﻿Artificial 
  and 
  Natural 
  Selection 
  803 
  

  

  vious 
  lecture 
  I 
  have 
  detailed 
  the 
  rapid 
  increase 
  

   of 
  the 
  wild-oats 
  in 
  certain 
  years, 
  and 
  described 
  

   the 
  experiments 
  of 
  Risler 
  and 
  Rimpau 
  in 
  the 
  

   running 
  out 
  of 
  select 
  varieties. 
  The 
  agency 
  is 
  

   always 
  the 
  same. 
  The 
  preferred 
  forms, 
  which 
  

   give 
  a 
  larger 
  harvest, 
  are 
  generally 
  more 
  

   sensitive 
  to 
  injurious 
  influences, 
  more 
  dependent 
  

   on 
  rich 
  manure 
  and 
  on 
  adequate 
  treatment. 
  

   The 
  native 
  varieties 
  have 
  therefore 
  the 
  advan- 
  

   tage, 
  when 
  climatic 
  or 
  cultural 
  conditions 
  are 
  

   unfavorable 
  for 
  the 
  fields 
  at 
  large. 
  They 
  suf- 
  

   fer 
  in 
  a 
  minor 
  degree, 
  and 
  are 
  thereby 
  enabled 
  

   to 
  propagate 
  themselves 
  afterwards 
  more 
  rap- 
  

   idly 
  and 
  to 
  defeat 
  the 
  finer 
  types. 
  This 
  

   struggle 
  for 
  life 
  is 
  a 
  constant 
  one, 
  and 
  can 
  

   easily 
  be 
  followed, 
  whenever 
  the 
  composition 
  

   of 
  a 
  strain 
  is 
  noted 
  in 
  successive 
  years. 
  It 
  is 
  

   well 
  appreciated 
  by 
  breeders 
  and 
  farmers, 
  be- 
  

   cause 
  it 
  is 
  always 
  liable 
  to 
  counteract 
  their 
  

   endeavors 
  and 
  to 
  claim 
  their 
  utmost 
  efforts 
  to 
  

   keep 
  their 
  races 
  pure. 
  There 
  can 
  be 
  no 
  doubt 
  

   that 
  exactly 
  the 
  same 
  struggle 
  exempt 
  from 
  

   man's 
  intrusion 
  is 
  fought 
  out 
  in 
  the 
  wild 
  state. 
  

   Local 
  races 
  of 
  wild 
  plants 
  have 
  not 
  been 
  

   the 
  object 
  for 
  field-observations 
  recently. 
  Some 
  

   facts 
  however, 
  are 
  known 
  concerning 
  them. 
  On 
  

   the 
  East 
  Friesian 
  Islands 
  in 
  the 
  North 
  Sea 
  the 
  

   flowers 
  are 
  strikingly 
  larger 
  and 
  brighter 
  col- 
  

   ored 
  than 
  those 
  of 
  the 
  same 
  species 
  on 
  the 
  

  

  