﻿660 
  Mutations 
  

  

  that 
  govern 
  the 
  production 
  of 
  anomalies, 
  and 
  

   we 
  may 
  assume 
  them 
  to 
  lie 
  within 
  reach 
  of 
  our 
  

   experiments. 
  The 
  experimental 
  treatment 
  of 
  

   the 
  origin 
  of 
  species 
  may 
  also 
  be 
  looked 
  upon 
  as 
  

   a 
  method 
  within 
  our 
  grasp. 
  

  

  The 
  validity 
  and 
  the 
  significance 
  of 
  these 
  

   considerations 
  will 
  at 
  once 
  become 
  clear, 
  if 
  we 
  

   choose 
  a 
  definite 
  example. 
  The 
  broadest 
  and 
  

   most 
  convincing 
  one 
  appears 
  to 
  me 
  to 
  be 
  af- 
  

   forded 
  by 
  the 
  cohesion 
  of 
  the 
  petals 
  in 
  gamo- 
  

   petalous 
  flowers. 
  According 
  to 
  the 
  current 
  

   views 
  the 
  families 
  with 
  the 
  petals 
  of 
  their 
  

   flowers 
  united 
  are 
  regarded 
  as 
  one 
  or 
  two 
  main 
  

   branches 
  of 
  the 
  whole 
  pedigree 
  of 
  the 
  vege- 
  

   table 
  kingdom. 
  Eichler 
  and 
  others 
  assume 
  

   them 
  to 
  constitute 
  one 
  branch, 
  and 
  therefore 
  one 
  

   large 
  subdivision 
  of 
  the 
  system. 
  Bessey, 
  on 
  the 
  

   other 
  hand, 
  has 
  shown 
  the 
  probability 
  of 
  a 
  sep- 
  

   arate 
  origin 
  for 
  those 
  groups 
  which 
  have 
  in- 
  

   ferior 
  ovaries. 
  Apart 
  from 
  such 
  divergencies 
  

   the 
  connation 
  of 
  the 
  petals 
  is 
  universally 
  recog- 
  

   nized 
  as 
  one 
  of 
  the 
  most 
  important 
  systematic 
  

   characters. 
  

  

  How 
  may 
  this 
  character 
  have 
  originated? 
  

   The 
  heath-family 
  or 
  the 
  Ericaceae 
  and 
  their 
  

   nearest 
  allies 
  are 
  usually 
  considered 
  to 
  be 
  the 
  

   lowest 
  of 
  the 
  gamopetalous 
  plants. 
  In 
  them 
  the 
  

   cohesion 
  of 
  the 
  petals 
  is 
  still 
  subject 
  to 
  rever- 
  

   sionary 
  exceptions. 
  Such 
  cases 
  of 
  atavism 
  may 
  

  

  