2 INTRODUCTION 



the important part which plants have in your own life, as 

 well as of the nature of plant life itself. 



Think of the many uses which we make of plants besides 

 their use as food. From plants we get the principal material 

 out of which homes are built, and it is plants that we use to 

 beautify the grounds around our homes. When a man 

 is able to make the sort of home he wants, he is sure to sur- 

 round it with grass and trees, with flowers and shrubs. 

 They seem a necessary part of the sort of home we all want. 

 Think, too, of the use of plants for clothing. Cotton and 

 linen are both made from materials taken from plants. 

 Wool and silk come from animals which live on plants. 



Food is the first need of man, and this need could not be 

 supplied at all except for plants. Shelter and clothing come 

 next in order of our needs, and for these too we depend very 

 largely upon plants. Houses are for shelter, but they would 

 be poor shelter in winter if they were not heated. Coal, 

 wood, and gas are the substances principally used in pro- 

 ducing heat, and all of these are derived from plants. Coal 

 is composed of the transformed bodies of plants which lived 

 many thousands of years ago, and gas is derived from coal. 

 Even when we use electricity we are usually depending 

 indirectly upon plants, for the power-houses which gen- 

 erate the electricity use steam engines, and coal is used 

 to generate the steam. The steam engines, in turn, run 

 the machines which generate the electricity. Think of all 

 the factories, and locomotive engines, and steamships 

 which also use coal. Evidently one of the principal uses 

 of plants to man is that they provide him, or have provided 

 him, with fuel. Gasoline has come to be one of the impor- 

 tant kinds of fuel, especially in connection with automo- 

 biles. It is derived from petroleum, and petroleum, like 



