SECTION I. PLANTS AND THE 

 ENVIRONMENT 



CHAPTER I 



THE RELATIONS OF PLANTS TO THE ENVIRONMENT 



Plant biology, or elementary botany, is chiefly concerned with 

 the structure and activities of plants and with their relations to 

 the living and lifeless objects and forces which surround them 

 and constitute their environment. It is evidently impossible at 

 the outset of our study to present more than a general survey 

 of the relations and functions of plants in nature, but it is 

 hoped that such a survey will stimulate the interest of the 

 student in the larger aspects of botany and will serve to give 

 him a new appreciation of the great importance of plants in 

 the world of living things. 



In order to present this more comprehensive idea of plant 

 life clearly and concisely we shall need to consider first the 

 peculiar relations of the world of vegetation to inanimate 

 nature, including the soil, the air, and such forces of its en- 

 vironment as light and gravity. This discussion can then be 

 logically followed by considering the relation which plants 

 sustain to animate nature, including man and other animals. 

 With this brief introduction we may proceed directly to the 

 consideration of these topics. 



THE INANIMATE ENVIRONMENT 



The forces. Light and gravity, which impinge upon the 

 bodies of plants from without, are used by the higher plants 

 in such a way as to secure the advantageous placing or ad- 

 justment of their leaves, roots, stems, and flowers in the soil 



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