WATER MOVEMENT IN PLANT 



171 



dinarily, it varies from one foot to six feet per hour, 

 though observations are on record showing that the 

 movement often reaches the rate of eighteen feet per 

 hour. It is evident, 

 then, that in an ac- 

 tively growing plant 

 it does not take long 

 for the water which is 

 in the soil to find its 

 way to the upper- 

 most parts of the 

 plant. 



The work of leaves 

 Whether water„ .^ ^^ -a ^ ^ ■ ^ ■ 



tia. 40. Magnmed root-nairs, showing 

 passes upward from how soil particles are attached to them. 



cell to cell or through 



especially provided tubes, it reaches at last the 

 leaves, where evaporation takes place. It is nec- 

 essary to consider in greater detail what takes place 

 in leaves in order that we may more clearly under- 

 stand the loss due to transpiration. One half or 

 more of every plant is made up of the element carbon. 

 The remainder of the plant consists of the mineral 

 substances taken from the soil (not more than two to 

 10 per cent of the dry plant) and water which has 

 been combined with the carbon and these mineral 

 substances to form the characteristic products of 

 plant life. The carbon which forms over half of the 



