I. NUTRITIVE ADAPTATIONS. 



§ I. ADAPTATIONS OF FORM AND STRUCTURE TO 

 ENVIRONMENT. 



CHAPTER XIX. 



FORMS OF VEGETATION. 



315. 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 material 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 them- 

 selves to the places in which they grow. This compulsion is 

 on pain of death. 



316. 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 ma- 

 turity. Far the greater number will be killed by being robbed 

 of light and of water by the overshadowing leaves and inter- 

 lacing roots of their companions. Since such competition 

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

 tions 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 



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