THE WALNUTS AND HICKORIES 75 



The Oligocene walnuts are not quite so plentiful as are those of 

 the Eocene and their records are almost entirely confined to the 

 Old World. This is undoubtedly merely an expression of the 

 incompleteness of the geological records of this time in North 

 America where there are practically no known plant beds of this 

 age. 



The Miocene has furnished upwards of two score species, the 

 majority of which are Old World forms distributed from Japan 

 on the East to western Europe. This again is due more to lack 

 of records in North America rather than to the absence of walnuts 

 at that time. There are Miocene species known from Idaho, 

 several from California and Oregon, and no less than four have 

 been found in the lake beds at Florissant, Colorado. 



The PHocene species are also numerous, a number of them having 

 survived unchanged from Miocene times. In all about 25 differ- 

 ent forms have been recorded from Pliocene deposits and several 

 of these are very close if not absolutely identical with still existing 

 species. From the late Pliocene of Germany nuts have been col- 

 lected from the lignite deposits which are exactly like those of 

 our present day black walnut and butternut, and sirnilar nuts 

 occur in deposits as young as the Pleistocene at Aldan in Siberia. 



Walnuts are not common in the knowm Pleistocene deposits, 

 but the fruit of Juglans regia is recorded from beds of tliis age in 

 southern France, and our black walnut has been found in the 

 late Pleistocene of Maryland and Alabama, both occurrences being 

 based upon the characteristic nuts preserved in the impure peat of 

 buried swamp deposits. 



The European walnut, although it is extensively planted through- 

 out southern Europe and the Orient, is now native in only the region 

 from Greece, where it is mentioned by Theophrastus, eastward 

 through Asia Minor, Transcaucasia, the northwestern Himalayan 

 region and in northern Burma, although it may eventually be 

 discovered in the mountains of China. It was not introduced into 

 Britain until the sixteenth century. In recent geological times its 

 range has probably become greatly restricted since in preglacial 

 times it is known to have been present in central France A con- 



