﻿416 
  Brown: 
  Silicious 
  skeleton 
  

  

  layer 
  in 
  most 
  of 
  the 
  fibers 
  is 
  thin 
  and 
  poorly 
  defined, 
  hence 
  what 
  

   remains 
  of 
  the 
  fiber 
  wall 
  after 
  thorough 
  maceration 
  is 
  composed 
  

   almost 
  wholly 
  of 
  secondary 
  thickening. 
  When 
  these 
  macerated 
  

   fibers 
  are 
  washed, 
  dried, 
  then 
  burned 
  on 
  a 
  mica 
  slip, 
  the 
  isolated 
  

   or 
  partly 
  isolated 
  rods, 
  and 
  their 
  relative 
  position 
  and 
  branching 
  

   may 
  be 
  observed. 
  In 
  By 
  Fig. 
  3, 
  is 
  seen 
  an 
  isolated 
  unbranched 
  

   rod 
  over 
  30 
  /i 
  in 
  length, 
  projecting 
  from 
  the 
  charred 
  end 
  of 
  a 
  partly 
  

   burned 
  fiber; 
  in 
  D 
  are 
  shown 
  three 
  such 
  rods. 
  Two 
  parallel 
  un- 
  

   branched 
  rods 
  (Fig. 
  3, 
  C) 
  were 
  traced 
  a 
  distance 
  of 
  90 
  /i, 
  partly 
  

   free 
  and 
  partly 
  imbedded 
  in 
  a 
  transparent 
  matrix 
  of 
  unburned 
  

   material, 
  as 
  showri 
  in 
  the 
  drawing. 
  In 
  burned 
  tracheids 
  of 
  

   Trochodendron, 
  unbranched 
  rods 
  1.15 
  mm. 
  in 
  length 
  were 
  found 
  in 
  

   one 
  instance. 
  Occasionally 
  the 
  rods 
  branch 
  as 
  shown 
  in 
  F, 
  from 
  

   Tecoma. 
  The 
  diameter 
  cannot 
  be 
  accurately 
  determined 
  from 
  

   burned 
  material, 
  since 
  products 
  of 
  combustion 
  and 
  fusion 
  adhere 
  

  

  to 
  the 
  outer 
  surface 
  of 
  the 
  rods. 
  It 
  is 
  probable 
  that 
  the 
  

  

  film 
  

  

  between 
  

  

  H, 
  Fig. 
  3, 
  are 
  merely 
  the 
  products 
  of 
  combustion 
  and 
  hence 
  not 
  a 
  

   structural 
  feature 
  of 
  the 
  skeleton. 
  From 
  such 
  data 
  the 
  structure 
  

   of 
  the 
  skeleton, 
  as 
  well 
  as 
  its 
  position 
  in 
  the 
  fiber 
  wall, 
  may 
  be 
  

   inferred. 
  The 
  essential 
  feature 
  of 
  the 
  skeleton 
  consists 
  in 
  the 
  

   presence 
  of 
  longitudinal 
  rods, 
  and 
  these 
  were 
  never 
  found 
  absent 
  

   from 
  the 
  fibers 
  and 
  tracheids 
  of 
  the 
  wood 
  or 
  in 
  the 
  fibers 
  of 
  the 
  bast 
  

   in 
  any 
  species 
  examined 
  by 
  the 
  writer. 
  Other 
  details 
  of 
  the 
  skele- 
  

   ton, 
  however, 
  may 
  vary 
  considerably, 
  according 
  to 
  the 
  species, 
  

   genus, 
  or 
  family 
  in 
  which 
  it 
  occurs. 
  Thus, 
  in 
  the 
  thin-walled 
  

  

  umber 
  

  

  ■pidosperma 
  

  

  Hicoria 
  

  

  r 
  J 
  — 
  

  

  and 
  of 
  extremely 
  small 
  diameter; 
  in 
  Pinus 
  Strohus, 
  they 
  are 
  

   relatively 
  much 
  branched; 
  in 
  Araucaria 
  brasiliana, 
  they 
  are 
  few 
  

   and 
  of 
  unequal 
  diameter. 
  Silicious 
  rods 
  are 
  present 
  in 
  the 
  fibrous 
  

   strands 
  in 
  the 
  haulms 
  of 
  Secale 
  cereale, 
  but 
  in 
  the 
  walls 
  of 
  the 
  

  

  more 
  

  

  burning, 
  the 
  cellular 
  structure 
  including 
  the 
  guard 
  cells 
  of 
  the 
  

   stomata 
  is 
  preserved. 
  

  

  .Chemical 
  composition. 
  —The 
  skeleton-rods 
  in 
  all 
  species 
  ex- 
  

   amined 
  were 
  found 
  to 
  be 
  composed, 
  in 
  large 
  part 
  at 
  least, 
  of 
  non- 
  

  

  