CHAPTER XI 

 ACCLIMATION AND YIELD 



A BOTANICAL suivey of the United States shows large, 

 well-defined regions, each with a characteristic native 

 flora. 



86. Considering the great length of time that native 

 vegetation has had in which to adjust itself, these various 



Fig. 36. — Prairie vegetation in the " short grass " region. The natiiral 

 vegetation indicates a very great difference in natural climate. 



regions must indicate different environmental conditions, 

 or else we should have a homogenous native vegetation 

 throughout the country. Those regions covered with a 

 forest vegetation must differ in environment (soil or cli- 

 mate) from a prairie region. There are various kinds of 

 forest regions, as evergreen and deciduous ; while in the 



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