﻿Stork: 
  Studies 
  in 
  the 
  genus 
  Taraxacum 
  201 
  

  

  vulgar 
  e 
  is 
  not 
  easily 
  interfered 
  with. 
  A 
  small 
  percentage 
  of 
  viable 
  

   seeds 
  were 
  found 
  in 
  heads 
  that 
  had 
  been 
  cut 
  down 
  at 
  the 
  time 
  of 
  

   their 
  flowering 
  and 
  left 
  to 
  lie 
  in 
  the 
  grass. 
  And 
  if 
  flower 
  heads 
  

   with 
  their 
  long 
  scapes 
  attached 
  were 
  cut 
  from 
  the 
  plant 
  and 
  put 
  

   under 
  a 
  bell 
  jar 
  in 
  the 
  laboratory, 
  the 
  achenes 
  would 
  complete 
  

   their 
  development 
  and 
  a 
  small 
  percentage 
  showed 
  gerrainability. 
  

   The 
  question 
  naturally 
  followed, 
  does 
  normal 
  fertilization 
  

   ever 
  take 
  place 
  In 
  these 
  species? 
  The 
  pollen 
  of 
  the 
  two 
  

  

  great 
  

  

  species 
  

   r. 
  In 
  

  

  its 
  development 
  it 
  shows 
  such 
  abnormalities 
  as 
  are 
  often 
  seen 
  in 
  

   the 
  pollen 
  formation 
  of 
  sterile 
  hybrids. 
  The 
  degree 
  of 
  this 
  abnor- 
  

  

  ^ 
  

  

  mality 
  varies 
  in 
  different 
  plants. 
  Numerous 
  examinations 
  of 
  

   stigmata 
  with 
  pollen 
  adhering 
  to 
  them 
  were 
  made 
  under 
  magni- 
  

   fication 
  for 
  evidence 
  of 
  pollen 
  tubes. 
  None 
  were 
  ever 
  observed 
  

   in 
  either 
  species. 
  The 
  media 
  used 
  by 
  various 
  workers 
  to 
  induce 
  

   the 
  germination 
  of 
  pollen 
  were 
  employed 
  in 
  an 
  effort 
  to 
  produce 
  

   pollen 
  tubes, 
  but 
  without 
  result. 
  Finally, 
  numerous 
  pistils, 
  col- 
  

   lected 
  at 
  a 
  time 
  just 
  before 
  their 
  wilting, 
  were 
  fixed, 
  embedded 
  in 
  

   paraffine 
  in 
  bundles 
  of 
  fifteen 
  to 
  twenty 
  and 
  sectioned 
  for 
  a 
  short 
  

   distance 
  from 
  the 
  stigmatic 
  end. 
  After 
  staining, 
  careful 
  examina- 
  

   tion 
  revealed 
  no 
  trace 
  anywhere 
  of 
  an 
  invading 
  pollen 
  tube. 
  All 
  

   this, 
  to 
  be 
  sure, 
  cannot 
  be 
  considered 
  conclusive 
  evidence 
  that 
  the 
  

   pollen 
  does 
  not 
  germinate 
  and 
  that 
  fertilization 
  never 
  takes 
  place 
  

   in 
  T. 
  vtilgare 
  and 
  T. 
  erythrospermum, 
  but 
  it 
  points 
  toward 
  that 
  

  

  r 
  

  

  conclusion. 
  In 
  this 
  connection, 
  Dahlstedt 
  (2) 
  expresses 
  the 
  

   opinion 
  that 
  in 
  species 
  generally 
  ''apogamous" 
  there 
  may 
  occur 
  

   single 
  embryos 
  arising 
  normally 
  from 
  a 
  fertih*zed 
  egg. 
  He 
  refers 
  

   to 
  the 
  results 
  of 
  Rosenberg 
  (8), 
  who 
  found 
  in 
  the 
  same 
  head 
  of 
  a 
  

   Hieracium 
  "Apogamie" 
  as 
  well 
  as 
  fertilization. 
  

  

  It 
  was 
  found, 
  as 
  will 
  appear 
  in 
  the 
  cytological 
  part 
  of 
  this 
  

   paper, 
  that 
  there 
  is 
  no 
  reduction 
  division 
  in 
  the 
  course 
  of 
  megas- 
  

   porogenesis. 
  Enough 
  embryological 
  preparations 
  were 
  made 
  to 
  

   show 
  that 
  the 
  embryo 
  develops— 
  at 
  least 
  usually, 
  for 
  it 
  was 
  true 
  

   in 
  all 
  observed 
  cases— 
  from 
  the 
  unfertilized 
  egg, 
  which 
  retains 
  

   the 
  2x 
  chromosome 
  number. 
  In 
  a 
  sense, 
  it 
  is 
  an 
  inaccuracy 
  to 
  

   call 
  this 
  cell 
  an 
  egg, 
  for 
  it 
  lacks 
  the 
  character 
  of 
  a 
  true 
  egg 
  of 
  

  

  reason 
  

  

  having 
  the 
  haploid 
  chromosome 
  number. 
  For 
  the 
  same 
  

  

  the 
  term 
  parthenogenesis 
  cannot 
  well 
  be 
  applied 
  unqualifiedly 
  to 
  

  

  