234 EDWARD W. BERRY 



to Japan. All of the known fossil occurrences of walnuts have 

 been plotted and are enclosed 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 additional 

 species of the walnut. 



THE GENUS ENGELHARDTIA 



The genus Engelhardtia was described by Leschen in 1825 and 

 contains about ten 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 tri-alate 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 Oreomunnea 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 may 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 Oreomunnea furnishes a strik- 

 ing illustration of the enormous changes which have taken place 

 in the flora of the world in the relatively short time, geologically 

 speaking, that has elapsed since the dawn of the Tertiary. 



The principle has frequetly been enunciated that when closely 

 related forms are found in the existing flora of the world, restricted 

 in range and isolated from their nearest relatives, or when other 



