﻿298 
  Retrograde 
  Varieties 
  

  

  that 
  both 
  are 
  present, 
  and 
  in 
  nearly 
  equal 
  num- 
  

   bers; 
  one-half 
  of 
  the 
  grains 
  remaining 
  smooth, 
  

   and 
  the 
  other 
  half 
  becoming 
  wrinkled. 
  

  

  The 
  corresponding 
  experiment 
  could 
  be 
  made 
  

   with 
  plants 
  of 
  a 
  pure 
  sugar-race 
  by 
  pollination 
  

   with 
  hybrid 
  pollen. 
  The 
  spikes 
  would 
  show 
  ex- 
  

   actly 
  the 
  same 
  mixture 
  as 
  in 
  the 
  above 
  case, 
  but 
  

   now 
  this 
  may 
  be 
  considered 
  as 
  conclusive 
  proof 
  

   that 
  half 
  the 
  pollen-grains 
  represent 
  the 
  quality 
  

   of 
  one 
  parent 
  and 
  the 
  other 
  half 
  the 
  quality 
  of 
  

   the 
  other. 
  

  

  Another 
  corollary 
  of 
  Mendel's 
  law 
  is 
  the 
  fol- 
  

   lowing. 
  In 
  each 
  generation 
  two 
  groups 
  return 
  

   to 
  purity, 
  and 
  one-half 
  remains 
  hybrid. 
  These 
  

   last 
  will 
  repeat 
  the 
  same 
  phenomenon 
  of 
  split- 
  

   ting 
  in 
  their 
  progeny, 
  and 
  it 
  is 
  easily 
  seen 
  

   that 
  the 
  same 
  rule 
  will 
  hold 
  good 
  for 
  all 
  succeed- 
  

   ing 
  generations. 
  According 
  to 
  Mendel's 
  prin- 
  

   ciple, 
  in 
  each 
  year 
  there 
  is 
  a 
  new 
  hybridization, 
  

   differing 
  in 
  no 
  respect 
  from 
  the 
  first 
  and 
  

   original 
  one. 
  If 
  the 
  hybrids 
  only 
  are 
  propa- 
  

   gated, 
  each 
  year 
  will 
  show 
  one-fourth 
  of 
  the 
  

   offspring 
  returning 
  to 
  the 
  specific 
  character, 
  

   one-fourth 
  assuming 
  the 
  type 
  of 
  the 
  variety 
  and 
  

   one-half 
  remaining 
  hybrid. 
  I 
  have 
  tested 
  this 
  

   with 
  a 
  hybrid 
  between 
  the 
  ordinary 
  nightshade 
  

   with 
  black 
  berries, 
  and 
  its 
  variety, 
  Solanum 
  

   nigrum 
  Morocarpum, 
  with 
  pale 
  yellow 
  fruits. 
  

  

  Eight 
  generations 
  of 
  the 
  hybrids 
  were 
  culti- 
  

  

  