ANALYSIS OF THE DAKOTA GltOUP FLORA. 239 



the nlHliatidii of tlic jieiuis is positivc-ly recognized t'roiu the Dakota Group, 

 through all the more recent .stages of the formations, to the present epoch. 



Ficus and Morus are the only genera of the urticaceous tribe Moreaj 

 represented in the present flora of the United States. Abundant remains 

 of Ficus have been recog-nized in the geological formations from the Ce- 

 nomanian upward, Ijut none of ilorus ; for the two leaves descriljed under 

 this generic ajjpellatiou by Massalongo, from the Tertiary of Ital}', are 

 still of uncertain atfiuit\". Fruits and leaves of Ficus have also been 

 found in the scliists of Atane and still more abundantlv in those of the Da- 

 kota Group. 



In the description of the numerous fossil leaves referred to Ficus, 

 Schimper separates them into two sections: First, those that are pinnately 

 nerved; second, those that are palmately nerved. The tii'st section lias by 

 far the largest iunnl)er of representatives, as the same author refers forty- 

 four species to it and only tweuty-fom* to the second. Two species only of 

 the palmately nerved leaves are repi'eseuted in the Dakt»ta Group and in 

 the schists of Atane, one bv Fi/its HeUaitdiana Heer, at Atane, the other by 

 a relative, F. dcfleja Lesq. All the others belong to the section of pimiately 

 nerved leaves, of which twenty are recorded in the Dakota Group flora, 

 and two in that of Atane. In more recent geological times the second 

 group is represented in Patoot by F. arctica Heer, and in the Upper Creta- 

 ceous of Wyoming (Princeton collection) by F. deffexa, already present in 

 the I )akota Group, and by the 1 jeautiful F. prodncta of Montana. This last 

 typically represents F. puh-horinta Sap., of tlics Sezanne Flora; F. phti/itos- 

 tata; F. psciidopopnlH-'i ; F. aijoiunigiana Le.sq., of the Laramie; F. Sch'nupcrl 

 Lesq., of the Mississippi Eocene ; and is still recognized in the different 

 stages of the Tertiary of both continents, especially in the onmipresent and 

 most variable F. tiluefoUa, which is recorded from the Laramie flora, and 

 is still represented in the Upper Miocene of the auriferous gravel dejiosits 

 of California. 



It would be an easy task but would take too long to follow the affili- 

 ation of the piimately nerved leaves of Ficus from the Cenomanian to the 

 present epoch. I may mention i>nly the fine leaves of F. proteo'ulcs; F. Ber- 

 thoiidi, of the Dakota Group; reproduced in their essential characters, nerva- 

 tion, form and size of leaves, in F. eJon(/af(illos.; F. JoiufifoVia llos., of the 

 Senonian of Westphalia; in F arenacea; F. Smithsoniniia, of the Laramie; 

 F. Ia)icei)l(if(i, F. miiltiiwrvis, the beautiful F. Uix/cri, and other species of the 

 Green River Group ; also in most of the stages of tlxQ European Miocene, 



