B22 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1913. 



of Europe. The late Miocene appears to have been the period of 

 widest extent of the hickories. From deposits of this age about 

 a dozen species are l<:nown. Trees were scattered all over Europe 

 and the genus extended to Iceland, Greenland, and Spitzbergen. 

 In North America there were species in Oregon and California, in 

 Colorado and in Vermont. A species very close to the existing pecan 

 occurs in the late Miocene of New Jersey. 



During the succeeding Pliocene period the hickories are as abund- 

 ant and vigorous as in the late Miocene in Europe although their 

 northern limit appears to have become somewhat restricted. Even 

 as late as the Upper Pliocene several species of hickory are abundant 

 in Italy and Germany, but none survived the ice age on that con- 

 tinent. 



A species resembling the pecan is represented by both leaves and 

 nuts in a late Pliocene lagoon deposit in southern Alabama. In 

 America there are numerous Pleistocene records, the leaves being 

 preserved in the clay deposits of the river terraces and the fruits 

 in the buried swamp deposits. The following still existing species 

 are recorded from the Pleistocene of this country; Hicoria pecan 

 from the old Mississippi bluffs at Columbus, K3'. ; Hicoria alba from 

 a cave in Pennsylvania, and from the interglacial beds near Toronto, 

 Canada ; Hicoria aquatica from North Carolina ; Hicoria ovata from 

 Pennsylvania, Maryland, and North Carolina; Hicoria vUlosa from 

 Alabama; and Hicoria glabra from Pennsylvania, Maryland, Vir- 

 ginia, and North Carolina. 



The accompanying map (fig. 1) shows the area occupied by the 

 existing species in solid black and the known Tertiary range by ver- 

 tical lining. It seems probable that the genus spread eastward over 

 Asia, but the latter continent has been so little explored that no 

 records are known. 



"Wliile the Ice Age exterminated tlie hickories from Eurasia^ the 

 genus survived safely in North America and is in no danger of 

 extermination except by the ax of the woodman. Their great toler- 

 ance of shade and their ability to respond to the stimulus of increased 

 light, combined with their longevity, are important factors in their 

 continued existence. A^^lile the rodents consume many of the fruits, 

 they have probably done so during the whole history of the genus, 

 for nuts gnawed by squirrels are not infrequent in Pleistocene depos- 

 its. This is not an unmixed evil, for various rodents not only dis- 

 tribute the species but bury the nuts in forgotten places, where they 

 are almost sure to grow. Before the advent of the " civilized ax " 

 many venerable old giant hickories were scattered through our Amer- 

 ican forests and there are numerous records of immense trunks show- 

 ing 350 or more annual rings. 



