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  Retrograde 
  Varieties 
  

  

  They 
  are 
  generally 
  called 
  atavists 
  or 
  rever- 
  

   sionists, 
  but 
  even 
  these 
  terms 
  are 
  sometimes 
  

   used 
  in 
  a 
  different 
  sense. 
  

  

  Lastly 
  it 
  is 
  to 
  be 
  said 
  that 
  the 
  empirical 
  and 
  

   experimental 
  evidence 
  as 
  to 
  the 
  question 
  of 
  con- 
  

   stancy 
  is 
  not 
  as 
  extensive 
  as 
  it 
  should 
  be. 
  The 
  

   experimental 
  conditions 
  are 
  seldom 
  described, 
  

   and 
  it 
  is 
  only 
  recently 
  that 
  an 
  interest 
  in 
  the 
  

   matter 
  has 
  been 
  awakened. 
  Much 
  remains 
  to 
  

   be 
  done. 
  Among 
  other 
  things 
  the 
  innumerable 
  

   varieties 
  of 
  trees, 
  shrubs 
  and 
  perennial 
  herbs 
  

   should 
  be 
  tested 
  as 
  to 
  their 
  constancy 
  when 
  

   grown 
  from 
  purely 
  fertilized 
  seeds. 
  Many 
  of 
  

   them 
  may 
  be 
  included 
  among 
  the 
  number 
  that 
  

   sport 
  constantly. 
  

  

  Leaving 
  aside 
  the 
  doubtful 
  or 
  insufficiently 
  

   studied 
  cases, 
  we 
  may 
  now 
  turn 
  our 
  attention 
  to 
  

   the 
  facts 
  that 
  prove 
  the 
  absolute 
  stability 
  of 
  

   a 
  large 
  number 
  of 
  varieties, 
  at 
  least 
  as 
  far 
  as 
  

   such 
  completeness 
  can 
  be 
  attained 
  by 
  experi- 
  

   ment 
  or 
  observation. 
  

  

  The 
  best 
  proof 
  is 
  afforded 
  by 
  the 
  varieties 
  

   which 
  grow 
  wild 
  in 
  localities 
  where 
  they 
  are 
  

   quite 
  isolated 
  from 
  the 
  species, 
  and 
  where 
  for 
  

   this 
  reason, 
  no 
  possibility 
  of 
  crossing 
  disturbs 
  

   the 
  significance 
  of 
  the 
  proof. 
  As 
  one 
  instance 
  

   the 
  rayless 
  form 
  of 
  the 
  wild 
  camomile, 
  or 
  the 
  

   Matricaria 
  Chamomilla 
  discoidea 
  may 
  be 
  men- 
  

   tioned. 
  Many 
  systematists 
  have 
  been 
  so 
  strong- 
  

  

  