﻿280 
  G. 
  B. 
  Wieland 
  — 
  On 
  Liassic 
  Floras. 
  

  

  succession 
  of 
  the 
  Rhatic 
  of 
  Skone. 
  With 
  the 
  latter 
  the 
  Born- 
  

   holm 
  flora 
  has 
  nineteen 
  species 
  in 
  common, 
  with 
  the 
  Rhatic 
  of 
  

   Franconia 
  the 
  same 
  number, 
  with 
  the 
  Rhatic 
  of 
  Poland 
  fifteen, 
  

   and 
  with 
  the 
  Inferior 
  Oolite 
  of 
  Scarborough 
  about 
  an 
  even 
  

   dozen. 
  These 
  species 
  common 
  to 
  Bornholm 
  and 
  Scarborough 
  

   it 
  is 
  of 
  convenience 
  to 
  recapitulate 
  here 
  as 
  follows 
  : 
  

  

  (1) 
  JEtjitisetites 
  columnaris 
  

  

  (2) 
  Sagenop>teris 
  Phittipsii 
  

  

  (3) 
  Cladophlebis 
  denticulata 
  

  

  (4) 
  Coniopteris 
  cf. 
  hymen 
  op 
  hylloides 
  

  

  (5) 
  Dictyophyllum 
  cf. 
  rugosum 
  

  

  (6) 
  Laccopteris 
  polypodioides 
  

   (1) 
  Podozamites 
  cf. 
  lanceolatus 
  

  

  (8) 
  Ginkgo 
  cf. 
  digitata 
  

  

  (9) 
  Baiera 
  cf. 
  gracilis 
  

  

  (10) 
  Czekanowskia 
  cf. 
  Murray 
  ana 
  

  

  (11) 
  Otozamites 
  obtusus 
  

  

  (12) 
  Dictyozamites 
  cf. 
  D. 
  Hawelli 
  

  

  (13) 
  JYilssonia 
  cf. 
  Compta 
  

  

  As 
  the 
  Bornholm 
  plants 
  include 
  Dictyozamites, 
  conifers, 
  

   and 
  Ginkgo, 
  so 
  far 
  an 
  exclusively 
  ^northern 
  type, 
  a 
  strong 
  par- 
  

   allel 
  with 
  the 
  Yorkshire 
  Coast 
  is 
  presented 
  despite 
  a 
  difference 
  

   in 
  age. 
  But 
  the 
  cycad 
  element 
  of 
  the 
  Bornholm 
  flora 
  also 
  

   includes 
  the 
  two 
  important 
  species 
  Otozamites 
  Jlolinianus 
  and 
  

   O 
  . 
  Mandelslohi 
  characteristic 
  of 
  the 
  Lias 
  of 
  continental 
  Europe 
  

   and 
  recurrent 
  in 
  Oaxaca. 
  When 
  therefore, 
  the 
  resemblances 
  

   to 
  the 
  Oaxacan 
  flora 
  to 
  be 
  found 
  at 
  Bornholm 
  and 
  the 
  York- 
  

   shire 
  Coast, 
  and 
  in 
  continental 
  Europe, 
  are 
  all 
  brought 
  together 
  

   (cf. 
  Table 
  I) 
  it 
  is 
  found 
  that 
  they 
  much 
  outweigh 
  the 
  resem- 
  

   blances 
  noted 
  in 
  the 
  Indian 
  series. 
  Moreover, 
  there 
  is 
  a 
  cer- 
  

   tain 
  unity 
  in 
  the 
  flora 
  of 
  the 
  northern 
  latitudes, 
  which 
  suggests 
  

   that 
  north 
  and 
  south 
  routes 
  were 
  the 
  ones 
  most 
  travelled 
  by 
  

   plants 
  in 
  the 
  early 
  Jura, 
  and 
  throws 
  into 
  much 
  doubt 
  the 
  exist- 
  

   ence 
  of 
  an 
  equatorial 
  Gondwanaland 
  center 
  of 
  origin 
  or 
  route 
  

   at 
  the 
  time 
  the 
  Oaxacan 
  plants 
  flourished. 
  Such 
  a 
  direct 
  con- 
  

   nection 
  with 
  the 
  old 
  world 
  should 
  have 
  resulted 
  in 
  far 
  sharper 
  

   resemblances 
  to 
  some 
  one 
  of 
  the 
  European 
  or 
  Indian 
  floras 
  

   than 
  any 
  so 
  far 
  detected. 
  In 
  the 
  equable 
  uniform 
  tropic 
  con- 
  

   ditions 
  of 
  a 
  hypothetic 
  Gondwanaland, 
  plant 
  migration 
  would 
  

   apparently 
  have 
  been 
  so 
  easy 
  and 
  rapid 
  as 
  to 
  readily 
  repro- 
  

   duce 
  in 
  the 
  early 
  Jura 
  striking 
  conformities 
  such 
  as 
  still 
  char- 
  

   acterized 
  vegetation 
  at 
  the 
  beginning 
  of 
  the 
  Mesozoic. 
  But 
  

   with 
  no 
  approach 
  to 
  any 
  such 
  uniformity 
  in 
  evidence, 
  it 
  is 
  far 
  

   safer 
  to 
  hypothesize 
  northern 
  and 
  southern 
  centers 
  of 
  origin. 
  

  

  To 
  rush 
  to 
  the 
  opposed 
  view 
  that, 
  since 
  in 
  all 
  probability 
  

   the 
  Oaxacan 
  series 
  belongs 
  to 
  the 
  very 
  early 
  Jura, 
  it 
  is 
  the 
  pre- 
  

  

  