Cornus canadensis
 
Bunchberry

Flower Side Opposite Petal

Duck Mountain Provincial Park
25-June-2007

The flower has an unusual pollination mechanism.  While the flower is still in bud, the anthers dehisce but do not release their pollen.  One of the four petals has an "antenna" arising near the petal apex.  When an insect bumps the antenna, the flower opens explosively.  The petals reflex and the anthers snap upwards from a reflexed position throwing pollen into the air.  Some of the pollen will land on the insect, which will sometimes transport it to the stigma of another flower.  The above is a summary of a description by Dr. A. Ceska.  His report can be found here.

Note that the filaments have a bend roughly midway along their length.

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Canadensis: Answers to key questions in Budd's Flora (BF) and Flora of Alberta (FOA) leading to this species. 
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low herbs; NOT [shrubs or small trees]

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leaves mostly whorled at summit of stem; NOT [leaves opposite]

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flowers in a dense head surrounded by an involucre of 4 large, petal-like, whitish bracts; NOT [flowers in cymes, not surrounded by an involucre]

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fruit red; NOT [fruit whitish]

 

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Cornaceae: Answers to key questions in Budd's Flora  leading to this family. Not all the answers apply to all members of this family, but they all do apply to this species.
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herbs; NOT [shrubs or trees]

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plants terrestrial or semiaquatic; NOT [plants aquatic, leaves submerged or floating]

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plants NOT with colored milky juice

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plants with more than one normal leaf

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leaves opposite, whorled, or basal; NOT [some or all leaves alternate]

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plants with an involucre of 4 petal-like bracts; NOT [plants without large petal-like bracts]

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flowers with two floral rings, and with each petal distinct from the others

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fruit a red drupe