﻿240 
  O'Neal: 
  Microsporogexesis 
  in 
  Datura 
  Stramonium 
  

  

  2. 
  Part 
  of 
  the 
  bivalent 
  chromosomes 
  are 
  cut 
  from 
  the 
  spirem 
  

   thread 
  as 
  loops, 
  which 
  if 
  twisted, 
  result 
  when 
  shortened 
  in 
  the 
  

   twisted 
  form 
  shown 
  in 
  the 
  figures; 
  if 
  the 
  ends 
  overlap, 
  or 
  unite, 
  

   the 
  ring-shaped 
  form 
  is 
  developed; 
  the 
  U-shaped 
  t^'pe 
  may 
  arise 
  

   from 
  a 
  loop 
  or 
  by 
  the 
  subsequent 
  bending 
  of 
  the 
  straight 
  part 
  of 
  

   the 
  thread. 
  

  

  \ 
  

  

  3^ 
  The 
  report 
  of 
  twelve 
  bivalents 
  made 
  by 
  Bonicke 
  is 
  con- 
  

   firmed. 
  

  

  4. 
  There 
  is 
  no 
  loss 
  of 
  the 
  individuality 
  of 
  the 
  chromosomes 
  

   from 
  the 
  time 
  that 
  they 
  are 
  cut 
  from 
  the 
  spirem 
  thread 
  till 
  the 
  

   telophase 
  of 
  the 
  second 
  division. 
  This 
  is 
  an 
  unusually 
  striking 
  

   phenomenon 
  in 
  Datura. 
  * 
  . 
  - 
  

  

  - 
  5. 
  The 
  exact 
  results 
  obtained 
  by 
  plant 
  breeders 
  from 
  this 
  plant 
  

   are 
  attributed 
  to 
  the 
  unusual 
  regularity 
  in 
  the 
  formation 
  and 
  

   behavior 
  of 
  the 
  chromosomes. 
  

  

  6. 
  No 
  physical 
  basis 
  for 
  the 
  Mendelian 
  characters 
  considered 
  

   can 
  be 
  found 
  in 
  the 
  chromosomes; 
  nor 
  is 
  any 
  cause 
  found 
  for 
  the 
  

   occurrence 
  of 
  mutants. 
  

  

  In 
  conclusion, 
  the 
  writer 
  

  

  expressing 
  his 
  very 
  great 
  obligation 
  to 
  Professor 
  D. 
  M. 
  Mottier, 
  

  

  m 
  

  

  of 
  Indiana 
  University, 
  under 
  whose 
  direction 
  this 
  work 
  was 
  brought 
  

   to 
  completion, 
  for 
  encouragement 
  and 
  valuable 
  aid 
  given; 
  and 
  to 
  

   the 
  board 
  of 
  trustees 
  of 
  the 
  Ohio 
  Wesleyan 
  University 
  for 
  a 
  relief 
  

   from 
  teaching 
  duties 
  that 
  has 
  made 
  possible 
  the 
  pursuance 
  of 
  this 
  

   investigation. 
  

  

  Indiana 
  University 
  

  

  Literature 
  cited 
  

  

  1. 
  Allen, 
  Charles 
  E. 
  The 
  basis 
  of 
  sex 
  inheritance 
  in 
  Sphaerocarpos. 
  

  

  Proc. 
  Am. 
  Phil. 
  Soc. 
  58: 
  289-316./. 
  7-27. 
  1919. 
  

  

  2. 
  Blakeslee, 
  A. 
  F., 
  & 
  Avery, 
  B. 
  T. 
  Aclzuki 
  beans 
  and 
  Jimson 
  weeds. 
  

  

  Jour, 
  Heredity 
  8: 
  125-133. 
  1917. 
  

  

  3. 
  Mutationsin 
  the 
  Jimson 
  weed. 
  Jour. 
  Heredity 
  10: 
  111-120. 
  

  

  1919. 
  

  

  4. 
  Bonicke, 
  L. 
  V- 
  Zur 
  Kenntniss 
  der 
  Prophasen 
  der 
  heterotypischen 
  

  

  Teilung 
  elmger 
  Pollenmutterzellen. 
  Ber. 
  Deuts. 
  Bot. 
  Ges. 
  

   29: 
  59-64. 
  1911. 
  

  

  5. 
  Coulter, 
  J. 
  M., 
  & 
  Chamberlain, 
  C, 
  J. 
  Morphology 
  of 
  angiosperms. 
  

  

  New 
  York. 
  1903. 
  

  

  