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  Elementary 
  Species 
  

  

  hibiting 
  slight 
  but 
  undoubted 
  differentiating 
  

   features, 
  and 
  reproduce 
  themselves 
  truly 
  by 
  

   seed. 
  Descriptions 
  were 
  formerly 
  difficult 
  and 
  

   so 
  complicated 
  that 
  the 
  ablest 
  writers 
  on 
  this 
  

   genus, 
  Fries 
  and 
  Nageli 
  are 
  said 
  not 
  to 
  have 
  

   been 
  able 
  to 
  recognize 
  the 
  separate 
  species 
  by 
  

   the 
  descriptions 
  given 
  by 
  each 
  other. 
  Are 
  these 
  

   types 
  to 
  be 
  considered 
  as 
  elementary 
  species, 
  

   or 
  only 
  as 
  individual 
  differences! 
  The 
  decis- 
  

   ion 
  of 
  course, 
  would 
  depend 
  upon 
  their 
  behav- 
  

   ior 
  in 
  cultures. 
  Such 
  tests 
  have 
  been 
  made 
  by 
  

   various 
  experimenters. 
  In 
  the 
  dandelion 
  the 
  

   bracts 
  of 
  the 
  involucre 
  give 
  the 
  best 
  characters. 
  

   The 
  inner 
  ones 
  may 
  be 
  linear 
  or 
  linear-lance- 
  

   olate, 
  with 
  or 
  without 
  appendages 
  below 
  the 
  tip 
  ; 
  

   the 
  outer 
  ones 
  may 
  be 
  similar 
  and 
  only 
  shorter, 
  

   or 
  noticeably 
  larger, 
  erect, 
  spreading 
  .or 
  even 
  

   reflexed, 
  and 
  the 
  color 
  of 
  the 
  involucre 
  may 
  be 
  

   a 
  pure 
  green 
  or 
  glaucous; 
  the 
  leaves 
  may 
  be 
  

   nearly 
  entire 
  or 
  pinnatifid, 
  or 
  sinuate-dentate, 
  

   or 
  very 
  deeply 
  runcinate-pinnatifid, 
  or 
  even 
  

   pinnately 
  divided, 
  the 
  whole 
  plant 
  being 
  more 
  

   or 
  less 
  glabrous. 
  

  

  Kaunkiaer, 
  who 
  has 
  studied 
  experimentally 
  a 
  

   dozen 
  types 
  from 
  Denmark, 
  found 
  them 
  con- 
  

   stant, 
  but 
  observed 
  that 
  some 
  of 
  them 
  have 
  no 
  

   pollen 
  at 
  all, 
  while 
  in 
  others 
  the 
  pollen, 
  though 
  

   present, 
  is 
  impotent. 
  It 
  does 
  not 
  germinate 
  on 
  

   the 
  stigma, 
  cannot 
  produce 
  the 
  ordinary 
  tube, 
  

  

  