﻿144 
  Retrograde 
  Varieties 
  

  

  light 
  for 
  development, 
  and 
  that 
  in 
  the 
  dark 
  or 
  in 
  

   a 
  faint 
  light 
  the 
  seedlings 
  are 
  apt 
  to 
  remain 
  

   green 
  when 
  they 
  should 
  become 
  purple, 
  but 
  

   aside 
  from 
  such 
  consideration 
  all 
  organs 
  always 
  

   come 
  true 
  to 
  their 
  color, 
  whether 
  pure 
  green 
  and 
  

   white, 
  or 
  whether 
  these 
  are 
  combined 
  with 
  the 
  

   blue 
  tinge. 
  This 
  constancy 
  is 
  so 
  absolute 
  that 
  

   the 
  colors 
  of 
  the 
  different 
  organs 
  convey 
  the 
  

   suggestion, 
  that 
  they 
  are 
  only 
  separate 
  marks 
  

   of 
  a 
  single 
  character. 
  

  

  It 
  is 
  on 
  this 
  suggestion 
  that 
  we 
  must 
  work, 
  as 
  

   it 
  indicates 
  the 
  cause 
  of 
  the 
  correlation. 
  Once 
  

   present, 
  the 
  faculty 
  of 
  producing 
  the 
  anthocyan, 
  

   the 
  color 
  in 
  question, 
  will 
  come 
  into 
  activity 
  

   wherever 
  and 
  whenever 
  opportunity 
  presents 
  

   itself. 
  It 
  is 
  the 
  cell-sap 
  of 
  the 
  ordinary 
  cell- 
  

   tissue 
  or 
  parenchyma, 
  which 
  is 
  colored 
  by 
  the 
  

   anthocyan, 
  and 
  for 
  this 
  reason 
  all 
  organs 
  pos- 
  

   sessing 
  this 
  tissue, 
  may 
  exhibit 
  the 
  color 
  in 
  ques- 
  

   tion. 
  

  

  Thus 
  the 
  color 
  is 
  not 
  a 
  character 
  belonging 
  to 
  

   any 
  single 
  organ 
  or 
  cell, 
  nor 
  is 
  it 
  bound 
  to 
  a 
  

   morphologic 
  unit 
  ; 
  it 
  is 
  a 
  free, 
  physiologic 
  qual- 
  

   ity. 
  It 
  is 
  not 
  localized, 
  but 
  belongs 
  to 
  the 
  en- 
  

   tire 
  plant. 
  If 
  we 
  wish 
  to 
  assume 
  for 
  its 
  basis 
  

   material 
  representative 
  particles, 
  these 
  parti- 
  

   cles 
  must 
  be 
  supposed 
  to 
  be 
  diffused 
  throughout 
  

   the 
  whole 
  body 
  of 
  the 
  plant. 
  

  

  This 
  conception 
  of 
  a 
  physiologic 
  unit 
  as 
  the 
  

  

  