326 ANNUAL REPOKT SMITHSONIAN INSTITUTION, 1913. 



ranean sea the Fayum was a delta with a heavy rainfall (as shown 

 by the flora), clothed with forests of an Indomalayan type and in- 

 habited b}^ ancestral elephants and other curious forms of ancient 

 animal life. No less than eight kinds of figs, as well as laurels and 

 camphor trees, have been described from this now arid and desiccated 

 region. Among these fossil plants are the remains of a species of 

 walnut, a striking commentary on the changes which have since 

 taken place. 



I have attempted to give a graphic summary of the present and 

 past range of the walnuts on the accompanying sketch map (fig. 2), 

 where the areas of distribution of the existing species (somewhat 

 exaggerated) are shown in solid black. It is possible that the part 

 of the range of Juglans regia in southern Asia should be extended 

 eastward over Tibet, through northern China to Japan. All of the 

 known fossil occurrences of walnuts have been plotted and are in- 

 closed within the vertically lined area. Probably the boundary of 

 the southward extension of the genus should be extended, at least 

 sufficiently far to include the South American existing species. It 

 is readily apparent from this map that the modern segregated species 

 are isolated remnants of a once world-wide distribution and that the 

 glacial epoch was an unimportant incident in their history on the 

 North American continent, while in Europe it greatly restricted the 

 range of Juglans regia and altogether exterminated one or two addi- 

 tional species of the walnut. 



THE GENUS ENGELHARDTIA. 



The genus Engelhardtia was described by Leschen in 1825 and con- 

 tains about 10 species of the southeastern Asiatic area. These range 

 from the northwestern Himalayan region, where they extend a short 

 distance north of the Tropic of Cancer through farther India and 

 Burma to Java and the Philippines. The pistillate flowers are small 

 and are grouped in paniculate spikes. They develop into small 

 drupe-like fruits, each of which is connate at the base to a large 

 expanded trialate involucre. 



A single little-known species, rarely represented in even the larger 

 herbaria^ occurs in Central America and is the type and only species 

 of the genus Oreonuinnea of Oersted. This is much more restricted 

 in its range than are its kin beyond the Pacific. Oreomunnea is 

 very close to Engelhardtia, and for the purposes of the paleobotanist 

 the two ma}' be considered as identical, since they represent the but 

 slightly modified descendants of a common ancestry which was of 

 cosmopolitan distribution during the early Tertiary. The present 

 isolation of Oreonvunnea furnishes a striking illustration of the 

 enormous changes which have taken place in the flora of the world 



