﻿646 
  Mutations 
  

  

  nected 
  with 
  one 
  another, 
  constituting 
  a 
  ring 
  

   which 
  narrowly 
  surrounds 
  the 
  stem, 
  and 
  which 
  

   would 
  impede 
  an 
  increase 
  in 
  thickness, 
  if 
  such 
  

   were 
  in 
  the 
  nature 
  of 
  the 
  plant. 
  But 
  since 
  the 
  

   stems 
  end 
  their 
  existence 
  during 
  the 
  summer 
  of 
  

   their 
  development, 
  this 
  structure 
  is 
  of 
  no 
  real 
  

   harm. 
  

  

  The 
  grouping 
  of 
  the 
  leaves 
  in 
  alternate 
  pairs 
  

   may 
  be 
  seen 
  within 
  the 
  bud 
  as 
  well 
  as 
  on 
  the 
  

   adult 
  stems. 
  In 
  order 
  to 
  do 
  this, 
  it 
  is 
  necessary 
  

   to 
  make 
  transverse 
  sections 
  through 
  the 
  heart 
  

   of 
  the 
  rosette 
  of 
  the 
  leaves 
  of 
  the 
  first 
  year. 
  

   If 
  cut 
  through 
  the 
  base, 
  the 
  pair 
  exhibit 
  connate 
  

   wings, 
  corresponding 
  to 
  the 
  water-cups 
  ; 
  if 
  cut 
  

   above 
  these, 
  the 
  leaves 
  seem 
  to 
  be 
  free 
  from 
  one 
  

   another. 
  

  

  In 
  order 
  to 
  compare 
  the 
  position 
  of 
  leaves 
  

   of 
  the 
  twisted 
  plants 
  with 
  this 
  normal 
  arrange- 
  

   ment, 
  the 
  best 
  way 
  is 
  to 
  make 
  a 
  corresponding 
  

   section 
  through 
  the 
  heart 
  of 
  the 
  rosette 
  of 
  the 
  

   first 
  year. 
  It 
  is 
  not 
  necessary 
  to 
  make 
  a 
  micro- 
  

   scopic 
  preparation. 
  In 
  the 
  fall 
  the 
  changed 
  dis- 
  

   position 
  may 
  at 
  once 
  be 
  seen 
  to 
  affect 
  the 
  central 
  

   leaves 
  of 
  the 
  group. 
  All 
  the 
  rosettes 
  of 
  the 
  

   whole 
  race 
  commence 
  with 
  opposite 
  leaves; 
  

   those 
  that 
  are 
  to 
  produce 
  straight 
  stems 
  remain 
  

   in 
  this 
  condition, 
  but 
  the 
  preparation 
  for 
  twist- 
  

   ing 
  begins 
  at 
  the 
  end 
  of 
  the 
  first 
  year 
  as 
  shown 
  

   by 
  a 
  special 
  arrangement 
  of 
  the 
  leaves. 
  This 
  

  

  