﻿Regeneration 
  in 
  Sphaerocarpos 
  Donnellii 
  

  

  H. 
  W. 
  RiCKETT 
  

  

  (with 
  twenty-five 
  text 
  figures) 
  

  

  Regeneration, 
  or 
  the 
  production 
  of 
  adventitious 
  shoots 
  from 
  

  

  F 
  

  

  the 
  vegetative 
  tissue, 
  has 
  been 
  described 
  in 
  Sphaerocarpos 
  by 
  

   Leitgeb 
  (4), 
  C, 
  and 
  R. 
  Douin 
  (2), 
  and 
  Goebel 
  (3). 
  Leitgeb 
  describes 
  

   regeneration 
  in 
  5, 
  MickeUi 
  Belh 
  (5, 
  terrestris 
  Sm) 
  as 
  occurring 
  

   from 
  both 
  the 
  lobes 
  and 
  the 
  midrib 
  of 
  the 
  thallus. 
  It 
  results 
  

   from 
  the 
  growth 
  of 
  a 
  single 
  cell 
  into 
  a 
  cylindrical 
  body, 
  whose 
  tip 
  

   gradually 
  broadens 
  out 
  and 
  becomes 
  flat, 
  forming 
  the 
  normal 
  

   plant 
  body. 
  As 
  in 
  the 
  case 
  of 
  sporelings, 
  sex 
  organs 
  are 
  formed 
  

   very 
  early 
  — 
  in 
  some 
  cases 
  before 
  the 
  young 
  shoot 
  has 
  assumed 
  

   the 
  flat 
  shape. 
  

  

  The 
  Douins 
  (2), 
  studying 
  5. 
  Michelii 
  and 
  S. 
  texanus 
  Aust. 
  

   (S. 
  calif 
  amicus 
  Aust.), 
  observed 
  regeneration 
  taking 
  place 
  from 
  

   the 
  midrib 
  and 
  from 
  the 
  involucres, 
  and 
  state 
  that 
  it 
  probably 
  

   occurs 
  also 
  from 
  the 
  lobes, 
  though 
  this 
  was 
  not 
  seen 
  by 
  them» 
  

   Regeneration 
  is 
  most 
  marked 
  in 
  connection 
  with 
  the 
  female 
  

   thalli. 
  When 
  these 
  are 
  destroyed 
  by 
  drought, 
  the 
  midrib 
  remains 
  

   alive 
  for 
  some 
  time, 
  and 
  if 
  a 
  period 
  of 
  humidity 
  follows, 
  each 
  fork 
  

   of 
  the 
  midrib 
  elongates, 
  forming 
  more 
  or 
  less 
  numerous 
  lobes 
  and 
  

   involucres. 
  Regeneration 
  also 
  occurs 
  from 
  the 
  involucres, 
  when 
  

   these 
  are 
  accidentally 
  bent 
  over 
  and 
  brought 
  into 
  contact 
  with 
  the 
  

   soil. 
  Certain 
  cells 
  of 
  the 
  involucre 
  in 
  these 
  cases 
  multiply 
  and 
  

   give 
  rise 
  to 
  new 
  thalli. 
  The 
  Douins* 
  figures 
  show 
  such 
  plants 
  

   arising 
  from 
  around 
  the 
  opening 
  of 
  the 
  involucre, 
  in 
  exactly 
  the 
  

   same 
  way 
  as 
  is 
  illustrated 
  in 
  my 
  FiG. 
  18. 
  The 
  regenerated 
  thalli 
  

   are 
  somewhat 
  different 
  from 
  the 
  old 
  ones, 
  especially 
  in 
  the 
  case 
  of 
  

   the 
  male, 
  showing 
  dorsal 
  lobes, 
  whose 
  form 
  leads 
  the 
  authors 
  to 
  

   conclude 
  that 
  they 
  are 
  modified 
  involucres. 
  

  

  Goebel 
  (3), 
  working 
  with 
  S. 
  Michelii 
  (possibly 
  mixed 
  with 
  

   S. 
  texanus, 
  if 
  the 
  latter 
  species 
  is 
  found 
  throughout 
  Europe 
  as 
  it 
  is 
  

   in 
  France), 
  found 
  that 
  regeneration 
  occurs 
  when 
  portions 
  of 
  the 
  

  

  347 
  

  

  