﻿Systematic 
  Atavism 
  653 
  

  

  the 
  tissues. 
  At 
  other 
  times 
  the 
  straightening 
  

   may 
  have 
  taken 
  place 
  directly 
  internal 
  to 
  a 
  leaf, 
  

   and 
  it 
  is 
  torn 
  and 
  may 
  be 
  seen 
  to 
  be 
  attached 
  to 
  

   the 
  stem 
  by 
  two 
  distinct 
  bases. 
  

  

  Summing 
  up 
  this 
  description 
  of 
  the 
  heredi- 
  

   tary 
  qualities 
  of 
  our 
  twisted 
  teasels 
  and 
  of 
  their 
  

   mechanical 
  consequences, 
  we 
  may 
  say 
  that 
  the 
  

   loss 
  of 
  the 
  normal 
  decussation 
  is 
  the 
  cause 
  of 
  all 
  

   the 
  observed 
  changes. 
  This 
  special 
  adaptation, 
  

   which 
  places 
  the 
  leaves 
  in 
  alternating 
  pairs, 
  re- 
  

   placed 
  and 
  concealed 
  the 
  old 
  and 
  universal 
  ar- 
  

   rangement 
  on 
  a 
  screw 
  line. 
  In 
  disappearing, 
  it 
  

   leaves 
  the 
  latter 
  free, 
  and 
  according 
  to 
  the 
  rule 
  

   of 
  systematic 
  atavism, 
  this 
  now 
  becomes 
  active 
  

   and 
  takes 
  its 
  place. 
  If 
  the 
  fibrovascular 
  con- 
  

   nection 
  of 
  the 
  leaf-bases 
  were 
  lost 
  at 
  the 
  same 
  

   time 
  the 
  stems 
  would 
  grow 
  and 
  become 
  straight 
  

   and 
  tall. 
  This 
  change 
  however, 
  does 
  not 
  occur, 
  

   and 
  the 
  bases 
  of 
  the 
  leaves 
  now 
  constitute 
  a 
  con- 
  

   tinuous 
  rope 
  instead 
  of 
  separate 
  rings, 
  and 
  

   thereby 
  impede 
  the 
  stretching 
  of 
  the 
  internodes. 
  

   These 
  in 
  their 
  turn 
  avoid 
  the 
  difficulty 
  by 
  twist- 
  

   ing 
  themselves 
  in 
  a 
  direction 
  opposite 
  to 
  that 
  

   of 
  the 
  spiral 
  of 
  the 
  leaves. 
  

  

  As 
  a 
  last 
  example 
  of 
  systematic 
  atavism 
  I 
  will 
  

   refer 
  to 
  the 
  reversionary 
  changes, 
  afforded 
  by 
  

   the 
  tomatoes. 
  Though 
  the 
  culture 
  of 
  this 
  plant 
  

   is 
  a 
  recent 
  one, 
  it 
  seems 
  to 
  be 
  at 
  present 
  in 
  a 
  

   state 
  of 
  mutability, 
  producing 
  new 
  strains, 
  or 
  

  

  