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  Fluctuations 
  

  

  Selection 
  is 
  founded 
  upon 
  different 
  qualities, 
  ac- 
  

   cording 
  to 
  the 
  use 
  to 
  be 
  made 
  of 
  the 
  new 
  sort. 
  

   Potatoes 
  for 
  the 
  factory 
  have 
  even 
  been 
  selected 
  

   for 
  their 
  amount 
  of 
  starch, 
  and 
  in 
  this 
  case 
  at 
  

   least, 
  fluctuating 
  variability 
  has 
  played 
  a 
  very 
  

   important 
  part 
  in 
  the 
  improvement 
  of 
  the 
  race. 
  

  

  Vegetative 
  propagation 
  has 
  the 
  great 
  advan- 
  

   tage 
  of 
  exempting 
  the 
  varieties 
  from 
  regression 
  

   to 
  mediocrity, 
  which 
  always 
  follows 
  multiplica- 
  

   tion 
  by 
  seeds. 
  It 
  affords 
  the 
  possibility 
  of 
  keep- 
  

   ing 
  the 
  extremes 
  constant, 
  and 
  this 
  is 
  not 
  its 
  

   only 
  advantage. 
  Another, 
  likewise 
  highly 
  in- 
  

   teresting, 
  side 
  of 
  the 
  question 
  is 
  the 
  uniformity 
  

   of 
  the 
  whole 
  strain. 
  This 
  is 
  especially 
  im- 
  

   portant 
  in 
  the 
  case 
  of 
  fruits, 
  though 
  ordinarily 
  

   it 
  is 
  regarded 
  as 
  a 
  matter 
  of 
  course, 
  but 
  there 
  

   are 
  some 
  exceptions 
  which 
  give 
  proof 
  of 
  the 
  

   real 
  importance 
  of 
  the 
  usual 
  condition. 
  For 
  ex- 
  

   ample, 
  the 
  walnut-tree. 
  Thousands 
  of 
  acres 
  of 
  

   walnut-orchards 
  consist 
  of 
  seedling 
  trees 
  

   grown 
  from 
  nuts 
  of 
  unknown 
  parentage. 
  The 
  

   result 
  is 
  a 
  great 
  diversity 
  in 
  the 
  types 
  of 
  trees 
  

   and 
  in 
  the 
  size 
  and 
  shape 
  of 
  the 
  nuts, 
  and 
  this 
  

   diversity 
  is 
  an 
  obvious 
  disadvantage 
  to 
  the 
  in- 
  

   dustry. 
  The 
  cause 
  lies 
  in 
  the 
  enormous 
  diffi- 
  

   culties 
  attached 
  to 
  grafting 
  or 
  budding 
  of 
  these 
  

   trees, 
  which 
  make 
  this 
  method 
  very 
  expensive 
  

   and 
  to 
  a 
  high 
  degree 
  uncertain 
  and 
  unsatis- 
  

   factory. 
  

  

  