﻿650 
  Mutations 
  

  

  to 
  one 
  another 
  than 
  would 
  correspond 
  to 
  the 
  

   original 
  proportion 
  of 
  5 
  turns 
  for 
  13 
  leaves. 
  

   In 
  fact, 
  10 
  or 
  even 
  13 
  leaves 
  may 
  not 
  rarely 
  

   be 
  counted 
  on 
  a 
  single 
  turn. 
  Or 
  the 
  twist 
  

   may 
  become 
  so 
  strong 
  locally 
  as 
  to 
  change 
  the 
  

   spiral 
  into 
  .a 
  longitudinal 
  line. 
  On 
  this 
  line 
  

   all 
  inserted 
  leaves 
  extend 
  themselves 
  in 
  the 
  

   same 
  direction, 
  resembling 
  an 
  extended 
  flag. 
  

  

  The 
  spiral 
  on 
  the 
  stem 
  is 
  simply 
  the 
  continua- 
  

   tion 
  of 
  the 
  spiral 
  line 
  from 
  within 
  the 
  rosettes 
  

   of 
  the 
  first 
  year. 
  Accordingly 
  it 
  is 
  seen 
  to 
  be- 
  

   come 
  gradually 
  less 
  steep 
  at 
  the 
  base. 
  For 
  this 
  

   reason 
  it 
  must 
  be 
  one 
  and 
  the 
  same 
  with 
  this 
  

   line, 
  and 
  in 
  extreme 
  youth 
  it 
  must 
  have 
  pro- 
  

   duced 
  its 
  leaves 
  at 
  the 
  same 
  mutual 
  distances 
  as 
  

   this 
  line. 
  Transverse 
  sections 
  of 
  the 
  growing 
  

   summits 
  of 
  the 
  stems 
  support 
  this 
  conclusion. 
  

  

  From 
  these 
  several 
  facts 
  we 
  may 
  infer 
  that 
  

   the 
  steepness 
  of 
  the 
  spiral 
  line 
  increases 
  on 
  the 
  

   stem, 
  as 
  it 
  is 
  gradually 
  changed 
  into 
  a 
  screw. 
  

   Originally 
  5 
  turns 
  were 
  needed 
  for 
  13 
  leaves, 
  

   but 
  this 
  number 
  diminishes 
  and 
  4 
  or 
  3 
  or 
  even 
  2 
  

   turns 
  may 
  take 
  the 
  same 
  number 
  of 
  foliar 
  

   organs, 
  until 
  the 
  screw 
  itself 
  is 
  changed 
  into 
  a 
  

   straight 
  line. 
  

  

  This 
  change 
  consists 
  in 
  an 
  unwinding 
  of 
  the 
  

   whole 
  spiral, 
  and 
  in 
  order 
  to 
  effect 
  this 
  the 
  stem 
  

   must 
  become 
  wound 
  up 
  in 
  the 
  opposite 
  direc- 
  

   tion. 
  The 
  winding 
  of 
  the 
  foliar 
  screw 
  must 
  

  

  