I. NUTRITIVE ADAPTATIONS, 



§ I. ADAPTATIONS OF FORM AND STRUCTURE 

 TO ENVIRONMENT. 



CHAPTER XIX. 



FORMS OF VEGETATION. 



416. Adaptation. — The various physical conditions which 

 make up the "climate" of any particular region of the 

 earth's surface, together with the nature of the substratum 

 upon or in which the plant grows, largely control the form 

 and functions of the plants found in that region. Stated in 

 other words, plants, in order to exist at all, are compelled to 

 adapt themselves to the places in which they grow. This 

 compulsion is on pain of death. 



417. The struggle for existence. — The competition be- 

 tween plants is intense. Only a very small portion of the 

 seedlings which start in any particular area can come to 

 maturity. Far the greater number will be killed by being 

 robbed of light and of water by the overshadowing leaves 

 and interlacing roots of their companions. Since such com- 

 petition exists, it is evident that only those best suited to the 

 conditions under which they grow will have any chance 

 whatever to survive. 



Not only are individuals subject to this competition, but 

 all individuals of a particular kind (a species) may be de- 

 stroyed in any region through the competition of other 

 species better suited to the conditions of that region. 



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