122 



that, considering merely the outlines of the leaves of our present Sassafras, it 

 would be as convenient, if they were found distributed in groups and in a 

 fossil state, to separate as species as large a number of them as it has been 

 done for the Sassafras leaves of the Dakota group. 



One species of Sassafras has been recognized in the more recent geolog- 

 ical formations of this continent, the miocene. Three species are described 

 from the Tertiary of Europe, one of which, S. ferretianum, is in the Miocene of 

 Greenland, as also in thesame formation of Italy. The wide range of distribution 

 of S. officinale, the only living species, also limited to this continent, is well 

 known. It extends from Canada to Florida, and, over the same latitude, from the 

 borders of the Atlantic to the "Western prairies, even as far west as the region 

 of the Dakota group, along the banks of the Missouri River near Omaha. 

 The distribution of this beautiful, odorant, and sanative shrub, which in good 

 situations becomes a tree of moderate size, is as remarkable as its exclusive 

 affection for the land of its origin. 1 



The division of the Gamopetale.ee, is not as positively and evidently rep- 

 resented in this Cretaceous flora as the former. Heer, however, has described 

 in the Phyllites du Nebraska one species of Andromeda, figured in this memoir 

 from better preserved specimens, and one species of Diospiros, to which two 

 others have been added from more recent discoveries. The references of 

 leaves of the Dakota group to these genera is therefore reliable. There is in 

 the Tertiary of Europe and of this continent a number of species of the same 

 genera. No less than twenty-four Diospiros species are described from the 

 Miocene ; among them, two from Alaska and Vancouver Island. Of nearly 

 one hundred species known of this genus in the flora of our time, D. virginiana, 

 the Persimmon, is the only one which has been left in ' the temperate regions 

 of the North American continent. None belongs to Europe. Of the two spe- 

 cies more intimately allied to the North American, one, D. lotus, a native of 

 China, is often cultivated in the south of Europe ; the other, D. kaki, is from 

 Japan ; both have eatable fruits. 



Proceeding further and coming to the division of the Apetalce, we find 

 among the fossil leaves of the Dakota group an Aralia leaf, similar in its 

 essential characters to one described by Heer from the Cretaceous of Europe. 

 There is a slight difference, which may be considered as specific, but generic 



1 Like that of our Comas florlda, the acclimatization of this species has not succeeded in foreign 

 countries. 



