﻿LECTUKE 
  XVII 
  

  

  THE 
  PKODUCTION 
  OF 
  DOUBLE 
  FLOWERS 
  

  

  Mutations 
  occur 
  as 
  often 
  among 
  cultivated 
  

   plants 
  as 
  among 
  those 
  in 
  the 
  wild 
  state. 
  Gar- 
  

   den 
  flowers 
  are 
  known 
  to 
  vary 
  markedly. 
  

   Much 
  of 
  their 
  variability, 
  however, 
  is 
  due 
  to 
  

   hybridism, 
  and 
  the 
  combination 
  of 
  characters 
  

   previously 
  separate 
  has 
  a 
  value 
  for 
  the 
  breeder 
  

   nearly 
  equal 
  the 
  production 
  of 
  really 
  new 
  qual- 
  

   ities. 
  Nevertheless 
  there 
  is 
  no 
  doubt 
  that 
  some 
  

   new 
  characters 
  appear 
  from 
  time 
  to 
  time. 
  

  

  In 
  a 
  previous 
  lecture 
  we 
  have 
  seen 
  that 
  

   varietal 
  characters 
  have 
  many 
  features 
  in 
  com- 
  

   mon. 
  One 
  of 
  them 
  is 
  their 
  frequent 
  recur- 
  

   rence 
  both 
  in 
  the 
  same 
  and 
  in 
  other, 
  often 
  very 
  

   distantly 
  related, 
  species. 
  This 
  recurrence 
  is 
  an 
  

   important 
  factor 
  in 
  the 
  choice 
  of 
  the 
  material 
  

   for 
  an 
  experimental 
  investigation 
  of 
  the 
  nature 
  

   of 
  mutations. 
  

  

  Some 
  varieties 
  are 
  reputed 
  to 
  occur 
  more 
  

   often 
  and 
  more 
  readily 
  than 
  others. 
  White-col- 
  

   ored 
  varieties, 
  though 
  so 
  very 
  common, 
  seem 
  for 
  

   the 
  most 
  part 
  to 
  be 
  of 
  ancient 
  date, 
  but 
  only 
  few 
  

  

  488 
  

  

  