184 TREE ANCESTORS 



While its range is extensive and its habitat varied it reaches the 

 largest size and commercial possibilities in the rich bottom lands 

 of mixed hardwoods in the maritime districts or coastal plain of 

 our southern States from the valley of the Great Pedee in South 

 Carolina to the valley of the Trinity River in Texas, and northward 

 along the bottoms of the Mississippi, Arkansas, Tennessee and 

 Ohio. In the more northern part of its range it inhabits swamp 

 borders and low wet swales. 



There are at least three additional existing species of Liquidam- 

 bar — one Liqiddamhar macrophylla Oersted, found in the mountains 

 of Central America, while the other two are Asiatic. Liquidamhar 

 formosana Hance is found on the Island of Formosa and in southern 

 China, and the other separated from it by the whole breadth of the 

 Asiatic continent, is found in a limited area in the mountains of 

 southwestern Asia Minor. The last was named Liquidamhar orien- 

 talis by Miller and is the source of the liquid storax of commerce. 



This disconnected distribution of the existing species of Liquid- 

 amhar, which can be better appreciated by a glance at the accom- 

 panying map, figure 39, is a sure indication of an ancient lineage 

 and a former occupation of the intervening areas where it is now 

 extinct. If the sweet gum stood alone in having such a remarkable 

 range its interest would seem much greater, but since the days of 

 Asa Gray's American Association address we have become accus- 

 tomed to many similar ties across the departed ages that formerly 

 connected and now explain the near kin found in Asia and North 

 America, exemphfied also by the magnoHa, sassafras, coffee-bean 

 and tulip-tree. 



Turning to the fossil record we find that about 20 extinct species 

 of Liquidamhar have been described. The oldest of these, Liquid- 

 amhar integrif alius, described by Lesquereux from the Upper 

 Cretaceous Dakota sandstone of Kansas and subsequently identi- 

 fied from Canada, Texas and South America, cannot be looked upon 

 as the Abraham of the race of gums for unfortunately for our story 

 its coriaceous and entire-margined leaves are not those of a Liquid- 

 amhar but probably represent a species of Stercuha — a tropical 

 genus of trees that was very common in Upper Cretaceous times 



