﻿326 
  Farr: 
  Pollex-mother-cell 
  of 
  Cobaea 
  scaxdens 
  alba 
  

  

  but 
  by 
  a 
  process 
  which 
  '* 
  involves 
  the 
  furrowing 
  of 
  the 
  protoplast 
  

   in 
  the 
  plane 
  midway 
  between 
  the 
  nuclei/' 
  • 
  

  

  ted 
  

  

  of 
  dicotyledons 
  formed 
  their 
  microspores 
  by 
  quadripartition. 
  

   Concerning 
  the 
  details 
  of 
  the 
  process 
  the 
  literature 
  is 
  somewhat 
  

  

  summary 
  

  

  Tuel 
  

  

  MirahiUs 
  

  

  stated 
  definitely 
  that 
  cell-plates 
  were 
  formed, 
  but 
  they 
  furnished 
  

   no 
  details 
  of 
  the 
  process 
  and 
  no 
  figures 
  to 
  illustrate 
  it. 
  

  

  Baranetsky 
  (1880) 
  in 
  his 
  study 
  of 
  Lathynis, 
  Hesperis, 
  and 
  

   Ipomoea, 
  was 
  unable 
  to 
  find 
  cell-plates. 
  His 
  figures 
  show 
  an 
  incip- 
  

   ient 
  furrowing 
  of 
  the 
  protoplasts, 
  but 
  he 
  made 
  no 
  comment 
  upon 
  

   this 
  fact. 
  

  

  Rosanoff 
  (1865) 
  in 
  Acacia; 
  Ishikawa 
  (191 
  1) 
  in 
  Dahlia; 
  Osawa 
  

   (1913) 
  in 
  Taraxacum; 
  Miss 
  Pace 
  (1912) 
  in 
  Parnassia; 
  Shoemaker 
  

   (1905) 
  in 
  Hamamelis; 
  Miss 
  Fraser 
  (1914) 
  in 
  Vicia; 
  and 
  Beer 
  

   (1912) 
  in 
  Crepis, 
  indicated 
  in 
  their 
  drawings 
  the 
  absence 
  of 
  cell- 
  

   plates 
  during 
  cell-division. 
  These 
  authors 
  do 
  not 
  discuss 
  the 
  

   possibility 
  of 
  cell-division 
  by 
  any 
  other 
  process. 
  

  

  Pringsheim 
  (1859) 
  in 
  the 
  study 
  of 
  Dahlia; 
  Rosenberg 
  (1907) 
  in 
  

   Hieracitim; 
  and 
  Guignard 
  (1897) 
  in 
  Magnolia, 
  likened 
  these 
  

   forms, 
  in 
  their 
  method 
  of 
  division, 
  to 
  other 
  forms 
  in 
  w^hich 
  the 
  

   process 
  involved 
  had 
  not 
  been 
  clearly 
  established. 
  

  

  Miss 
  Digby 
  (1912) 
  in 
  the 
  study 
  oi 
  Primula, 
  and 
  Cannon 
  (1903) 
  

   in 
  cotton, 
  discussed 
  and 
  figured 
  the 
  constriction 
  of 
  the 
  pollen- 
  

   mother-cells 
  but 
  failed 
  to 
  state 
  whether 
  or 
  not 
  cell-plates 
  were 
  

   formed. 
  

  

  A 
  difference 
  of 
  opinion 
  arose 
  concerning 
  the 
  process 
  of 
  division 
  

   in 
  the 
  pollen-mother-cells 
  of 
  Althaea, 
  Wimmel 
  (1850) 
  reported 
  

   cell-plates; 
  von 
  Mohl 
  (1853), 
  a 
  combination 
  of 
  cell-plates 
  and 
  fur- 
  

   rowing; 
  and 
  Pringsheim 
  (1854) 
  reported 
  furrowing. 
  The 
  asser- 
  

   tions 
  again 
  lack 
  the 
  necessarj^ 
  background 
  of 
  detail. 
  

  

  Gates. 
  (1907) 
  showed 
  a 
  cell-plate 
  in 
  a 
  diagram 
  of 
  a 
  pollen- 
  

   mother-cell 
  of 
  Oenothera. 
  It 
  is 
  accompanied 
  by 
  no 
  explanation 
  of 
  

   the 
  process. 
  

  

  Naegeli 
  (1842) 
  in 
  Oenothera, 
  Bryonia, 
  and 
  Cticurbita 
  Pepo; 
  

   Sachs 
  (1872) 
  in 
  Tropaeolum; 
  Strasburger 
  (1873) 
  in 
  Tropaeolum; 
  

  

  \ 
  

  

  