﻿180 
  

  

  INTRODUCTION 
  TO 
  BOTANY 
  

  

  171. 
  Principles 
  upon 
  which 
  wheat 
  breeding 
  depends. 
  1 
  The 
  

   work 
  of 
  the 
  earliest 
  breeders 
  of 
  wheat 
  was 
  not 
  based 
  on 
  any 
  

   general 
  knowledge 
  of 
  the 
  laws 
  of 
  plant 
  variation 
  and 
  inheri- 
  

   tance. 
  The 
  principles 
  of 
  breeding, 
  as 
  applied 
  to 
  the 
  small 
  

  

  grains, 
  were 
  first 
  worked 
  out 
  

   by 
  Professor 
  W. 
  M. 
  Hays 
  

   of 
  the 
  University 
  of 
  Minne- 
  

   sota 
  Agricultural 
  Experi- 
  

   ment 
  Station, 
  and 
  by 
  Dr. 
  

   Hjalmar 
  Nilsson, 
  director 
  

   of 
  the 
  experiment 
  station 
  

   at 
  Svalof, 
  Sweden. 
  Some 
  of 
  

   the 
  main 
  principles 
  upon 
  

   which 
  wheat 
  breeding 
  de- 
  

   pends 
  may 
  be 
  stated 
  as 
  

   follows: 
  

  

  1. 
  Every 
  species 
  of 
  cereal 
  

   usually 
  comprises 
  many 
  

   well-marked 
  varieties, 
  or, 
  as 
  

   they 
  are 
  sometimes 
  called, 
  

   I'lnnentary 
  species. 
  Some- 
  

   times 
  several 
  hundreds 
  of 
  

   these 
  are 
  included 
  in 
  each 
  

  

  of 
  the 
  longest-cultivated 
  spe- 
  

  

  The 
  hybrid 
  is 
  in 
  the 
  middle. 
  It 
  is 
  somewhat 
  t 
  + 
  i 
  ,Kl, 
  r 
  

  

  intermediate 
  between 
  the 
  parents, 
  being 
  Cies 
  of 
  grain; 
  this 
  is 
  notably 
  

  

  nearly 
  (though 
  not 
  quite) 
  beardless, 
  like 
  the 
  true 
  in 
  the 
  case 
  of 
  wheat, 
  

  

  right-hand 
  parent, 
  with 
  a 
  length 
  of 
  head 
  9 
  rpi 
  vqr 
  i 
  P 
  tips 
  while 
  

   intermediate 
  between 
  the 
  two 
  and 
  with 
  

  

  the 
  grains 
  and 
  their 
  covering 
  bracts 
  stout, 
  still 
  growing 
  in 
  the 
  field, 
  

  

  as 
  in 
  the 
  left-hand 
  parent. 
  Photograph 
  by 
  , 
  diatinffuiahed 
  bv 
  

   Minnesota 
  Agrienltm-al 
  Experiment 
  Station 
  

  

  such 
  botanical 
  characters 
  as 
  

  

  the 
  position, 
  shape, 
  size, 
  and 
  bearded 
  or 
  beardless 
  condition 
  of 
  

   the 
  head 
  ; 
  the 
  form, 
  size, 
  and 
  appendages 
  of 
  the 
  spikelets 
  which 
  

   it 
  contains 
  ; 
  and 
  the 
  size, 
  shape, 
  color, 
  and 
  hardness 
  of 
  the 
  grain. 
  2 
  

  

  * 
  See 
  De 
  Vries, 
  Plant 
  Breeding. 
  The 
  Open 
  Court 
  Publishing 
  Company, 
  

   Chicago. 
  

  

  2 
  The 
  hardness 
  cannot 
  be 
  accurately 
  known 
  until 
  the 
  grain 
  is 
  ripe 
  and 
  dry. 
  

  

  FIG. 
  155. 
  A 
  hybrid 
  wheat 
  and 
  the 
  parent 
  

   forms 
  

  

  