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  Retrograde 
  Varieties 
  

  

  variety 
  are 
  essentially 
  different. 
  The 
  charac- 
  

   ter 
  in 
  question 
  may 
  be 
  present 
  in 
  the 
  given 
  spe- 
  

   cies 
  or 
  it 
  may 
  be 
  lacking, 
  but 
  present 
  in 
  the 
  other 
  

   group. 
  In 
  the 
  first 
  case 
  a 
  variety 
  can 
  only 
  be 
  

   formed 
  by 
  the 
  loss 
  of 
  the 
  character, 
  in 
  the 
  sec- 
  

   ond 
  case 
  it 
  arises 
  by 
  the 
  addition 
  of 
  a 
  new 
  one. 
  

  

  The 
  first 
  mode 
  may 
  be 
  called 
  a 
  negative 
  pro- 
  

   cess, 
  while 
  the 
  second 
  is 
  then 
  to 
  be 
  designated 
  

   as 
  positive. 
  And 
  as 
  it 
  is 
  more 
  easy 
  to 
  lose 
  what 
  

   one 
  has 
  than 
  to 
  obtain 
  something 
  new, 
  negative 
  

   varieties 
  are 
  much 
  more 
  common 
  than 
  are 
  posi- 
  

   tive 
  ones. 
  

  

  Let 
  us 
  now 
  take 
  an 
  instance 
  of 
  a 
  character 
  

   that 
  is 
  apt 
  to 
  vary 
  in 
  both 
  ways, 
  for 
  this 
  is 
  ob- 
  

   viously 
  the 
  best 
  way 
  of 
  making 
  clear 
  what 
  is 
  

   meant 
  by 
  a 
  negative 
  and 
  a 
  positive 
  change. 
  

  

  In 
  the 
  family 
  of 
  the 
  composites 
  we 
  find 
  a 
  

   group 
  of 
  genera 
  with 
  two 
  forms 
  of 
  florets 
  on 
  

   each 
  flower-head. 
  The 
  hermaphrodite 
  ones 
  are 
  

   tubular 
  with 
  5, 
  or 
  rarely 
  4, 
  equal 
  teeth, 
  and 
  oc- 
  

   cupy 
  the 
  center 
  of 
  the 
  head. 
  These 
  are 
  often 
  

   called 
  the 
  flosculous 
  florets 
  or 
  disk-florets. 
  

   Those 
  of 
  the 
  circumference 
  are 
  ligulate 
  and 
  

   ordinarily 
  unisexual, 
  without 
  stamens. 
  In 
  many 
  

   cases 
  they 
  are 
  sterile, 
  having 
  only 
  an 
  imperfect 
  

   ovary. 
  They 
  are 
  large 
  and 
  brightly 
  colored 
  and 
  

   are 
  generally 
  designated 
  as 
  ray-florets. 
  As 
  in- 
  

   stances 
  we 
  may 
  cite 
  the 
  camomile 
  (Anthemis 
  

   nobilis), 
  the 
  wild 
  camomile 
  (Matricaria 
  Cham- 
  

  

  