Ii8 NOT ALTOGETHER ABOUT PLANTS 



Physics deals with the states of matter. That water 

 exists in a liquid state is a fact which physics considers. 

 Chemistry deals with the composition of matter. That 

 water is composed of hydrogen and oxygen is a fact which 

 chemistry considers. Since plant life, or any life, is based 

 on states and composition of matter, you evidently need 

 to know a little physics and chemistry ; at least as much 

 as we have given in this chapter. 



Life a Procession of Changes. Physics and chemistry 

 also deal with changes in the states and composition of 

 matter. Life, too, deals with changes. It is based on 

 changes. It has no more fundamental characteristic than 

 changes, the changes which constantly occur in protoplasm, 

 the living matter. It cannot exist without these constant 

 changes. When they stop, life is gone. It is like a whirl- 

 pool. When the water stops moving, the whirlpool is 

 gone. 



Here arises one of the great questions of science. Are 

 these life changes simply physical and chemical, operating 

 under the laws which are familiar to physicists and to 

 chemists? Or are they outside the laws of physics and 

 chemistry, operating under some mysterious law of life? 

 The change of water into steam is a physical change. The 

 change of wood in burning is both a physical and a chemi- 

 cal change. Apparently the life changes are different from 

 the boiling of water and the burning of wood only in com- 

 plexity. 



Though we are yet very ignorant of the precise character 

 of life changes, we have learned a great deal more about 

 them in late years than was formerly known. Each year 

 this knowledge increases. Yet all that science has re- 



