﻿Retrograde 
  Varieties 
  149 
  

  

  cial 
  spots 
  or 
  lines 
  or 
  tracings 
  are 
  to 
  be 
  seen 
  on 
  a 
  

   white 
  or 
  on 
  a 
  colored 
  background. 
  That 
  such 
  

   spots 
  and 
  lines 
  are 
  separate 
  units 
  is 
  obvious 
  

   and 
  is 
  demonstrated 
  by 
  the 
  fact 
  that 
  some- 
  

   times 
  spotless 
  varieties 
  occur, 
  which 
  in 
  all 
  other 
  

   respects 
  have 
  kept 
  the 
  colors 
  of 
  the 
  species. 
  

   The 
  complexity 
  of 
  the 
  color 
  is 
  equally 
  evident, 
  

   whenever 
  it 
  is 
  built 
  up 
  of 
  constituents 
  of 
  the 
  

   anthocyan 
  and 
  of 
  the 
  yellow 
  group. 
  The 
  an- 
  

   thocyan 
  dye 
  is 
  limited 
  to 
  the 
  sap-cavity 
  of 
  the 
  

   cells, 
  while 
  the 
  yellow 
  and 
  pure 
  orange 
  colors 
  

   are 
  fixed 
  in 
  special 
  organs 
  of 
  the 
  protoplasm. 
  

   The 
  observation 
  under 
  the 
  microscope 
  shows 
  at 
  

   once 
  the 
  different 
  units, 
  which 
  though 
  lying 
  in 
  

   the 
  same 
  cell 
  and 
  in 
  almost 
  immediate 
  vicinity 
  

   of 
  each 
  other 
  are 
  always 
  wholly 
  separated 
  from 
  

   one 
  another 
  by 
  the 
  wall 
  of 
  the 
  vacuole 
  or 
  sap- 
  

   filled 
  cell-cavity. 
  

  

  The 
  combination 
  of 
  red 
  and 
  yellow 
  gives 
  a 
  

   brown 
  tinge, 
  as 
  in 
  the 
  cultivated 
  wall-flower, 
  or 
  

   those 
  bright 
  hues 
  of 
  a 
  dark 
  orange-red, 
  which 
  

   are 
  so 
  much 
  sought 
  in 
  tulips. 
  By 
  putting 
  such 
  

   flowers 
  for 
  a 
  short 
  time 
  in 
  boiling 
  water, 
  the 
  

   cells 
  die 
  and 
  release 
  the 
  red 
  pigment, 
  which 
  be- 
  

   comes 
  diffused 
  in 
  the 
  surrounding 
  fluids 
  and 
  the 
  

   petals 
  are 
  left 
  behind 
  with 
  their 
  yellow 
  tinge. 
  

   In 
  this 
  way 
  it 
  is 
  easy 
  to 
  separate 
  the 
  constitu- 
  

   ents, 
  and 
  demonstrate 
  the 
  compound 
  nature 
  of 
  

   the 
  original 
  colors. 
  

  

  