﻿532 
  Mutations 
  

  

  served 
  any 
  trace 
  of 
  reversion 
  to 
  the 
  lamarck- 
  

   iana 
  type. 
  I 
  have 
  also 
  cultivated 
  them 
  in 
  suc- 
  

   cessive 
  generations 
  with 
  the 
  same 
  result. 
  In 
  

   a 
  former 
  lecture 
  we 
  have 
  seen 
  that 
  contrary 
  to 
  

   the 
  general 
  run 
  of 
  horticultural 
  belief, 
  varieties 
  

   are 
  as 
  constant 
  as 
  the 
  best 
  species, 
  if 
  kept 
  free 
  

   from 
  hybrid 
  admixtures. 
  This 
  is 
  a 
  general 
  rule, 
  

   and 
  the 
  exceptions, 
  or 
  cases 
  of 
  atavism 
  are 
  ex- 
  

   tremely 
  rare. 
  In 
  this 
  respect 
  it 
  is 
  of 
  great 
  inter- 
  

   est 
  to 
  observe 
  that 
  this 
  constancy 
  is 
  not 
  an 
  ac- 
  

   quired 
  quality, 
  but 
  is 
  to 
  be 
  considered 
  as 
  innate, 
  

   because 
  it 
  is 
  already 
  fully 
  developed 
  at 
  the 
  very 
  

   moment 
  when 
  the 
  original 
  mutation 
  takes 
  place. 
  

   From 
  its 
  first 
  leaves 
  to 
  the 
  rosette 
  period, 
  

   and 
  through 
  this 
  to 
  the 
  lengthening 
  of 
  the 
  stem, 
  

   the 
  dwarfs 
  are 
  easily 
  distinguished 
  from 
  any 
  

   other 
  of 
  their 
  congeners. 
  The 
  most 
  remarkable 
  

   feature 
  is 
  the 
  shape 
  of 
  the 
  leaves. 
  They 
  are 
  

   broader 
  and 
  shorter, 
  and 
  especially 
  at 
  the 
  base 
  

   they 
  are 
  broadened 
  in 
  such 
  a 
  way 
  as 
  to 
  become 
  

   apparently 
  sessile. 
  The 
  stalk 
  is 
  very 
  brittle, 
  

   and 
  any 
  rough 
  treatment 
  may 
  cause 
  the 
  leaves 
  

   to 
  break 
  off. 
  The 
  young 
  seedlings 
  are 
  

   recognizable 
  by 
  the 
  shape 
  of 
  the 
  first 
  two 
  or 
  

   three 
  leaves, 
  and 
  when 
  more 
  of 
  them 
  are 
  pro- 
  

   duced, 
  the 
  rosettes 
  become 
  dense 
  and 
  strikingly 
  

   different 
  from 
  others. 
  Later 
  leaves 
  are 
  more 
  

   nearly 
  like 
  the 
  parent-type, 
  but 
  the 
  petioles 
  re- 
  

   main 
  short. 
  The 
  bases 
  of 
  the 
  blades 
  are 
  fre- 
  

  

  