B. ELEMENTARY SPECIES 

 Lecture II 



ELEMENTAEY SPECIES IN NATURE 



What are species? Species are considered 

 as the true units of nature by the vast majority 

 of biologists. They have gained this high 

 rank in our estimation principally through the 

 influence of Linnaeus. They have supplanted 

 the genera which were the accepted units before 

 Linnaeus. They are now to be replaced in their 

 turn, by smaller types, for reasons which do not 

 rest upon comparative studies but upon direct 

 experimental evidence. 



Biological studies and practical interests 

 alike make new demands upon systematic bot- 

 any. Species are not only the subject-material 

 of herbaria and collections, but they are living 

 entities, and their life-history and life-condi- 

 tions command a gradually increasing interest. 

 One phase of the question is to determine the 

 easiest manner to deal with the collected forms 

 of a country, and another feature is the problem 



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