628 KLUliA OF TICK I.Al.'AMIi; (iK'oIT. 



table forms upon the earth's surface, as all know, is very varied, and 

 several learued and largely successfnl attempts have been made to 

 trace the lines of migration of plants during their long and often tor- 

 tuous pilgrimages since Miocene times, driven as they have been by 

 successive alterations of climate, of sea and laud surface, and of mount- 

 ain and ])lain. But we have seen that the flora of the globe, even as 

 early as the Cretaceous, was far from uniform at all points, and that 

 that of the eastern and western hemis|)heres in late Cretaceous and 

 early Tertiary time was widely different. We now find that the de- 

 gree of change since those epochs has been ditt'erent at ditferent points 

 and far greater in Europe than in America. The data contained in the 

 footnotes to our table enable us to demonstrate this, and also to show what 

 parts of the globe contain at the present time the leading elements of 

 each of the fossil floras under consideration. If we exclude those gen- 

 era which are abundant in all three formations, and take only those that 

 are either wholly or principally confined to ont> of them, we shall per- 

 ceive that the greater part of 'the properly Laramie genera are repre- 

 sented to their fullest extent in the present flora of North America or 

 eastern Asia, though many belong to the warmer parts of America, 

 and to India. On the other band we are struck by the very large num- 

 ber of Australian and African forms in the Eocene flora. The Pro- 

 teacea; and Myrtaceie abound in the Eocene n^ do the Legumiuosa;, 

 the latter chiefly of South African types. We also find that the Seno- 

 nian flora must be separated into two classes, those from British Amer- 

 ica and Greenland falling into the same general geographical group as 

 those of the Laramie, while those of the European beds I'esemble the 

 Eocene flora in this respect. I had intended to elaborate these choro- 

 logical features more at length and to give a detailed analysis of the 

 three floras from this point of view, but space will not admit of this in 

 the present paper, and as all the data for such an analysis exist in the 

 preceding table of distribution the work of compilation may be left to 

 such as are jtarticularly interested in this feature of the discussion. The 

 results upon their face fully bear out the statement already made that 

 the tlora of the Laramie group furnishes evidence ot having descended 

 more or less directly from that of the Cretaceous of this continent, and 

 in many cases the lines of descent can be traced through the npper, or 

 Senonian beds to those of the Dakota group, or American Cenomauian. 



We are now prepai-ed to compare the three floras under considera- 

 tion from the usual point of view of their specific relationships, and if 

 the treatment of this part of the subject is brief it is for the very rea- 

 son that it has already been largely accomjilished by others. Still, as 

 already remarked, Mr. Lesquereux only embraces the flora of tlie lower 

 districts, exclusive of Carbon and Evanston and a few I'piier Yellow- 

 stone localities, in his Laramie group, while our table combines all 

 these beds with the entire Fort Union deposit of the Upper Missouri 



