﻿R. 
  E. 
  Call 
  — 
  Silicijied 
  Woods 
  of 
  Eastern 
  Arkansas. 
  397 
  

  

  were 
  eroded 
  away, 
  the 
  portion 
  of 
  the 
  trunk 
  which 
  had 
  been 
  

   buried 
  therein 
  was 
  subjected 
  to 
  the 
  action 
  of 
  waters 
  contain- 
  

   ing 
  silica 
  in 
  solution 
  and 
  the 
  lignitic 
  matter 
  was 
  rej^laced 
  by 
  

   silica. 
  

  

  The 
  silica 
  is, 
  of 
  course, 
  all 
  present 
  as 
  secondary 
  quartz, 
  is 
  

   often 
  massive 
  but, 
  also, 
  frequently 
  crystallized. 
  Especially 
  is 
  

   holocrystalline 
  quartz 
  abundant 
  in 
  specimens 
  of 
  wood 
  that 
  

   were 
  partially 
  decayed 
  when 
  the 
  older 
  lignification 
  process 
  

   began. 
  In 
  the 
  drusy 
  cavities 
  of 
  such 
  lignite 
  are 
  found 
  large 
  

   numbers 
  of 
  perfect 
  and 
  rather 
  large 
  quartz 
  crystals. 
  These 
  are 
  

   often, 
  in 
  some 
  specimens 
  always, 
  characterized 
  by 
  a 
  uniform 
  

   dark 
  or 
  brownish 
  color 
  which 
  is 
  due 
  to 
  inclusions 
  of 
  limonite.* 
  

  

  Professor 
  F. 
  H. 
  Knowlton, 
  of 
  the 
  U. 
  S. 
  Geological 
  Survey, 
  

   has 
  studied 
  microscopically 
  both 
  the 
  lignite 
  and 
  silicified 
  woods 
  

   found 
  in 
  eastern 
  Arkansas. 
  The 
  results 
  of 
  his 
  work 
  may 
  be 
  

   found 
  in 
  vol. 
  ii 
  of 
  the 
  Arkansas 
  Geological 
  Survey, 
  Reports 
  

   for 
  1889. 
  His 
  studies 
  have 
  developed 
  the 
  interesting 
  fact 
  

   that 
  the 
  woods 
  belong 
  to 
  both 
  dicotyledonous 
  and 
  coniferous 
  

   types. 
  This 
  occurrence 
  is 
  the 
  first 
  known 
  dicotyledonous 
  wood 
  

   found 
  in 
  this 
  country 
  in 
  rocks 
  older 
  than 
  Pleistocene 
  and 
  is 
  

   the 
  first 
  dicotyledonous 
  form 
  determined 
  by 
  internal 
  structure. 
  

   If, 
  therefore, 
  examinations 
  of 
  both 
  lignites 
  and 
  silicified 
  woods 
  

   are 
  made 
  and 
  it 
  results 
  that 
  the 
  same 
  form 
  or 
  forms 
  are 
  repre- 
  

   sented 
  in 
  both, 
  a 
  strong 
  reason 
  exists 
  for 
  genetically 
  connect- 
  

   ing 
  the 
  silicified 
  woods 
  with 
  the 
  lignites. 
  

  

  Unfortunately 
  for 
  taxonomic 
  purposes 
  all 
  the 
  forms 
  described 
  

   by 
  Prof. 
  Knowlton 
  are 
  new, 
  but 
  some 
  otherwise 
  valuable 
  

   results 
  have 
  been 
  reached. 
  In 
  the 
  first 
  place 
  he 
  finds, 
  among 
  

   the 
  four 
  new 
  species 
  studied, 
  two 
  forms 
  which 
  are 
  clearly 
  dicot-* 
  

   yledonous, 
  and 
  two 
  others 
  distinctly 
  coniferous 
  in 
  relationship. 
  

   The 
  species 
  are 
  : 
  

  

  Coniferous. 
  Dicotyledonous. 
  

  

  Cupressinoxylon 
  Arkansanum, 
  Laurinoxylon 
  JBranneri^ 
  

   Cupressinoxylon 
  Calli, 
  Laurinoxylon 
  Lesquereuxiana. 
  

  

  There 
  was 
  also 
  a 
  single 
  additional 
  specimen 
  whose 
  affinities 
  

   appeared 
  to 
  be 
  dicotyledonous 
  and 
  to 
  belong 
  to 
  Laurinoxylon 
  ; 
  

   the 
  condition 
  of 
  the 
  material 
  would 
  not 
  admit 
  of 
  closer 
  deter- 
  

   mination. 
  The 
  specimens 
  found 
  indicate 
  comparatively 
  few 
  

   species 
  but 
  these 
  few 
  must 
  have 
  existed 
  in 
  great 
  numbers. 
  

   One 
  of 
  the 
  most 
  valuable 
  and 
  pertinent 
  facts 
  in 
  this 
  connec- 
  

   tion 
  is 
  the 
  finding 
  of 
  the 
  dicotyledonous 
  Laicrinoxylon 
  Bran- 
  

   neri 
  in 
  the 
  lignite 
  bed 
  of 
  Bolivar 
  Creek, 
  as 
  lignite, 
  deeply 
  

   buried 
  in 
  Eocene 
  clays 
  in 
  massive 
  form. 
  

  

  * 
  An 
  especially 
  fine 
  example 
  of 
  this 
  nature 
  was 
  taken 
  from 
  a 
  section 
  in 
  Ter- 
  

   tiary 
  sands 
  1 
  3 
  miles 
  southeast 
  of 
  the 
  town 
  of 
  Camden 
  on 
  the 
  line 
  of 
  the 
  Camden 
  

   and 
  Alexandria 
  railroad. 
  Of 
  the 
  many 
  thousands 
  of 
  quartz 
  crystals 
  which 
  this 
  

   specimen 
  exhibits 
  not 
  one 
  has 
  been 
  seen 
  which 
  is 
  free 
  from 
  inclusions 
  of 
  limonite. 
  

  

  