﻿508 
  Mutations 
  

  

  and 
  towards 
  the 
  autumn, 
  when 
  all 
  those 
  of 
  the 
  

   first 
  group 
  are 
  faded 
  away, 
  and 
  only 
  a 
  weak 
  

   though 
  large 
  section 
  of 
  the 
  heads 
  is 
  still 
  flower- 
  

   ing, 
  the 
  whole 
  aspect 
  of 
  the 
  variety 
  gradually 
  

   retrogrades. 
  The 
  same 
  law 
  of 
  dependency 
  and 
  

   periodicity 
  is 
  prevalent 
  everywhere. 
  In 
  my 
  

   own 
  cultures 
  of 
  the 
  improved 
  field-marigold 
  I 
  

   have 
  observed 
  it 
  frequently. 
  The 
  number 
  of 
  the 
  

   rav-florets 
  mav 
  be 
  considered 
  as 
  a 
  direct 
  re- 
  

  

  / 
  t/ 
  

  

  sponse 
  to 
  nourishment, 
  both 
  when 
  this 
  is 
  deter- 
  

   mined 
  by 
  external 
  circumstances, 
  and 
  when 
  it 
  

   depends 
  on 
  the 
  particular 
  strength 
  of 
  the 
  

   branch, 
  which 
  bears 
  the 
  head 
  in 
  question. 
  It 
  is 
  

   a 
  case 
  exactly 
  similar 
  to 
  that 
  of 
  the 
  supernumer- 
  

   ary 
  carpels 
  of 
  the 
  pistilloid 
  poppy, 
  and 
  the 
  de- 
  

   ductions 
  arrived 
  at 
  with 
  that 
  variety 
  may 
  be 
  

   applied 
  directly 
  to 
  double 
  flowers. 
  

  

  This 
  dependency 
  upon 
  nourishment 
  is 
  of 
  high 
  

   practical 
  importance 
  in 
  combination 
  with 
  the 
  

   usual 
  effect 
  of 
  the 
  doubling 
  which 
  makes 
  

   the 
  flowers 
  sterile. 
  It 
  is 
  a 
  general 
  rule 
  that 
  the 
  

   most 
  perfect 
  flowers 
  do 
  not 
  produce 
  seed. 
  At 
  

   the 
  height 
  of 
  the 
  flowering 
  period 
  the 
  external 
  

   circumstances 
  are 
  the 
  most 
  favorable, 
  and 
  the 
  

   flowering 
  branches 
  still 
  constitute 
  the 
  stronger 
  

   axes 
  of 
  the 
  plants. 
  Hence 
  we 
  may 
  infer 
  that 
  

   sterility 
  will 
  prevail 
  precisely 
  in 
  this 
  period. 
  

   Many 
  varieties 
  are 
  known 
  to 
  yield 
  only 
  seeds 
  

   from 
  the 
  very 
  last 
  flowers, 
  as 
  for 
  instance 
  some 
  

  

  