﻿200 
  Retrograde 
  Varieties 
  

  

  Once 
  sure 
  of 
  this 
  preliminary 
  condition, 
  the 
  

   experiment 
  simply 
  consists 
  in 
  growing 
  a 
  variety 
  

   at 
  a 
  given 
  distance 
  from 
  its 
  species 
  and 
  allow- 
  

   ing 
  the 
  insects 
  to 
  transfer 
  the 
  pollen. 
  After 
  

   harvesting 
  the 
  seed 
  thus 
  subjected 
  to 
  the 
  pre- 
  

   sumed 
  cause 
  of 
  the 
  impurities, 
  it 
  must 
  be 
  

   sown 
  in 
  quantities, 
  large 
  enough 
  to 
  bring 
  to 
  

   light 
  any 
  slight 
  anomaly, 
  and 
  to 
  be 
  examined 
  

   during 
  the 
  period 
  of 
  blooming. 
  

  

  The 
  wild 
  seashore 
  aster, 
  Aster 
  Tripolium, 
  

   will 
  serve 
  as 
  an 
  example. 
  It 
  has 
  pale 
  violet 
  or 
  

   bluish 
  rays, 
  but 
  has 
  given 
  rise 
  to 
  a 
  white 
  va- 
  

   riety, 
  which 
  on 
  testing, 
  I 
  have 
  found 
  pure 
  from 
  

   seed. 
  Four 
  specimens 
  of 
  this 
  white 
  variety 
  

   were 
  cultivated 
  at 
  a 
  distance 
  of 
  nearly 
  100 
  

   meters 
  from 
  a 
  large 
  lot 
  of 
  plants 
  of 
  the 
  bluish 
  

   species. 
  I 
  left 
  fertilization 
  to 
  the 
  bees, 
  har- 
  

   vested 
  the 
  seeds 
  of 
  the 
  four 
  whites 
  separately 
  

   and 
  had 
  from 
  them 
  the 
  following 
  year 
  more 
  than 
  

   a 
  thousand 
  flowering 
  plants. 
  All 
  of 
  them 
  were 
  

   of 
  the 
  purest 
  white, 
  with 
  only 
  one 
  exception, 
  

   which 
  was 
  a 
  plant 
  with 
  the 
  bluish 
  rays 
  of 
  the 
  

   species, 
  wholly 
  reverting 
  to 
  its 
  general 
  type. 
  As 
  

   the 
  variety 
  does 
  not 
  give 
  such 
  reversions 
  when 
  

   cultivated 
  in 
  isolation, 
  this 
  sport 
  was 
  obviously 
  

   due 
  to 
  some 
  cross 
  in 
  the 
  former 
  year. 
  In 
  the 
  

   same 
  way 
  I 
  tried 
  the 
  white 
  Jacob's 
  ladder, 
  

   Polemonium 
  coeruleum 
  album 
  in 
  the 
  neighbor- 
  

   hood 
  of 
  the 
  blue-flowered 
  species, 
  the 
  distance 
  

  

  