﻿564 
  Mutations 
  

  

  incompleteness 
  of 
  heredity, 
  but 
  in 
  vain. 
  The 
  

   succeeding 
  generations, 
  if 
  produced 
  from 
  true 
  

   representatives 
  of 
  the 
  new 
  type, 
  and 
  with 
  pure 
  

   fertilization, 
  have 
  repeated 
  the 
  splitting 
  in 
  the 
  

   same 
  numerical 
  proportions. 
  The 
  instability 
  

   seems 
  to 
  be 
  here 
  as 
  permanent 
  a 
  quality 
  as 
  the 
  

   stability 
  in 
  other 
  instances. 
  Even 
  here 
  no 
  se- 
  

   lection 
  has 
  been 
  adequate 
  to 
  change 
  the 
  original 
  

   form. 
  

  

  IV. 
  Some 
  of 
  the 
  new 
  strains 
  are 
  evidently 
  ele- 
  

   mentary 
  species, 
  while 
  others 
  are 
  to 
  be 
  consid- 
  

   ered 
  as 
  retrograde 
  varieties. 
  

  

  It 
  is 
  often 
  difficult 
  to 
  decide 
  whether 
  a 
  given 
  

   form 
  belongs 
  to 
  one 
  or 
  another 
  of 
  these 
  two 
  

   groups. 
  I 
  have 
  tried 
  to 
  show 
  that 
  the 
  best 
  

   and 
  strictest 
  conception 
  of 
  varieties 
  limits 
  

   them 
  to 
  those 
  forms 
  that 
  have 
  probably 
  

   originated 
  by 
  retrograde 
  or 
  degressive 
  steps. 
  

   Elementary 
  species 
  are 
  assumed 
  to 
  have 
  been 
  

   produced 
  in 
  a 
  progressive 
  way, 
  adding 
  one 
  

   new 
  element 
  to 
  the 
  store. 
  Varieties 
  differ 
  from 
  

   their 
  species 
  clearly 
  in 
  one 
  point, 
  and 
  this 
  is 
  

   either 
  a 
  distinct 
  loss, 
  or 
  the 
  assumption 
  of 
  a 
  

   character, 
  which 
  may 
  be 
  met 
  with 
  in 
  other 
  

   species 
  and 
  genera. 
  Laevifolia 
  is 
  distin- 
  

   guished 
  by 
  the 
  loss 
  of 
  the 
  crinkling 
  of 
  the 
  

   leaves, 
  lorevistylis 
  by 
  the 
  partial 
  loss 
  of 
  the 
  

   epigynous 
  qualities 
  of 
  the 
  flowers, 
  and 
  nanella 
  is 
  

   a 
  dwarf. 
  These 
  three 
  new 
  forms 
  are 
  therefore 
  

  

  