PENNSYLVANIA TREE FERN COMPRESSIONS 3 



3) Cast consisting of ironstone in gray shale. Traces of vas- 

 cular bundle are present, but cell structure is not preserved 



4) Cast in sandstone. No internal features are preserved. 



Prefix designations of specimen numbers indicate the source 

 collection and present location of material studied: 



ISGS - Illinois State Geological Survey, Urbana, Illinois 



ISM - Illinois State Museum, Springfield, Illinois 



PP, UP, or UC - Field Museum of Natural History, Chicago, 

 Illinois 



USNM - United States National Museum, Washington, D.C. 



Harvard - Department of Biology, Harvard University, 

 Cambridge, Massachusetts 



Acknowledgments 



I wish to express my 

 gratitude to Mr. R. L. Leary, 

 Curator, Illinois State Museum, 

 Springfield, and Dr. E. S. Rich- 

 ardson, Curator, Field Museum of 

 Natural History, Chicago, for 

 their hospitality while I studied 

 specimens in their museums. Most 

 helpful were discussions of liv- 

 ing tree ferns with Professor 

 Rolla Tryon, Dr. Alice F. Tryon, 

 and their students at Harvard 

 University. Professor Tom L. 

 Phillips, University of Illinois, 

 introduced me to the study of 

 structurally preserved tree ferns 

 and thus influenced my interest 

 in the tree ferns. I thank Pro- 

 fessor Tom L. Phillips, Professor 

 Rolla Tryon, and Dr. Benton N. 

 Stidd, Western Illinois Univer- 

 sity, for critically reading this 

 manuscript and making helpful 

 suggestions; their cooperation 

 does not imply that they agree 

 with all of my conclusions. 



Text fig. 2 - Localities at which stems of 

 tree ferns have been found in Illinois 

 (1 - Braidwood; 2 - Morris; 3 - Herrin; 

 4 - Murphysboro; 5 - Peoria; 6 - Bay 

 City; 7 - Westville; 8 - Carmi) . 

 Limits of the Pennsylvanian System 

 in Illinois are shown. 



