154 TREE .\NCESTORS 



Carolina. Five Eocene species have been described, and with 

 the exception of 1 from Mississippi and 2 from Wyoming and 

 North Dakota, these all belong to the middle and upper part of 

 the Eocene. Two were found in the Green River basin deposits 

 and the balance occur in those temperate forests which ranged so 

 far to the northward during the late Eocene, and these last records 

 of ancestral water elms include Greenland, Iceland, Alaska, Man- 

 churia and Sachalin Island. 



A single OKgocene form is known from Italy and Saxony. Two 

 nominal Miocene species had a very wide range and have been 

 found in beds of that age all over southern Europe from France to 

 Greece, in Japan, and in Virginia, Colorado and Oregon. The 

 water elms were e\adently not yet reduced in numbers or range 

 in the later days of the Tertiary, or PHocene time, for we find 3 

 forms represented in France, Italy, Germany, Styria, and Slavonia; 

 in New Jersey on our east coast; and in the Altai Mountains of 

 central Asia. Then came the Pleistocene with its glaciations which 

 seems to have effectually exterminated these trees in Asia, unless 

 indeed their geologic record on that continent represent wrong 

 identifications of what were really fossil leaves of some species of 

 the alHed genus Zelkova. A single form appears to have survived 

 into the Pleistocene of Italy, but there are none in modem Europe. 

 North American Pleistocene records of these trees include Mary- 

 land, North Carolina, Kentucky and Alabama. 



THE HACKBERRIES 



The hackberries as delimited in recent American botanical 

 practice comprise a small group of large or medium sized trees, 

 and shrubs, of ancient origin, and represented at the present time 

 in both the eastern and the western United States, and in eastern 

 Asia. The question whether the closely allied forms of lower lati- 

 tudes should be referred to the same genus is a disputed one. They 

 are evidently very near of kin, and if all are grouped under the 

 generic name of Celtis, the scientific designation of the group to 

 which the hackberries belong, and derived from a name that PHny 

 used for an African lotus-tree, then this genus has between 80 and 



