﻿LECTURE 
  III 
  

  

  ELEMENTARY 
  SPECIES 
  OF 
  CULTIVATED 
  PLANTS 
  

  

  Recalling 
  the 
  results 
  of 
  the 
  last 
  lecture, 
  we 
  

   see 
  that 
  the 
  species 
  of 
  the 
  systematists 
  are 
  not 
  

   in 
  reality 
  units, 
  though 
  in 
  the 
  ordinary 
  course 
  

   of 
  floristic 
  studies 
  they 
  may, 
  as 
  a 
  rule, 
  seem 
  to 
  

   be 
  so. 
  In 
  some 
  cases 
  representatives 
  of 
  the 
  

   same 
  species 
  from 
  different 
  countries 
  or 
  re- 
  

   gions, 
  when 
  compared 
  with 
  one 
  another 
  do 
  not 
  

   exactly 
  agree. 
  Many 
  species 
  of 
  ferns 
  afford 
  

   instances 
  of 
  this 
  rule, 
  and 
  Lindley 
  and 
  other 
  

   great 
  systematists 
  have 
  frequently 
  been 
  puz- 
  

   zled 
  by 
  the 
  wide 
  range 
  of 
  differences 
  between 
  

   the 
  individuals 
  of 
  a 
  single 
  species. 
  

  

  In 
  other 
  cases 
  the 
  differing 
  forms 
  are 
  ob- 
  

   served 
  to 
  grow 
  near 
  each 
  other, 
  sometimes 
  in 
  

   neighboring 
  provinces, 
  sometimes 
  in 
  the 
  same 
  

   locality, 
  growing 
  and 
  flowering 
  in 
  mixtures 
  of 
  

   two 
  or 
  three 
  or 
  even 
  more 
  elementary 
  types. 
  

   The 
  violets 
  exhibit 
  widespread 
  ancient 
  types, 
  

   from 
  which 
  the 
  local 
  species 
  may 
  be 
  taken 
  to 
  

   have 
  arisen. 
  The 
  common 
  ancestors 
  of 
  the 
  

   whitlow-grasses 
  are 
  probably 
  not 
  to 
  be 
  found 
  

  

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