An. Rpt. Office of Experiment Stations, 1906. 



Plate XI. 



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H 



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D 



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c 

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71 

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H 

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H 



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2 



cn 



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O 



33 



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H 



> 



> 



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> 



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33 

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 CO 



o 



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m 

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3J 



> 



