﻿Elementary 
  Species 
  in 
  Nature 
  49 
  

  

  ways. 
  All 
  in 
  all 
  there 
  are 
  constant 
  differences 
  

   which 
  are 
  so 
  great 
  that 
  it 
  has 
  been 
  possible 
  to 
  

   distinguish 
  and 
  to 
  describe 
  large 
  numbers 
  of 
  

   types. 
  

  

  Many 
  of 
  them 
  have 
  been 
  tested 
  as 
  to 
  their 
  

   constancy 
  from 
  seed. 
  Jordan 
  made 
  numerous 
  

   cultures, 
  some 
  of 
  which 
  lasted 
  ten 
  or 
  twelve 
  

   years; 
  Thuret 
  has 
  verified 
  the 
  assertion 
  con- 
  

   cerning 
  their 
  constancy 
  by 
  cultures 
  extending 
  

   over 
  seven 
  years 
  in 
  some 
  instances 
  ; 
  Villars 
  and 
  

   de 
  Bary 
  made 
  numerous 
  trials 
  of 
  shorter 
  dura- 
  

   tion. 
  All 
  agree 
  as 
  to 
  the 
  main 
  points. 
  The 
  local 
  

   races 
  are 
  uniform 
  and 
  come 
  true 
  from 
  seed 
  ; 
  the 
  

   variability 
  of 
  the 
  species 
  is 
  not 
  of 
  a 
  fluctuating, 
  

   but 
  of 
  a 
  polymorphous 
  nature. 
  A 
  given 
  ele- 
  

   mentary 
  species 
  keeps 
  within 
  its 
  limits 
  and 
  can- 
  

   not 
  vary 
  beyond 
  them, 
  but 
  the 
  whole 
  group 
  

   gives 
  the 
  impression 
  of 
  variability 
  by 
  its 
  wide 
  

   range 
  of 
  distinct, 
  but 
  nearly 
  allied 
  forms. 
  

  

  The 
  geographic 
  distribution 
  of 
  these 
  ele- 
  

   mentary 
  species 
  of 
  the 
  whitlow-grass 
  is 
  quite 
  

   distinct 
  from 
  that 
  of 
  the 
  violets. 
  Here 
  predom- 
  

   inant 
  species 
  are 
  limited 
  to 
  restricted 
  locali- 
  

   ties. 
  Most 
  of 
  them 
  occupy 
  one 
  or 
  more 
  depart- 
  

   ments 
  of 
  France, 
  and 
  in 
  Holland 
  two 
  of 
  them 
  

   are 
  spread 
  over 
  several 
  provinces. 
  An 
  import- 
  

   ant 
  number 
  are 
  native 
  in 
  the 
  centre 
  of 
  Europe, 
  

   and 
  from 
  the 
  vicinity 
  of 
  Lyons, 
  Jordan 
  suc- 
  

   ceeded 
  in 
  establishing 
  about 
  fifty 
  elementary 
  

  

  