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  Mutations 
  

  

  must 
  obviously 
  be 
  due 
  to 
  this 
  most 
  universal 
  

   agency. 
  Indirect 
  vicinism 
  also 
  plays 
  some 
  part, 
  

   and 
  probably 
  affords 
  the 
  explanation 
  of 
  some 
  

   reputed 
  mutative 
  productions 
  of 
  the 
  variety. 
  

   So, 
  for 
  instance, 
  in 
  the 
  case 
  of 
  Sinning, 
  who 
  aft- 
  

   er 
  sowing 
  the 
  seeds 
  of 
  the 
  common 
  ash, 
  got 
  as 
  

   large 
  a 
  proportion 
  as 
  2$ 
  of 
  monophyllous 
  trees 
  

   in 
  a 
  culture 
  of 
  some 
  thousand 
  plants. 
  It 
  is 
  

   probable 
  that 
  his 
  seeds 
  were 
  taken 
  partly 
  from 
  

   normal 
  plants, 
  and 
  partly 
  from 
  hybrids 
  between 
  

   the 
  normal 
  and 
  the 
  * 
  ' 
  one-bladed 
  ' 
  ' 
  type, 
  assum- 
  

   ing 
  that 
  these 
  hybrids 
  have 
  pinnate 
  leaves 
  like 
  

   their 
  specific 
  parent, 
  and 
  bear 
  the 
  characters 
  of 
  

   the 
  other 
  parent 
  only 
  in 
  a 
  latent 
  condition. 
  

  

  Our 
  third 
  example 
  relates 
  to 
  peltate 
  leaves. 
  

   They 
  have 
  the 
  stalk 
  inserted 
  in 
  the 
  middle 
  of 
  

   the 
  blade, 
  a 
  contrivance 
  produced 
  by 
  the 
  conna- 
  

   tion 
  of 
  the 
  two 
  basal 
  lobes. 
  The 
  water-lilies 
  

   are 
  a 
  well 
  known 
  instance, 
  exhibiting 
  sagit- 
  

   tate 
  leaves 
  in 
  the 
  juvenile 
  stage 
  and 
  changing 
  

   in 
  many 
  species, 
  into 
  nearly 
  circular 
  pel- 
  

   tate 
  forms, 
  of 
  which 
  Victoria 
  regia 
  is 
  a 
  very 
  

   good 
  example, 
  although 
  its 
  younger 
  stages 
  do 
  

   not 
  always 
  excite 
  all 
  the 
  interest 
  they 
  deserve. 
  

   The 
  Indian 
  cress 
  (Tropaeolum), 
  the 
  marsh- 
  

   pennywort 
  or 
  Hydrocotyle, 
  and 
  many 
  other 
  in- 
  

   stances 
  could 
  be 
  quoted. 
  Sometimes 
  the 
  peltate 
  

   leaves 
  are 
  not 
  at 
  all 
  orbicular, 
  but 
  are 
  elon- 
  

   gated, 
  oblong 
  or 
  elliptic, 
  and 
  with 
  only 
  the 
  lobes 
  

  

  