PENNSYLVANIA^ FLORA OF NORTHERN ILLINOIS 15 



P. arborescens (Brongniart) Sternberg 



P. pennaeformis (Brongniart) Sternberg 



P. dentata Brongniart 



P. unita Brongniart 



Ptyehocarpus unita (Brongniart) Weiss 



7. Odontopteridae: 



Odontopteris subcuneata Bunbery 

 O. wortheni Lesquereux 



8. Alethopteridae: 



Alethopteris serlii (Brongniart) Goeppert 

 A. davreuxi (Brongniart) Goeppert 

 A. grandini (Brongniart) Goeppert 



9. Callipteridae: 



Callipteridium sullivanti (Lesquereux) Weiss 

 10. Fern stems: 



Megaphyton spec. 

 Ptychopteris spec. 

 Cycadofilicales and Cordaitales: 



Staphylopteris sagittatus Lesquereux 

 Codonotheca caduca Sellards 

 Codonospermum anomalum Brongniart 

 Tripterospermum rostratum Brongniart 

 Trigonocarpum noeggerathi Sternberg 

 Pachytesta incrassata Brongniart 

 Cardiocarpus orbicularis Ettingshausen 

 Cordaitales: 



Cordaites grandifolius Lesquereux 

 Cordaianthus gemmifer Grand Eury 



DISCUSSION OF FIGURED ORDERS AND GENERA 



Equisetales 

 The Paleozoic Equisetales, remnants of which are preserved, must have 

 been arborescent forms. Undoubtedly, herbaceous species, from which 

 our modern Equisetum descended, must also have existed. The name, 

 Calamites, always designates a stem form. Independently, leaves and 

 smaller branches were found which were called Annularia or Calamocladus 

 and fructifications, which were named Calamostachys. These are, there- 

 fore, not biological genus names but form types, because a Calamites, an 

 Annularia, and a Calamostachys grew on the same individual plant. How- 

 ever, it is not known, except in very few instances, which species of these 

 genera belonged together. For practical purposes, particularly for use as 

 stratigraphic index fossils, it is immaterial to know how they were com- 

 bined. The biological paleobotanist or, better called, fossil plant morpholo- 

 gist would, of course, like to know more of these combinations in order to 

 explain the phylogeny of the Paleozoic Equisetales, but in order to study 

 this aspect with hope of success it will be necessary to obtain a great deal 

 more material, especially petrified or coal ball specimens. 



