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Plants rarely grow singly. Different kinds usually grow together, 

 forming groups such as a patch of weeds on waste-land, a zone 

 of sedges and grasses bordering a lake, or a group of trees form- 

 ing a woods. Groupings or communities of plants are so universal 

 that they require careful description and study. 



A plant grouping is a collection of plants of one to many 

 species growing together and having a certain unity. This unity 

 is formed in the first place because the plants are living close to- 

 gether in a common habitat; and it increases by the interrelation- 

 ships formed between them. In the more complex communities, 

 composed of plants of various life-forms, interrelationships be- 

 come more numerous and diversified. Interspecific association of 

 species becomes more pronounced, and thus the dependence of 

 one species upon another within the general framework of the 

 environment increases as well.^^^ The independence of a species 

 may be greatly modified when it is growing in association with 

 other species as compared to growing alone. 



