CHAPTER XXXI 



PLANT SOCIETIES 



384. What Plant Societies Are. — In the long course 

 of evolution, in which plants have been accommodating 

 themselves to the varying conditions in which they are 

 obliged to grow, they have become modified to every 

 different environment. Certain plants, therefore, may live 

 together or near each other, all enjoying the same conditions 

 and surroundings. These aggregations of plants adapted 

 to similar conditions are known as plant societies. 



385. Moisture and temperature are the leading factors 

 in determining plant societies. The great geographical 

 societies or aggregations of the plant world are for con- 

 venience associated chiefly with the moisture-supply. These 

 are: (1) hydrophytic or wet-region societies, comprising 

 aquatic and bog vegetation (Fig. 395); (2) xerophytic or 

 arid-region societies, comprising desert and much sand-region 

 vegetation (Fig. 371); (3) mesophytic or mid-region societies, 

 comprising the vegetation in intermediate conditions (Fig. 

 396). Mesophytic vegetation is characteristic of most regions 

 that are fitted for agriculture. The halophytic or salt-loving 

 societies are also distinguished, comprising the seashore and 

 salt-area vegetation. Much of the characteristic scenery of 

 any place is due to its plant societies (365). Xerophytic 

 plants usually have small and hard leaves, apparently to 

 prevent too rapid transpiration. Usually, also, they are 

 characterized by stiff growth, hairy covering, spines, or a 

 much-contracted plant-body, and often by large under- 

 ground parts for the storage of water. Halophytic plants 

 are often fleshy. 



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