﻿\ 
  

  

  Vol. 
  47 
  

  

  No. 
  5 
  

  

  BULLETIN 
  

  

  OF 
  THE 
  

  

  TORREY 
  BOTANICAL 
  CLUB 
  

  

  MAY, 
  1920 
  

  

  Studies 
  in 
  the 
  genus 
  Taraxacum 
  

  

  Harvey 
  E, 
  Stork 
  

  

  (with 
  plates 
  6 
  AND 
  7) 
  

  

  Loss 
  OF 
  SEXUALITY 
  IN 
  TARAXACUM 
  

  

  The 
  genus 
  Taraxacum 
  presents 
  some 
  interesting 
  problems 
  

   taxonomic, 
  cytological 
  and 
  geneticaL 
  The 
  classical 
  castration 
  

   experiments 
  by 
  Raunkiaer 
  (7) 
  in 
  1903 
  showed 
  the 
  common 
  

   dandelion, 
  T. 
  vulgare 
  (Lam.) 
  Schrk. 
  {T. 
  officinale 
  Weber), 
  to 
  be 
  

   capable 
  of 
  setting 
  viable 
  seeds 
  without 
  pollination. 
  Since 
  Schwere 
  

   (10) 
  had 
  previously 
  described 
  the 
  development 
  of 
  the 
  embryo 
  

   from 
  the 
  egg 
  cell, 
  the 
  condition 
  was 
  spoken 
  of 
  as 
  *' 
  parthenogene- 
  

   sis," 
  and 
  Raunkiaer 
  concluded 
  that 
  all 
  species 
  of 
  Taraxacum 
  w^re 
  

   parthenogenetic. 
  This 
  was 
  questioned 
  by 
  Dahlstedt 
  (2) 
  in 
  

   1907, 
  and 
  two 
  years 
  later 
  Rosenberg 
  (9) 
  showed 
  T. 
  confertum 
  to 
  be 
  

   normally 
  sexual. 
  Likewise, 
  Ikeno 
  and 
  Osawa 
  (6) 
  showed 
  that 
  of 
  

   two 
  species 
  growing 
  side 
  by 
  side 
  in 
  Japan, 
  T, 
  platycarpum 
  Dahlst. 
  

   and 
  T. 
  alhidiim 
  Dahlst,, 
  the 
  former 
  is 
  normally 
  sexual 
  while 
  the 
  

   latter 
  requires 
  no 
  pollination 
  for 
  the 
  production 
  of 
  viable 
  seeds. 
  

  

  careful 
  studies 
  had 
  been 
  made 
  as 
  to 
  mega- 
  

   sporogenesis 
  and 
  other 
  cytological 
  features 
  in 
  the 
  genus: 
  that 
  of 
  

  

  two 
  

  

  Juel 
  

  

  Japanese 
  species. 
  At 
  that 
  time 
  it 
  was 
  suggested 
  to 
  

  

  writer 
  by 
  Professor 
  D. 
  M. 
  Mottier 
  

  

  growing 
  

  

  Accordingly, 
  in 
  

  

  writer 
  

  

  cytological 
  work 
  of 
  JucI 
  

  

  [The 
  Bulletin 
  for 
  April 
  (47= 
  i37-i98- 
  Pi- 
  SS) 
  was 
  issued 
  May 
  17, 
  1920] 
  

  

  199 
  

  

  