I. NUTRITIVE ADAPTATIONS. 



§ I. ADAPTATIONS OF FORM AND STRUCTURE 

 TO ENVIRONMENT. 



CHAPTER XIX. 



FORMS OF VEGETATION. 



416. Adaptation. — The various jjhysical conditions which 

 make up the "climate" of an)' particular region of the 

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

 upon or in which the ])laiit 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 

 ada])t 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. Onh- a verv small ]")Ortion of the 

 seedlings which start in any particular area can come to 

 maturity. Far the greater number will be killed bv being 

 robbed of light and of water bv the o\'ersIiadowing lea\-es 

 and interlacing roots of their C(im|ianions. Since such com- 

 ])etition exists, it is eviilent that only those best sinted to the 

 conditions under which they grow will have any chance 

 whatever to survixe. 



Not only are indi\'i(hials subject to this competitiiui, but 

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

 stroyed in any region through tlie com]ietition of other 

 species better suited to the conditions of that region. 



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