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TEXTBOOK OF BOTANY 



Aralia (10 sp.), Eucalijptiis (5 sp.), Sassafras (4 sp.), Querciis (12 

 sp. ), Ficus (8 sp.), and Salix (2 sp. ). Monocots were present in very 

 small numbers, but included palms, grasses, sedges and cattails. Another 

 remarkable feature of this widespread flora was the uniformity in 

 composition from such widely separated areas as Greenland and Texas. 

 This is the last of the widespread and uniform floras. 



Cenozoic floras. Tertiary floras became more and more differentiated 

 as the climate of the polar regions became colder, and mountain-making 

 and volcanic activities in the western mountains broke up the uniform 

 temperate region into areas with different rainfall regimes, various 

 amounts of precipitation, increased or decreased humidity, and zonation 

 of environments on mountain slopes. 



During the early Tertiary there was a migration of angiosperms to 

 Australia, New Zealand, South Africa, and South America; and also a 

 rapid development and differentiation of modern genera and species. 

 Plants and plant communities very similar to those of modern temperate 

 climates occurred in polar regions in both America and Eurasia. Warm 

 temperate plants were characteristic of the middle latitudes, and sub- 

 tropical plants were abundant in the southern half of the United States. 

 Throughout the Tertiary there was a progressive cooling and these 

 three zones of plants were gradually shifted southward; the arctic floras 

 emerged in the north. Redwoods that earlier grew in circumpolar re- 

 gions ( Fig. 356 ) are now represented bv a meager remnant in Oregon 

 and California. Some of the subtropical plants have survived only in 



Fig. 365. Animals and plants in western Nebraska during the middle of the 

 Pliocene. Restoration by C. R. Knight, American Museum of Natmal History, 

 New York. 



