22 THE EVOLUTION OF PLANTS 



throughout the period, and about the same pro- 

 portions as at present. The Tertiary period is 

 very interesting to botanists because it covers 



Tertiary 



Cretaceous 



Carboniferous 



Upper Silurian 



Lower Silurian 



Mesozoic 



the evolution of many of the families of the 

 higher Flowering Plants; at present, however, 

 the time is not ripe for dealing with these ques- 



