2o6 F. H. KNOWLTON 



we find ancient if not really ancestral angiosperms, and many of 

 the same types are found in beds of approximately the same age (that 

 is Albian) at Circal in Portugal. Although we are here much nearer 

 the origin of the angiosperms than was before known, we are proba- 

 bly still some distance from their actual point of origin, but just 

 where or when that was we do not, and may never know. 



No sooner were they fairly introduced, however, than they multi- 

 plied with astonishing rapidity and in the upper members of the Poto- 

 mac series — Raritan — they had become dominant, the ferns and 

 cycads having mostly disappeared and the conifers having taken a 

 subordinate position. 



By the close of the Comanchan, or Lower Cretaceous, they had 

 spread as far north as Alaska and Greenland, and a large number 

 of modern genera were established. 



' Climatic conditions during Comanchan. — The climate over this 

 vast area was certainly much milder than at the present time, for such 

 well-known plants as elms, oaks, maples, magnolias, and many others 

 were growing 72° N., in Greenland and nearly as far north in Alaska. 

 It was at least what we would now call warm temperate. 



Upper Cretaceous. — With the inauguration of the Upper Cretace- 

 ous the angiospermous flora was in full swing. 



On the Atlantic border we have the Magothy, which extended from 

 Maryland over New York, Long Island, and as far as Martha's Vine- 

 yard. The flora is a rich one, embracing about one hundred and fifty 

 species. 



In the interior, in approximately the same position, is the Dakota, 

 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 



