196 J. S. Newberry — Flora of the Great Falls Coal Field. 



peat that has now become coal. So far we have found among 

 the remains of these plants not a single dicotyledonous leaf, 

 but judging from the flora of the Potomac group and that of 

 the Some beds which have so many species in common with 

 the Kootanie and Great Falls deposits, we may expect in the 

 future to And a few angiosperms, the remains of the pioneers 

 and advanced guard of the great army which here mingled 

 with the cycads and conifers, and soon, through some inscruta- 

 ble influence, mostly superseded them. 



After the Kootanie epoch the eastern half of the North 

 American continent was depressed and the sea gradually rose 

 upon it, moving inwards, spreading a sheet of sea beach as far 

 as it extended [the Dakota sandstone] and ultimately covering 

 with 2,000 feet or more of marine sediments [the Colorado 

 group] all the great depressed area lying between the Cumber- 

 land and Canadian highlands and the Wasatch. 



The third great period of the Cretaceous age was the gradual 

 emergence of this portion of the continent from the sea and 

 the formation of the Laramie group with its great series of 

 coal beds, its abundant land flora and its horned Dinosaurs. 

 This closes the history of the Cretaceous age in North America. 



The record which we have of the plant life of the continent 

 during this long and varied interval is of special interest be- 

 cause we can reproduce the topography of the continent and 

 in imagination clothe all its highlands with the successive 

 phases of vegetation which we have disinterred in such abun- 

 dance from the lacustrine and estuary deposits of its different 

 epochs. The first Cretaceous forests were composed chiefly of 

 cycads and conifers, showing great variety, because this was a 

 part of their golden age. With these were numerous ferns 

 more nearly allied to those of the present day than those of 

 the Trias or Jura, several of the genera, as Gleichenia, Asple- 

 nium and Aspidium, continuing to the present day. This 

 was the Kootanie epoch or that of the Great Falls coal basin, 

 perhaps synchronous with, but more likely a little anterior to 

 the Potomac epoch, in as much as we have found no angio- 

 sperms in the Kootanie flora. 



Then came the Potomac group with a wonderful variety of 

 conifers and cycads and with about one-fourth of its species 

 angiosperms. Later still the epoch of the Amboy clays and 

 Dakota sandstones when two-thirds to three-fourths of the 

 species were angiosperms, but no palms had yet appeared. 



Finally came the Laramie epoch, when the cycads and coni- 

 fers constituted not more than one-tenth of the flora and the 

 botanical aspects of the vegetation were essentially those of to- 

 day, only palms were numerous as far north as the Canadian 

 line, and the temperature was a little higher than at present. 



