﻿232 
  O'Neal: 
  Microsporogexesis 
  

  

  r 
  

  

  additional 
  material 
  was 
  secured 
  and^ 
  the 
  study 
  of 
  the 
  problem 
  

   renewed, 
  

  

  MateriaL 
  — 
  The 
  191 
  5 
  collection 
  was 
  made 
  from 
  the 
  purple- 
  

   colored, 
  spiny-fruited 
  plants 
  found 
  growing 
  in 
  an 
  abandoned 
  

   barnyard 
  near 
  Delaware, 
  Ohio; 
  that 
  collected 
  in 
  1919 
  came 
  from 
  

   plants 
  growing 
  on 
  the 
  Indiana 
  University 
  campus 
  and 
  in 
  a 
  neigh- 
  

   boring 
  garden. 
  The 
  plants 
  from 
  both 
  of 
  the 
  latter 
  places 
  were 
  

   from 
  seed 
  furnished 
  by 
  A. 
  F. 
  Blakeslee, 
  Those 
  in 
  the 
  garden 
  

   plot 
  were 
  known 
  to 
  be 
  homozygous 
  for 
  the, 
  dominant 
  characters, 
  

   purple 
  color 
  and 
  spiny 
  fruit. 
  The 
  plants 
  on 
  the 
  campus 
  had 
  come 
  

   about 
  through 
  a 
  series 
  of, 
  rather 
  indiscriminate 
  crosses 
  between 
  

   the 
  purple, 
  spiny-fruited 
  type 
  and 
  the 
  green, 
  smooth-fruited 
  

   plants 
  described 
  by 
  Blakeslee 
  (2). 
  In 
  making 
  collections 
  from 
  

   this 
  plot 
  care 
  was 
  taken 
  to 
  select 
  flowers 
  from 
  plants 
  showing 
  the 
  

   two 
  dominant 
  characters, 
  but 
  since 
  the 
  ancestry 
  was 
  not 
  definitely 
  

   known, 
  some 
  anthers 
  used 
  may 
  have 
  been 
  taken 
  from 
  heterozygous 
  

   plants. 
  A 
  careful 
  consideration 
  of 
  the 
  stained 
  cells 
  from 
  the 
  

   three 
  sources 
  failed 
  to 
  show 
  any 
  appreciable 
  distinction 
  and 
  no 
  

   attempt 
  was 
  made 
  to 
  keep 
  the 
  preparations 
  separate, 
  buf 
  most 
  of 
  

   the 
  work 
  was 
  done 
  with 
  the 
  Blakeslee 
  strain. 
  

  

  Method. 
  — 
  Parts 
  of 
  the 
  corollas 
  bearing 
  stamens 
  with 
  anthers 
  

   in 
  various 
  stages 
  of 
  development 
  were 
  killed 
  in 
  the 
  chromo-osmo- 
  

   acetic 
  and 
  chromo-acetic 
  solutions, 
  washed, 
  dehydrated, 
  embedded 
  

   in 
  paraffin, 
  and 
  cut 
  into 
  sections 
  3-5 
  m 
  thick. 
  The 
  killing 
  fluid 
  

   containing 
  osmium 
  gave 
  uniformly 
  better 
  fixation 
  and, 
  in 
  the 
  

   latter 
  part 
  of 
  the 
  work, 
  its 
  use 
  was 
  adhered 
  to 
  strictly. 
  Haiden- 
  

   hain's 
  haematoxylin 
  and 
  the 
  modified 
  triple 
  stain 
  were 
  used. 
  

   The 
  orange 
  G 
  of 
  the 
  latter 
  combination 
  was 
  used 
  in 
  clove 
  oil 
  as 
  

   recommended 
  by 
  Chamberlain 
  and 
  others. 
  

  

  Adaptability 
  of 
  material, 
  — 
  ^The 
  pollen 
  mother 
  cells 
  of 
  Datura 
  

  

  h 
  

  

  offer 
  fair 
  conditions 
  for 
  cytological 
  investigation. 
  Since 
  the 
  

  

  F 
  

  

  anthers 
  in 
  a 
  bud 
  mature 
  their 
  pollen 
  simultaneously, 
  it 
  is 
  necessary 
  

   to 
  examine 
  a 
  large 
  number 
  to 
  secure 
  the 
  various 
  stages. 
  Some 
  

   difficulty 
  is 
  attached 
  to 
  the 
  removal 
  of 
  the 
  young 
  cells 
  for 
  the 
  

   preliminar>- 
  examination. 
  This 
  probably 
  explains 
  why 
  they 
  have 
  

  

  ned 
  cytologically 
  before. 
  The 
  sporogenous 
  cells 
  

  

  exam 
  

  

  very 
  

  

  material 
  is 
  fairiy 
  abundant 
  for 
  a 
  dicotyledonous 
  plant. 
  Com- 
  

  

  