EAELY PENNSYLVANIA FLORA FROM WEST-CENTRAL ILLINOIS 



15 



The systematic position of the Noeggerathiales was always uncer- 

 tain, and different workers arranged them quite differently in the sys- 

 tem. Boureau (196I+, p. 1+81 ) lists the older suggestions. The Noeggera- 

 thiales were compared with Ferns, Gymnosperms , and Tmesipteris (Browne, 

 1933; Bierhorst, 1971). Other authors considered them to be of uncer- 

 tain position, and Boureau (1964) used a separate division, Noeggerathi- 

 ophyta. Beck (1976) suggested the possibility that the Noeggerathiales 

 might be the pteridophytic descendants of the Progymnosperms . We agree 

 with Beck that the external morphological characters of several Noegger- 

 athiales are very similar to the Archaeopteridales. The Noeggerathiales 

 are characterized by heterospory, by cones of radial structure, and, in 

 many specimens by wedge-shaped sterile pinnules (or leaves?) with open 

 dichotomous venation. The sterile foliage closely resembles that of 

 Archaeopteris . The heterospory is another characteristic common to 

 Noeggerathiales and Progymnosperms. Structural and palynological infor- 

 mation will be necessary to verify this hypothesis. 



The age distribution of all fructification and foliage genera 

 that have any morphological similarities to Progymnosperms or Noeggera- 

 thiales is shown in text figure 6. The figure shows that such forms are 

 present throughout the Pennsylvanian and the lower Permian. It demon- 

 strates at the same time how incomplete the record is. Any ideas about 

 natural relationships between these genera would be premature. We do 

 not even suggest that all genera shown belong to the same order or class, 



UPPER 

 DEVONIAN 



Archaeopteris 



PERMIAN 



-Fructification 



Foliage 



Text fig. 6 - Stratigraphic ranges of foliage and fructifications of Progym- 

 nosperms, Noeggerathiales, and similar foliage. S = Saaropteris , N = 

 Noeggerathiostrobus , T = Tingiostachya, P = Palaeopteridium. 



