LUTHER BURBANK 



of the north pole, During the so-called Mesozoic 

 age, the conditions of the northern hemisphere 

 were those that would nowadays be described as 

 tropical or sub-tropical. There were palms grow- 

 ing in Europe, and such species as the sequoia, 

 the plane trees, maples, and magnolias grew even 

 at a relatively late period as far north as the 

 seventieth degree of latitude. Remains of conifers 

 have been found within nine degrees of the pole 

 itself; remains of palms in Alaska coal measures, 

 and of the sassafras along the western coast 



At this early period the flora of the entire 

 northern hemisphere was, as regards its trees, 

 essentially comparable to the existing flora of 

 America to-day. 



There were oaks and beeches scarcely dis- 

 tinguishable from existing species. 



There were birches and planes and willows 

 closely related to the living species known as Salix 

 cambida. 



- There were laurels not unlike their modern 

 representatives, the sassafras and cinnamon tree, 

 and myrtles and ivies that are represented by 

 existing descendants of allied forms. 



And there were magnolias and tulip trees of 

 which the existing tulip tree of the United States 

 is an obviously direct and not very greatly modi- 

 fied descendant. 



[182] 



