Ixiii. 



panied with a rapid multiplication of species. During the 

 succeeding Miocene and Pliocene ages the land continued to 

 increase in the Northern Hemisphere. A gradual diminution of 

 heat was brought about towards the close, accompanied with a 

 less equable climate and a subsidence of land in the temperate 

 regions. The summers were cooler, the winters longer, and 

 more severe, which brought about the destruction of many 

 delicate plants, which removed off to southern regions. The 

 Arctic plants, which had widely distributed themselves retreated 

 to the mountain tops, or to their northern homes when a temper- 

 ate climate returned. As Great Britain belongs to the European 

 Continent it has no endemic plants, her flora consists mainly of 

 Germanic types and species which migrated during the post- 

 glacial age, when the North Sea was dry land and there was a 

 free communication with the Continent. 



Plants reached their full development long before the appear- 

 ance of the placental Mammalia, the most advanced group of the 

 Animal Kingdom. They appeared for the first time in the early 

 Eocene age. We have seen above that the Dicotyledonous 

 Angiosperms appeared at the close of the Lower Cretaceous Age, 

 when a decline of the Monocotyledons and Cycads had set in. 



Saporta, who was a strong evolutionist, observing the sudden 

 appearance of so many highly differentiated Dicotyledonous 

 plants, attributed it to their having passed the early stage of 

 evolution in some undiscovered isolated region, or having been 

 produced by an unusual multiplication of flower-haunting insects, 

 and sums up by saying " Whatever hypothesis we may prefer, the 

 fact of the rapid multiplication of Dicotyledons, and their 

 simultaneous appearance in a great number of places in the 

 northern hemisphere at the commencement of the Lower 

 Cretaceous age, cannot be disputed." The most remarkable 

 beds connected with the flora of the world are those of the 

 Dakota group, which is well developed in the Kansas, Nebraska, 

 Arkansas, and the Minnesota States of America. They are all 

 lacustrine and rest on the Trias. This vast region, which 

 extends from the Missouri to the Rocky Mountains, after its 



