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PRACTICAL COURSE IN BOTANY 



indicate. Local conditions in limited areas may lead to the 

 segregation of smaller and more compact groups called socie- 

 ties. This term, however, is used rather loosely, being treated 

 in some works as synonymous with formations, in others as 

 analogous with what have here been defined as colonies. 



317. Principles of subdivision. -- The mixed associations 

 described in the last paragraph are quite independent of 



FIG. 414. A colony of Alabama primroses ((Enothcra speciosa). 



botanical relationships, and any of the factors named in 

 310, or others of a different kind, could be made the basis of 

 their classification. They might be grouped, for instance, 

 according to their economic uses, or according to origin, 

 whether native or introduced, as best suited the purpose of 

 the classification in each case. The moisture factor, however, 

 has been generally agreed upon as the one most convenient 

 for ordinary purposes. Upon this principle plants are divided 

 into three great groups : 



