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  Elementary 
  Species 
  

  

  and 
  even 
  the 
  most 
  skillful 
  historians, 
  by 
  sifting 
  

   the 
  evidence 
  afforded 
  by 
  the 
  older 
  writers, 
  and 
  

   that 
  obtained 
  by 
  comparative 
  linguistic 
  investi- 
  

   gations 
  have 
  been 
  able 
  to 
  do 
  little 
  more 
  than 
  

   frame 
  the 
  most 
  general 
  outline 
  of 
  the 
  cultural 
  

   history 
  of 
  the 
  most 
  common 
  and 
  most 
  widely 
  

   used 
  plants. 
  

  

  Some 
  authors 
  assume 
  that 
  cultivation 
  itself 
  

   might 
  have 
  been 
  the 
  principal 
  cause 
  of 
  variabil- 
  

   ity, 
  but 
  it 
  is 
  not 
  proved, 
  nor 
  even 
  probable, 
  that 
  

   cultivated 
  plants 
  are 
  intrinsically 
  more 
  variable 
  

   than 
  their 
  wild 
  prototypes. 
  Appearances 
  in 
  

   this 
  case 
  are 
  very 
  deceptive. 
  Of 
  course 
  widely 
  

   distributed 
  plants 
  are 
  as 
  a 
  rule 
  richer 
  in 
  subspe- 
  

   cies 
  than 
  forms 
  with 
  limited 
  distribution, 
  and 
  

   the 
  former 
  must 
  have 
  had 
  a 
  better 
  chance 
  to 
  be 
  

   taken 
  into 
  cultivation 
  than 
  the 
  latter. 
  In 
  many 
  

   cases, 
  especially 
  with 
  the 
  more 
  recent 
  cultivated 
  

   species, 
  man 
  has 
  deliberately 
  chosen 
  variable 
  

   forms, 
  because 
  of 
  their 
  greater 
  promise. 
  

   Thirdly, 
  wide 
  variability 
  is 
  the 
  most 
  efficient 
  

   means 
  of 
  acclimatization, 
  and 
  only 
  species 
  with 
  

   many 
  elementary 
  units 
  would 
  have 
  offered 
  

   the 
  adequate 
  material 
  for 
  introduction 
  into 
  new 
  

   countries. 
  

  

  From 
  this 
  discussion 
  it 
  would 
  seem 
  that 
  it 
  is 
  

   more 
  reasonable 
  to 
  assert 
  that 
  variability 
  is 
  one 
  

   of 
  the 
  causes 
  of 
  the 
  success 
  of 
  cultivation, 
  than 
  

   to 
  assume 
  that 
  cultivation 
  is 
  a 
  cause 
  of 
  variabil- 
  

  

  