154 TREES IN UNDRESS. 



are now throwing out their bare, gray branches, 

 were evergreens ; but as the cold increased at the 

 poles, where they first grew with other types of 

 vegetation in all their luxuriance, they were grad- 

 ually modified and especially adapted to grow and 

 thrive in our north temperate zone, as the hardy 

 foxes, bears, owls and snow-buntings have been 

 fitted to live under the rigorous conditions of the 

 polar regions. 



The few kinds of evergreens that still linger in 

 our forests are mostly of the pine family, and 

 probably have not changed materially from those 

 that grew in the Arctics before the tertiary period. 

 Their leaves are tough and needle-like, and conse- 

 quently suffer but little by the harsh wind of our 

 northern Winters. Others, of different genera 

 and species, bearing larger leaves, retreated before 

 the cold wave, and planted themselves in the 

 tropics. Some, it is believed, fell out of the race 

 southward, and were lost. A few, such as the 

 oaks, elms, maples, ashes, etc., lingered far to the 

 northward of the tropical goal, and have made 

 special arrangements to meet the buffetings of 

 a colder climate. From the first. Nature had 

 whispered to the leaves, " Boreas and King Frost 

 will be cruel to you. Your broad surfaces and 

 succulent flesh will be nipped and lacerated, and 

 you will be broken off by the million, and bled 

 profusely at every pore. Under such difficulties 



