﻿234 
  O^Neal: 
  Microsporogexesis 
  in 
  Datura 
  Stramonium 
  

  

  berlain, 
  5); 
  this 
  accounts 
  for 
  their 
  comparatively 
  small 
  number. 
  

   In 
  the 
  resting 
  stage 
  they 
  are 
  about 
  25 
  n 
  in 
  diameter 
  and 
  have 
  

   large 
  prominent 
  nuclei. 
  The 
  cytoplasm 
  is 
  very 
  dense 
  and 
  in 
  the 
  

   stained 
  preparations 
  seems 
  to 
  be 
  composed 
  of 
  minute 
  particles 
  

   closely 
  placed. 
  As 
  development 
  proceeds 
  these 
  particles 
  become 
  

   more 
  or 
  less 
  clumped 
  and 
  arranged 
  in 
  strands 
  as 
  shown 
  in 
  the 
  

   figures. 
  No 
  evidence 
  of 
  mitochondria 
  or 
  other 
  extra-nuclear 
  

   bodies 
  was 
  found, 
  but 
  it 
  is 
  not 
  doubted 
  that 
  such 
  might 
  be 
  revealed 
  

   if 
  proper 
  fixing 
  and 
  staining 
  methods 
  were 
  used. 
  

  

  Nucleus, 
  — 
  In 
  the 
  so-called 
  resting 
  stage 
  the 
  nucleus 
  has 
  a 
  

   diameter 
  about 
  two 
  thirds 
  that 
  of 
  the 
  containing 
  cell. 
  It 
  usually 
  

   has 
  a 
  single 
  darkly 
  staining 
  nucleolus, 
  but 
  occasionally 
  tAVO 
  are 
  

   found. 
  The 
  linin 
  reticulum 
  is 
  composed 
  of 
  very 
  delicate 
  fibers 
  

   upon 
  which 
  the 
  chromatin 
  material 
  is 
  arranged 
  in 
  the 
  form 
  of 
  

   minute 
  bodies" 
  (Fig. 
  i). 
  In 
  the 
  preparations 
  the 
  threads 
  arc 
  

   * 
  sometimes 
  broken 
  or 
  else 
  do 
  not 
  take 
  the 
  stain 
  properly, 
  but 
  there 
  

   seems 
  to 
  be 
  no 
  regular 
  arrangement 
  of 
  either 
  the 
  threads 
  or 
  the 
  

   chromatin 
  bodies 
  upon 
  them. 
  The 
  material 
  collected 
  was 
  too 
  

   far 
  advanced 
  to 
  show 
  the 
  telophase 
  of 
  the 
  preceding 
  division, 
  but 
  

  

  to 
  all 
  appearances 
  the 
  chromosomes 
  of 
  this 
  phase 
  lose 
  their 
  indi- 
  

   viduality 
  in 
  the 
  maze 
  of 
  fibers 
  and 
  very 
  small 
  arid 
  numerous 
  

   granules 
  seen 
  in 
  the 
  resting 
  stage. 
  It 
  would 
  seem 
  impossible 
  to 
  

   trace 
  a 
  definite 
  set 
  of 
  these 
  fibers 
  and 
  chromatin 
  masses 
  to 
  a 
  

   particular 
  chromosome, 
  as 
  Nothnagel 
  (11) 
  was 
  able 
  to 
  do 
  in 
  the 
  

   case 
  of 
  Allium. 
  

  

  REST 
  IN 
  

  

  ■ 
  

  

  The 
  synaptic 
  condition 
  Is 
  reached 
  while 
  the 
  anthers 
  are 
  still 
  

   quite 
  young 
  (Fig. 
  4). 
  The 
  initiation 
  of 
  this 
  stage 
  is 
  marked 
  by 
  a 
  

   thickening 
  and 
  consequent 
  contraction 
  of 
  the 
  linin 
  threads 
  (Fig. 
  2), 
  

   which 
  when 
  continued 
  results 
  in 
  their 
  withdrawal 
  from 
  the 
  peri- 
  

   phery 
  of 
  the 
  nucleus 
  as 
  shown 
  in 
  Fig. 
  3; 
  Before 
  the 
  thickening 
  

   has 
  proceeded 
  far 
  t|ie 
  threads 
  stain 
  readily 
  and 
  their 
  ramifications 
  

   may 
  be 
  made 
  out 
  easily. 
  The 
  ^tage 
  represented 
  by 
  Fig. 
  2 
  was 
  

   studied 
  carefully 
  for 
  evidence 
  of 
  the 
  two 
  spirem 
  threads 
  reported 
  

   by 
  Bonicke 
  (4) 
  for 
  this 
  plant. 
  It 
  wnll 
  be 
  noticed 
  that 
  the 
  threads 
  

   apparently 
  anastomose 
  freely 
  and 
  occasionally 
  approximate 
  as 
  

   shown 
  in 
  the 
  jniddle 
  of 
  the 
  figure. 
  Whether 
  or 
  not 
  the 
  two 
  ap- 
  

  

  