THE AMERICAN NATURALIST [Vol. XL VI 



had always been with us, disguised as paleozoic ferns, and 

 the story of its recognition and rehabilitation is about the 

 most sensational one in the annals of paleobotany. This 

 meant that Cordaitales had a companion group, and that 

 there were two great gymnosperm assemblages during 

 the Paleozoic. Then the question arose as to the rela- 

 tionship of these two groups. There was no historical 

 sequence to answer the question, for the two groups were 

 observed side-by-side, and very distinct, as far back as 

 the records go. This threw the answer back upon com- 

 parative structures, and this testimony is clear. If the 

 two groups have been derived from ancient ferns, and 

 the structure of Cycadofilicales hardly admits of any 

 other conclusion, it is evident that the Cordaitales have 

 departed much further from that origin. Therefore, if 

 the two groups are related to one another genetically, and 

 the discovery at various paleozoic horizons of persisting 

 synthetic forms that combine features of both groups 

 seems to make this reasonably assured, the Cordaitales 

 were derived from Cycadofilicales older than any we 

 know. 



The beginning of our perspective, therefore, is that 

 very ancient ferns, earlier than any of our records of 

 vascular plants, gave rise to a Cycadofilicales stock, which 

 persisted throughout the Paleozoic; and that this stock, 

 also earlier than any of our records, gave rise to the Cor- 

 daitales branch. The records begin with these two stocks 

 working along towards their modern expression, and all 

 Mesozoic and modern gymnosperms can be referred to 

 them. In other words, the gymnosperm genealogical tree 

 comes into sight as two strong branches of a dichotomized 

 trunk whose existence and character are hypothetical. 



The Mesozoic branches from these two paleozoic stocks 

 furnish us with another triumph of paleobotany, and this 

 achievement is of peculiar interest to Americans. 



The Cycadofilicales of the Paleozoic contributed to the 

 Mesozoic the gymnosperms once known as "fossil cy- 

 cads," a group so dominant and so characteristic that the 



