﻿Farr: 
  Pollen-mother-cell 
  of 
  Cobaea 
  scaxdens 
  alba 
  327 
  

  

  Lawson 
  (1898) 
  in 
  Cobaea; 
  Tischler 
  (1906) 
  in 
  Bryonia 
  and 
  Ribes; 
  

   the 
  same 
  author 
  (1908) 
  in 
  Podophyllum; 
  and 
  Johnson* 
  (1914) 
  in 
  

   P^^^rc^m/a, 
  [indicated 
  by 
  their 
  figures 
  a 
  type 
  of 
  division 
  dififering 
  

  

  L 
  

  

  from 
  that 
  In 
  which 
  cell-plates 
  are 
  formed. 
  In 
  every 
  instance, 
  how- 
  

   ever, 
  the 
  statement 
  was 
  made 
  that 
  cell-plates 
  were 
  formed. 
  

  

  Miss 
  Nichols 
  (1908) 
  in 
  her 
  study 
  of 
  Sarracenia 
  reported 
  a 
  

   process 
  of 
  division 
  by 
  constriction 
  of 
  the 
  protoplast, 
  but 
  gave 
  no 
  

   figures 
  to 
  support 
  the 
  idea, 
  

  

  Andrews 
  (1901) 
  reported 
  a 
  combination 
  of 
  cell-plates 
  and 
  fur- 
  

   rowing 
  in 
  the 
  division 
  of 
  the 
  pollen-mother-cells 
  of 
  Magnolia, 
  

   No 
  details 
  of 
  the 
  process 
  were 
  discussed. 
  

  

  The 
  early 
  studies 
  of 
  Wimmel 
  (1850) 
  upon 
  Althaea 
  and 
  of 
  Hof- 
  

   meister 
  (1867) 
  upon 
  Pa55t/?ora 
  indicate, 
  in 
  the 
  light 
  of 
  the 
  recent 
  

   study 
  by 
  C. 
  H. 
  Farr, 
  a 
  grasp 
  of 
  the 
  essentials 
  of 
  the 
  furrowing 
  

   process. 
  Perhaps 
  the 
  lack 
  of 
  detail 
  In 
  their 
  presentations, 
  fol- 
  

   lowed 
  by 
  the 
  launching 
  of 
  the 
  more 
  carefully 
  established 
  cell-plate 
  

   theory, 
  accounted 
  for 
  the 
  lack 
  of 
  recognition 
  of 
  furrowing 
  as 
  a 
  

   distinct 
  type 
  of 
  pollen-mother-cell 
  division. 
  Special 
  mention 
  is 
  

   also 
  due 
  Cannon 
  and 
  Miss 
  Digby, 
  who 
  discussed 
  and 
  figured 
  

   constriction 
  furrows 
  but 
  failed 
  to 
  report 
  the 
  absence 
  of 
  cell-plates; 
  

   to 
  say 
  nothing 
  of 
  the 
  large 
  group 
  of 
  Investigators 
  whose 
  figures 
  

   Indicate 
  the 
  absence 
  of 
  a 
  cell-plate, 
  but 
  who 
  do 
  not 
  commit 
  them- 
  

   selves 
  concerning 
  the 
  nature 
  of 
  the 
  division. 
  

  

  Such 
  fragmentary 
  and 
  contradictory 
  evidence, 
  however, 
  had 
  

   resulted 
  in 
  leaving 
  the 
  general 
  impression 
  that 
  quadripartltion 
  in 
  

   dicotyledons 
  was 
  accompanied 
  by 
  the 
  formation 
  of 
  cell-plates. 
  

   It 
  remained 
  for 
  the 
  presentation 
  of 
  a 
  more 
  complete 
  series 
  of 
  

   stages 
  from 
  the 
  dividing 
  pollen-mother-cells 
  of 
  Nicoiiana 
  Tabacum, 
  

   as 
  presented 
  in 
  C. 
  H. 
  Farr's 
  paper, 
  to 
  clearly 
  establish 
  the 
  process 
  

   of 
  quadripartition 
  by 
  furrowing. 
  It 
  is 
  there 
  shown 
  that 
  the 
  nuclei 
  

   of 
  the 
  polIen-mother-cells 
  enlarge 
  during 
  pre-synapsis 
  and 
  synapsis 
  ; 
  

   that 
  a 
  thickening 
  of 
  the 
  mother 
  wall 
  also 
  begins 
  during 
  synap- 
  

   sis 
  and 
  continues 
  throughout 
  the 
  nuclear 
  divisions; 
  and 
  that 
  no 
  

   cytoplasmic 
  division 
  occurs 
  after 
  the 
  first 
  nuclear 
  division. 
  Dur- 
  

   ing 
  the 
  metaphases 
  of 
  the 
  homoeotypic 
  division 
  the 
  remaining 
  

  

  Johnson. 
  D. 
  S. 
  Studies 
  of 
  the 
  development 
  of 
  the 
  Piperaceae.— 
  II. 
  The 
  

   structure 
  and 
  development 
  of 
  Peperomia 
  hispidula. 
  Amer. 
  Joun 
  Bot. 
  I; 
  323~339- 
  

   ph 
  36-38. 
  1914. 
  Other 
  references 
  to 
  the 
  papers 
  here 
  cited 
  are 
  given 
  by 
  C. 
  H. 
  Farr, 
  

  

  