﻿Systematic 
  Atavism 
  647 
  

  

  disposition 
  may 
  then 
  be 
  seen 
  to 
  extend 
  to 
  the 
  

   very 
  center 
  of 
  the 
  rosette, 
  by 
  use 
  of 
  microscop- 
  

   ical 
  sections. 
  Examining 
  sections 
  made 
  in 
  the 
  

   spring, 
  the 
  original 
  arrangement 
  of 
  the 
  leaves 
  

   of 
  the 
  stem 
  is 
  observed 
  to 
  continue 
  until 
  

   the 
  beginning 
  of 
  the 
  growth 
  of 
  the 
  shoot. 
  

   It 
  is 
  easy 
  to 
  estimate 
  the 
  number 
  of 
  leaves 
  cor- 
  

   responding 
  to 
  a 
  given 
  number 
  of 
  spiral 
  circuits 
  

   in 
  these 
  sections 
  and 
  the 
  proportion 
  is 
  found 
  to 
  

   indicate 
  13 
  leaves 
  on 
  5 
  turns. 
  These 
  figures 
  

   are 
  the 
  same 
  as 
  those 
  given 
  above 
  for 
  the 
  ordi- 
  

   nary 
  arrangement 
  of 
  alternate 
  leaves 
  in 
  the 
  

   main 
  lines 
  of 
  the 
  pedigree 
  of 
  the 
  vegetable 
  king- 
  

   dom. 
  

  

  Leaving 
  aside 
  for 
  the 
  moment 
  the 
  subsequent 
  

   changes 
  of 
  this 
  spiral 
  arrangement, 
  it 
  becomes 
  

   at 
  once 
  clear 
  that 
  here 
  we 
  have 
  a 
  case 
  of 
  sys- 
  

   tematic 
  atavism. 
  The 
  twisted 
  teasels 
  lose 
  their 
  

   decussation, 
  but 
  in 
  doing 
  so 
  the 
  leaves 
  are 
  not 
  

   left 
  in 
  a 
  disorderly 
  dispersion, 
  but 
  a 
  distinct 
  new 
  

   arrangement 
  takes 
  its 
  place, 
  which 
  is 
  to 
  be 
  

   assumed 
  as 
  the 
  normal 
  one 
  for 
  the 
  ancestors 
  

   of 
  the 
  teasel 
  family. 
  The 
  case 
  is 
  to 
  be 
  consid- 
  

   ered 
  as 
  one 
  of 
  atavism. 
  Obviously 
  no 
  

   other 
  explanation 
  is 
  possible, 
  than 
  the 
  sup- 
  

   position 
  that 
  the 
  5-13 
  spiral 
  is 
  still 
  latent, 
  

   though 
  not 
  displayed 
  by 
  the 
  teasels. 
  But 
  in 
  

   the 
  very 
  moment 
  when 
  the 
  faculty 
  of 
  decussa- 
  

   tion 
  disappears, 
  it 
  resumes 
  its 
  place, 
  and 
  be- 
  

  

  