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  Elementary 
  Species 
  

  

  may 
  be 
  cultivated 
  in 
  the 
  same 
  garden 
  without 
  

   any 
  real 
  danger 
  of 
  their 
  intercrossing. 
  They 
  

   remain 
  as 
  pure 
  as 
  under 
  perfect 
  isolation. 
  

  

  It 
  is 
  very 
  interesting 
  to 
  observe 
  the 
  aspect 
  of 
  

   such 
  types, 
  when 
  growing 
  near 
  each 
  other. 
  

   Hundreds 
  of 
  rosettes 
  exhibit 
  one 
  type, 
  and 
  are 
  

   undoubtedly 
  similar. 
  The 
  alternative 
  group 
  is 
  

   distinguishable 
  at 
  first 
  sight, 
  though 
  the 
  differ- 
  

   entiating 
  marks 
  are 
  often 
  so 
  slight 
  as 
  to 
  be 
  

   traceable 
  with 
  difficulty. 
  Two 
  elementary 
  spe- 
  

   cies 
  occur 
  in 
  Holland, 
  one 
  with 
  narrow 
  leaves 
  in 
  

   the 
  western 
  provinces 
  and 
  one 
  with 
  broader 
  

   foliage 
  in 
  the 
  northern 
  parts. 
  I 
  have 
  cultivated 
  

   them 
  side 
  by 
  side, 
  and 
  was 
  as 
  much 
  struck 
  with 
  

   the 
  uniformity 
  within 
  each 
  group, 
  as 
  with 
  the 
  

   contrast 
  between 
  the 
  two 
  sets. 
  

  

  Nearly 
  all 
  organs 
  show 
  differences. 
  The 
  

   most 
  marked 
  are 
  those 
  of 
  the 
  leaves, 
  which 
  may 
  

   be 
  small 
  or 
  large, 
  linear 
  or 
  elliptic 
  or 
  oblong 
  and 
  

   even 
  rhomboidal 
  in 
  shape, 
  more 
  or 
  less 
  hairy 
  

   with 
  simple 
  or 
  with 
  stellate 
  branched 
  hairs, 
  and 
  

   finally 
  of 
  a 
  pure 
  green 
  or 
  of 
  a 
  glaucous 
  color. 
  

   The 
  petals 
  are 
  as 
  a 
  rule 
  obcordate, 
  but 
  this 
  type 
  

   may 
  be 
  combined 
  with 
  others 
  having 
  more 
  or 
  

   less 
  broad 
  emarginations 
  at 
  the 
  summit, 
  and 
  

   with 
  differences 
  in 
  breadth 
  which 
  vary 
  from 
  al- 
  

   most 
  linear 
  types 
  to 
  others 
  which 
  touch 
  along 
  

   their 
  margins. 
  The 
  pods 
  are 
  short 
  and 
  broad, 
  

   or 
  long 
  and 
  narrow, 
  or 
  varying 
  in 
  sundry 
  other 
  

  

  