﻿G. 
  R. 
  Wieland 
  on 
  the 
  Cycadophyta. 
  399 
  

  

  may 
  be 
  enumerated, 
  Zamiopsis 
  (Fontaine) 
  2 
  , 
  Ctenopsis, 
  

   Thinnfeldia, 
  and 
  Dicro'idium. 
  3 
  The 
  furcate 
  Cycado- 
  

   phytan 
  leaf 
  type 
  is 
  so 
  striking 
  in 
  the 
  Rhsetic 
  that 
  evolu- 
  

   tion 
  of 
  Ginkgoid 
  leaves 
  from 
  more 
  fern-like 
  forms 
  seems 
  

   to 
  go 
  on 
  before 
  one 
  's 
  eyes. 
  

  

  That 
  Bessey 
  was 
  justified 
  in 
  including 
  within 
  the 
  Cyca- 
  

   dophytes 
  a 
  great 
  Ginkgo 
  series 
  is 
  as 
  certain 
  as 
  anything 
  

   in 
  paleobotany. 
  But 
  such 
  a 
  group 
  or 
  equivalent 
  family 
  

   is 
  not 
  added 
  here 
  because 
  discovery 
  within 
  it 
  may 
  any 
  day 
  

   lead 
  to 
  a 
  more 
  felicitous 
  nomenclature 
  than 
  is 
  now 
  possi- 
  

   ble 
  to 
  propose. 
  These 
  Ginkgoid 
  forms, 
  with 
  the 
  Arau- 
  

   carinesB, 
  represent 
  the 
  older 
  boundary 
  lines. 
  

  

  More 
  terminal 
  is 
  the 
  approximation 
  of 
  the 
  Holophytse 
  

   to 
  the 
  clicotyls. 
  These 
  forms 
  must 
  be 
  regarded 
  as 
  a 
  

   relatively 
  generalized 
  line. 
  A 
  certain 
  degree 
  of 
  speciali- 
  

   zation 
  in 
  the 
  ovulate 
  cone 
  need 
  not 
  mislead 
  us. 
  That 
  

   would 
  be 
  less 
  evident 
  in 
  the 
  few 
  seeded 
  forms 
  which 
  must 
  

   certainly 
  have 
  occurred. 
  The 
  disk 
  is 
  entirely 
  plastic. 
  

   The 
  leaves 
  present 
  variety 
  and 
  are 
  not 
  highly 
  xerophyl- 
  

   lous 
  ; 
  the 
  stems 
  may 
  be 
  small, 
  and 
  were 
  capable 
  of 
  varia- 
  

   tion 
  in 
  branching. 
  There 
  is 
  excellent 
  reason 
  for 
  believing 
  

   that 
  large, 
  normally 
  forest-making 
  tree 
  types 
  are 
  

   included. 
  

  

  Hardly 
  one 
  of 
  these 
  facts 
  is 
  true 
  of 
  the 
  Cycadacese, 
  and 
  

   the 
  suspicion 
  is 
  always 
  strong 
  that 
  far 
  back 
  in 
  time 
  the 
  

   spinose 
  or 
  highly 
  xerophyllous 
  and 
  Podozamites-like 
  

   fronds 
  belong 
  either 
  to 
  the 
  Pericycadeoids 
  or 
  the 
  Cycads. 
  

   There 
  need 
  be 
  little 
  hesitation 
  in 
  making 
  of 
  such 
  forms 
  

   an 
  arbitrary 
  group 
  and 
  placing 
  it 
  terminally 
  to 
  the 
  Cyca- 
  

   dacese, 
  next 
  to 
  the 
  Pericycadeoids 
  as 
  done 
  herein. 
  Inclu- 
  

   sion 
  of 
  Stangerites 
  (McClellan) 
  is 
  theoretic; 
  but 
  this 
  leaf 
  

   type 
  could 
  as 
  readily 
  go 
  with 
  carpels 
  as 
  with 
  cones 
  

   [Zamise], 
  Stangerites 
  has 
  scarcely 
  had 
  the 
  attention 
  it 
  

   merits. 
  Also, 
  this 
  doubtful 
  boundary 
  has 
  on 
  its 
  remoter 
  

   side 
  the 
  Holophytse. 
  

  

  The 
  generalized 
  plastic 
  Apocycadeoids 
  therefore 
  lie 
  

   near 
  to 
  the 
  theoretic 
  persisting 
  type.' 
  The 
  Pericyca- 
  

   deoids 
  were 
  the 
  Proangiosperms 
  of 
  Saporta, 
  but 
  these 
  

   Apocycadeoids 
  come 
  near 
  to 
  or 
  into 
  actual 
  contact 
  with 
  

   the 
  theoretic 
  ancestors 
  of 
  the 
  angiosperms, 
  the 
  Hemian- 
  

   giosperms 
  of 
  Arber 
  and 
  Parkin 
  (1907). 
  

  

  2 
  Fontaine, 
  W. 
  M., 
  The 
  Older 
  Mesozoic 
  Flora 
  of 
  Virginia, 
  Monographs 
  

   of 
  the 
  U. 
  S. 
  Geol. 
  Surv., 
  vol. 
  6, 
  Washington, 
  18S3, 
  pp. 
  144, 
  pi. 
  LIV. 
  

  

  3 
  Anteys, 
  Ernst. 
  Die 
  Gattnngen 
  Thinnfeldia 
  Ett. 
  und 
  Dicroidium 
  Goth. 
  

   Knngl. 
  Svenska, 
  Vet. 
  Ak- 
  Hand., 
  51, 
  No. 
  6, 
  1914, 
  pp. 
  69, 
  pis. 
  5. 
  

  

  