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  Rickett; 
  Sphaerocarpos 
  Doxxellii 
  

  

  ma}'- 
  continue 
  their 
  growth 
  by 
  the 
  production 
  of 
  adventitious 
  

   shoots. 
  

  

  My 
  observations 
  seem 
  to 
  warrant 
  the 
  conclusion 
  that 
  regen- 
  

   eration 
  IS 
  a 
  rather 
  common 
  phenomenon 
  in 
  Sphaerocarpos, 
  resulting 
  

   from 
  particular 
  nutritive 
  conditions 
  in 
  the 
  thalli 
  or 
  in 
  parts 
  of 
  

   the 
  thalli, 
  rather 
  than 
  merely 
  from 
  a 
  direct 
  response 
  to 
  occasional 
  

   accidental 
  stimuli. 
  

  

  The 
  descriptions 
  that 
  follow 
  are 
  based 
  on 
  data 
  obtained 
  from 
  

   female 
  plants, 
  these 
  being 
  more 
  abundant 
  and 
  more 
  convenient 
  

   for 
  study 
  than 
  the 
  male. 
  In 
  a 
  few 
  male 
  plants 
  that 
  were 
  studied, 
  

   the 
  phenomena 
  observed 
  were 
  similar 
  to 
  those 
  here 
  described. 
  

   The 
  plants 
  produced 
  by 
  regeneration 
  were 
  in 
  all 
  cases 
  of 
  the 
  same 
  

   sex 
  as 
  the 
  parent 
  plant. 
  Several 
  cultures 
  of 
  female 
  plants, 
  w^hich 
  

   were 
  started 
  by 
  sowing 
  involucres 
  separated 
  from 
  the 
  thalli, 
  on 
  

   soil, 
  are 
  still 
  growing 
  vigorously 
  at 
  the 
  present 
  time, 
  nearly 
  twelve 
  

   months 
  afterwards, 
  and 
  are 
  still 
  purely 
  female. 
  

  

  In 
  order 
  to 
  study 
  in 
  detail 
  the 
  method 
  of 
  formation 
  of 
  the 
  

   adventitious 
  shoots, 
  involucres, 
  lobes, 
  and 
  small 
  portions 
  of 
  the 
  

   midrib 
  were 
  cut 
  off 
  and 
  placed 
  on 
  moist 
  filter 
  paper 
  in 
  petri 
  dishes. 
  

   At 
  the 
  end 
  of 
  two 
  w^eeks 
  or 
  thereabouts 
  (in 
  one 
  case 
  after 
  six 
  days), 
  

   these 
  small 
  pieces 
  of 
  tissue 
  were 
  covered 
  with 
  outgrowths 
  in 
  

   various 
  stages 
  of 
  development. 
  They 
  were 
  then 
  removed, 
  killed 
  

   by 
  placing 
  In 
  a 
  dilute 
  solution 
  of 
  chrom-acetic 
  acid 
  (chromic 
  acid, 
  

   0-3 
  g-; 
  glacial 
  acetic 
  acid, 
  0.7 
  cc; 
  distilled 
  water, 
  99 
  cc), 
  stained 
  

   in 
  eosin, 
  and 
  mounted 
  in 
  glycerin. 
  

  

  When 
  regeneration 
  is 
  about 
  to 
  occur, 
  the 
  contents 
  of 
  a 
  single 
  

   cell 
  become 
  more 
  dense 
  and 
  richer 
  in 
  chlorophyll 
  content. 
  Such 
  a 
  

   cell 
  may 
  be 
  isolated, 
  or 
  there 
  may 
  be 
  a 
  group 
  of 
  similar 
  cells 
  

   adjoining 
  or 
  In 
  close 
  proximity 
  to 
  one 
  another. 
  Cell 
  division 
  

   then 
  occurs, 
  without 
  an 
  accompanying 
  growth 
  of 
  the 
  mother 
  cell. 
  

   The 
  relative 
  position 
  of 
  the 
  walls 
  formed 
  in 
  these 
  divisions 
  is 
  

   quite 
  variable. 
  Figs, 
  i, 
  2, 
  3, 
  4, 
  13, 
  and 
  14 
  represent 
  groups 
  of 
  

   cells 
  formed 
  in 
  this 
  way- 
  It 
  makes 
  no 
  particular 
  difference 
  

   whether 
  the 
  original 
  cell 
  was 
  on 
  the 
  edge 
  or 
  in 
  the 
  middle 
  of 
  the 
  

   tissue 
  of 
  the 
  parent 
  plant, 
  nor 
  does 
  its 
  size 
  or 
  shape 
  have 
  any 
  

   influence 
  on 
  the 
  course 
  of 
  development. 
  Very 
  commonly, 
  indeed 
  

   in 
  the 
  majority 
  of 
  cases, 
  the 
  walls 
  are 
  set 
  in 
  at 
  acute 
  angles 
  to 
  

   each 
  other, 
  and 
  in 
  the 
  case 
  of 
  the 
  involucral 
  cells 
  these 
  divisions 
  

  

  