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Elementary Botany 



about by different series of rays. The least refrangible, those 

 towards the red end of the spectrum, have the greatest chenaical 

 effect ; the most refrangible, those towards the blue end of 

 the spectrum, possess the greatest retarding influence. 



Sachs gives the following table as the result of his experi- 

 ments upon the amount of carbon dioxide decomposed by the 

 various rays of the spectrum (that decomposed by the yellow 

 being reckoned loo) : — 



If plants are grown surrouhded by glass vessels, in the one 

 case filled with a solution of potassium bichromate, which only 

 allows red, orange, and yellow rays to pass through, and in the 

 other case with a solution of ammoniacal copper oxide, which 

 only allows green, blue, and violet rays to pass, in the former 

 case no bending takes place, whilst in the latter case the helio- 

 tropism is as great as in the light. 



