﻿104 
  PRINCIPAL 
  DAWSON 
  ON 
  PPvOTOTAXITES 
  AND 
  

  

  the 
  intercellular 
  flocculent 
  matter 
  produced 
  by 
  decay 
  of 
  the 
  outer 
  

   surfaces 
  of 
  the 
  cells 
  or 
  their 
  connecting 
  tissue, 
  such 
  as 
  I 
  have 
  

   described 
  in 
  the 
  silicified 
  trunks 
  of 
  Prototaxites. 
  

  

  The 
  lighter-coloured 
  variety 
  has 
  probably 
  been 
  originally 
  preser- 
  

   ved 
  in 
  a 
  similar 
  manner 
  ; 
  but 
  the 
  woody 
  envelope 
  of 
  the 
  fibres 
  has 
  

   been 
  entirely 
  removed, 
  leaving 
  only 
  the 
  siliceous 
  internal 
  casts, 
  

   which 
  are 
  so 
  lax 
  that 
  they 
  can 
  be 
  scraped 
  into 
  water 
  and 
  viewed 
  as 
  

   transparent 
  objects 
  without 
  slicing. 
  This 
  is 
  precisely 
  the 
  state 
  of 
  

   the 
  asbestos-like 
  silicified 
  Coniferous 
  wood 
  found 
  in 
  the 
  gold 
  gravels 
  

   of 
  California. 
  These 
  rod-like 
  siliceous 
  casts 
  preserve 
  on 
  their 
  sur- 
  

   faces 
  distinct 
  traces 
  of 
  the 
  irregularly 
  spiral 
  ligneous 
  lining 
  of 
  the 
  

   perished 
  cell-wall. 
  A 
  few 
  of 
  them 
  also 
  show 
  rounded 
  bodies 
  of 
  

   brownish 
  colour 
  in 
  their 
  interior. 
  These 
  may 
  be 
  ferruginous 
  con- 
  

   cretions, 
  but 
  are 
  possibly 
  granules 
  of 
  resinous 
  matter, 
  in 
  which 
  case 
  

   such 
  tubes 
  may 
  represent 
  resin-cells. 
  

  

  In 
  all 
  the 
  above 
  particulars 
  these 
  specimens 
  confirm 
  my 
  original 
  

   determination 
  of 
  the 
  woody 
  character 
  of 
  Prototaxites, 
  to 
  which 
  genus 
  

   they 
  undoubtedly 
  belong. 
  They 
  differ, 
  however, 
  from 
  P. 
  Logani 
  in 
  

   the 
  smaller 
  diameter 
  of 
  the 
  fibres, 
  and 
  in 
  the 
  ligneous 
  lining, 
  which 
  

   presents 
  the 
  appearance 
  of 
  interrupted 
  transverse 
  bands 
  rather 
  than 
  

   regular 
  spirals. 
  These 
  characters 
  would 
  seem 
  to 
  indicate 
  a 
  distinct 
  

   species, 
  which 
  may 
  therefore 
  be 
  named 
  P. 
  Hicksii, 
  in 
  honour 
  of 
  its 
  

   discoverer*. 
  I 
  may 
  recall 
  here 
  a 
  statement 
  made 
  in 
  my 
  report 
  on 
  

   the 
  Devonian 
  plants 
  of 
  Canada, 
  that 
  in 
  1870, 
  when 
  Mr. 
  Etheridge 
  

   was 
  so 
  kind 
  as 
  to 
  permit 
  me 
  to 
  examine 
  the 
  slabs 
  in 
  the 
  Jermyn- 
  

   Street 
  Museum, 
  with 
  Pachytheca 
  of 
  Hooker 
  from 
  the 
  Ludlow, 
  I 
  

   recognized, 
  associated 
  with 
  this, 
  fragments 
  of 
  wood 
  having 
  the 
  

   structure 
  of 
  Prototaxites. 
  The 
  similar 
  association 
  in 
  Dr. 
  Hicks's 
  spe- 
  

   cimens 
  and 
  the 
  peculiar 
  fibrous 
  structure 
  of 
  the 
  walls 
  of 
  Pachytheca, 
  

   as 
  figured 
  by 
  Mr. 
  Etheridge, 
  may 
  well 
  excite 
  the 
  suspicion 
  that 
  these 
  

   bodies 
  are 
  connected 
  with 
  Prototaxites, 
  especially 
  as 
  similar 
  round 
  

   bodies 
  are 
  seen 
  in 
  beds 
  holding 
  this 
  fossil 
  in 
  Canada, 
  though 
  without 
  

   distinct 
  structure. 
  In 
  this 
  connexion 
  it 
  is 
  to 
  be 
  observed 
  that 
  the 
  

   bodies 
  in 
  question 
  are 
  probably 
  seeds 
  rather 
  than 
  spore-cases, 
  and 
  

   that 
  they 
  have 
  the 
  structure 
  of 
  JEtheotesta, 
  to 
  which, 
  in 
  a 
  recent 
  

   paper 
  in 
  the 
  Journal 
  of 
  the 
  Geological 
  Societyt, 
  I 
  have 
  referred 
  a 
  

   similar 
  seed, 
  found 
  in 
  the 
  Devonian 
  of 
  Scotland. 
  

  

  With 
  reference 
  to 
  the 
  affinities 
  of 
  Prototaxites, 
  I 
  have 
  not 
  made 
  

   the 
  crude 
  assertion 
  attributed 
  to 
  me, 
  that 
  this 
  plant 
  " 
  belonged 
  to 
  

   Taxinese." 
  I 
  merely 
  compared 
  its 
  structure 
  to 
  the 
  lax 
  spiral 
  fibre 
  of 
  

   some 
  Taxine 
  trees, 
  and 
  especially 
  to 
  certain 
  Taxine 
  woods 
  fossilized 
  

   after 
  long 
  immersion 
  in 
  water, 
  with 
  which 
  we 
  are 
  familiar 
  in 
  the 
  

   Tertiary 
  formations. 
  This 
  was 
  all 
  that 
  was 
  intended 
  by 
  the 
  name 
  

   Prototaxites, 
  except 
  to 
  suggest 
  that 
  this 
  plant 
  was 
  one 
  of 
  the 
  proto- 
  

   typal 
  gymnosperms 
  of 
  the 
  Palasozoic 
  period. 
  Further, 
  in 
  consequence 
  

   of 
  its 
  upper 
  limit 
  in 
  Canada 
  being 
  apparently 
  the 
  Lower 
  Devonian, 
  

   where 
  it 
  comes 
  into 
  contact 
  with 
  the 
  wood 
  of 
  the 
  earliest 
  species 
  of 
  

   Dadoxylon, 
  I 
  have 
  conjectured 
  that 
  it 
  would 
  be 
  found 
  in 
  much 
  older 
  

  

  * 
  Instead 
  of 
  Nematophycus 
  HicJcsii, 
  as 
  proposed 
  by 
  Mr. 
  Etheridge. 
  

   t 
  Vol. 
  xxxvii. 
  p. 
  306, 
  pi. 
  xii. 
  fig. 
  14. 
  

  

  