﻿Rickett: 
  Sphaerocarpos 
  Donnellii 
  349 
  

  

  had 
  developed 
  were 
  more 
  favorable. 
  In 
  the 
  cases 
  first 
  noted 
  

   the 
  young 
  plants 
  were 
  growing 
  among 
  older 
  plants, 
  which 
  over- 
  

   shadowed 
  them 
  to 
  a 
  large 
  extent, 
  and 
  the 
  elongated 
  ribbon 
  form 
  is 
  

   probably 
  a 
  resultant 
  of 
  these 
  conditions. 
  

  

  Regeneration 
  also 
  occurred 
  from 
  the 
  involucres 
  of 
  several 
  

   female 
  plants 
  which 
  were 
  being 
  cultivated 
  singly 
  on 
  soil. 
  Con- 
  

   ditions 
  here 
  were 
  such 
  as 
  to 
  produce 
  the 
  extreme 
  leafy 
  form 
  of 
  the 
  

   thallus 
  described 
  in 
  a 
  previous 
  paper 
  (5) 
  ; 
  as 
  the 
  posterior 
  part 
  of 
  

   the 
  thallus 
  died, 
  small 
  masses 
  of 
  cells 
  protruded 
  from 
  the 
  involucres 
  

   in 
  this 
  region 
  and 
  later 
  grew 
  out 
  into 
  young 
  thalli. 
  

  

  Attempts 
  were 
  made 
  to 
  induce 
  regeneration 
  by 
  artificial 
  

   means, 
  such 
  as 
  the 
  wounding 
  of 
  the 
  female 
  thalli. 
  In 
  cases 
  In 
  

   which 
  involucres 
  or 
  lobes 
  were 
  almost 
  or 
  completely 
  separated 
  

   from 
  the 
  plant 
  body, 
  regeneration 
  occurred 
  abundantly, 
  though 
  

   not 
  usually 
  at 
  points 
  show^Ing 
  any 
  definite 
  relation 
  to 
  the 
  cut 
  sur- 
  

   faces. 
  The 
  rest 
  of 
  the 
  plant 
  continued 
  to 
  grow 
  in 
  a 
  ^normal 
  

   manner, 
  although 
  occasionally 
  adventitious 
  shoots 
  w^ere 
  formed 
  

   on 
  the 
  midrib, 
  often 
  near 
  places 
  where 
  portions 
  had 
  been 
  cut 
  off. 
  

   I 
  have 
  never 
  observed 
  regenerated 
  shoots 
  to 
  arise 
  directly 
  from 
  

   one 
  of 
  the 
  w^ounded 
  surfaces. 
  Very 
  frequently 
  rhizolds 
  developed 
  

   from 
  the 
  cut 
  end 
  of 
  the 
  separated 
  portion 
  of 
  the 
  thallus; 
  these 
  

   appeared 
  without 
  any 
  spatial 
  relation 
  to 
  the 
  adventitious 
  shoots 
  

  

  r 
  

  

  and 
  sometimes 
  before 
  the 
  latter 
  became 
  evident. 
  

  

  Attempts 
  were 
  also 
  made, 
  in 
  every 
  case 
  unsuccessfully, 
  to 
  

   induce 
  regeneration, 
  using 
  the 
  same 
  or 
  similar 
  methods, 
  from 
  the 
  

   sex 
  organs, 
  and 
  also 
  from 
  young 
  sporophytes. 
  

  

  The 
  occurrence 
  of 
  regeneration 
  is 
  frequent 
  in 
  cultures, 
  espe- 
  

   cially 
  from 
  the 
  female 
  thalli, 
  and 
  seems 
  to 
  be 
  a 
  regular 
  method 
  of 
  

   vegetative 
  multiplication, 
  rather 
  than 
  merely 
  a 
  response 
  to 
  abnor- 
  

   mal 
  conditions. 
  After 
  the 
  development 
  of 
  sporophytes, 
  the 
  

   mother 
  plants 
  often 
  die 
  in 
  large 
  part, 
  and 
  growth 
  continues 
  after 
  

   a 
  time 
  by 
  means 
  of 
  regeneration 
  from 
  their 
  surviving 
  portions. 
  

   C. 
  Douin 
  (i), 
  describing 
  the 
  life 
  history 
  of 
  S. 
  Michelii 
  under 
  

   natural 
  conditions 
  in 
  Europe, 
  states 
  that 
  the 
  old 
  thalli 
  are 
  usually 
  

   buried 
  by 
  the 
  tilling, 
  and 
  that 
  the 
  spores 
  produced 
  on 
  these 
  plants 
  

   germinate 
  with 
  the 
  spring 
  rains. 
  If 
  regeneration 
  occurs 
  as 
  

   abundantly 
  under 
  natural 
  conditions 
  as 
  it 
  does 
  in 
  cultures, 
  it 
  

   „^ 
  — 
  ^ 
  ^^+ 
  ;r^r^/^ce;Ki<:. 
  tVi^t 
  f>ip 
  olrl 
  i-hplH 
  thus 
  burlcd 
  in 
  the 
  sonnc 
  

  

  