﻿LECTURE 
  XIX 
  

  

  EXPERIMENTAL 
  PEDIGREE-CULTURES 
  

  

  The 
  observation 
  of 
  the 
  production 
  of 
  mutants 
  

   in 
  the 
  field 
  at 
  Hilversum, 
  and 
  the 
  subsequent 
  

   cultivation 
  of 
  the 
  new 
  types 
  in 
  the 
  garden 
  at 
  

   Amsterdam, 
  gives 
  ample 
  proof 
  of 
  the 
  mutability 
  

   of 
  plants. 
  Furthermore 
  it 
  furnishes 
  an 
  analogy 
  

   with 
  the 
  hypothetical 
  origin 
  of 
  the 
  swarms 
  of 
  

   species 
  of 
  Draba 
  and 
  Viola. 
  Last 
  but 
  not 
  least 
  

   important 
  it 
  affords 
  material 
  for 
  a 
  complete 
  

   systematic 
  and 
  morphologic 
  study 
  of 
  the 
  new- 
  

   ly 
  arisen 
  group 
  of 
  forms. 
  

  

  The 
  physiologic 
  laws, 
  however, 
  which 
  gov- 
  

   ern 
  this 
  process 
  are 
  only 
  very 
  imperfectly 
  re- 
  

   vealed 
  by 
  such 
  a 
  study. 
  The 
  instances 
  are 
  too 
  

   few. 
  Moreover 
  the 
  seeds 
  from 
  which 
  the 
  mu- 
  

   tants 
  spring, 
  escape 
  observation. 
  It 
  is 
  simply 
  

   impossible 
  to 
  tell 
  from 
  which 
  individual 
  plants 
  

   they 
  have 
  been 
  derived. 
  The 
  laevifolia 
  and 
  the 
  

   brevistylis 
  have 
  been 
  found 
  almost 
  every 
  year, 
  

   the 
  first 
  always 
  recurring 
  on 
  the 
  same 
  spot, 
  the 
  

   second 
  on 
  various 
  parts 
  of 
  the 
  original 
  field. 
  It 
  

   is 
  therefore 
  allowable 
  to 
  assume 
  a 
  common 
  

  

  547 
  

  

  