﻿34 
  ME. 
  A. 
  C. 
  SEWAKD 
  ON 
  CYCADEOIDEA 
  GIGANTEA. 
  [Feb. 
  1 
  89 
  7, 
  

  

  cylinder 
  of 
  striated 
  tissue 
  everywhere 
  penetrated 
  by 
  medullary 
  rays- 
  

   Fruits 
  borne 
  on 
  secondary 
  axis 
  not 
  protruding 
  beyond 
  the 
  bases 
  of 
  

   the 
  petioles/ 
  1 
  

  

  The 
  elliptical 
  form 
  of 
  the 
  stem 
  in 
  transverse 
  section 
  is 
  a 
  character 
  

   of 
  somewhat 
  doubtful 
  value, 
  and 
  should 
  not 
  be 
  regarded 
  as 
  a- 
  

   feature 
  of 
  primary 
  importance, 
  owing 
  to 
  the 
  difficulty 
  of 
  determining 
  

   how 
  far 
  such 
  a 
  form 
  is 
  due 
  to 
  secondary 
  causes. 
  In 
  an 
  important 
  

   monograph 
  on 
  Italian 
  Cycadean 
  fossil 
  stems, 
  Solms-Laubach 
  uses 
  the 
  

   generic 
  name 
  Bennettites 
  for 
  such 
  stems 
  as 
  possess 
  the 
  lateral 
  

   inflorescences, 
  showing 
  the 
  characteristic 
  features 
  which 
  have 
  been 
  sa 
  

   fully 
  described 
  in 
  the 
  case 
  of 
  B. 
  Gibsonianus, 
  Carr. 
  2 
  The 
  important 
  

   difference 
  between 
  the 
  present 
  fossil 
  stem 
  and 
  B. 
  Gibsonianusr 
  

   consists 
  in 
  the 
  absence 
  in 
  the 
  former 
  of 
  any 
  lateral 
  inflorescences. 
  

   A 
  careful 
  examination 
  of 
  the 
  surface 
  of 
  the 
  trunk 
  has 
  failed 
  to 
  reveal 
  

   any 
  indication 
  of 
  the 
  small 
  flattened 
  bracts 
  which 
  surround 
  the 
  

   inflorescence 
  of 
  Bennettites. 
  In 
  other 
  respects 
  there 
  is 
  the 
  closest 
  

   agreement 
  between 
  the 
  large 
  Portland 
  trunk 
  and 
  B. 
  Gibsonianus^ 
  

   Seeing 
  that 
  the 
  surface-features 
  are 
  imperiectly 
  preserved, 
  it 
  would 
  

   be 
  rash, 
  on 
  the 
  strength 
  of 
  negative 
  evidence, 
  to 
  assume 
  that 
  in 
  the 
  

   stem 
  before 
  us 
  the 
  flowers 
  were 
  produced 
  at 
  the 
  apex 
  as 
  in 
  recent 
  

   species. 
  The 
  evidence, 
  indeed, 
  so 
  far 
  as 
  it 
  goes, 
  tends 
  to 
  support 
  

   such 
  an 
  assumption. 
  

  

  In 
  such 
  species 
  as 
  B. 
  Gibsonianus 
  and 
  B 
  . 
  (Cycadeoidea) 
  porila 
  adieus 
  

   (Carr.) 
  3 
  the 
  lateral 
  inflorescences 
  are 
  easily 
  seen 
  on 
  the 
  stem-surface, 
  

   and 
  if 
  such 
  existed 
  in 
  the 
  present 
  specimen 
  one 
  would 
  certainly 
  

   expect 
  to 
  find 
  traces 
  of 
  them 
  among 
  the 
  casts 
  of 
  the 
  leaf-stalk 
  bases. 
  

  

  Although 
  no 
  trace 
  has 
  been 
  found 
  of 
  a 
  lateral 
  inflorescence 
  of 
  

   the 
  Bennettitean 
  type, 
  a 
  small 
  bud 
  was 
  discovered 
  in 
  a 
  tangential 
  

   section 
  taken 
  from 
  the 
  lower 
  portion 
  of 
  the 
  stem. 
  In 
  PI. 
  Y. 
  fig. 
  16 
  

   a 
  tangential 
  section 
  is 
  shown, 
  slightly 
  enlarged, 
  in 
  which 
  portions 
  

   of 
  three 
  petioles 
  are 
  seen 
  separated 
  by 
  the 
  densely-packed 
  ramenta, 
  r. 
  

   At 
  b 
  a 
  smaller 
  oval 
  structure, 
  8 
  mm. 
  in 
  length, 
  is 
  cut 
  across 
  trans- 
  

   versely 
  ; 
  it 
  consists 
  in 
  the 
  main 
  of 
  parenchymatous 
  tissue 
  with 
  

   numerous 
  secretory 
  sacs. 
  

  

  At 
  the 
  periphery 
  of 
  b 
  the 
  epidermis 
  and 
  cuticle 
  are 
  distinct, 
  with 
  

   some 
  ramenta 
  seen 
  in 
  connexion 
  with 
  the 
  surface-cells. 
  Below 
  the 
  

   epidermis 
  the 
  tissue 
  consists 
  of 
  flat 
  and 
  crushed 
  cells, 
  which 
  by 
  their 
  

   apparently 
  radial 
  arrangement 
  suggest 
  periderm. 
  Next 
  to 
  this 
  

   bandjp' 
  there 
  is 
  parenchyma 
  with 
  numerous 
  secretory 
  sacs. 
  At 
  j?' 
  

   there 
  is 
  a 
  band 
  of 
  tissue 
  similar 
  to 
  p', 
  and 
  consisting 
  of 
  radially- 
  

   disposed 
  cells. 
  The 
  centre 
  is 
  occupied 
  by 
  parenchyma 
  containing 
  

   numerous 
  secretory 
  cells 
  with 
  dark-coloured 
  contents. 
  

  

  In 
  the 
  parenchymatous 
  tissue 
  occasional 
  groups 
  of 
  smaller 
  

   elements 
  are 
  seen, 
  which 
  may 
  be 
  vascular 
  bundles. 
  From 
  this 
  

   section 
  alone 
  it 
  seemed 
  impossible 
  to 
  interpret 
  the 
  meaning 
  of 
  the 
  

   structure 
  b 
  embedded 
  in 
  the 
  mass 
  of 
  ramental 
  tissue. 
  In 
  figs. 
  IT 
  

   & 
  18 
  two 
  more 
  sections 
  are 
  represented, 
  which 
  were 
  cut 
  parallel 
  

  

  1 
  Carrutkers, 
  Trans. 
  Linn. 
  Soc. 
  yol. 
  xxvi. 
  (1870) 
  p. 
  694. 
  

  

  2 
  For 
  a 
  general 
  account 
  of 
  Bennettites, 
  see 
  Cat. 
  Brit. 
  Mus. 
  ' 
  Wealden 
  Flora/ 
  

   toL 
  ii. 
  (1895) 
  pp. 
  134 
  et 
  seqq. 
  3 
  Carruthers, 
  op. 
  supra 
  cit. 
  pi. 
  lxi. 
  

  

  