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leaves oblong-lanceolate to linear; NOT [leaves cordate to oblong]

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lower stem leaves lanceolate; NOT [lower stem leaves ovate or deltoid]

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lower stem leaves entire to remotely dentate; NOT [lower stem leaves sharply dentate]

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heads several to many; NOT [heads solitary or few]

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involucral bracts obtuse or merely acutish; NOT [involucral bracts definitely acute]

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involucral bracts bearing a tuft of long hairs at or just within the tip; NOT [tips of involucral bracts not markedly more hairy than the body]

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pappus straw-coloured or brownish; NOT [pappus often white]

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pappus barbellate; NOT [pappus often subplumose]

 

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Arnica: Answers to key questions in Budd's Flora  and Flora of Alberta leading to this genus. 
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juice watery; NOT [juice milky]

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leaves opposite; NOT [leaves alternate or basal]

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involucral bracts usually one series, not or scarcely imbricated; NOT [involucral bracts in 2 or more series, well imbricated] (BF)

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receptacle naked (FOA)

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flower heads with florets both tubular and ray

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ligulate flowers when present pistillate or neuter; NOT [flowers all perfect]

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ray florets yellow; NOT [rays white, to pink, purple or blue]

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stamens united to form a tube around the pistil

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pappus composed of hairs; NOT [pappus chaffy, or of firm awns, or of bristles, or of scales, or a crown or none]