PLANT LEAVES 



199 



Experiment 103. 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 flower pot 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 flower pot. 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. 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 forming 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 103. 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 probably 

 six tons of water every twenty-four hours. 



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

 there is not enough left to provide for the making and 



A SUNFLOWER PLANT. 



