﻿678 
  Mutations 
  

  

  to 
  the 
  assumption 
  of 
  independent 
  and 
  parallel 
  

   mutations. 
  

  

  For 
  the 
  purpose 
  of 
  a 
  comparison 
  with 
  the 
  

   Hehvingia 
  type 
  we 
  are 
  however, 
  not 
  at 
  all 
  con- 
  

   cerned 
  with 
  the 
  species 
  to 
  which 
  the 
  trif 
  urea- 
  

   turn 
  variety 
  belongs, 
  but 
  only 
  with 
  the 
  varietal 
  

   mark 
  itself. 
  The 
  spikelets 
  may 
  be 
  one-, 
  two- 
  or 
  

   three-flowered, 
  according 
  to 
  the 
  species. 
  If 
  we 
  

   choose 
  for 
  further 
  consideration 
  the 
  hexasti- 
  

   chum 
  type, 
  each 
  spikelet 
  produces 
  three 
  nor- 
  

   mal 
  flowers 
  and 
  afterwards 
  three 
  normal 
  grains. 
  

   Morphologically 
  however, 
  the 
  spikelet 
  is 
  not 
  

   homologous 
  to 
  those 
  parts 
  of 
  other 
  grasses 
  

   which 
  have 
  the 
  same 
  name. 
  It 
  is 
  constituted 
  of 
  

   three 
  real 
  spikelets, 
  and 
  thus 
  deserves 
  the 
  name 
  

   of 
  a 
  triple 
  construction. 
  Each 
  of 
  these 
  three 
  

   little 
  organs 
  has 
  its 
  normal 
  pair 
  of 
  outer 
  scales 
  

   or 
  glumae. 
  These 
  are 
  linear 
  and 
  short, 
  ending 
  

   in 
  a 
  long 
  and 
  narrow 
  spine. 
  Those 
  of 
  the 
  mid- 
  

   dle-most 
  spikelets 
  stand 
  on 
  its 
  outer 
  side, 
  while 
  

   those 
  of 
  the 
  lateral 
  part 
  are 
  placed 
  transversely. 
  

   In 
  this 
  way 
  they 
  form 
  a 
  kind 
  of 
  involucre 
  

   around 
  the 
  central 
  parts. 
  The 
  latter 
  consist 
  

   of 
  the 
  inner 
  and 
  outer 
  palets 
  or 
  scales, 
  each 
  two 
  

   of 
  which 
  include 
  one 
  of 
  the 
  flowers. 
  The 
  outer 
  

   palet 
  is 
  to 
  be 
  considered 
  as 
  the 
  metamorphosed 
  

   leaf, 
  in 
  the 
  axil 
  of 
  which 
  the 
  flower 
  is 
  produced. 
  

   In 
  the 
  common 
  sorts 
  of 
  barley 
  it 
  bears 
  a 
  long 
  

   awn, 
  giving 
  thereby 
  its 
  typical 
  aspect 
  to 
  the 
  

  

  