i8 



PLANTS AND WATER 



shows that the leaves of plants growing in a rather dry 

 atmosphere must have a constant supply of water, or they 

 can not remain fresh. Second, it shows that the water is 

 taken in through the stem. Third, it shows that, in uncut 

 plants, the water must come into the stem from the root, 

 because our stems were cut at the surface of the ground. 



Evaporation through Leaves If we fill two bottles 

 of the same size with water, and insert in the neck of one 

 of them several small twigs from a growing plant, we 

 shall find that the surface of the water will lower much 

 faster in the bottle containing the twigs, than in the other 

 bottle. Where has this water gone? If now we. place 

 a cool fruit jar over the twigs and hold it there a short 

 time, we shall be able to answer this question. Water 

 from the leaves will gather on the inside of the glass, so 

 that we can easily see it. If we leave the jar over the 

 twigs for half an hour, drops of water will flow down its 

 inside surface. This shows that 

 some of the water taken up by the 

 roots or plants passes off, or trans- 

 pires, through the leaves. The pass- 

 ing off of moisture from the leaves of 

 plants is called transpiration. 



Leaves do not Take in Water. 

 If we take the fresh bean plant out 

 of the water and put one of its 

 leaves instead of the stem into the 

 water, we shall find that the other 



F.c.9.- Leaves do leaV6S SOOn dr P' ( Fi g UFe 9-) 



not absorb water. This shows that the leaves of 

 the bean plant can not take in much water, even 



