﻿452 
  

  

  Prof. 
  W. 
  C. 
  Williamson 
  on 
  the 
  [June 
  10, 
  

  

  III. 
  u 
  On 
  tlie 
  Organization 
  of 
  the 
  Fossil 
  Plants 
  of 
  the 
  Coal-mea- 
  

   sures. 
  — 
  Part 
  VII. 
  Myelopteris, 
  Psaronius, 
  and 
  Kaloxylon." 
  

   By 
  W. 
  C. 
  Willi 
  amson,, 
  Professor 
  of 
  Natural 
  History 
  in 
  the 
  

   Owens 
  College, 
  Manchester. 
  Received 
  June 
  3 
  ; 
  1875. 
  

   (Abstract.) 
  

  

  In 
  his 
  ' 
  Dendrolithen 
  ' 
  Cotta 
  first 
  figured 
  some 
  supposed 
  stems 
  under 
  

   the 
  name 
  of 
  Medullosa, 
  to 
  one 
  of 
  which 
  he 
  gave 
  the 
  name 
  of 
  Medidlosa 
  

   elegans. 
  Corda 
  subsequently 
  figured 
  a 
  portion 
  of 
  the 
  same 
  plant, 
  in 
  his 
  

   ' 
  Flora 
  der 
  Vorwelt/ 
  under 
  the 
  name 
  of 
  Palmacites 
  carhonigerus, 
  in 
  the 
  

   belief 
  that 
  it 
  was 
  the 
  stem 
  of 
  an 
  arborescent 
  palm. 
  M. 
  Brongniart 
  next 
  

   gave 
  to 
  the 
  plant 
  the 
  name 
  of 
  Myeloceylon, 
  and 
  at 
  the 
  same 
  time 
  ex- 
  

   pressed 
  strong 
  doubts 
  respecting 
  its 
  monocotyledonous 
  character. 
  Groep- 
  

   pert 
  gave 
  this 
  plant 
  the 
  generic 
  name 
  of 
  Stengelia. 
  Iu 
  1872 
  Mr. 
  

   Binney 
  expressed 
  his 
  belief 
  that 
  the 
  plant 
  was 
  " 
  the 
  rachis 
  of 
  a 
  fern, 
  or 
  

   of 
  a 
  plant 
  allied 
  to 
  one." 
  At 
  the 
  Meeting 
  of 
  the 
  British 
  Association 
  at 
  

   Bradford, 
  in 
  September 
  1873, 
  the 
  author 
  described 
  this 
  plant, 
  and 
  

   pointed 
  out 
  his 
  reasons 
  for 
  believing 
  it 
  to 
  be 
  not 
  only 
  a 
  fern, 
  but 
  to 
  

   belong 
  to 
  the 
  interesting 
  family 
  of 
  the 
  Marattiacese 
  ; 
  and 
  in 
  the 
  subse- 
  

   quent 
  January 
  Professor 
  Renault 
  read 
  a 
  description 
  of 
  the 
  plant 
  to 
  the 
  

   Academy 
  of 
  Sciences 
  at 
  Paris, 
  when, 
  on 
  independent 
  evidence, 
  he 
  arrived 
  

   at 
  the 
  same 
  conclusion, 
  viz. 
  that 
  it 
  was 
  one 
  of 
  the 
  Marattiaceae. 
  SHghtly 
  

   modifying 
  M. 
  Brongniart's 
  generic 
  name, 
  M. 
  Renault 
  designates 
  the 
  plant 
  

   Myelopteris. 
  

  

  The 
  author 
  has 
  obtained 
  well-marked 
  examples 
  of 
  this 
  plant 
  from 
  the 
  

   Lower 
  Coal-measures 
  near 
  Oldham, 
  from 
  a 
  rachis 
  nearly 
  an 
  inch 
  in 
  diameter 
  

   to 
  the 
  smallest 
  leaf 
  -bearing 
  twigs 
  and 
  leaflet-petioles. 
  It 
  consists 
  of 
  a 
  

   mass 
  of 
  parenchyma 
  encased 
  in 
  a 
  hypodermal 
  layer 
  of 
  sclerenchymatoiis 
  

   prosenchyina, 
  arranged 
  in 
  anastomosing 
  longitudinal 
  bands, 
  separated, 
  

   when 
  seen 
  in 
  tangential 
  sections, 
  by 
  vertically 
  elongated 
  areolae 
  of 
  paren- 
  

   chyma, 
  which 
  latter 
  has 
  probably 
  spread 
  out 
  as 
  a 
  thin 
  epidermal 
  layer 
  in- 
  

   vesting 
  the 
  entire 
  rachis. 
  These 
  fibrous 
  bands 
  project 
  inwards 
  with 
  

   sharp 
  wedge-shaped 
  angles 
  ; 
  and 
  in 
  some 
  examples 
  portions 
  of 
  them 
  be- 
  

   come 
  isolated 
  as 
  free 
  fibrous 
  bundles, 
  running 
  vertically 
  through 
  the 
  

   peripheral 
  portion 
  of 
  the 
  inner 
  parenchyma 
  of 
  the 
  rachis. 
  Numerous 
  

   vascular 
  bundles 
  run 
  vertically 
  through 
  this 
  parenchyma. 
  In 
  trans- 
  

   verse 
  sections, 
  not 
  distorted 
  by 
  pressure, 
  these 
  bundles 
  are 
  arranged 
  

   in 
  some 
  degree 
  of 
  regular 
  order. 
  This 
  is 
  especially 
  the 
  case 
  with 
  

   a 
  circle 
  composed 
  of 
  the 
  peripheral 
  series 
  of 
  bundles. 
  Their 
  com- 
  

   ponent 
  vessels 
  are 
  spiral 
  in 
  the 
  case 
  of 
  some 
  of 
  the 
  smaller 
  ones, 
  and 
  

   barred, 
  very 
  rarely 
  reticulate, 
  in 
  a 
  few 
  of 
  the 
  larger 
  vessels. 
  Scattered 
  

   abundantly 
  throughout 
  the 
  parenchyma 
  are 
  numerous 
  narrow 
  intercel- 
  

   lular 
  gum-canals. 
  The 
  majority 
  of 
  these 
  are 
  isolated 
  ; 
  but 
  in 
  most 
  of 
  

   the 
  specimens 
  there 
  runs 
  side 
  by 
  side 
  with 
  the 
  vessels, 
  and 
  enclosed 
  

   within 
  the 
  special 
  cellular 
  sheath 
  which 
  imperfectly 
  encloses 
  each 
  bundle, 
  

  

  