CYCADOFILICALES 59 



from loosely arranged sporophylls that have retained features of the 

 foliage, to the very compactly arranged and much modified sporophylls 

 of such a strobilus as that of Zamia. It is this tendency among the 

 cycads that may be added to the burden of testimony indicating the 

 origin of all cycads from a group in which no strobili were organized 

 and no sporophylls differentiated. 



It may be said that in microsporangiate structures the Cycadofili- 

 cales made very little progress; but these are also fernlike in both 

 Bennettitales and Cycadales. In megasporangiate structures, the 

 CycadofiUcales are far advanced, for the seeds are distinctly of the 

 so-called cycadean type, and so far removed from the fern level that 

 we seem to be no nearer the origin of seeds than before the discovery 

 of the group. 



The relationship of Cycadofilicales to Bennettitales and Cycadales 

 seems so evident, the historical sequence being as definite as the mor- 

 phological, that Nathorst and Worsdell (72) have adopted the 

 name Cycadophyta for the phylum including these three groups. It 

 would seem as if this gymnosperm phylum, extending from early 

 Paleozoic to the present time, is thoroughly weU established. 



The relationship of Cycadofilicales to the other gymnosperm 

 groups is by no means so clear, but their intimate association with 

 the Cordaitales, as well as the morphological resemblances of the two 

 groups, suggests that Cordaitales may be the beginning of another 

 gymnosperm phylum which diverged from Cycadofilicales much 

 earlier than did the cycad phylum. The presentation of this testi- 

 mony wiU be given under Cordaitales. 



In any event, there seem to have been two, great phyla of 

 gymnosperms, both differentiating from the Cycadofilicales, or each 

 arising independently from the progenitors of the Cycadofilicales. 

 One of these phyla has already been called the Cycadophytes, and 

 includes the Cycadofilicales, Bennettitales, and Cycadales; the other, 

 which arose either from the more ancient Cycadofilicales or their 

 immediate ancestors, and includes Cordaitales, Ginkgoales, and 

 Coniferales, may be called the Coniferophytes. The reasons for 

 excluding Gnetales from these connections will appear in the dis- 

 cussion of that group; but as between the two phyla proposed, the 

 Gnetales would certainly be related to the second. 



