﻿40 
  Elementary 
  Species 
  

  

  aid 
  of 
  insects, 
  and 
  is 
  widely 
  dispersed 
  in 
  culti- 
  

   vated 
  fields. 
  The 
  third 
  form, 
  F. 
  alpestris, 
  

   grows 
  in 
  the 
  Alps, 
  but 
  is 
  of 
  lesser 
  importance 
  

   for 
  our 
  present 
  discussion. 
  

  

  Anywhere 
  throughout 
  the 
  central 
  part 
  of 
  

   Europe 
  F. 
  tricolor 
  and 
  F. 
  arvensis 
  may 
  be 
  seen, 
  

   each 
  occupying 
  its 
  own 
  locality. 
  They 
  may 
  be 
  

   considered 
  as 
  ranging 
  among 
  the 
  most 
  common 
  

   native 
  plants 
  of 
  the 
  particular 
  regions 
  they 
  in- 
  

   habit. 
  They 
  vary 
  in 
  the 
  color 
  of 
  the 
  flowers, 
  

   branching 
  of 
  the 
  stems, 
  in 
  the 
  foliage 
  and 
  other 
  

   parts, 
  but 
  not 
  to 
  such 
  an 
  extent 
  as 
  to 
  consti- 
  

   tute 
  distinct 
  strains. 
  They 
  have 
  been 
  brought 
  

   into 
  cultivation 
  by 
  Jordan, 
  Wittrock 
  and 
  others, 
  

   but 
  throughout 
  Europe 
  each 
  of 
  them 
  constitutes 
  

   a 
  single 
  type. 
  

  

  These 
  types 
  must 
  be 
  very 
  old 
  and 
  constant, 
  

   fluctuating 
  always 
  within 
  the 
  same 
  distinct 
  and 
  

   narrow 
  limits. 
  No 
  slow, 
  gradual 
  changes 
  can 
  

   have 
  taken 
  place. 
  In 
  different 
  countries 
  their 
  

   various 
  habitats 
  are 
  as 
  old 
  as 
  the 
  historical 
  

   records, 
  and 
  probably 
  many 
  centuries 
  older. 
  

   They 
  are 
  quite 
  independent 
  of 
  one 
  another, 
  the 
  

   distance 
  being 
  in 
  numerous 
  cases 
  far 
  too 
  great 
  

   for 
  the 
  exchange 
  of 
  pollen 
  or 
  of 
  seeds. 
  If 
  slow 
  

   and 
  gradual 
  changes 
  were 
  the 
  rule, 
  the 
  types 
  

   could 
  not 
  have 
  remained 
  so 
  uniform 
  throughout 
  

   the 
  whole 
  range 
  of 
  these 
  two 
  species. 
  They 
  

   would 
  necessarily 
  have 
  split 
  up 
  into 
  thousands 
  

  

  