256 Plant Life and Evolution 



and Tertiary fossils, that many genera once grew 

 freely there, which are now quite extinct, but which 

 have survived in America and Asia. Among these 

 were cypresses, closely allied to our southern bald- 

 cypress; Sequoias, related to the California big-trees, 

 and redwoods; hickories, sassafras, tulip-trees, 

 magnolias, gums, and other familiar denizens of 

 our American forests. Some of these genera still 

 survive in Eastern Asia, where conditions during 

 the period of glaciation were quite like those in 

 America, and where the present climatic conditions 

 are also very much the same. In both Eastern 

 Asia and America there is a continuous land ex- 

 tension southward, and the mountains run north 

 and south, so that no barriers prevented the retreat 

 of the vegetation before the encroaching glaciers, 

 and the plants returned northward as the glaciers 

 receded. 



Similarity in Floras of Eastern Asia and Eastern 

 America. The great similarity in the general char- 

 acter of the floras of the Manchurian and Japanese 

 regions, and to some extent that of China and the 

 Himalayas, and that of Atlantic North America, is 

 most marked. This is especially seen in the occur- 

 rence of certain small peculiar genera with no repre- 

 sentatives in the intervening countries. This sub- 

 ject was one to which Professor Asa Gray gave 

 much attention, and his work is of very great value 

 and interest. He cites a long list of genera common 

 to these two regions, but absent from the regions- 



