﻿174 
  INTRODUCTION 
  TO 
  BOTANY 
  

  

  165. 
  Unit 
  characters. 
  1 
  Much 
  more 
  definiteness 
  has 
  recently 
  

   been 
  given 
  to 
  the 
  discussion 
  of 
  questions 
  relating 
  to 
  plant 
  

   breeding 
  by 
  the 
  introduction 
  of 
  the 
  idea 
  of 
  unit 
  characters. 
  

   Every 
  species 
  or 
  variety 
  of 
  animal 
  or 
  plant 
  is 
  considered 
  by 
  

   many 
  authorities 
  to 
  be 
  composed 
  of 
  a 
  set 
  of 
  unit 
  characters, 
  

   or 
  simple 
  features 
  by 
  which 
  it 
  is 
  distinguished 
  from 
  other 
  

   species 
  or 
  varieties. 
  -lust 
  what 
  this 
  statement 
  means 
  will 
  ap- 
  

   pear 
  more 
  clearly 
  if 
  some 
  of 
  the 
  unit 
  characters 
  which 
  belong 
  

   to 
  different 
  varieties 
  of 
  a 
  familiar 
  species 
  of 
  plant 
  are 
  set 
  

   down. 
  In 
  the 
  case 
  of 
  timothy, 
  our 
  most 
  important 
  grass 
  for 
  

   haymaking, 
  twenty-eight 
  opposing 
  character 
  pairs 
  have 
  been 
  

   noted. 
  Some 
  of 
  these 
  are 
  

  

  Heads 
  

  

  Long 
  or 
  short 
  

  

  Continuous 
  or 
  interrupted 
  

  

  Large-seeded 
  or 
  small-seeded 
  

  

  (and 
  8 
  others) 
  

   Leaves 
  

  

  Long 
  or 
  short 
  

  

  (and 
  4: 
  others) 
  

   Stem* 
  

  

  Tall 
  or 
  short 
  

  

  .Many 
  or 
  tV\v 
  branches 
  from 
  the 
  base 
  of 
  the 
  stem 
  

  

  (and 
  4 
  others) 
  

   Nodes 
  

  

  Near 
  together 
  or 
  widely 
  separated 
  

  

  (and 
  2 
  others) 
  

   Habit 
  character* 
  

  

  Inclined 
  to 
  blow 
  down 
  or 
  remaining 
  erect 
  

  

  1! 
  list 
  .ing 
  readily 
  or 
  rust-resistant 
  

  

  Marly 
  or 
  late 
  maturing 
  

  

  Careful 
  breeding 
  would 
  probably 
  soon 
  give 
  a 
  variety 
  with 
  

   any 
  one 
  of 
  these 
  twenty-eight 
  characters 
  strongly 
  marked, 
  

   and 
  several 
  of 
  them 
  could 
  be 
  combined 
  in 
  a 
  single 
  variety 
  if 
  

   desired. 
  

  

  1 
  See 
  the 
  valuable 
  .summary 
  of 
  this 
  subject., 
  Driven 
  by 
  Professor 
  Herbert 
  J. 
  

   Wdihcr 
  in 
  his 
  address 
  before 
  the 
  American 
  Breeders' 
  Association, 
  Science, 
  

   April 
  11), 
  1912. 
  

  

  