[Chap. LIl PLANTS OF THE PAST 739 



Darrah, W. C. Principles of Paleobotany. Chronica Botanica Company. 



Leiden. 1939. 

 Goldring, Winifred. The oldest known forest. Sci. Monthly. 23:514-529. 1927. 

 Hirmer, Max. Handbuch der Palaobotanik. R. Oldenbourg. Berlin. 1927. 

 Roy, S. K. How old are fossils? Geology Leaflet 9. Field Museum, Chicago. 



1927. 

 Schuchert, C. Outlines of Historical Geology. 2nd ed. J. Wiley & Sons, Inc. 



1931. 



