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 pg@l 
_ plant. ae 
The work of leaves 
Wh ether wate lina. 40. Magnified root-hairs, 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 
