﻿G. 
  R. 
  Wieland 
  — 
  On 
  Liassic 
  Floras. 
  271 
  

  

  Summarily 
  put 
  : 
  In 
  the 
  Rhatic 
  flora 
  half 
  of 
  the 
  plants 
  are 
  

   ferns 
  or 
  " 
  Pteridosperms," 
  one-third 
  are 
  cycads, 
  one-tenth 
  are 
  

   modern 
  gymnospermous 
  types 
  ; 
  while 
  the 
  dwindling 
  but 
  still 
  

   distinct 
  Equisetum 
  element 
  forms 
  a 
  twentieth 
  part, 
  and 
  Cor- 
  

   daites 
  still 
  persists.* 
  In 
  the 
  Liassic 
  only 
  a 
  strong 
  third 
  

   of 
  the 
  plants 
  are 
  ferns 
  mostly 
  of 
  markedly 
  modern 
  type, 
  

   while 
  the 
  cycads 
  increase 
  from 
  40 
  to 
  50 
  per 
  cent 
  of 
  all 
  

   plants 
  and 
  Equisetums 
  and 
  Cordaites 
  tend 
  to 
  disappear 
  with 
  

   the 
  advent 
  of 
  modern 
  coniferous 
  types. 
  Obviously, 
  as 
  already 
  

   inferred, 
  the 
  later 
  Khatic 
  and 
  early 
  Lias 
  witnessed 
  some 
  of 
  

   the 
  most 
  profound 
  changes 
  known 
  in 
  the 
  history 
  of 
  plants. 
  

   In 
  the 
  Rhatic, 
  then, 
  diversity 
  of 
  Pterophyllums 
  with 
  the 
  com- 
  

   plete 
  recession 
  of 
  the 
  Equisetums 
  and 
  Cordaitaleans 
  are 
  the 
  

   dominant 
  features. 
  But 
  the 
  old 
  types 
  of 
  ferns, 
  presumably 
  still 
  

   including 
  many 
  seed-bearing 
  kinds, 
  still 
  continue 
  to 
  outnumber 
  

   all 
  other 
  groups, 
  and 
  the 
  displacement 
  of 
  the 
  Cordaitaleans 
  

   only 
  seems 
  to 
  foreshadow 
  the 
  advent 
  of 
  the 
  conifers, 
  as 
  yet 
  far 
  

   from 
  abundant 
  or 
  well 
  marked. 
  

  

  The 
  course 
  of 
  change 
  as 
  the 
  Liassic 
  advances 
  is 
  w 
  T 
  ell 
  indi- 
  

   cated 
  by 
  the 
  Bornholm 
  and 
  Yorkshire 
  Coast 
  florae, 
  which 
  are 
  

   here 
  appended 
  in 
  their 
  proper 
  order, 
  and 
  followed 
  by 
  a 
  resume 
  

   in 
  Table 
  Y, 
  in 
  which 
  are 
  also 
  included 
  the 
  more 
  recent 
  florae 
  

   of 
  Graham 
  Land 
  and 
  Oroville, 
  along 
  with 
  the 
  Rajmahal 
  Hills 
  

   proportions. 
  

  

  Table 
  IV&. 
  — 
  Liassic 
  Flora 
  of 
  Bornholm. 
  

  

  Ferns 
  (of 
  old 
  and 
  modern 
  type) 
  27 
  species 
  = 
  35*5$ 
  

  

  Cycadophytans 
  (one-fifth 
  Pterophyllums) 
  _ 
  25 
  " 
  = 
  33 
  

  

  Conifers 
  * 
  13 
  " 
  =17 
  

  

  Ginkgos 
  7 
  " 
  = 
  9 
  

  

  Equisetums.. 
  4 
  " 
  = 
  5 
  

  

  76 
  species 
  

  

  *It 
  is 
  instructive 
  to 
  go 
  back 
  a 
  step 
  further 
  and 
  note 
  general 
  proportions 
  

   in 
  the 
  Lunz 
  of 
  Austria. 
  This 
  highly 
  interesting 
  flora 
  has 
  recently 
  received 
  

   the 
  attention 
  of 
  Krasser, 
  although 
  yet 
  lacking 
  a 
  final 
  description. 
  The 
  Lunz 
  

   flora 
  of 
  some 
  41 
  determined 
  species 
  consists 
  of 
  44 
  per 
  cent 
  ferns, 
  39 
  per 
  cent 
  

   cycadophytans, 
  2 
  per 
  cent 
  conifers, 
  5 
  per 
  cent 
  Cordaitaleans, 
  and 
  10 
  per 
  

   cent 
  Equisetums 
  and 
  Calamariales. 
  The 
  pre- 
  Jurassic 
  type 
  of 
  this 
  flora 
  is 
  

   quite 
  apparent 
  when 
  the 
  large 
  Equisetum 
  element 
  is 
  noted, 
  and 
  it 
  is 
  suffi- 
  

   ciently 
  emphasized 
  that 
  the 
  rather 
  high 
  percentage 
  of 
  cycadophytans 
  is 
  due 
  

   to 
  the 
  fact 
  that 
  the 
  Pterophyllums 
  culminate 
  in 
  the 
  Lunz 
  and 
  thus 
  form 
  in 
  

   that 
  period 
  the 
  crest 
  of 
  the 
  first 
  wave 
  of 
  the 
  Cycadophytan 
  advance 
  in 
  the 
  

   Mesozoic, 
  which 
  reaches 
  its 
  climax 
  in 
  the 
  Lias. 
  Similarly 
  the 
  litigious 
  genera 
  

   Ctenis 
  and 
  Pseudoctenis 
  provisionally 
  included 
  in 
  Cycadophytans 
  go 
  to 
  swell 
  

   the 
  cycad 
  percentages 
  of 
  the 
  Oolite. 
  To 
  f 
  ally 
  understand 
  the 
  percentages 
  

   one 
  must 
  hold 
  such 
  facts 
  in 
  mind. 
  

  

  