WALNUTS AND HICKOKIES BEERY. 329 



(Wilcox group) of northern Mississippi. The type figure of this 

 form is reproduced in figure 3. This is not the only known species 

 from America, however, as fossil leaves of this or other species occur 

 at the same horizon, and an additional species with smaller fruits 

 has recently been discovered by the writer in the middle Eocene 

 (Claiborne group) of southern Arkansas. 



The accompanying sketch map (fig. 4) shows the existing area of 

 distribution of the genus Engelhardtia in the Orient and Oreomun- 

 nea in the Occident in solid black. These areas are somewhat gener- 

 alized and exaggerated in order to be visible on so small a scale map. 



The areas where Tertiary species of Engelhardtia have been found 

 are covered by horizontal lining, and while not as extensive as might 

 be desired, indicate very clearly what was stated a fcAv paragi-aphs 

 back, that forms closely allied to the modern Engelhardtia were 

 widespread during the Tertiary period when the more extensive 

 warm climate enabled them to penetrate more than half way across 

 the North Temperate Zone. It seems probable that they also pushed 

 southward into the South Temperate Zone, but we can not verify nor 

 disprove this theory since practically no fossil plants of Tertiary age 

 have been discovered in South America, Africa, or Australia. 

 Another probability is that careful exploration will disclose the living 

 representatives of this widespread Tertiary stock in western Brazil, 

 especially as they have survived in Central America north of the 

 Equator. 



In a general way Engelhardtia fruits are not unlike those of 

 Carpinus. There seems to be little occasion for confusion, however, 

 even in poorly preserved fossil material. The fruit proper is de- 

 cidedly different, although this is seldom well enough preserved in 

 fossils to be decisive. The involucre is also markedly different in the 

 two genera. Carpinus involucres are usualh^ smaller, with the me- 

 dian wing much wider and longer than the lateral wings and with 

 somewhat different venation. 



The margins are also toothed, while in Engelhardtia they are 

 always entire. I have examined fruits of all the existing species of 

 Carpinus and experience no difficulty in readily distinguishing them 

 from those of Engelhardtia^ the American species of the former being 

 especially different in appearance from those of Engelhardtia. I 

 have seen involucres of the Old World Carpinus hetulus from trees 

 cultivated in this country in wdiich the wings had entire or nearly 

 entire margins, but the aspect of the specimens as a whole, because 

 of their different proportions and venation, was markedly unlike 

 Engelhardtia^ and if they had been found as fossils no competent 

 paleobotanist would have been at a loss regarding their botanical 

 affinity for a single instant. 



