Cirsium arvense
 
Canada Thistle

Female Flower Close-Up

Regina
18-July-2009

Note the presence of an anther tube.  However, it is sterile rendering the flower functionally pistillate.  It is also shorter than the anther tube of the staminate flower.  There are two style branches which are fused for almost their entire length.

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Arvense: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 
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perennial plants

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plants from deep creeping rootstocks; NOT [plants without creeping rootstocks]

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male and female flowers on separate plants; NOT [male and female florets on the same plant or flower head]

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bracts of involucre only slightly, if at all, cobwebby, and if so the inner bracts twisted and not spine-tipped; NOT [bracts of involucre covered with cobwebby hairs, and all bracts spine-tipped]

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heads small, less than 2.5 cm high; NOT [heads larger, more than 2.5 cm high]

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involucres 1-2 cm high; NOT [involucres more than 2 cm high]

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involucres rarely over 12 mm wide; NOT [involucres usually more than 12 mm wide]

 

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Cirsium: 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 with spiny margins

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bracts of involucre not dry or parchmenty, usually green; NOT [bracts of involucre dry, parchmenty or membranous, not green]

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some involucral bracts spiny-tipped

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involucral bracts without hooked bristles

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receptacle densely bristly; NOT [receptacle naked]

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flower heads with all florets tubular

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stamens united to form a tube around the pistil

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pappus present, distinct; NOT [pappus none or inconspicuous]

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pappus of capillary bristles; NOT [pappus of scales, or of awns, or a crown or none]

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pappus bristles much longer than achene; NOT [pappus hairs not longer than achene]

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pappus bristles plumose; NOT [pappus bristles naked or merely minutely barbellate]