THE DOGWOOD AND GUM 243 



flora have been discovered at various scattered localities throughout 

 that vast area, as have also the remains of a considerable repre- 

 sentation of the terrestrial animal life commonly known as the 

 Hipparion fauna from the abundance of the remains of extinct 

 horses of that genus that have been found in it. 



The Pleistocene or glacial period, which fills the interval in 

 geological history between the Tertiary and the present has yielded 

 the remains of dogwoods of 2 existing species in Europe, namely, 

 Cornus sanguinea in England and Germany, and Cornus mas in 

 Holland and Hungary, A single seed of an undetermined species 

 of dogwood has been found in the Pleistocene deposits of New Jer- 

 sey, and recently a second species based upon the seeds has been 

 reported from a deposit of this age in the city of Washington. 

 Doubtless a comprehensive study of American Pleistocene plant 

 beds, which has never been made, would add much to the last 

 stages of dogwood history. 



THE GUMS 



The various trees embraced under this name are better known 

 to the professional botanist and lumberman than they are to the 

 layman. They comprise the tupelo, cotton, and sour gum, and 

 are not related to the sweet gum, Liquidambar, whose history has 

 been sketched in an earlier chapter. The gums are referred to a 

 genus known as Nyssa, the name of a water nymph, in allusion to 

 the fact that most of the gums grow in wet soils, and one in partic- 

 ular is found in standing water in the sloughs or swamps of 

 our southern States, in which situation it swells out its butt just 

 like that of the bald cypress. 



There are 6 or 7 existing species of gum, all of which are confined 

 to southeastern North America except a single form which is found 

 in southeastern Asia from the eastern Himalayas to the island of 

 Java, thus furnishing another link in the chain of evidence that 

 shows that these two regions are vast plant preserves where the 

 glaciation of the Pleistocene was unable to destroy the Tertiary 

 forest population that so largely perished in all other parts of the 

 Northern Hemisphere at that time. 



