﻿504 
  Mutations 
  

  

  barren, 
  and 
  incapable 
  of 
  the 
  reproduction 
  of 
  the 
  

  

  race. 
  

  

  This 
  last 
  is 
  therefore, 
  of 
  necessity, 
  always 
  

   continued 
  by 
  means 
  of 
  individuals 
  whose 
  devia- 
  

   tion 
  from 
  the 
  mean 
  average 
  is 
  the 
  least. 
  But 
  

   in 
  many 
  cases 
  the 
  varieties 
  are 
  so 
  highly 
  dif- 
  

   ferentiated 
  that 
  selection 
  has 
  become 
  quite 
  su- 
  

   perfluous 
  for 
  practical 
  purposes. 
  I 
  have 
  al- 
  

   ready 
  discussed 
  the 
  question 
  as 
  to 
  the 
  actual 
  

   moment, 
  in 
  which 
  the 
  change 
  of 
  the 
  grandiflor- 
  

   um 
  variety 
  into 
  the 
  new 
  plenum 
  form 
  must 
  be 
  

   assumed 
  to 
  have 
  taken 
  place. 
  In 
  this 
  respect 
  

   some 
  stress 
  is 
  to 
  be 
  laid 
  on 
  the 
  fact 
  that 
  the 
  im- 
  

   provement 
  through 
  selection 
  has 
  been 
  gradual 
  

   and 
  continuous, 
  though 
  very 
  rapid 
  from 
  the 
  first 
  

   moment. 
  But 
  with 
  the 
  appearance 
  of 
  the 
  first 
  

   stray 
  rays 
  within 
  the 
  disk, 
  this 
  continuity 
  sud- 
  

   denly 
  changed. 
  All 
  the 
  children 
  of 
  this 
  original 
  

   mutated 
  plant 
  showed 
  the 
  new 
  character, 
  the 
  

   rays 
  within 
  the 
  disk, 
  without 
  exception. 
  Not 
  

   on 
  all 
  the 
  heads, 
  nor 
  even 
  on 
  the 
  majority 
  of 
  the 
  

   heads 
  on 
  some 
  individuals, 
  but 
  on 
  some 
  heads 
  all 
  

   gave 
  clear 
  proof 
  of 
  the 
  possession 
  of 
  the 
  new 
  

   attribute. 
  This 
  was 
  present 
  in 
  all 
  the 
  repre- 
  

   sentatives 
  of 
  the 
  new 
  race, 
  and 
  had 
  never 
  been 
  

   seen 
  in 
  any 
  of 
  their 
  parents 
  and 
  grandparents. 
  

   Here 
  there 
  was 
  evidently 
  a 
  sudden 
  leap, 
  at 
  

   least 
  in 
  the 
  external 
  form 
  of 
  the 
  plants. 
  And 
  it 
  

   seems 
  to 
  me 
  to 
  be 
  the 
  most 
  simple 
  conception, 
  

  

  