﻿394 
  G. 
  R. 
  Wieland 
  on 
  the 
  Cycadophyta. 
  

  

  Xathorst's 
  elaboration 
  of 
  Wielandiella 
  with 
  its 
  Nilssoni- 
  

   oid 
  foliage, 
  small 
  freely 
  bifurcate 
  stems, 
  and 
  reduced 
  

   flowers, 
  soon 
  followed. 
  The 
  supplementary 
  discoveries 
  

   affecting 
  the 
  cycad 
  classification 
  most 
  profoundly 
  were 
  

   thus 
  made 
  in 
  rapid 
  succession. 
  The 
  American 
  studies 
  

   proved 
  the 
  floral 
  type 
  to 
  be 
  one 
  theoretically 
  plastic 
  ; 
  and 
  

   Nathorst's 
  determinations 
  showed 
  (with 
  some 
  further 
  

   study) 
  the 
  presence 
  of 
  far 
  greater 
  variety 
  in 
  foliage 
  as 
  

   well 
  as 
  small 
  reduced 
  stems 
  and 
  flowers. 
  It 
  had 
  become 
  

   evident 
  that 
  much 
  if 
  not 
  most 
  of 
  the 
  cycadeous 
  vegetation 
  

   of 
  the 
  Mesozoic 
  had 
  more 
  affinity 
  to 
  Cycadeoidea 
  and 
  Wie- 
  

   landiella 
  than 
  to 
  modern 
  forms. 
  In 
  fact 
  fossil 
  types 
  pos- 
  

   itively 
  referable 
  to 
  the 
  latter 
  are 
  few, 
  and 
  cannot 
  be 
  cited 
  

   beyond 
  the 
  Jurassic, 
  although 
  theoretically 
  the 
  ancestry 
  

   must 
  go 
  back 
  to 
  the 
  Paleozoic 
  as 
  a 
  discrete 
  line. 
  

  

  It 
  was 
  at 
  this 
  point 
  (1902) 
  that 
  Nathorst 
  proposed 
  as 
  

   a 
  term 
  of 
  convenience 
  the 
  Cycadophyta 
  to 
  include 
  all 
  

   plants 
  with 
  cycadeous 
  foliage 
  existing 
  and 
  extinct. 
  That 
  

   many 
  relatives 
  with 
  types 
  of 
  foliage 
  not 
  distinctly 
  cyca- 
  

   deous 
  must 
  formerly 
  have 
  existed 
  was 
  at 
  the 
  same 
  time 
  

   emphasized. 
  The 
  usableness 
  of 
  the 
  term 
  Cycadophyta 
  

   was 
  presently 
  recognized, 
  and 
  in 
  1907 
  Bessey, 
  a 
  keen 
  

   systematist, 
  suggested 
  the 
  following 
  extension: 
  Cyca- 
  

   dophyta. 
  — 
  I, 
  Cycadofilices, 
  Lyginopteridese, 
  Medullosese, 
  

   Cladoxyleas, 
  Protopityse, 
  Araucarioxylese 
  ; 
  II, 
  Cordaiti- 
  

   nese 
  ; 
  III, 
  Bennettitinese 
  ; 
  IV, 
  Cycadinese, 
  V, 
  Ginkgoinese. 
  

   The 
  logic 
  of 
  Bessey 
  's 
  suggestion 
  is 
  firmly 
  grounded 
  on 
  

   both 
  the 
  paleontologic 
  record 
  and 
  well-known 
  structural 
  

   features. 
  It 
  properly 
  emphasizes 
  the 
  lapse 
  of 
  time 
  

   through 
  which 
  the 
  cycadeous 
  foliar 
  structures 
  have 
  appar- 
  

   ently 
  dominated 
  the 
  vegetation 
  of 
  the 
  globe 
  — 
  from 
  the 
  

   Devonian 
  to 
  the 
  Cretaceous. 
  The 
  question 
  is 
  thus 
  raised 
  

   as 
  to 
  whether 
  the 
  dicotyl 
  blade 
  is 
  equally 
  longevous. 
  And 
  

   just 
  as 
  there 
  is 
  the 
  proximate 
  question 
  of 
  mid-Mesozoic 
  

   transition 
  from 
  Cycadophytes 
  to 
  dicotyl 
  foliage, 
  so 
  there 
  

   is 
  the 
  ulterior 
  question 
  as 
  to 
  mid-Devonian 
  transition 
  

   from 
  the 
  Bornia-Pseudobornia 
  foliage 
  to 
  more 
  bladed 
  

   types 
  like 
  Archa?opteris, 
  theoretically 
  leading 
  into 
  the 
  

   earliest 
  Cycadophyta. 
  

  

  Now, 
  having 
  recalled 
  the 
  larger 
  outlines 
  of 
  the 
  Cyca- 
  

   dophyta, 
  and 
  the 
  more 
  crucial 
  discoveries 
  leading 
  up 
  to 
  

   recognition 
  of 
  this 
  gymnospermous 
  leaf-type 
  as 
  a 
  forest 
  

   constituent, 
  let 
  nil 
  en 
  lion 
  be 
  turned 
  to 
  the 
  appended 
  pro- 
  

   visional 
  classification 
  based 
  on 
  the 
  general 
  structure, 
  

  

  