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had been discovered. Now we have to refer the origin of our noble tree to 

 a more ancient epoch. 



Like that of Fagus and Liquidambar, the Cretaceous type of Plata/mis 

 has not widely varied and multiplied ; neither does it appear to have 

 changed its habitat in a marked degree, at least not in latitude. One species 

 only, P. aceroides, and its variety, P. guilklma, is abundantly distributed in 

 the Miocene of Europe, from Greenland as far south as North Italy, over an 

 area of about twenty-six degrees of latitude, while the range of P. occidentalis 

 is from the great lakes to the Gulf of Mexico, passing still farther south into 

 Mexico by its analogous P. mexkana. From Europe it has passed eastwai-d 

 as P. orientalis in the same way as it has gone west from our country as rep- 

 resented by P. racemosa of California. 



In the Laurinece we have leaves referable, by their form and nervation, 

 to the genus Laurus or Persea, and a well-preserved fruit, Laurus macrocarpa, 

 which, comparable, also, to the fruits of Cinnamomum and Sassafras, is, from 

 its association in the same localities with leaves of Laurus, admitted as 

 belonging to this genus. It seems a southern type in comparing it to the 

 other species of the Dakota group, but it is rather, I think, a shore-type. 

 Our Laurus (Persea?) caroliniana extends in following the shores from Vir- 

 ginia to Louisiana and farther west in Texas. It is a meager remnant of a 

 number of species of the same genus which inhabited our North American 

 continent and that of Europe during the Tertiary period. We find some of 

 them already in our Eocene, especially in Mississippi. Eight species of 

 Laurus and two of Persea have been described from the Miocene of Europe. 

 The genus enters by three species into the Miocene flora of the Baltic, but it 

 has as yet no representative farther north. None has been described from 

 the arctic regions. 



Sassafras belongs to the same family. The leaves of Sassafras are found 

 in such great proportion in the southern area of the Dakota group, especially 

 in Kansas, that the genus seems to have represented there a large part of the 

 land-vegetation. Our pi-esent S. officinale is, by its leaves, scarcely distinguish- 

 able from some of the varieties or forms of the leaves of the Cretaceous species, 

 which, like the present one, seems to have had a remarkable disposition to 

 variability. I have explained with the description of the fossil leaves what 

 reasons have induced me to separate as species some of the more peculiar 

 forms, and to refer all these forms to the'same genus. I must say, however, 

 IGl 



