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  Fluctuations 
  

  

  Improved 
  races 
  for 
  scientific 
  investigation 
  

   can 
  be 
  kept 
  free 
  from 
  infection, 
  and 
  protected 
  

   against 
  numerous 
  other 
  injuries. 
  In 
  the 
  exper- 
  

   imental 
  garden 
  they 
  may 
  find 
  conditions 
  which 
  

   cannot 
  be 
  realized 
  elsewhere. 
  They 
  may 
  show 
  

   a 
  luxuriant 
  growth, 
  and 
  prove 
  to 
  be 
  excellent 
  

   material 
  for 
  research, 
  but 
  have 
  features 
  which, 
  

   having 
  been 
  overlooked 
  at 
  the 
  period 
  of 
  selec- 
  

   tion, 
  would 
  at 
  once 
  condemn 
  them 
  if 
  left 
  to 
  

   ordinary 
  conditions, 
  or 
  to 
  the 
  competition 
  of 
  

   other 
  species. 
  

  

  Considering 
  all 
  these 
  obstacles, 
  it 
  is 
  only 
  nat- 
  

   ural 
  that 
  breeders 
  should 
  use 
  every 
  means 
  to 
  

   reach 
  their 
  goal. 
  Only 
  in 
  very 
  rare 
  instances 
  

   do 
  they 
  follow 
  methods 
  analogous 
  to 
  scientific 
  

   processes, 
  which 
  tend 
  to 
  simplify 
  the 
  questions 
  

   as 
  much 
  as 
  possible. 
  As 
  a 
  rule, 
  the 
  practical 
  

   way 
  is 
  the 
  combination 
  of 
  as 
  many 
  causes 
  of 
  

   variability 
  as 
  possible. 
  Now 
  the 
  three 
  great 
  

   sources 
  of 
  variability 
  are, 
  as 
  has 
  been 
  pointed 
  

   out 
  on 
  several 
  occasions, 
  the 
  original 
  multi- 
  

   formity 
  of 
  the 
  species, 
  fluctuating 
  variability, 
  

   and 
  hybridization. 
  Hence, 
  in 
  practical 
  experi- 
  

   ments, 
  all 
  three 
  are 
  combined. 
  Together 
  they 
  

   yield 
  results 
  of 
  the 
  highest 
  value, 
  and 
  Bur- 
  

   bank's 
  improved 
  fruits 
  and 
  flowers 
  give 
  testi- 
  

   mony 
  to 
  the 
  practical 
  significance 
  of 
  this 
  com- 
  

   bination. 
  

  

  From 
  a 
  scientific 
  point 
  of 
  view 
  however, 
  it 
  is 
  

  

  