FERNS, FOSSILS AND FUEL 
During the Middle Tertiary a subtropical flora covered 
Europe. It was a cosmopolitan type of vegetation which 
contained a great many floral elements that are now 
found in Asia, Australia, North and South America, 
and Africa. Not since Pennsylvanian times was there 
such a uniformity of vegetation all over the world. This 
flora was abundant, and, in consequence, left great coal 
deposits besides innumerable localities rich in fossil plants. 
It was the second great epoch of plant abundance in 
the history of the earth. We do not know why it hap¬ 
pened that only during the Pennsylvanian and during the 
middle of the Tertiary the plant kingdom was abundant 
and so uniform all over the world. The fossil plants 
of the time indicate a climate which must have been 
warm and moist all over the world. There are innumer¬ 
able beds of Middle Tertiary plants found close to the 
north pole, and we are forced to accept a warm climate 
for that time throughout the Arctics. 
During the closing epoch of the Tertiary period, we 
notice a lowering of temperature over the northern hemi¬ 
sphere, and an approach to the vegetation that exists 
now in North America, especially in the Pacific states. 
Late Tertiary floras are also known from Europe and 
Eastern Asia. All indicate a tendency to cooler climate 
and a southward migration of plant life. 
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