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  Retrograde 
  Varieties 
  

  

  brambles 
  and 
  some 
  garden-varieties 
  of 
  the 
  tur- 
  

   nip 
  (Brassica). 
  

  

  In 
  such 
  cases 
  of 
  parallel 
  variations 
  the 
  single 
  

   instances 
  obviously 
  follow 
  the 
  same 
  rules 
  and 
  

   are 
  therefore 
  to 
  be 
  designated 
  as 
  analogous. 
  

   Pitchers 
  or 
  ascidia, 
  formed 
  by 
  the 
  union 
  of 
  the 
  

   margins 
  of 
  a 
  leaf, 
  are 
  perhaps 
  the 
  best 
  proof. 
  

   They 
  were 
  classified 
  by 
  Morren 
  under 
  two 
  heads, 
  

   according 
  to 
  their 
  formation 
  from 
  one 
  or 
  more 
  

   leaves. 
  Monophyllous 
  pitchers 
  obey 
  the 
  same 
  

   law, 
  viz. 
  : 
  that 
  the 
  upper 
  side 
  of 
  the 
  leaf 
  has 
  be- 
  

   come 
  the 
  inner 
  side 
  of 
  the 
  pitcher. 
  Only 
  one 
  

   exception 
  to 
  this 
  rule 
  is 
  known 
  to 
  me. 
  It 
  is 
  af- 
  

   forded 
  by 
  the 
  pitchers 
  of 
  the 
  banyan 
  or 
  holy 
  

   fig-tree, 
  Ficus 
  religiosus, 
  but 
  it 
  does 
  not 
  seem 
  to 
  

   belong 
  to 
  the 
  same 
  class 
  as 
  other 
  pitchers, 
  

   since 
  as 
  far 
  as 
  it 
  has 
  been 
  possible 
  to 
  ascertain 
  

   the 
  facts, 
  these 
  pitchers 
  are 
  not 
  formed 
  by 
  a 
  

   few 
  leaves 
  as 
  in 
  all 
  other 
  cases, 
  but 
  by 
  all 
  the 
  

   leaves 
  of 
  the 
  tree. 
  

  

  In 
  some 
  cases 
  pitchers 
  are 
  only 
  built 
  up 
  of 
  

   part 
  of 
  the 
  leaf-blade. 
  Such 
  partial 
  malforma- 
  

   tions 
  obey 
  a 
  rule, 
  that 
  is 
  common 
  to 
  them 
  and 
  to 
  

   other 
  foliar 
  enations, 
  viz. 
  : 
  that 
  the 
  side 
  of 
  the 
  

   leaf 
  from 
  which 
  they 
  emerge, 
  is 
  always 
  their 
  

   outer 
  side. 
  The 
  inner 
  surface 
  of 
  these 
  ena- 
  

   tions 
  corresponds 
  to 
  the 
  opposite 
  side 
  of 
  the 
  

   leaf, 
  both 
  in 
  color 
  and 
  in 
  anatomical 
  structure. 
  

  

  The 
  last 
  of 
  the 
  four 
  rules 
  above 
  mentioned 
  is 
  

  

  