﻿CHAPTER 
  XII 
  

   PLANT 
  BREEDING 
  

  

  164. 
  The 
  basis 
  of 
  plant 
  breeding. 
  It 
  is 
  the 
  business 
  of 
  the 
  

   professional 
  plant 
  breeder 
  to 
  discover 
  or 
  originate 
  desirable 
  

   varieties 
  of 
  plants 
  and 
  then 
  to 
  perpetuate 
  them. 
  As 
  soon 
  

   as 
  he 
  becomes 
  certain 
  that 
  he 
  has 
  obtained 
  a 
  really 
  valuable 
  

   new 
  variety, 
  he 
  proceeds 
  to 
  multiply 
  it 
  until 
  he 
  can 
  offer 
  to 
  

   growers 
  everywhere 
  its 
  seeds, 
  bulbs, 
  or 
  other 
  means 
  of 
  repro- 
  

   ducing 
  it. 
  

  

  The 
  possibility 
  of 
  producing 
  new 
  varieties 
  rests 
  largely 
  

   upon 
  two 
  highly 
  important 
  facts 
  : 
  

  

  1. 
  That 
  all 
  the 
  Myher 
  plants 
  vary 
  from 
  generation 
  to 
  

   generation. 
  

  

  2. 
  That 
  the 
  higher 
  plants 
  sometimes 
  mutate. 
  

  

  Variations 
  are 
  familiar 
  enough 
  to 
  every 
  observing 
  person. 
  No 
  

   two 
  corn 
  plants, 
  bean 
  plants, 
  or 
  tomato 
  plants 
  are 
  just 
  alike, 
  

   even 
  though 
  they 
  may 
  have 
  been 
  grown 
  from 
  seed 
  from 
  the 
  

   same 
  ear, 
  the 
  same 
  bean 
  pod, 
  or 
  the 
  same 
  tomato. 
  The 
  varia- 
  

   tions 
  may 
  be 
  noticed 
  in 
  the 
  root, 
  stem, 
  leaf, 
  flower, 
  or 
  fruit, 
  

   or 
  in 
  several 
  or 
  all 
  of 
  these. 
  The 
  term 
  mutation 
  is 
  less 
  com- 
  

   monly 
  used 
  than 
  the 
  term 
  variation. 
  It 
  is 
  the 
  scientific 
  name 
  

   for 
  the 
  kind 
  of 
  abrupt 
  appearances 
  of 
  forms, 
  extremely 
  unlike 
  

   the 
  parent, 
  long 
  known 
  to 
  horticulturists 
  as 
  sports. 
  A 
  single 
  

   bud 
  upon 
  a 
  peach 
  tree 
  may 
  mutate 
  and 
  produce 
  a 
  branch 
  which 
  

   will 
  bear 
  nectarines, 
  and 
  a 
  bud 
  upon 
  a 
  tree 
  which 
  bore 
  purple 
  

   plums 
  has 
  been 
  observed 
  to 
  grow 
  into 
  a 
  branch 
  which 
  bore 
  

   only 
  yellow 
  plums 
  of 
  a 
  kind 
  previously 
  unknown. 
  Some 
  of 
  

   the 
  most 
  valuable 
  varieties 
  of 
  the 
  grains 
  are 
  seed 
  sports, 
  or 
  

   mutations 
  first 
  noticed 
  in 
  the 
  seedling 
  grown 
  from 
  the 
  seed 
  

   of 
  a 
  very 
  different 
  variety. 
  

  

  173 
  

  

  