INTRODUCTION. 



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solely from a desire of simplifying the generic clia- 



racters. 



What is a genus, or what is a species, is a point upon 



which scarcely two botanists are agreed at the present 

 day. With regard to the former, however much it may 

 be necessary to subdivide in a system comprehending 

 the known plants of the whole world, so as to retain 

 only a limited number of species in each genus, the 

 same does not apply to a local Flora ; and it is there pre- 

 ferable to constitute sections or subgenera, particularly 

 when the limiting characters are inconstant, difficult, or 

 obscure. A species cannot be so treated : it is formed, 

 by our Maker, as essentially distinct from all other spe- 

 cies as man is from the brute creation ; it can neither 

 for convenience be united with others, nor be split into 

 several ; but the difficulty is to ascertain what is such a 

 primitive or natural species ; and it is here so great a dif- 

 ference of opinion exists. Some pronounce a species to 

 be distinct if it presents a different habit or appearance 

 to the eye, particularly if this be constant, although often 

 indefinable : others consider it a species, although exhibit- 

 ing only a slight or no difference of aspect, provided that 

 constant characters can be assigned to it, even although the 

 differences are so minute that they can be detected^only by 

 the microscope ; Avhile a third party is of opinion that the 

 validity of a species may be proved by the permanency 



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of certain assigned characters under cultivation. The 

 Authors are not inclined to believe that any one of these 

 tests is sufficient. Of the first there are few advocates. 

 The second provides us with artificial or Booh species, 

 arising from the morbid appetite for novelties inherent in 

 the human race, which, when truly new species can no 

 longer be detected in Europe, induces those, whose talents 

 would be better devoted to the study of the numerous ex- 

 tra-European plants that lie undescribed in large herbaria, 

 to split up previously received and well known species 



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