LESSONS WITH PLANTS 315 



a plant cannot supply itself rapidly enough with fresh water 

 from the roots it wilts. 



Place a cherry, maple, or other leafy twig in a bottle of 

 water. Note the height of the water. Close the mouth of 

 the bottle to prevent evaporation. Note the rate at which 

 the twig absorbs the water and the leaves give it off to the 

 air. 



This current of water flowing through the plant is neces- 



FiG. 118. Transpiration. 



sary, in order that fresh mineral matter may be brought in 

 from the soil for the nourishment of the plant. 



Leaves are green. Why? Bring in some celery stalks, 

 or some potato or carrot sprouts that have grown in the 

 cellar in the dark. Note their blanched condition. Lay a 

 board a few days upon the green grass, and on removal note 

 the yellowish or bleached place left by the board. Note 

 that the grass turns green again in the sunlight. Place some 

 of the cellar-grown sprouts in the sunlight to grow. Note 

 the greenish color that appears after several days. Sunlight 



