﻿Stork: 
  Studies 
  in 
  the 
  genus 
  Taraxacum 
  209 
  

  

  w 
  

  

  .over 
  the 
  entire 
  spindle 
  (Fig. 
  14) 
  but 
  soon 
  move 
  toward 
  the 
  equa- 
  

  

  orde 
  

  

  ^3f 
  15 
  ^^d 
  16). 
  Meantime 
  the 
  spindle 
  shortens 
  somewhat 
  and 
  

   has 
  all 
  the 
  appearance 
  of 
  a 
  spindle 
  in 
  a 
  vegetative 
  cell. 
  In 
  fact, 
  

   It 
  is 
  frequently 
  possible 
  to 
  compare 
  it 
  with 
  a 
  spindle 
  in 
  the 
  vegeta- 
  

   tive 
  tissue 
  of 
  the 
  ovule 
  In 
  the 
  same 
  preparation 
  and, 
  except 
  for 
  the 
  

  

  somewhat 
  smaller 
  size 
  of 
  the 
  latter, 
  no 
  difference 
  Is 
  to 
  he 
  nbserved. 
  

  

  romosomes 
  

  

  is 
  quickly 
  completed. 
  Fig. 
  17 
  represents 
  the 
  completed 
  division. 
  

   In 
  the 
  daughter 
  nuclei 
  the 
  chromatin 
  becomes 
  arranged 
  Into 
  an 
  

   Indefinite 
  network, 
  but 
  the 
  chromosomes 
  do 
  not 
  immediately 
  lose 
  

   their 
  identity 
  in 
  this 
  network 
  but 
  remain 
  as 
  irregular 
  enlarge- 
  

  

  ments 
  

  

  gra 
  

  

  No 
  second 
  division 
  takes 
  place 
  to 
  form 
  a 
  tetrad. 
  The 
  chalazal 
  

   daughter 
  cell 
  quickly 
  enlarges 
  to 
  form 
  the 
  mother-cell 
  of 
  the 
  

   embryo-sac 
  while 
  its 
  sister 
  cell 
  degenerates 
  and 
  is 
  crowded 
  into 
  a 
  

   gelatinous 
  cap* 
  (Figs. 
  19 
  and 
  20). 
  At 
  this 
  stage 
  the 
  pollen 
  In 
  the 
  

   same 
  flower 
  Is 
  mature, 
  but 
  the 
  loculi 
  are 
  still 
  unopened. 
  

  

  A 
  single 
  division 
  of 
  the 
  megaspore-mother-cell 
  takes 
  place 
  

   also 
  in 
  T. 
  vulgare, 
  and 
  the 
  same 
  condition 
  has 
  been 
  reported 
  in 
  

   the 
  ooapogamous 
  T. 
  albidum 
  by 
  Osawa 
  (6) 
  ; 
  the 
  sexual 
  species, 
  

   however, 
  T. 
  platycarpum 
  (6) 
  Osawa, 
  and 
  T. 
  confertum 
  (Rosenberg, 
  

   9), 
  show 
  two 
  divisions 
  to 
  produce 
  tetraspores. 
  From 
  this 
  it 
  

   appears 
  that 
  with 
  the 
  loss 
  of 
  sexuality 
  has 
  gone 
  the 
  loss 
  of 
  one 
  of 
  

   the 
  divisions 
  of 
  the 
  megaspore-mother 
  cell. 
  

  

  Material 
  was 
  fixed 
  principally 
  In 
  Flemming's 
  medium 
  solution 
  

   and 
  stained 
  with 
  Flemmlng's 
  triple 
  stain, 
  as 
  used 
  in 
  Mottler's 
  

   laboratory, 
  though 
  Haldenheln's 
  haematoxylin 
  method 
  was 
  also 
  

   used. 
  The 
  use 
  of 
  turpentine, 
  as 
  recommended 
  by 
  Professor 
  

   Mottler 
  for 
  bleaching 
  after 
  osmium 
  fixers, 
  was 
  found 
  almost 
  

   indispensable 
  In 
  gaining 
  clear 
  preparations. 
  My 
  best 
  thanks 
  are 
  

  

  ) 
  Professor 
  Mottle 
  

  

  Cornell 
  University. 
  

  

  Literature 
  cited 
  

  

  1. 
  Beer, 
  R. 
  Studies 
  in 
  spore 
  development. 
  11. 
  On 
  the 
  structure 
  

  

  and 
  division 
  of 
  the 
  nuclei 
  in 
  the 
  Compositac. 
  Ann. 
  Bot. 
  26: 
  

  

  705-726. 
  pL 
  66, 
  67. 
  1912. 
  

  

  2. 
  Dahlstedt, 
  H. 
  Ueber 
  einige 
  im 
  bergianischen 
  Garten 
  kultivierten 
  

  

  Taraxaca, 
  

  

  -f 
  /. 
  1-8, 
  1907 
  

  

  