HOW PLANTS OBTAIN FOOD FROM AIR 



45 



air coining from the lungs is also vitiated 

 air. We have thus learnt that both the air acted 

 upon by burning bodies and the air coming from the 

 lungs will not support combustion. 



If we were to place a living animal in this 

 vitiated air it would quickly die, showing that the 

 vitiated air will not support life. 



We see then from all these experiments that 

 breathing animals and burning fires are all preparing 

 this vitiated air, so that we should expect that by 

 this time all the air on the earth would be unbreath- 

 able, unless there is some way in which the air can be 

 purified and restored to its former state. 



Vitiated Air restored by Plants in Sunlight 



Let us see whether it is growing plants that 

 exercise such an influence 

 on the air as to purify it. 



Experiment 28 



Place the wide-mouthed 

 bottle, full of water, upside 

 down in the basin as be- 

 fore and fill it with viti- 

 ated air from the lungs, 



and then, leaving it standing upside down in the 

 basin, put a young vigorous plant up into it, with the 



