﻿CHROMOSOMES 
  OF 
  TEADESCANTIA 
  VIKGINICA. 
  559 
  

  

  On 
  the 
  Structure 
  and 
  Development 
  of 
  the 
  

   Somatic 
  and 
  Heterotype 
  Chromosomes 
  

   of 
  Tradescantia 
  Virginica. 
  

  

  By 
  

  

  J. 
  B. 
  Farmer, 
  F.K.S., 
  and 
  Dorothy 
  Sliovc. 
  

  

  With 
  Plates 
  42 
  and 
  43. 
  

  

  The 
  object 
  of 
  this 
  paper 
  is 
  to 
  attempt 
  to 
  elucidate 
  the 
  

   series 
  of 
  changes 
  that 
  occur 
  during 
  the 
  evolution 
  of 
  the 
  

   chromosomes 
  from 
  the 
  resting 
  nucleus. 
  We 
  have 
  expressly 
  

   excluded 
  all 
  matter 
  relating 
  to 
  the 
  formation 
  of 
  the 
  spindle, 
  

   the 
  cell 
  wall, 
  and 
  other 
  irrelevant 
  structures 
  from 
  our 
  account. 
  

  

  I. 
  Somatic 
  Mitoses. 
  

  

  Tradescantia 
  virginica 
  has 
  proved 
  a 
  more 
  suitable 
  

   object 
  for 
  cytological 
  study 
  than 
  might 
  have 
  been 
  anticipated 
  

   from 
  the 
  known 
  difficulties 
  it 
  presents 
  in 
  the 
  way 
  of 
  good 
  

   fixation 
  of 
  the 
  cell 
  contents. 
  This 
  difficulty 
  has 
  been 
  experi- 
  

   enced 
  by 
  others 
  as 
  well 
  as 
  by 
  ourselves. 
  Thus 
  Strasburger 
  

   has 
  commented 
  upon 
  the 
  tendency 
  of 
  the 
  nuclear 
  contents 
  to 
  

   assume 
  a 
  condition 
  during 
  the 
  prophase 
  of 
  the 
  heterotype 
  

   mitosis 
  that 
  obscures 
  all 
  the 
  finer 
  details 
  of 
  structure. 
  

   We 
  have 
  found 
  that 
  Flemming's 
  strong 
  solution 
  and 
  

   Hermann's 
  fixative 
  give 
  fair 
  results 
  when 
  allowed 
  to 
  act 
  

   for 
  a 
  long 
  time, 
  aiid 
  the 
  tissues 
  are 
  carefully 
  washed 
  and 
  de- 
  

   hydrated 
  afterwards. 
  But 
  on 
  the 
  whole 
  the 
  best 
  material 
  

   was 
  yielded 
  after 
  fixing 
  with 
  a 
  mixture 
  of 
  absolute 
  alcohol 
  

   and 
  glacial 
  acetic 
  acid 
  in 
  the 
  proportions 
  of 
  2:1. 
  The 
  fixa- 
  

  

  