II. THE MATERIAL OF WHICH PLANTS 

 ARE MADE UP 



7. The plant is an engine. — The plant is a 

 machine, and is composed of many more separate 

 parts than a watch or locomotive. The construc- 

 tion of a watch or locomotive may be learned by 

 tearing one to pieces, or by building it up from its 

 separate parts. After this has been done it is much 

 easier to understand the action of these machines. 

 The same is true of the plant. 



The composition of the plant might be found by 

 separating it into its different substances, after the 

 manner of the chemist, or by building it up from the 

 materials of which it may be composed. Neither of 

 these methods is entirely satisfactory when used 

 alone, because they cannot be completely carried 

 out. The substances or compounds in protoplasm are 

 so delicate that when we seek to separate them they 

 are destroyed. The result is the same as if we 

 attempted to tear down a build hig made of bricks 

 so fragile that they would crumble at the touch ; 



