THE COMANCHEAN PERIOD. 



131 



to have overrun all the continent. This is one of the most radical 

 evolutions in the known history of the plant kingdom. While the 

 precise time and place of origin of the angiosperms remains a question 



Fig. 384. — A cycadian trunk from the Black Hills, Dakota, Cycadeoidea dakotensis 

 Ward, Lower Cretaceous. (After Ward.) 



yet to be solved, present data seem to hedge it about more closely 

 than most such questions. The evidence, as it now stands, points 

 to the borders of the North Atlantic as the place of origin, and the 

 late Jurassic or earliest Comanchean as perhaps the time, though the 



