﻿Stork: 
  Studies 
  in 
  the 
  genus 
  Taraxacum 
  

  

  203 
  

  

  (2) 
  remarks 
  that 
  ''probably 
  quite 
  likely 
  the 
  genus 
  has 
  at 
  one 
  time 
  

   been 
  and 
  is 
  still 
  perhaps 
  in 
  a 
  period 
  of 
  mutation.'* 
  It 
  is 
  believed 
  

   that 
  careful 
  study, 
  through 
  cultures, 
  of 
  the 
  plants 
  of 
  both 
  sexual 
  

  

  and 
  apogamous 
  species 
  may 
  throw 
  some 
  light 
  on 
  such 
  questions 
  

   as 
  these. 
  In 
  whatever 
  manner 
  the 
  ooapogamous 
  condition 
  arose, 
  

   it 
  was 
  doubtless 
  attended 
  by 
  an 
  increase 
  In 
  the 
  chromosome 
  num- 
  

   ber, 
  as 
  will 
  appear 
  from 
  the 
  following 
  table: 
  

  

  Sexual 
  forms 
  

  

  Haploid 
  

  

  Diploid 
  

  

  Ooapogamous 
  forms 
  

  

  Haploid 
  

  

  Diploid 
  

  

  T, 
  vulgare 
  

  

  T» 
  confertum 
  

  

  T. 
  erytkrospermum 
  

   T. 
  albidum 
  

  

  T. 
  platycarpum 
  

  

  8 
  

  

  

  13 
  

  

  16 
  

  

  

  i 
  

  

  8 
  

  

  16 
  

  

  

  26 
  

  

  26-30 
  

  

  36-40 
  

  

  Perhaps 
  the 
  numbers 
  under 
  the 
  ooapogamous 
  forms 
  should 
  be 
  

   spoken 
  of 
  as 
  diploid 
  and 
  tetraploid, 
  for 
  it 
  seems 
  that 
  the 
  ooapo- 
  

   gamous 
  condition 
  is 
  attended 
  by 
  a 
  doubling 
  of 
  the 
  chromosome 
  

   numbers. 
  The 
  higher 
  figures 
  may 
  be 
  inaccurate 
  because 
  of 
  

   difficulties 
  in 
  making 
  the 
  counts 
  of 
  the 
  small 
  chromosomes, 
  or 
  

   the 
  number 
  may 
  be 
  irregular 
  as 
  an 
  expression 
  of 
  the 
  abnormal 
  

   condition 
  that 
  exists. 
  As 
  Rosenberg 
  (9) 
  has 
  pointed 
  out, 
  In 
  all 
  

   cases 
  of 
  ooapogamy 
  in 
  seed 
  plants 
  where 
  chromosome 
  counts 
  are 
  

   available, 
  the 
  ooapogamous 
  species 
  of 
  a 
  genus 
  have 
  a 
  larger 
  

  

  T 
  

  

  number 
  of 
  chromosomes 
  than 
  the 
  sexual 
  species, 
  and 
  the 
  number 
  

   is 
  usually 
  double. 
  One 
  striking 
  exception 
  occurs 
  in 
  the 
  genus 
  

   Rumex, 
  which 
  should 
  be 
  further 
  investigated. 
  The 
  significance 
  of 
  

   this 
  connection 
  between 
  ooapogamy 
  and 
  the 
  doubling 
  of 
  chromo- 
  

   some 
  numbers 
  can 
  be 
  only 
  a 
  matter 
  of 
  speculation 
  at 
  the 
  present 
  

  

  time. 
  

  

  Variation 
  in 
  Taraxacum 
  

  

  great 
  

  

  Both 
  r. 
  erytkrospermum 
  and 
  T. 
  vulgare 
  present 
  

   bility, 
  and 
  it 
  is 
  possible 
  that 
  the 
  tendency 
  to 
  var>' 
  may 
  be 
  due 
  

   to 
  the 
  large 
  chromosome 
  content. 
  It 
  would 
  be 
  interesting 
  to 
  

   know 
  whether 
  sexual 
  forms 
  with 
  the 
  8 
  (i6) 
  chromosome-number 
  

   show 
  a 
  similar 
  tendency 
  to 
  variation. 
  The 
  literature 
  gives 
  us 
  no 
  

   evidence 
  in 
  this 
  matter. 
  With 
  the 
  chromosome 
  content 
  abcior- 
  

   mally 
  increased, 
  one 
  might 
  expect 
  mutations. 
  Should. 
  a 
  mutation 
  

  

  