Cenozoic Floras Around the Northern Pacific 71 



North America which was characterized by annual precipita- 

 , tion of at least 40 inches, probably more evenly distributed 

 throughout the year than at present. The mild, uniform tempera- 

 ture in which frost played an inconspicuous part was controlled 

 by the adjacent Pacific, whose influence extended farther inland 

 than it does today, extensive highlands not being present until 

 a later epoch of the Tertiary. 



The second Miocene element, now missing from the forests of 

 North America, comprises a group of genera and species which 

 have survived in Asia. Such genera as Cercidiphyllum, Gink^go, 

 Glyptostrobus, and Trapa no longer occur outside of Asia. Other 

 genera, still represented in North America, have species living in 

 Asia which are more similar to the Miocene members of these 

 genera; examples, with the fossil species in parentheses, are 

 Acer pictiim (A. scottiae), Castanea henryi (C. orientalis), Cra- 

 taegus pinnatifida (C. newberryi), Querciis myrsinae folia (0. 

 consimilis, in part), Rhus sylvestris (R. rnerrillii), and Ulmus 

 par vi folia (U. brotvnellii) . 



In this connection, it is of interest to note that the genus 

 Sequoia, now extinct in Eurasia, was widely distributed over that 

 continent in the Tertiary. If the specific characters of various 

 dicotyledonous species from the Miocene of Asia were better 

 known to the writer, it seems probable that he would be able to 

 include in addition a list of modern species from North America 

 which are as closely related to them as are the living Asiatic 

 species of their genera, or even more nearly than these. In any 

 event, although the Miocene floras of Asia are at present incom- 

 pletely studied, it is apparent that they include numerous genera 

 such as Acer, Alnus, Carpinus, Fagus, Populus, Sequoia, and 

 Tilia, which are characteristic of this epoch in North America. 

 There appears to be much less difference between the Miocene 



