﻿Elementary 
  Species 
  in 
  Nature 
  43 
  

  

  proved 
  to 
  be 
  constant 
  in 
  his 
  pedigree-cultures. 
  

   Some 
  of 
  them 
  have 
  produced 
  other 
  forms, 
  re- 
  

   lated 
  to 
  them 
  in 
  the 
  way 
  of 
  varieties. 
  They 
  all 
  

   have 
  nearly 
  the 
  same 
  general 
  habit 
  and 
  do 
  not 
  

   exhibit 
  any 
  marked 
  differences 
  in 
  their 
  growth, 
  

   in 
  the 
  structure 
  and 
  branching 
  of 
  the 
  stems, 
  or 
  

   in 
  the 
  character 
  of 
  their 
  foliage. 
  Differentiat- 
  

   ing 
  points 
  are 
  to 
  be 
  found 
  mainly 
  in 
  the 
  colors 
  

   and 
  patterns 
  of 
  the 
  flowers. 
  The 
  veins, 
  which 
  

   radiate 
  from 
  the 
  centre 
  of 
  the 
  corolla 
  are 
  

   branched 
  in 
  some 
  and 
  undivided 
  in 
  others; 
  in 
  

   one 
  elementary 
  species 
  they 
  are 
  wholly 
  lack- 
  

   ing. 
  The 
  purple 
  color 
  may 
  be 
  absent, 
  leav- 
  

   ing 
  the 
  flowers 
  of 
  a 
  pale 
  or 
  a 
  deep 
  yellow. 
  Or 
  

   the 
  purple 
  may 
  be 
  reddish 
  or 
  bluish. 
  Of 
  

   the 
  petals 
  all 
  five 
  may 
  have 
  the 
  purple 
  hue 
  

   on 
  their 
  tips, 
  or 
  this 
  attribute 
  may 
  be 
  limited 
  to 
  

   the 
  two 
  upper 
  ones. 
  Contrasting 
  with 
  this 
  wide 
  

   variability 
  is 
  the 
  stability 
  of 
  the 
  yellow 
  spot 
  in 
  

   the 
  centre, 
  which 
  is 
  always 
  present 
  and 
  becomes 
  

   inconspicuous 
  only, 
  when 
  the 
  whole 
  petals 
  are 
  

   of 
  the 
  same 
  hue. 
  It 
  is 
  a 
  general 
  conception 
  

   that 
  colors 
  and 
  color-markings 
  are 
  liable 
  to 
  

   great 
  variability 
  and 
  do 
  not 
  constitute 
  reliable 
  

   standards. 
  But 
  the 
  cultures 
  of 
  Wittrock 
  have 
  

   proved 
  the 
  contrary, 
  at 
  least 
  in 
  the 
  case 
  of 
  the 
  

   violets. 
  No 
  pattern, 
  however 
  quaint, 
  appears 
  

   changeable, 
  if 
  one 
  elementary 
  species 
  only 
  is 
  

   considered. 
  Hundreds 
  of 
  plants 
  from 
  seeds 
  

  

  