﻿G. 
  R. 
  Wieland 
  — 
  On 
  Liassic 
  Floras. 
  269 
  

  

  In 
  Table 
  III 
  several 
  lesser 
  rectifications 
  are 
  made, 
  the 
  princi- 
  

   pal 
  one 
  being 
  the 
  cutting 
  out 
  of 
  the 
  most 
  of 
  the 
  cjcad 
  fruits 
  of 
  

   the 
  upper 
  beds. 
  Since 
  but 
  three 
  to 
  four 
  characteristic 
  William- 
  

   sonian 
  fruit 
  species 
  were 
  found 
  in 
  the 
  lower 
  beds, 
  it 
  is 
  better 
  

   to 
  take 
  arbitrarily 
  a 
  similar 
  number 
  from 
  the 
  upper 
  beds 
  

   instead 
  of 
  the 
  eight 
  or 
  ten 
  species 
  there 
  found. 
  By 
  so 
  doing, 
  

   the 
  comparison 
  is 
  made 
  to 
  rest 
  on 
  foliage 
  forms 
  as 
  it 
  mainly 
  

   should, 
  recovery 
  of 
  fruits 
  being 
  as 
  yet 
  more 
  a 
  matter 
  of 
  chance; 
  

   while 
  the 
  number 
  of 
  species 
  compared 
  remains 
  about 
  the 
  same 
  

   because 
  of 
  the 
  passage 
  of 
  Pterophyllum 
  and 
  Otozamites 
  Reglei 
  

   forms 
  from 
  the 
  lower 
  into 
  the 
  upper 
  beds. 
  The 
  great 
  prepon- 
  

   derance 
  of 
  Cycadophytan 
  frond 
  species 
  in 
  the 
  lower 
  beds 
  is 
  

   thus 
  brought 
  out. 
  And 
  in 
  fact 
  it 
  seems 
  certain 
  that 
  this 
  excess 
  

   is 
  more 
  likely 
  to 
  be 
  increased 
  than 
  diminished 
  by 
  future 
  col- 
  

   lecting. 
  Most 
  of 
  the 
  non-determinable 
  material 
  occurs 
  in 
  the 
  

   lower 
  beds, 
  and 
  it 
  seems 
  probable 
  that 
  they 
  will 
  always 
  be 
  

   found 
  to 
  contain 
  from 
  6 
  to 
  10 
  percent 
  more 
  cycad 
  species 
  than 
  

   the 
  upper 
  beds. 
  

  

  The 
  apparent 
  suppression 
  of 
  the 
  ferns 
  in 
  the 
  collections 
  from 
  

   the 
  lower 
  strata 
  of 
  the 
  plant 
  beds 
  of 
  the 
  Seccion 
  Consuelo 
  is, 
  

   however, 
  believed 
  to 
  be 
  due 
  solely 
  to 
  the 
  fact 
  that 
  collecting 
  

   has 
  not 
  progressed 
  far 
  enough 
  to 
  bring 
  to 
  light 
  as 
  representa- 
  

   tive 
  a 
  list 
  as 
  in 
  the 
  case 
  of 
  the 
  cycads. 
  That 
  a 
  list 
  of 
  ferns 
  

   comparable 
  in 
  variety 
  of 
  species 
  to 
  that 
  of 
  the 
  Yorkshire 
  Coast 
  

   oolites 
  or 
  the 
  JBornholm 
  Lias 
  will 
  yet 
  be 
  obtained, 
  is 
  deemed 
  

   most 
  likely 
  ; 
  but 
  that 
  the 
  cycads 
  will 
  continue 
  to 
  form 
  over 
  

   half 
  the 
  recovered 
  flora 
  seems 
  still 
  more 
  probable. 
  They 
  seem 
  

   even 
  to 
  so 
  sharply 
  thrust 
  the 
  ferns 
  aside 
  as 
  to 
  suggest 
  that 
  be- 
  

   tween 
  the 
  wane 
  of 
  the 
  older 
  seed 
  ferns 
  and 
  the 
  appearance 
  

   of 
  the 
  modern 
  fern 
  genera 
  there 
  was 
  an 
  interim 
  distinctly 
  

   poor 
  in 
  ferns. 
  

  

  (b) 
  Relative 
  Abundance 
  of 
  Cyeadophytans 
  in 
  the 
  

   Mixtecan 
  Flora. 
  

  

  As 
  just 
  pointed 
  out, 
  the 
  great 
  and 
  dominant 
  feature 
  of 
  the 
  

   Mixteca 
  Alta 
  flora 
  is 
  its 
  70 
  percent 
  of 
  Cyeadophytans. 
  In 
  fact 
  

   these 
  forms 
  are 
  so 
  strikingly 
  abundant 
  that 
  comparisons 
  with 
  

   other 
  florae, 
  made 
  with 
  direct 
  reference 
  to 
  the 
  cycads, 
  are 
  most 
  

   desirable. 
  These 
  we 
  shall 
  proceed 
  to 
  give, 
  after 
  remarking 
  

   that 
  it 
  seems 
  improbable 
  that 
  future 
  collection 
  will 
  markedly 
  

   change 
  the 
  proportions 
  observed. 
  Indeed, 
  evidence 
  for 
  the 
  

   presence 
  of 
  various 
  well-marked 
  cycad 
  species 
  additional 
  to 
  

   those 
  described 
  [in 
  my 
  memoir] 
  was 
  at 
  various 
  times 
  noted 
  in 
  

   the 
  field. 
  And, 
  moreover, 
  in 
  my 
  judgment, 
  a 
  distinctly 
  if 
  not 
  

   over-conservative 
  method 
  has 
  been 
  followed 
  in 
  referring 
  to 
  a 
  

   large 
  proportion 
  of 
  the 
  cycads 
  collected 
  as 
  varieties, 
  in 
  order 
  

   to 
  avoid 
  duplications 
  of 
  species 
  which 
  might 
  later 
  embarrass 
  

   workers 
  with 
  more 
  extensive 
  material 
  in 
  their 
  hands. 
  Hence 
  

  

  