﻿PLANT 
  BREEDING 
  177 
  

  

  in 
  this 
  respect, 
  so 
  that 
  it 
  is 
  sometimes 
  necessary 
  to 
  select 
  

   only 
  about 
  one 
  best 
  beet 
  out 
  of 
  every 
  thousand 
  to 
  grow 
  seed 
  

   for 
  the 
  next 
  crop. 
  

  

  In 
  the 
  case 
  of 
  plants 
  grown 
  for 
  the 
  production 
  of 
  seed 
  of 
  

   standard 
  varieties 
  for 
  the 
  market, 
  as 
  beans, 
  peas, 
  or 
  any 
  of 
  

   the 
  many 
  flowers 
  (such 
  as 
  sweet 
  peas), 
  in 
  regard 
  to 
  which 
  

   there 
  is 
  much 
  competition, 
  great 
  attention 
  is 
  paid 
  to 
  weeding 
  

   out 
  and 
  destroying 
  plants 
  that 
  do 
  not 
  conform 
  to 
  the 
  standard. 
  

   This 
  process 
  is 
  called 
  roguing. 
  The 
  maintenance 
  of 
  the 
  breed 
  

   depends 
  largely 
  upon 
  the 
  intelligence 
  and 
  thoroughness 
  with 
  

   which 
  it 
  is 
  carried 
  out. 
  

  

  168. 
  Ancient 
  and 
  modern 
  plant 
  breeding. 
  No 
  one 
  knows 
  

   when 
  plant 
  breeding 
  began, 
  because 
  the 
  earliest 
  attempts 
  of 
  

   man 
  to 
  cultivate 
  useful 
  plants 
  date 
  back 
  to 
  unknown 
  antiquity, 
  

   and 
  it 
  is 
  highly 
  probable 
  that 
  the 
  first 
  growers 
  of 
  plants 
  for 
  

   human 
  food 
  more 
  or 
  less 
  unconsciously 
  selected 
  the 
  best 
  seeds 
  

   to 
  be 
  sown 
  for 
  a 
  new 
  crop, 
  and 
  were 
  thus 
  really 
  practicing 
  

   plant 
  breeding. 
  Among 
  the 
  Chinese, 
  agriculture 
  began 
  at 
  

   least 
  4600 
  years 
  ago, 
  and 
  for 
  a 
  considerable 
  part 
  of 
  that 
  time 
  

   they 
  have 
  paid 
  much 
  attention 
  to 
  the 
  perpetuation 
  of 
  desirable 
  

   varieties 
  of 
  the 
  plants 
  of 
  the 
  farm 
  and 
  garden. 
  

  

  Modern 
  plant 
  breeding 
  did 
  not 
  begin 
  at 
  any 
  definite 
  date. 
  

   Some 
  valuable 
  work 
  was 
  done 
  in 
  selecting 
  and 
  propagating 
  

   improved 
  varieties 
  of 
  wheat 
  in 
  Great 
  Britain 
  as 
  early 
  as 
  the 
  

   first 
  quarter 
  of 
  the 
  nineteenth 
  century, 
  but 
  it 
  was 
  not 
  until 
  

   toward 
  the 
  middle 
  of 
  the 
  century 
  that 
  many 
  investigators 
  

   began 
  to 
  try 
  to 
  put 
  plant 
  breeding 
  on 
  a 
  scientific 
  foundation, 
  

   working 
  with 
  plants 
  ranging 
  all 
  the 
  way 
  from 
  the 
  cereals 
  to 
  

   sugar 
  beets. 
  One 
  of 
  the 
  main 
  problems 
  in 
  plant 
  breeding 
  is 
  

   that 
  of 
  predicting 
  the 
  way 
  in 
  which 
  the 
  characters 
  of 
  a 
  plant 
  

   will 
  be 
  inherited 
  by 
  its 
  descendants. 
  In 
  a 
  large 
  number 
  of 
  

   cases, 
  a 
  number 
  which 
  is 
  rapidly 
  increasing, 
  it 
  is 
  possible 
  to 
  

   make 
  such 
  predictions 
  with 
  scientific 
  accuracy. 
  These 
  are 
  

   based 
  on 
  the 
  immense 
  mass 
  of 
  data 
  which 
  has 
  been 
  gained 
  

   from 
  tens 
  of 
  thousands 
  of 
  experiments 
  made 
  by 
  scientific 
  

   investigators 
  and 
  by 
  practical 
  plant 
  breeders 
  everywhere. 
  

  

  