﻿Systematic 
  Atavism 
  645 
  

  

  loose 
  one 
  disperses 
  them. 
  According 
  to 
  such 
  

   fluctuating 
  deviations 
  the 
  number 
  of 
  leaves, 
  in- 
  

   serted 
  upon 
  a 
  given 
  number 
  of 
  spiral 
  circuits, 
  is 
  

   different 
  in 
  different 
  species. 
  In 
  a 
  vast 
  major- 
  

   ity 
  of 
  cases 
  13 
  leaves 
  are 
  found 
  on 
  5 
  circuits, 
  

   and 
  as 
  we 
  have 
  only 
  to 
  deal 
  with 
  this 
  propor- 
  

   tion 
  in 
  the 
  teasels 
  we 
  will 
  not 
  consider 
  others. 
  

  

  In 
  the 
  teasels 
  this 
  screw-arrangement 
  has 
  dis- 
  

   appeared, 
  and 
  has 
  been 
  replaced 
  by 
  a 
  decussate 
  

   grouping. 
  The 
  leaves 
  are 
  combined 
  into 
  pairs, 
  

   each 
  pair 
  occupying 
  the 
  opposite 
  sides 
  of 
  one 
  

   node. 
  The 
  succeeding 
  pairs 
  alternate 
  with 
  one 
  

   another, 
  so 
  as 
  to 
  place 
  their 
  leaves 
  at 
  right 
  

   angles. 
  The 
  leaves 
  are 
  thus 
  arranged 
  on 
  the 
  

   whole 
  stem 
  in 
  four 
  equidistant 
  rows. 
  

  

  On 
  the 
  normal 
  stem 
  of 
  a 
  teasel 
  the 
  two 
  mem- 
  

   bers 
  of 
  a 
  pair 
  are 
  tied 
  to 
  one 
  another 
  in 
  a 
  com- 
  

   paratively 
  complicated 
  way. 
  The 
  leaves 
  are 
  

   broadly 
  sessile 
  and 
  their 
  bases 
  are 
  united 
  so 
  as 
  

   to 
  constitute 
  a 
  sort 
  of 
  cup. 
  The 
  margins 
  of 
  

   these 
  cups 
  are 
  bent 
  upward, 
  thereby 
  enabling 
  

   them 
  to 
  hold 
  water, 
  and 
  after 
  a 
  rainfall 
  they 
  

   may 
  be 
  seen 
  filled 
  to 
  the 
  brim. 
  It 
  is 
  believed 
  

   that 
  these 
  little 
  reservoirs 
  are 
  useful 
  to 
  the 
  

   plant 
  during 
  the 
  flowering 
  period, 
  because 
  they 
  

   keep 
  the 
  ants 
  away 
  from 
  the 
  honey. 
  Consider- 
  

   ing 
  the 
  internal 
  structure 
  of 
  the 
  stern 
  at 
  the 
  base 
  

   of 
  these 
  cups 
  we 
  find 
  that 
  the 
  vascular 
  bundles 
  

   of 
  the 
  two 
  opposite 
  leaves 
  are 
  strongly 
  con- 
  

  

  