﻿Unbalanced 
  Crosses 
  261 
  

  

  crossing 
  it 
  with 
  the 
  parent-types. 
  Such 
  experi- 
  

   ments 
  however, 
  have 
  miscarried 
  owing 
  to 
  the 
  

   too 
  stable 
  nature 
  of 
  the 
  unit-characters. 
  

  

  This 
  stability 
  and 
  this 
  absence 
  of 
  the 
  split- 
  

   ting 
  shown 
  by 
  varietal 
  marks 
  in 
  the 
  offspring 
  

   of 
  hybrids 
  is 
  one 
  of 
  the 
  best 
  proofs 
  of 
  unisex- 
  

   ual 
  unions. 
  It 
  is 
  often 
  obscured 
  by 
  the 
  accom- 
  

   panying 
  varietal 
  marks, 
  or 
  overlooked 
  for 
  this 
  

   reason. 
  Only 
  in 
  rare 
  cases 
  it 
  is 
  to 
  be 
  met 
  with 
  

   in 
  a 
  pure 
  state 
  and 
  some 
  examples 
  are 
  given 
  of 
  

   this 
  below. 
  

  

  Before 
  doing 
  so, 
  I 
  must 
  call 
  your 
  attention 
  

   to 
  another 
  feature 
  of 
  the 
  unbalanced 
  unions. 
  

   This 
  is 
  the 
  diminution 
  of 
  the 
  fertility, 
  a 
  phe- 
  

   nomenon 
  universally 
  known 
  as 
  occurring 
  in 
  

   hybridizations. 
  It 
  has 
  two 
  phases. 
  First, 
  the 
  

   diminished 
  chance 
  of 
  the 
  crosses 
  themselves 
  of 
  

   giving 
  full 
  crops 
  of 
  seed, 
  as 
  compared 
  with 
  the 
  

   pure 
  fertilization 
  of 
  either 
  parent. 
  And, 
  sec- 
  

   ondly, 
  the 
  fertility 
  of 
  the 
  hybrids 
  themselves. 
  

   Seemingly, 
  all 
  grades 
  of 
  diminished 
  fertility 
  

   occur 
  and 
  the 
  oldest 
  authors 
  on 
  hybrids 
  have 
  

   pointed 
  out 
  that 
  a 
  very 
  definite 
  relation 
  exists 
  

   between 
  the 
  differences 
  of 
  the 
  parents 
  and 
  the 
  

   degree 
  of 
  sterility, 
  both 
  of 
  the 
  cross 
  and 
  of 
  the 
  

   hybrid 
  offspring. 
  In 
  a 
  broad 
  sense 
  these 
  two 
  

   factors 
  are 
  proportionate 
  to 
  each 
  other, 
  the 
  

   sterility 
  being 
  the 
  greater, 
  the 
  lesser 
  the 
  affin- 
  

   ity 
  between 
  the 
  parents. 
  Many 
  writers 
  have 
  

  

  