CHAPTER IV 



PLANT SOCIETIES 



In the long course of time in which plants have been 

 accommodating themselves to the varying conditions in 

 which they are obliged to grow, they have become adapted 

 to every different environment. Certain plants, therefore, 

 may live together or near each other, all enjoying the 

 same general conditions and surroundings. These aggre- 

 gations of plants that are adapted to similar general con-' 

 ditions are known as plant societies. 



Moisture and temperature are the leading factors in ( 

 determining plant societies. The great geographical 

 societies or aggregations of the plant world may con- 

 veniently be associated chiefly with the moisture supply, 

 as : wet-region societies, comprising aquatic and bog 

 vegetation (Fig. 8); arid-region societies, comprising desert 

 and most sand-region vegetation ; mid-region societies, 

 comprising the mixed vegetation in intermediate regions 

 (Fig. 9), this being the commonest type. Much of the 

 characteristic scenery of any place is due to its plant 

 societies. Arid-region plants usually have small and hard 

 leaves, apparently preventing too rapid loss of water. 

 Usually, also, they are characterized by stiff growth, hairy 

 covering, spines, or a much-contracted plant-body, and 

 often by large underground parts for the storage of water. 



Plant societies may also be distinguished with reference 

 to latitude and temperature. There are tropical societies, 

 temperate-region societies, boreal or cold-region societies. 



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