82 THE MAKING OF THE LIVING MATTEE 



Much more water is absorbed by the roots than is used in 

 growth, and this surplus water is given off from the leaves 

 into the atmosphere by an evaporation process knoivn as 

 transpiration. The transpiration takes place more abun- 

 dantly from the under surfaces of leaves, and through the 

 pores or stomates. It has been found that a sunflower 

 plant of the height of a man, during an active period of 



116. To illustrate transpiration. 



growth, gives off more than a quart of water per day. A 

 large oak tree may transpire 150 gallons per day during the 

 summer. For every ounce of dry matter produced, it is 

 estimated that from fifteen to twenty -five pounds of water 

 must pass through the plant. Cut off a succulent shoot of 

 any plant, stick the end of it through a hole in a cork and 

 stand it in a small bottle of water. Invert over this bottle 

 a large-mouthed bottle (as a fruit-jar), and notice that a 



