﻿560 
  J. 
  B. 
  FAEMEK 
  AND 
  L). 
  SHOVK. 
  

  

  tive 
  was 
  allowed 
  to 
  act 
  for 
  15 
  — 
  20 
  minutes^ 
  and 
  the 
  tissues 
  

   were 
  then 
  thoroughly 
  Avashed 
  with 
  absolute 
  alcohol, 
  and 
  then 
  

   embedded 
  as 
  rapidly 
  as 
  possible 
  by 
  the 
  usual 
  methods. 
  

  

  We 
  made 
  a 
  study 
  of 
  the 
  cells 
  of 
  the 
  root, 
  in 
  order 
  to 
  follow 
  

   out 
  the 
  changes 
  in 
  the 
  divisions 
  of 
  vegetative 
  tissues. 
  For 
  

   this 
  purpose 
  plants 
  were 
  potted, 
  and 
  gently 
  forced 
  till 
  they 
  

   provided 
  a 
  plentiful 
  crop 
  of 
  young 
  roots. 
  

  

  While 
  the 
  nucleus 
  is 
  the 
  resting 
  state 
  the 
  chromatin 
  is 
  

   fairly 
  evenly 
  distributed 
  throughout 
  its 
  substance, 
  and 
  there 
  

   is 
  a 
  large 
  nucleolus, 
  often 
  excentrically 
  situated. 
  The 
  first 
  

   signs 
  of 
  approaching 
  mitosis 
  is 
  seen 
  in 
  a 
  tendency 
  on 
  the 
  part 
  

   of 
  the 
  chromatin 
  to 
  aggregate 
  into 
  broad 
  band-like 
  areas, 
  

   between 
  which 
  are 
  left 
  comparatively 
  clear 
  spaces. 
  The 
  

   nucleolus 
  becomes 
  replaced 
  by 
  a 
  number 
  of 
  denser 
  nucleoli 
  

   which 
  lie 
  in 
  close 
  juxtaposition 
  to 
  the 
  bands, 
  though 
  they 
  are 
  

   not 
  arranged 
  in 
  any 
  very 
  definite 
  order. 
  

  

  The 
  band-like 
  agglomerations 
  of 
  chromatin, 
  when 
  they 
  first 
  

   make 
  their 
  appearance, 
  are 
  not 
  distributed 
  throughout 
  the 
  

   nucleus, 
  but 
  are 
  commonly 
  visible 
  in 
  one 
  region, 
  whilst 
  they 
  

   fade 
  away 
  in 
  another 
  into 
  the 
  homogeneous 
  granular 
  arrange- 
  

   ment 
  characteristic 
  of 
  the 
  resting 
  nucleus. 
  

  

  It 
  is 
  important 
  to 
  notice 
  that 
  when 
  a 
  baud 
  is 
  carefully 
  

   examined 
  the 
  chromatin 
  is 
  seen 
  to 
  merely 
  represent 
  a 
  closer 
  

   and 
  denser 
  granular 
  aggregation.^ 
  It 
  is 
  only 
  at 
  a 
  much 
  later 
  

   stage 
  that 
  the 
  spireme, 
  with 
  its 
  single 
  row 
  of 
  granules 
  is 
  

   formed. 
  The 
  contraction 
  of 
  the 
  bands 
  soon 
  follows, 
  and 
  a 
  

   reticulum, 
  as 
  shown 
  in 
  figs. 
  2 
  and 
  2a, 
  is 
  the 
  result. 
  The 
  

   separate 
  granules 
  have 
  now 
  disappeared, 
  and 
  the 
  chromatic 
  

   reticulum 
  appears 
  merely 
  to 
  be 
  rather 
  irregular 
  in 
  thickness, 
  

   and 
  it 
  readily 
  takes 
  the 
  ordinary 
  basic 
  dyes. 
  The 
  next 
  stage 
  

   is 
  marked 
  by 
  the 
  more 
  definite 
  appearance 
  of 
  a 
  spireme. 
  This 
  

   seems 
  to 
  be 
  formed 
  by 
  the 
  gradual 
  breaking 
  doAvn 
  of 
  the 
  

   original 
  points 
  of 
  anastomosis, 
  and 
  the 
  consequent 
  restriction 
  

   of 
  the 
  chromatin 
  to 
  a 
  linear 
  arrangement. 
  

  

  It 
  is 
  excessively 
  difiicult 
  to 
  ascertain 
  whether 
  a 
  continuous 
  

  

  * 
  Gregoire 
  and 
  Wygaerts 
  (' 
  Beiliefie 
  z. 
  Bot. 
  Centralbl./ 
  xiv) 
  Lave 
  observed 
  

   similar 
  arrangements 
  in 
  the 
  roots 
  of 
  the 
  plants 
  examined 
  by 
  them. 
  

  

  