﻿PRINCIPAL 
  DAWSON-^-PROTOTAXITES 
  AND 
  PACHYTHECA. 
  103 
  

  

  9. 
  Notes 
  on 
  Prototaxites 
  and 
  Pachytheca 
  discovered 
  by 
  Dr. 
  Hicks 
  

   in 
  the 
  Denbighshire 
  Grits 
  of 
  Corwen, 
  N". 
  "Wales. 
  By 
  Prin- 
  

   cipal 
  Dawson, 
  LL.D., 
  F.R.S., 
  &c, 
  M'Gill 
  College, 
  Montreal. 
  

   (Eead 
  November 
  16, 
  1881.) 
  

  

  Specimens 
  of 
  the 
  first-mentioned 
  fossil 
  were 
  kindly 
  sent 
  to 
  me 
  by 
  

   Dr. 
  Hicks, 
  at 
  my 
  request, 
  but 
  unfortunately 
  arrived 
  when 
  I 
  was 
  at 
  

   my 
  summer 
  residence 
  at 
  Little 
  Metis. 
  Though 
  without 
  the 
  means 
  

   of 
  examining 
  them 
  microscopically, 
  I 
  ventured 
  to 
  write, 
  after 
  

   studying 
  them 
  with 
  a 
  good 
  pocket-lens, 
  that 
  they 
  resembled 
  Pro- 
  

   totaxites, 
  and 
  could 
  not 
  be 
  referred 
  to 
  Algae. 
  The 
  latter 
  conclu- 
  

   sion 
  might 
  appear 
  rash 
  ; 
  but 
  there 
  are, 
  to 
  the 
  practised 
  eye, 
  indi- 
  

   cations 
  in 
  specimens 
  of 
  this 
  kind 
  which 
  can 
  scarcely 
  deceive. 
  

   The 
  fibrous 
  and 
  highly 
  carbonaceous 
  nature 
  of 
  the 
  darker 
  speci- 
  

   mens, 
  and 
  the 
  silky 
  and 
  incoherent 
  texture 
  of 
  the 
  lighter-coloured 
  

   ones, 
  are 
  characters 
  never 
  found 
  in 
  any 
  fossil 
  plants 
  except 
  those 
  

   having 
  durable 
  woody 
  tissues. 
  Further, 
  the 
  occurrence 
  of 
  the 
  

   material 
  in 
  angular 
  fragments 
  and 
  in 
  a 
  condition 
  approaching 
  to 
  

   that 
  of 
  the 
  mineral 
  charcoal 
  of 
  -the 
  Coal-measures, 
  proves 
  subaerial 
  

   decay, 
  little 
  likely 
  to 
  have 
  occurred 
  in 
  the 
  case 
  of 
  aquatic 
  plants. 
  

   From 
  the 
  state 
  of 
  preservation 
  of 
  the 
  specimens, 
  I 
  also 
  inferred 
  that, 
  

   if 
  really 
  of 
  the 
  nature 
  of 
  Prototaxites, 
  they 
  might 
  throw 
  some 
  addi- 
  

   tional 
  light 
  on 
  its 
  structure, 
  as 
  the 
  specimens 
  previously 
  studied 
  had 
  

   been 
  from 
  entire 
  trunks 
  in 
  a 
  silicified 
  state. 
  

  

  On 
  my 
  return 
  to 
  town, 
  I 
  found 
  awaiting 
  me 
  the 
  Journal 
  of 
  the 
  

   Geological 
  Society 
  containing 
  Dr. 
  Hicks's 
  paper 
  ; 
  and 
  the 
  figures 
  

   there 
  given 
  showed 
  at 
  once 
  the 
  correctness 
  of 
  the 
  reference 
  made 
  by 
  

   Mr. 
  Etheridge 
  of 
  the 
  plant 
  to 
  Prototaxites, 
  and 
  its 
  close 
  resemblance 
  

   to 
  P. 
  Logani*, 
  except 
  in 
  the 
  appearance 
  of 
  bifurcating 
  fibres, 
  a 
  cha- 
  

   racter 
  which 
  I 
  have 
  not 
  observed, 
  and 
  which 
  may 
  be 
  merely 
  an 
  

   error 
  in 
  observation 
  or 
  in 
  drawing. 
  

  

  Portions 
  of 
  the 
  specimens 
  sent 
  by 
  Dr. 
  Hicks 
  were 
  at 
  once 
  pre- 
  

   pared, 
  not 
  only 
  by 
  slicing 
  but 
  by 
  treatment 
  with 
  boiling 
  nitric 
  acid, 
  

   and 
  by 
  diffusion 
  of 
  the 
  more 
  lax 
  fibres 
  in 
  water 
  and 
  in 
  Canada 
  

   balsam. 
  On 
  examination 
  they 
  gave 
  the 
  results 
  stated 
  below. 
  

  

  In 
  state 
  of 
  preservation 
  the 
  two 
  kinds 
  of 
  specimens 
  examined 
  

   are 
  somewhat 
  different. 
  The 
  dark 
  variety 
  has 
  the 
  long 
  cells 
  or 
  

   woody 
  fibres 
  filled 
  with 
  rods 
  of 
  transparent 
  siliceous 
  matter, 
  and 
  

   the 
  walls 
  are 
  represented 
  by 
  a 
  thick 
  structureless 
  layer 
  of 
  carbon, 
  

   which 
  often 
  shows 
  angular 
  cracks, 
  such 
  as 
  appear 
  in 
  the 
  walls 
  of 
  

   thick-walled 
  woody 
  fibres 
  when 
  carbonized. 
  These 
  cracks 
  are 
  some- 
  

   times 
  transverse, 
  giving 
  a 
  scalariform 
  appearance, 
  but 
  they 
  do 
  not 
  

   represent 
  a 
  true 
  structure. 
  The 
  internal 
  siliceous 
  casts, 
  when 
  bared 
  

   by 
  nitric 
  acid 
  of 
  their 
  carbonaceous 
  coating, 
  show 
  here 
  and 
  there 
  

   transverse 
  or 
  spiral 
  markings, 
  produced 
  by 
  the 
  projection 
  of 
  the 
  

   ligneous 
  lining 
  on 
  the 
  inner 
  side 
  of 
  the 
  cells. 
  There 
  is 
  no 
  trace 
  of 
  

  

  * 
  Eeport 
  on 
  Devonian 
  Plants 
  of 
  Canada, 
  1871, 
  pi. 
  ii. 
  

   Q. 
  J. 
  G. 
  S. 
  No. 
  150. 
  i 
  

  

  