57 



shores from Yirgioia to Louisiana, aud farther west iu Texas. It is a 

 meager remuant of a uumber of species of the same genus which inhab- 

 ited our North American continent and tbatof Europe during the Terti- 

 ary period. We find some of them ah^eady in our Eocene, especially in 

 Mississippi. Eight species of Laurtis and two of Persea have been 

 described from the Mioceueof Europe. The geuusenters by three species 

 into the Miocene flora of the Baltic, but it has as yet no representative 

 farther north. J^oue bas 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 8. officinalis is, by its leaves, 

 scarcely distinguishable from some of the varieties of 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 de- 

 scription of the fossil leaves what reasons have induced me to separate 

 as species some of the more peculiar forms. I must say, however, that 

 considering merely the outlines of the leaves of our present sassafras, it 

 w^ould be as convenient, if they were found distributed per groups and in 

 a fossil state, to separate, as species, as large a number of these forms, as 

 it has been done for the sassafras leaves of the Dakota group. 



No species of sassafras lias yet beenrecognized in the more recent geolog- 

 ical formations of this continent. Three species are described from the 

 Tertiary of Europe, one of which, 8. Ferretianum, is in the Miocene of 

 Greenland, as also in the same formation of Italy. The wide range 

 of distribution of *S'. officinalis, the only living species, also limited 

 to this continent, is well known. It extends from Canada to Florida, 

 aud 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 Eiver 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 affec- 

 tion for the land of its origin.* 



The division of the Gamopetaleai is not as positively and evidently 

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

 recognized iu the Phyllites du Nebraska leaves referable to Andromeda 

 and Diospiros, two genera still present in the flora of this country. The 

 leaves are fragmentary. But the celebrated author considers the refer- 

 ence as certain. There is in the Tertiary of Europe and of this continent 

 a number of species of the same genera. No less than tweuty-four i)^- 

 ospiros species are described from the Miocene ; among them, two from 

 Alaska and Vancouver Island. Of nearly one hundred of species known 

 of the flora of our time, D. virginiana, the persimon, is the only one 

 which has been left in the temperate regions of the North American con- 

 tinent. None belongs to Europe. Of the two species more intimately 

 allied to the North American one, D. Lotus, a native of China, is often 

 cultivated in the south of Europe j the other, D. KaM, is from Japan ; 

 both have eatable fruits. 



Proceeding further and coming to the division of the Apetaloe, 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 a specific, 

 but generic identity is undoubtful ; an Hedera whose affinity is marked 



*Liko that of our Cornus florida, the acclimatization of this species hasnot succeeded in 

 foreign countries. 



