Academy of Science. . 47 



that the Dakota epoch of Kansas, Nebraska, and some portions of the Rocky 

 Mountain region, was the true and original nativity of the latter forests now 

 fossilized in the deposits of Greenland. 



To do this, the facts will be a little clearer if we show, by the labors of Prof. 

 Lesquereux, the close resemblance of the Dakota forests, and those now living in 

 the temperate portion of the United States. In his "Cretaceous Flora," and other 

 publications, Prof. Lesquereux has given us a careful description of 164 species 

 mostly of forest trees. Of these about three-fourths are dicotyledons, or repre- 

 sentations of our forest and fruit trees of the temperate zone, excepting the ever- 

 greens. They are distributed among nineteen orders and fifty-two genera. 

 They embrace the Oak, Willow, Poplar, Magnolia, Sassafras, Buttonwood, Tulip 

 tree, and also Pyrus and Pruntia, to which our best fruit trees belong ; and in 

 addition a few semi-tropical forms, like the Fig, which now grows wild in Florida. 

 Of Prof. Lesquereux's list of fossil plants fnmi the Dakota, fifty-six per cent, of 

 the genera are identical with those now living east of the Rocky Mountains, in 

 the temperate zone of the United States. To this must be added twenty-four per 

 cent, which are apparently identical, represented by Populites, Betulites, 

 Acerites, Negundoides. Laurophyllum, etc. Of the remaining twenty per cent., a 

 few, like the Fig and Cinnamon, are now living in the tropics, while a few genera 

 have become extinct. 



When we examine the species under these genera, we find some exactly identical 

 with those now living, and many others apparently so. Sassafras officinale, now 

 the only species growing in the United States, was first discovered in the Dakota, 

 by the writer, and named by Prof. Lesquereux, 8. ^ludyii, but on careful examin- 

 ation by him and Prof. O. Heer, the identity of the Dakota and living species is 

 well settled. This species, and apparently other species, have been found in 

 Greenland, and one closely allied to it in Europe. Fagus polijclacla, of our Dakota, 

 " is an exact representative of the only species of beach in America." Persea 

 Sternbergii from the same deposits compares closely with P. gratissima of 

 Cuba and Brazil. Others, like Giniiamomum Scheuchzeri, though not coming down 

 to the present time, hold their specific characters, from the early Cretacei)us of 

 America to the Miocene of Europe. 



The Conifers show even a stronger persistence in retaining their characteristics. 

 Saporta and Marion, in their ?"'lora of Gelinden, i-peakiug of Pinus Qnenstedti, 

 which is found in our Dakota and in the L^pper Cretaceous of Greenland, say, 

 "This species does not differ in character from the living Mexican species with 

 quinate leaves." Sequoia gigantea, our big redwood of California, is recognized 

 as the S. Sternbergii of the Miocene, found at Disco. So Sequoia fastigiata in the 

 deposits of Kansas, Moletin and the Greenland upper Cretaceous, is considered 

 by Lesquereux very nearly the same as S. condita, fossil, and the living S. gignntea 

 and <S. xempervirens. 



Prof. Gray expresses his idea of the close resemblance in the following terms : 

 The twigs of the Sequoia in the Eocene, are " so very like *s'. gigantea of the 

 Sierra Nevada, that if such fossil twigs, with leaves and cones, had been dug 

 up in California, instead of Europe, it would confidently be affirmed that we had 

 resurrected the veritable ancestors of our giant trees." 



The Bald Cypress, now our only living species, has a close ally in the fossil Olyp- 

 trostrobus ; "a sort of modified Taxodium, about as much alike as one species of 

 redwood is like another." 



As the Conifers are a very old family, coming down from the close of the Silu- 

 rian Age, this resemblance and persistence of features does not impress so strongly. 



