244 TREE ANCESTORS 



The gums all yield a tough wood which has an intricately con- 

 torted and twisted grain, and are hence not extensively utilized by 

 man because of this difficulty of working it. The gum fruits are 

 stone fruits with a thin oily acidulous flesh which is utilized and 

 distributed by birds, and by mammals other than man. In the 

 fall of the year such bears as are left in our southern States invade 

 the somewhat drier swamps of this season in search of gum fruits. 

 The stones are rather characteristic being bony and compressed, 

 with longitudinal wings or ridges, and they have frequently been 

 found fossil. 



A large number of fossil forms of gums have been described. 

 Leaves that are apparently those of extinct species have been 

 found in Upper Cretaceous deposits in Wyoming, Nebraska, Kan- 

 sas, and Alabama. During the early Tertiary gums are extraor- 

 dinarily abundant with many different species. From the iso- 

 lated and restricted Hgnite deposit at Brandon, Vermont, which 

 has been mined sporadically when coal was scarce or prohibitive 

 in price in that region, 18 different kinds of stones of gum fruits 

 have been described. 



It is worthy of comment that all of the Upper Cretaceous and 

 Eocene gums are North American or Arctic, none being known 

 from the numerous plant beds of Europe until OHgocene times. 

 Besides the abundance of Eocene gum stones in New England, 

 which we infer from their abundance in the tiny lignite deposit in 

 Vermont, Eocene gums have been recorded from Montana, Wyom- 

 ing, Colorado, New Mexico, Tennessee, Louisiana and Texas. In 

 the far north they occurred at that time in Alaska, Greenland and 

 Spitzbergen. 



There are 8 known Oligocene forms of gum. The scene, in so 

 far as the actual geological record is preserved had now shifted from 

 the New to the Old World, but this is due entirely to the absence 

 of Oligocene records in North America, and probably not at all to 

 the absence of gums in the North American forests of those times, 

 especially in eastern North America, although it is quite probable 

 that by Oligocene time they may have become extinct or extremely 

 hmited by the dr}'ing of the climate brought about by the eleva- 



