﻿406 
  G. 
  R. 
  Wieland 
  on 
  the 
  Cycadophyta. 
  

  

  back 
  in 
  time, 
  as 
  they 
  are 
  today. 
  But 
  I 
  follow 
  R. 
  B. 
  Thom- 
  

   son 
  in 
  regarding 
  aplospory 
  and 
  diplospory 
  fundamental. 
  

   Also, 
  Van 
  Tieghem's 
  view 
  that 
  the 
  Ginkgo 
  sporophyll 
  is 
  

   simple 
  (diplosporous), 
  I 
  am 
  forced 
  to 
  adopt, 
  as 
  earlier 
  

   inclined 
  (Am. 
  Fos. 
  Cy., 
  vol. 
  I, 
  p. 
  232). 
  For 
  this 
  and 
  

   other 
  reasons, 
  as 
  well 
  as 
  inferences 
  from 
  fossil 
  types 
  like 
  

   Beania 
  and 
  Dicro'idiwm, 
  Ginkgo 
  is 
  put 
  hard 
  by 
  the 
  Cyca- 
  

  

  &^Po^ 
  

  

  '* 
  

  

  j> 
  

  

  Gnetales 
  

   Anpiosperms 
  

  

  Diagram 
  3. 
  The 
  gymnosperm 
  phylum. 
  

  

  dales. 
  Placing 
  the 
  Abietineans 
  next 
  to 
  the 
  Ginkgoales, 
  

   however, 
  partly 
  accords 
  with 
  Lignier's 
  scheme, 
  above; 
  

   though 
  some 
  botanists 
  would 
  certainly 
  bring 
  the 
  yews 
  

   nearer 
  the 
  Cordaites. 
  The 
  Araucarians 
  are 
  perhaps 
  the 
  

   most 
  difficult 
  of 
  all 
  the 
  gymnosperms 
  to 
  place; 
  theory 
  

   has 
  run 
  the 
  entire 
  gamut 
  from 
  separate 
  derivation 
  

   through 
  a 
  lycopod 
  stock, 
  to 
  Mesozoic 
  origin 
  from 
  the 
  

   Abietineae. 
  The 
  latter 
  view 
  is 
  absurd. 
  

  

  Osborn 
  Botanical 
  Laboratory, 
  

  

  Yale 
  University, 
  New 
  Haven. 
  

  

  