THE PHYLOGENY OF GYMNOSPERMS 



171 



In the present state of knowledge, it is scarcely necessary to 

 recapitulate the arguments which favor a filicinean origin for 

 the Cycads, especially since this view seems to meet with general 

 consent. 



Approaching the subject from the historical standpoint, we 

 find that the Filicales represent an extremely ancient line, prob- 

 ably the most ancient of the Pteridophyte lines, reaching back 

 in history at least into the Silurian^ The group is such an 

 ancient one that in all of its known history it seems to be en- 

 tirely independent of the other series of Pteridophytes. In the 

 Carboniferous the display of Filicales was an extraordinary one. 

 Associated with true Ferns was an almost equally extensive 

 group which the paleobotanists have called Cycadofilices. The 

 latter forms so much resembled the Ferns in outward aspect 

 that they Avere originally all included among the Ferns; but 

 subsequent study has revealed the fact that their anatomical 

 structure shows a remarkable commingling of Fern and Cjcad 

 characters. Unfortunately, the sporangia_^of Cycadofilices are 

 unknown, and the group must at present remain .of indefinite 

 limitation. The main fact, in the present discussion, however, 

 is that a very extensive group, showing characters intermediate 

 between Ferns and Cycads, existed during the Carboniferous 

 period in connection with undoubted Ferns. From the great 

 antiquity of the Filicales, the conclusion seems to be rational 

 that during the great vegetative display of the Carboniferous 

 there was a differentiation of the phylum, which gave rise to the 

 Cycadofilices, the old Fern stock continuing to display itself in 

 forms which would be recognized to-day as members of the 

 Marattiaceae. The first conclusion, therefore, would be that 

 the Gymnosperm phylum began with the separation of the 

 Cycadofilices from ancient marattiaceous Filicales. 



Associated with the Cycaclp^liS_diiring the Carboniferous 

 was the greaFgroup Cordaitales, undoubted Gymnosperms, and 

 related to both Cycads and Ferns in such a way as to suggest 

 very definitely an origin similar to that of the Cycads. Whether 

 the Cordaitales came directly and indejjgjidejiiLy from the Fili- 

 cales or not is doubtful, but our judgment favors the latter view, 

 since we are inclined to regard the Cycadofilices as represent- 

 ing the original indefinite plexus out of which all the Gymno- 

 sperm lines have been derived. 



