112 F. H. KNOWLTON 



which has afforded a splendid flora of over five hundred species, and 

 occurs in Kansas, Nebraska, Wyoming, Minnesota, along the inter- 

 national boundary, and some of the same forms as far as central Alaska 

 and south to Argentina. 



Of the succeeding members of the Upper Cretaceous the Colorado 

 being largely marine has but a small flora, although in southwestern 

 Wyoming there is a small flora, made up mainly of modern types of 

 ferns (Gleichenia), that finds its closest affinity in the Upper Creta- 

 ceous of Greenland. 



Montana. — As this represents alternations of marine with brackish- 

 and fresh-water conditions we have a larger flora, although the total 

 number of known species probably does not exceed one hundred and 

 fifty. Nothing particularly new was established at this time, the 

 genera there being largely of older formations, though the species are 

 mainly different. 



Laramie. — As the uppermost member of the Cretaceous series 

 above the marine Fox Hills, the Laramie has had many vicissitudes 

 of interpretation and was made to include beds now known to belong 

 to the Montana, Arapahoe, Denver, Fort Union, etc. As logically 

 restricted to the original definition of King, the plant-bearing Laramie 

 is confined largely to the Denver Basin of Colorado and adjacent areas 

 to the southward, with the probability of its being demonstrated to 

 exist west of the mountains in Colorado, Wyoming, and New Mexico. 

 As above restricted the Laramie flora comprises about one hundred 

 and twenty-five species, and proves to be remarkably distinct from 

 that of the Montana below as well as from the Arapahoe, Denver, 

 and Fort Union above. 



Tertiary. — The close of the Upper Cretaceous saw a considerable 

 percentage of the modern angiospermous types of vegetation fully 

 established, not only in North America but throughout the world, 

 and the ferns, cycads, and conifers relegated permanently to a sub- 

 ordinate position. Certain types of dicotyledons, such, for instance, 

 as magnolias, tulip-trees, sassafras trees, etc., had their maximum 

 development in the Cretaceous, and in the Eocene and subsequent 

 stage were greatly reduced until in the modern flora they are often 

 represented by a few or even single species of very restricted habitat. 

 The most noticeable feature of the Eocene flora, broadly considered, 



