﻿Yol. 
  53.] 
  ME. 
  A. 
  C. 
  SEWARD 
  Otf 
  CYCADEOZDEA 
  GIGANTEA. 
  

  

  23 
  

  

  are 
  less 
  clearly 
  shown 
  than 
  in 
  the 
  other 
  portions 
  of 
  the 
  stem. 
  A 
  

   short 
  distance 
  above 
  the 
  base 
  the 
  preservation 
  is 
  particularly 
  good, 
  

   .and 
  much 
  of 
  the 
  internal 
  structure 
  of 
  the 
  peripheral 
  tissues 
  is 
  fairly 
  

   well 
  preserved. 
  A 
  transverse 
  section 
  has 
  an 
  elliptical 
  outline 
  (fig. 
  2), 
  

  

  Pig. 
  2. 
  — 
  Transverse 
  section 
  of 
  the 
  stem 
  of 
  Cycadeoidea 
  gigantea, 
  

  

  sp. 
  nov. 
  

  

  measuring 
  41 
  cm. 
  along 
  the 
  greater 
  diameter, 
  and 
  19 
  cm. 
  along 
  the 
  

   smaller. 
  The 
  section, 
  as 
  drawn 
  in 
  fig. 
  2, 
  is 
  taken 
  from 
  about 
  the 
  

   middle 
  of 
  the 
  stem 
  ; 
  one 
  side 
  is 
  almost 
  flat, 
  while 
  the 
  other 
  has 
  

   a 
  more 
  distinctly 
  convex 
  form. 
  The 
  present 
  shape 
  of 
  the 
  stem 
  is 
  

   no 
  doubt 
  largely 
  the 
  result 
  of 
  pressure, 
  but 
  it 
  is 
  possible 
  that 
  the 
  

   trunk 
  was 
  originally 
  rather 
  broadly 
  oval 
  than 
  circular 
  in 
  section. 
  

  

  Covering 
  the 
  surface 
  of 
  the 
  specimen 
  there 
  is 
  the 
  characteristic 
  

   Cycadean 
  armour 
  of 
  the 
  persistent 
  bases 
  of 
  spirally-arranged 
  leaf- 
  

   stalks. 
  Among 
  recent 
  Cycads, 
  the 
  majority 
  of 
  species 
  present 
  an 
  

   appearance 
  practically 
  identical 
  with 
  that 
  of 
  the 
  fossil, 
  but 
  in 
  a 
  few 
  

   living 
  forms 
  the 
  surface 
  of 
  the 
  stem 
  has 
  a 
  very 
  different 
  appearance, 
  

   the 
  regular 
  petiole-bases 
  being 
  replaced 
  by 
  irregular 
  transverse 
  

   ridges 
  and 
  corky 
  protuberances. 
  This 
  less 
  known 
  and 
  more 
  un- 
  

   common 
  form 
  is 
  well 
  illustrated 
  by 
  such 
  plants 
  as 
  Zamia 
  STcinneri, 
  

   "Warsz., 
  Z. 
  Loddigesii, 
  Miq., 
  and 
  several 
  others. 
  1 
  In 
  most 
  Cycads, 
  

   however, 
  after 
  the 
  fronds 
  have 
  withered, 
  they 
  become 
  detached 
  and 
  

   the 
  lower 
  portion 
  of 
  the 
  petiole 
  remains 
  for 
  a 
  longer 
  time 
  on 
  the 
  

   stem 
  ; 
  finally 
  the 
  ragged 
  petiole 
  is 
  cut 
  off 
  by 
  a 
  clean 
  surface 
  covered 
  

   with 
  corky 
  tissue. 
  The 
  surface 
  of 
  the 
  old 
  stem 
  in 
  certain 
  recent 
  

   genera 
  is 
  thus 
  covered 
  with 
  the 
  regularly-disposed 
  persistent 
  bases 
  

   of 
  the 
  large 
  leaves. 
  In 
  the 
  genus 
  Cycas 
  the 
  stem 
  shows 
  a 
  distinctly 
  

   marked 
  alternation 
  of 
  large 
  persistent 
  bases 
  of 
  fronds, 
  and 
  smaller 
  

   bases 
  of 
  old 
  bud- 
  scales 
  ; 
  while 
  in 
  such 
  a 
  genus 
  as 
  Encephalartos 
  the 
  

   bases 
  of 
  bud-scales 
  and 
  fronds 
  present 
  no 
  such 
  regular 
  alternation, 
  

   and 
  cannot 
  be 
  readily 
  distinguished 
  in 
  the 
  older 
  portion 
  of 
  a 
  large 
  

   stem. 
  The 
  surface 
  of 
  the 
  fossil 
  trunk 
  is 
  completely 
  covered 
  with 
  

   rhomboidal 
  leaf-bases, 
  approximately 
  of 
  the 
  same 
  size, 
  and 
  it 
  is 
  

   impossible 
  to 
  draw 
  any 
  definite 
  distinction 
  between 
  those 
  of 
  bud- 
  

   scales 
  and 
  the 
  larger 
  foliage-leaves. 
  

  

  1 
  See 
  A. 
  C. 
  Seward, 
  'Annals 
  Bot.' 
  vol. 
  x. 
  no. 
  xxxviii. 
  (1896) 
  p. 
  218, 
  pi. 
  xiv. 
  

   £gs. 
  1 
  & 
  2. 
  

  

  