DIFFUSION OF GASES. 53 



125. Note. If we kill the plant, for example, by placing it for a short time in 

 nearly boiling water, oxygen will not be given off when the plant is placed in 

 the sunlight in water. In other words the plant must be alive. P'arther, if 

 we introduce C0 2 in the water by blowing into it and have not introduced 

 oxygen, oxygen will not be evolved. Not only must the plant be alive, it 

 must have access to oxygen, which we will see later is very essential to the 

 continuance of one of the important life processes. 



