LEAVES 



385 



not for the leaf manufactory run by the sun's power, life, 

 as we know it, would cease. Even plants that lack chloro- 

 phyll, like the mushroom, must live on the food manu- 

 factured by the chlorophyll of the green plants. 



Experiment 123. Procure a small, thrifty plant growing in a 

 flower-pot. Take two straight-edged pieces of cardboard sufficiently 

 large to cover the top of the flowerpot and notch the centers of 

 the edges so that they can be slipped over the stem of the plant 

 and thus entirely cover the top of the flowerpot. Fasten the edges 

 of the cardboard together by pasting on a strip of paper. The 

 top of the pot will now be entirely covered by the cardboard but 

 the stem of the plant will extend up 

 through the notches of the edges. 

 Cover the plant with a bell jar. 

 (Figure 123.) No moisture can get 

 into the bell jar from the soil in the 

 pot, as it is entirely covered. Set the 

 plant thus arranged in a warm, sunny 

 place. Moisture will collect on the 

 inside of the bell jar. This must 

 have been given out by the plant 

 leaves. 



Since all the processes of form- 

 ing new material by the plant 

 require large amounts of water, 

 it can readily be seen why water is so essential to plant 

 development. The water from which the food materials 

 have been taken is thrown off by the leaves, as seen in 

 Experiment 123. The amount of water thus thrown off by 

 plants is very great. A single sunflower plant about six 

 feet tall gives from its leaves about a quart of water in a 

 day, and an acre of lawn in dry, hot weather gives off prob- 

 ably six tons of water every twenty-four hours. 



If the water passes out of a plant too rapidly so that 



FIGURE 123 



