﻿180 
  Retrograde 
  Varieties 
  

  

  the 
  f 
  orai 
  of 
  the 
  common 
  beech-leaves. 
  It 
  is 
  not 
  

   a 
  bud-variation 
  at 
  all, 
  and 
  it 
  is 
  to 
  be 
  met 
  with 
  

   quite 
  commonly 
  while 
  the 
  true 
  reversions 
  by 
  

   buds 
  are 
  very 
  rare 
  and 
  are 
  of 
  the 
  nature 
  of 
  

   sports 
  appearing 
  suddenly 
  and 
  remaining 
  con- 
  

   stant 
  on 
  the 
  same 
  twig. 
  Analogous 
  phenomena 
  

   of 
  wide 
  variability 
  with 
  true 
  reversion 
  may 
  be 
  

   seen 
  in 
  the 
  variety 
  of 
  the 
  European 
  hornbeam 
  

   called 
  Carpinus 
  Betulus 
  heteropliylla. 
  The 
  

   leaves 
  of 
  this 
  tree 
  generally 
  show 
  the 
  greatest 
  

   diversity 
  in 
  form. 
  Some 
  other 
  cases 
  have 
  been 
  

   brought 
  together 
  by 
  Darwin. 
  In 
  the 
  first 
  place 
  

   a 
  subvariety 
  of 
  the 
  weeping-willow 
  with 
  leaves 
  

   rolled 
  up 
  into 
  a 
  spiral 
  coil. 
  A 
  tree 
  of 
  this 
  kind 
  

   kept 
  true 
  for 
  twenty-five 
  years 
  and 
  then 
  threw 
  

   out 
  a 
  single 
  upright 
  shoot 
  bearing 
  flat 
  leaves. 
  

   The 
  barberry 
  (Berberis] 
  offers 
  another 
  case; 
  

   it 
  has 
  a 
  well 
  known 
  variety 
  with 
  seedless 
  fruit, 
  

   which 
  can 
  be 
  propagated 
  by 
  cuttings 
  or 
  layers, 
  

   but 
  its 
  runners 
  are 
  said 
  always 
  to 
  revert 
  to 
  the 
  

   common 
  form, 
  and 
  to 
  produce 
  ordinary 
  berries 
  

   with 
  seeds. 
  Most 
  of 
  the 
  cases 
  referred 
  to 
  bv 
  

  

  */ 
  

  

  Darwin, 
  however, 
  seem 
  to 
  be 
  doubtful 
  and 
  can- 
  

   not 
  be 
  considered 
  as 
  true 
  proofs 
  of 
  atavism 
  until 
  

   more 
  is 
  known 
  about 
  the 
  circumstances 
  under 
  

   which 
  they 
  were 
  produced. 
  

  

  Eed 
  or 
  brown-leaved 
  varieties 
  of 
  trees 
  and 
  

   shrubs 
  also 
  occasionally 
  produce 
  green-leaved 
  

   branches, 
  and 
  in 
  this 
  way 
  revert 
  to 
  the 
  type 
  

  

  