THE POWER OB ENERGY OF THE PLANT 189 



altered sufl&ciently to be sensible to any other living 

 thing. 



Furthermore, plants are capable of using nearly 

 two hundred times as much carbon dioxide as they 

 now get in the atmosphere, so that there is no 

 actual balance between plants and animals so far 

 as the atmosphere is concerned. 



228. Energy of physical attraction. — It has 

 been seen that the attraction of sugar for Avater 

 results in pulling water into the plant containing 

 food. It is also known that this same action car- 

 ries fluids from one part of the body to another, 

 and serves especially in aiding to carry the current 

 of water from the roots to the leaves. It is this 

 power of attraction of one substance f6r another 

 which fills the cells with water, making them tense 

 and firm. The firmness of the cells filled with 

 water in this manner is all that holds up the soft 

 stems of herbaceous plants. When the water is 

 driven off by heat this work is no longer accom- 

 plished, and the stems wilt and fall over. Water 

 is attracted into the cells by certain substances, and 

 if substances with stronger attractive power are 

 placed outside the plant, the water wiU be with- 



