86 MORPHOLOGY OF GYMNOSPERMS 



mesozoic deposits occur, ranging through North America, Europe, 

 and Asia, and extending into the arctic regions; so that Bennettitales 

 were evidently a world-wide type of great prominence. It is to be 

 expected that investigations in the southern hemisphere, and espe- 

 cially in the mountainous region of western China, may much extend 

 our knowledge of the group. 



6. Relationship to other gymnosperms 



The question of the gymnosperm relationship of Bennettitales is 

 concerned with the relation to Cycadofilicales and Cycadales, the 

 two other members of the cycadophyte phylum. It is hardly worth 

 while at present to consider the vague suggestions of relationship to 

 the Cordaitales, to the Ginkgoales, and even to the Gnetales. The 

 present evidence for such connections is too slight to merit serious 

 discussion. 



There seems to be no good reason for doubting that the mesozoic 

 Bennettitales were derived from the paleozoic Cycadofilicales. This 

 view has been expressed by including both groups in the cycadophyte 

 phylum, and this view seems to be justified by both history and struc- 

 ture. The Bennettitales began to rise into prominence as the Cycado- 

 filicales declined, and undoubtedly lingering members of the latter 

 group continued into the early Mesozoic, and early members of the 

 former group existed during late Paleozoic; so that Bennettitales 

 may be said to have carried forward into the Mesozoic many of the 

 primitive features of the Cycadofilicales, associating with these fea- 

 tures others of more advanced type in the phylum. 



A summary of these primitive features will serve to emphasize 

 the connection with Cycadofilicales. The ramentum is a character 

 that indicates the general connection of both groups with ferns. The 

 vascular anatomy and the direct leaf traces of the Bennettitales agree 

 so closely with those of the siphonostelic Cycadofilicales that the rela- 

 tionship seems obvious. The lateral branching of a monopodial 

 axis is a feature of both groups, the more open and widely branching 

 bodies of Cycadofilicales being carried forward into the Bennettitales in 

 such forms as Williamsonia angustijolia (Anomozamiles) and Wielandi- 

 ella, but becoming much compacted in the later members of the group. 

 This more compact body arose in connection with the organization of 



