﻿Rickett: 
  Sphaerocarpos 
  Donnellii 
  

  

  351 
  

  

  occur 
  mostly 
  at 
  one 
  end 
  of 
  the 
  mother 
  cell, 
  the 
  other 
  end 
  being 
  

   divided 
  into 
  only 
  two 
  or 
  three 
  comparatively 
  large 
  and 
  clear 
  

   cells 
  (Figs, 
  t, 
  2), 
  The 
  end 
  cell 
  of 
  a 
  row 
  of 
  cells 
  formed 
  in 
  this 
  

   way 
  suggests 
  a 
  wedge-shaped 
  apical 
  cell, 
  cutting 
  off 
  segments 
  

   alternately 
  to 
  right 
  and 
  to 
  left. 
  The 
  process 
  is, 
  however, 
  too 
  

   variable 
  to 
  justify 
  the 
  conclusion 
  that 
  the 
  growth 
  of 
  adventitious 
  

   shoots 
  is 
  regularly 
  due 
  at 
  first 
  to 
  the 
  activity 
  of 
  such 
  an 
  apical 
  cell. 
  

  

  Figs. 
  i-6. 
  Single 
  involucral 
  cells 
  dividing 
  to 
  form 
  adventitious 
  shoots. 
  The 
  

   shading 
  indicates 
  the 
  extent 
  of 
  the 
  original 
  mother 
  cells, 
  the 
  darker 
  portions 
  repre- 
  

   senting 
  those 
  of 
  the 
  densest 
  contents. 
  FiG. 
  i. 
  Two 
  adjacent 
  mother 
  cells 
  at 
  an 
  

   early 
  stage 
  of 
  regeneration. 
  Figs. 
  2, 
  3. 
  The 
  young 
  shoots 
  beginning 
  to 
  project 
  

   above 
  the 
  surface 
  of 
  the 
  parent 
  tissue. 
  Fig. 
  4. 
  Shoot 
  arising 
  from 
  a 
  marginal 
  

   mother 
  cell. 
  Figs, 
  s* 
  6. 
  Shoots 
  arising 
  from 
  adjoining 
  marginal 
  mother 
  cells: 
  

   Xf 
  X, 
  adjacent 
  involucral 
  cells 
  also 
  dividing. 
  Figs. 
  1-4, 
  6, 
  X 
  150; 
  Fig. 
  5, 
  X 
  200. 
  

  

  As 
  cell 
  division 
  continues, 
  the 
  cell 
  mass 
  so 
  fofmed 
  begins 
  to 
  

   protrude 
  above 
  the 
  surface 
  of 
  the 
  parent 
  tissue 
  at 
  one 
  end 
  of 
  the 
  

   mother 
  cell 
  (Fig. 
  2). 
  This 
  seems 
  to 
  be 
  due 
  simply 
  to 
  a 
  bulging 
  

   up 
  of 
  the 
  mass 
  of 
  cells, 
  followed 
  by 
  cell 
  divisions 
  in 
  planes 
  more 
  

   or 
  less 
  nearly 
  parallel 
  to 
  the 
  surface 
  of 
  the 
  tissue 
  from 
  which 
  the 
  

   shoot 
  is 
  growing. 
  If 
  regeneration 
  occurs 
  from 
  the 
  margin 
  of 
  the 
  

   parent 
  tissue 
  instead 
  of 
  in 
  the 
  middle, 
  this 
  bulging 
  out 
  commonly 
  

   does 
  not 
  occur; 
  the 
  young 
  plant 
  grows 
  straight 
  out 
  from 
  the 
  

  

  portion 
  

  

  more 
  erect 
  position. 
  

  

  