﻿108 
  PRINCIPAL 
  DAWSON 
  ON 
  PROTOTAXITES 
  AND 
  

  

  thought 
  that 
  Sir 
  Joseph 
  Hooker 
  was 
  justified 
  in 
  referring 
  it 
  to 
  

   Lycopodiaceee 
  from 
  the 
  materials 
  at 
  his 
  command. 
  He 
  had 
  long 
  

   known 
  that 
  PachytJieca 
  had 
  a 
  cellular 
  structure 
  filling 
  its 
  inte- 
  

   rior, 
  consisting 
  of 
  tubular 
  cells 
  like 
  those 
  of 
  the 
  Avail, 
  but 
  matted 
  

   together. 
  He 
  was 
  inclined 
  to 
  doubt 
  whether 
  they 
  are 
  really 
  vege- 
  

   table, 
  and 
  may 
  not 
  be 
  animal 
  remains. 
  Mr. 
  Storrie, 
  of 
  Cardiff, 
  had 
  

   sent 
  him, 
  years 
  ago, 
  well-preserved 
  and 
  beautifully 
  prepared 
  sections 
  

   of 
  PachytJieca 
  showing 
  the 
  whole 
  from 
  centre 
  to 
  circumference 
  ; 
  

   these 
  led 
  him 
  to 
  doubt 
  their 
  vegetable 
  origin. 
  He 
  wished 
  that 
  

   zoologists 
  would 
  examine 
  PacJiytheca. 
  He 
  was 
  satisfied, 
  from 
  the 
  

   specimens 
  on 
  the 
  table 
  exhibited 
  by 
  Dr. 
  Sterry 
  Hunt, 
  that 
  the 
  

   Eopteris 
  of 
  Saporta 
  is 
  really 
  not 
  a 
  plant 
  but 
  a 
  crystallization 
  of 
  

   pyrites, 
  as 
  suggested 
  by 
  M. 
  Meunier-Chalmas. 
  

  

  Dr. 
  Duncan 
  remarked 
  upon 
  the 
  wonderful 
  discrepancies 
  of 
  opinion 
  

   that 
  prevailed. 
  He 
  did 
  not 
  regard 
  the 
  central 
  part 
  of 
  PachytJieca 
  as 
  

   a 
  mycelium. 
  He 
  regarded 
  it 
  as 
  the 
  float 
  or 
  conceptacle 
  of 
  a 
  seaweed. 
  

  

  Prof. 
  Judd 
  stated 
  that 
  he 
  exhibited, 
  on 
  behalf 
  of 
  Mr. 
  Thiselton 
  

   Dyer, 
  two 
  sections 
  of 
  PachytJieca. 
  Mr. 
  Thiselton 
  Dyer 
  regretted 
  

   that 
  he 
  was 
  unable 
  to 
  be 
  present 
  at 
  the 
  Meeting, 
  but 
  had 
  sent 
  Prof, 
  

   Judd 
  a 
  letter, 
  from 
  which 
  he 
  read 
  the 
  following 
  extract 
  : 
  — 
  

  

  " 
  Kew, 
  

  

  November 
  15, 
  1881. 
  

  

  " 
  I 
  have 
  to 
  thank 
  you 
  for 
  drawing 
  my 
  attention 
  to 
  the 
  paper 
  and 
  

   discussion 
  in 
  the 
  August 
  number 
  of 
  the 
  Quarterly 
  Journal. 
  Having 
  

   read 
  this, 
  I 
  venture 
  to 
  think 
  that 
  the 
  specimens 
  which 
  I 
  am 
  placing 
  

   in 
  your 
  hands 
  my 
  be 
  found 
  of 
  some 
  importance 
  if 
  exhibited 
  at 
  the 
  

   meeting. 
  

  

  " 
  Their 
  history 
  is 
  briefly 
  this. 
  Some 
  time 
  ago 
  Sir 
  Joseph 
  Hooker 
  

   received 
  from 
  Mr. 
  Grindrod 
  a 
  number 
  of 
  specimens 
  of 
  PachytJieca 
  

   in 
  situ 
  on 
  pieces 
  of 
  rock. 
  As 
  these 
  examples 
  of 
  the 
  fossils 
  were 
  

   apparently 
  well 
  preserved, 
  two 
  or 
  three 
  were 
  detached 
  and 
  intrusted 
  

   to 
  Mr. 
  Norman, 
  who 
  made 
  the 
  sections 
  which 
  are 
  now 
  in 
  your 
  

   hands. 
  Sir 
  Joseph 
  Hooker 
  did 
  not 
  see 
  his 
  way 
  to 
  any 
  definite 
  con- 
  

   clusion 
  as 
  regards 
  the 
  structure 
  which 
  they 
  exhibited. 
  He, 
  how- 
  

   ever, 
  allowed 
  me 
  to 
  examine 
  them, 
  and 
  they 
  have 
  since 
  remained 
  in 
  

   my 
  possession. 
  The 
  conclusion 
  which 
  I 
  arrived 
  at 
  was 
  that 
  their 
  

   structure 
  agreed, 
  in 
  general 
  plan, 
  with 
  that 
  of 
  Codium, 
  as 
  shown 
  

   in 
  Kiitzing, 
  ' 
  Phycologia 
  Generalis,' 
  pi. 
  42. 
  f. 
  1. 
  

  

  " 
  As 
  a 
  possible 
  algal 
  nature 
  has 
  been 
  suggested 
  for 
  Pachyiheca 
  by 
  

   Mr. 
  Etheridge, 
  I 
  think 
  it 
  may 
  not 
  be 
  considered 
  presumptuous 
  on 
  

   my 
  part 
  to 
  now 
  state 
  that 
  I 
  have 
  been 
  of 
  opinion, 
  ever 
  since 
  I 
  

   studied 
  the 
  sections, 
  that 
  Prototaocites 
  and 
  Pachytheca 
  are 
  both 
  refer- 
  

   able 
  to 
  the 
  same 
  morphological 
  type 
  of 
  structure. 
  The 
  radiating 
  

   cells 
  in 
  the 
  latter 
  terminate 
  internally 
  in 
  loosely 
  interlacing 
  slender 
  

   filaments, 
  with 
  which 
  the 
  central 
  cavity 
  has 
  been 
  apparently 
  filled. 
  

   Pachytheca 
  does 
  not 
  resemble 
  any 
  type 
  of 
  sporangium 
  with 
  which 
  I 
  

   am 
  acquainted 
  ; 
  the 
  structure, 
  as 
  displayed 
  in 
  the 
  specimens, 
  has 
  a 
  

   certain 
  resemblance 
  to 
  that 
  of 
  the 
  sporocarp 
  of 
  Pilularia; 
  but 
  .'I 
  

   cannot 
  reconcile 
  what 
  I 
  have 
  seen 
  of 
  it 
  with 
  the 
  supposition 
  thatat 
  

  

  