VOLUME XXIII NUMBER 4 



THE 



JOURNAL OF GEOLOGY 



MAY-JUNE 191 5 



THE EVOLUTION OF HERBACEOUS PLANTS AND ITS 



BEARING ON CERTAIN PROBLEMS OF 



GEOLOGY AND CLIMATOLOGY 



EDMUND W. SINNOTT and IRVING W. BAILEY 

 Bussey Institution, Harvard University 



Evidence from living and fossil plants has often proved of value 

 in geological investigations. A large part of our information as to 

 the climate of the various regions of the earth during ancient times, 

 particularly in the Mesozoic and Tertiary, has been derived from a 

 study of the plants composing the various fossil floras with reference 

 to the climatic conditions under which their modern representatives 

 live. A gradual differentiation and refrigeration of climate in the 

 north and south temperate zones since the close of the Cretaceous 

 have been pretty clearly indicated by such investigations.^ Botan- 

 ical evidence, particularly that derived from a study of the distri- 

 bution of Hving and fossil plants, has also been of value to the 

 student of ancient geography in providing support for such theories 

 as that of a closer connection between North America and eastern 

 Asia just before the Glacial period; a recent elevation of the coastal 

 bench in eastern North America; and a more or less intimate 

 union between Australia, New Zealand, and South America in 

 recent times by means of an antarctic continent or archipelago. 



' There is, of course, ample evidence that similar periods of refrigeration have 

 occurred earlier in the earth's history, notably in Cambrian and Permian times. 



Vol. XXIII, No. 4 289 



