﻿^°^ 
  53-] 
  MK 
  ' 
  A 
  « 
  C. 
  SEWAKD 
  ON" 
  CYCADEOIDEA 
  GIGANTEA. 
  37 
  

  

  in 
  a 
  striking 
  manner, 
  and 
  they 
  furnish 
  undoubted 
  evidence 
  of 
  a 
  very- 
  

   close 
  alliance 
  of 
  Ferns 
  and 
  Oycads 
  in 
  an 
  earlier 
  stage 
  of 
  plant- 
  

   evolution. 
  In 
  all 
  probability 
  these 
  synthetic 
  forms 
  warrant 
  the 
  

   conclusion 
  that 
  the 
  characteristic 
  features 
  of 
  existing 
  Cycadean 
  

   plants 
  have 
  been 
  derived 
  from 
  an 
  ancient 
  fern-like 
  stock. 
  1 
  It 
  is 
  

   of 
  interest, 
  therefore, 
  to 
  discover 
  in 
  the 
  ramental 
  scales 
  of 
  Mesozoic 
  

   Cycadean 
  species 
  a 
  remnant 
  of 
  this 
  relationship 
  between 
  the 
  two 
  

   sets 
  of 
  plants 
  ; 
  although 
  in 
  the 
  structure 
  of 
  its 
  reproductive 
  organs 
  

   the 
  genus 
  Bennettites 
  has 
  advanced 
  a 
  stage 
  beyond 
  that 
  repre- 
  

   sented 
  by 
  recent 
  Cycads. 
  In 
  describing 
  a 
  section 
  of 
  Rachiopteris 
  

   Williamsoni 
  in 
  1894, 
  2 
  I 
  referred 
  to 
  the 
  occurrence 
  of 
  a 
  mass 
  oi 
  

   parenchymatous 
  tissue 
  attached 
  to 
  the 
  surface 
  of 
  the 
  petiole, 
  con- 
  

   sisting 
  of 
  thin-walled 
  and 
  elongated 
  parenchymatous 
  cells. 
  Probably 
  

   this 
  tissue 
  is 
  of 
  the 
  same 
  nature 
  as 
  the 
  palese 
  on 
  the 
  petioles 
  of 
  recent 
  

   ferns, 
  and 
  the 
  laminar 
  outgrowths 
  in 
  Bennettites 
  and 
  Cycadeoidea 
  

   gigantea. 
  Bachiopteris 
  Williamsoni, 
  as 
  Scott 
  and 
  Williamson 
  have 
  

   suggested, 
  should 
  probably 
  be 
  included 
  in 
  the 
  list 
  of 
  plants 
  which 
  

   occupy 
  a 
  position 
  in 
  the 
  borderland 
  between 
  fern-like 
  and 
  Cycadean 
  

   forms. 
  Unfortunately 
  we 
  have 
  as 
  yet 
  no 
  evidence 
  of 
  the 
  form 
  of 
  

   the 
  fronds 
  which 
  crowned 
  the 
  stem 
  of 
  Cycadeoidea 
  gigantea. 
  The 
  

   palaeobotanist 
  must 
  often 
  perforce 
  be 
  content 
  to 
  describe 
  leaves 
  and 
  

   stems 
  under 
  separate 
  names, 
  and 
  wait 
  for 
  additional 
  evidence 
  as 
  to 
  

   the 
  connexion 
  between 
  the 
  detached 
  fossil 
  portions 
  of 
  the 
  same 
  

   plant. 
  

  

  My 
  thanks 
  are 
  due 
  to 
  Mr. 
  Gepp, 
  of 
  the 
  Botanical 
  Department, 
  

   British 
  Museum, 
  for 
  the 
  photographs 
  reproduced 
  in 
  Pis. 
  I. 
  & 
  II. 
  ; 
  

   and 
  to 
  Dr. 
  Henry 
  Woodward 
  I 
  am 
  indebted 
  for 
  facilities 
  afforded 
  

   me 
  in 
  the 
  examination 
  of 
  the 
  British 
  Museum 
  specimens. 
  Mr. 
  

   H. 
  H. 
  W. 
  Pearson, 
  of 
  Christ's 
  College, 
  has 
  rendered 
  me 
  valuable 
  

   assistance 
  in 
  the 
  preparation 
  of 
  sections 
  of 
  recent 
  plants. 
  

  

  EXPLANATION 
  OF 
  PLATES 
  I.-V. 
  

  

  (The 
  sections 
  of 
  Cycadeoidea 
  gigantea, 
  twelve 
  in 
  number, 
  are 
  in 
  the 
  Geological 
  

   Department 
  of 
  the 
  British 
  Museum, 
  Natural 
  History.) 
  

  

  Plate 
  I. 
  

  

  Cycadeoidea 
  gigantea, 
  £ 
  nat. 
  size. 
  (From 
  a 
  photograph 
  by 
  

   Mr. 
  Gepp, 
  of 
  the 
  British 
  Museum.) 
  

  

  Plate 
  II. 
  

  

  Fig. 
  1. 
  The 
  apex 
  of 
  the 
  stem 
  shown 
  in 
  PI. 
  I. 
  About 
  ^ 
  nat. 
  size. 
  

  

  2. 
  Leaf-bases 
  and 
  rawenta 
  from 
  the 
  lower 
  portion 
  of 
  the 
  stem. 
  (Both 
  

   figures 
  from 
  Mr. 
  Gepp's 
  photographs.) 
  About 
  ^ 
  nat. 
  size. 
  

  

  1 
  On 
  this 
  question 
  see 
  Williamson 
  & 
  Scott, 
  Phil. 
  Trans, 
  vol. 
  clxxxvi. 
  (1895) 
  

   p. 
  770. 
  As 
  regards 
  the 
  connexion 
  between 
  recent 
  Cycads 
  and 
  Ferns, 
  see 
  Eichler, 
  

   in 
  Engler 
  & 
  Prantl's 
  ' 
  Die 
  natiirlichen 
  Pflanzenfamilien,' 
  pt. 
  ii. 
  (1889) 
  p. 
  20. 
  

  

  2 
  ' 
  Annals 
  Bot.' 
  vol. 
  viii. 
  no. 
  xxx. 
  (1894) 
  p. 
  209, 
  pi. 
  xiii. 
  fig. 
  2 
  a. 
  

  

  