﻿Balanced 
  Crosses 
  279 
  

  

  in 
  unbalanced 
  unions 
  in 
  all 
  possible 
  degrees, 
  ac- 
  

   cording 
  to 
  the 
  amount 
  of 
  difference 
  between 
  the 
  

   parents. 
  If 
  this 
  amount 
  is 
  slight, 
  if 
  for 
  in- 
  

   stance, 
  only 
  one 
  unit-character 
  causes 
  the 
  dif- 
  

   ference, 
  the 
  injury 
  to 
  fertility 
  may 
  be 
  so 
  small 
  

   as 
  to 
  be 
  practically 
  nothing. 
  Hence 
  we 
  see 
  that 
  

   this 
  test 
  would 
  not 
  enable 
  us 
  to 
  judge 
  of 
  the 
  

   doubtful 
  cases, 
  although 
  it 
  is 
  quite 
  sufficient 
  as 
  

   a 
  proof 
  in 
  cases 
  of 
  wider 
  differences. 
  

  

  Our 
  second 
  assertion 
  related 
  to 
  the 
  reciprocal 
  

   crosses. 
  This 
  is 
  the 
  name 
  given 
  to 
  two 
  sexual 
  

   combinations 
  between 
  the 
  same 
  parents, 
  but 
  

   with 
  interchanged 
  places 
  as 
  to 
  which 
  furnishes 
  

   the 
  pollen. 
  In 
  unbalanced 
  crosses 
  of 
  the 
  genus 
  

   OenotJiera 
  the 
  hybrids 
  of 
  such 
  reciprocal 
  unions 
  

   are 
  often 
  different, 
  as 
  we 
  have 
  previously 
  

   shown. 
  Sometimes 
  both 
  resemble 
  the 
  pollen- 
  

   parent 
  more, 
  in 
  other 
  instances 
  the 
  pistil-parent. 
  

   In 
  varietal 
  crosses 
  no 
  such 
  divergence 
  is 
  as 
  yet 
  

   known. 
  It 
  would 
  be 
  quite 
  superfluous 
  to 
  ad- 
  

   duce 
  single 
  cases 
  as 
  proofs 
  for 
  this 
  rule, 
  which 
  

   was 
  formerly 
  conceived 
  to 
  hold 
  good 
  for 
  hy- 
  

   brids 
  in 
  general. 
  The 
  work 
  of 
  the 
  older 
  hybrid- 
  

   ists, 
  such 
  as 
  Koelreuter 
  and 
  Gaertner 
  affords 
  

   numerous 
  instances. 
  

  

  Our 
  third 
  rule 
  is 
  of 
  a 
  wholly 
  different 
  nature. 
  

   Formerly 
  the 
  distinction 
  between 
  elementary 
  

   species 
  and 
  varieties 
  was 
  not 
  insisted 
  upon, 
  and 
  

   the 
  principle 
  which 
  stamps 
  retrograde 
  changes 
  

  

  