48 Transactions of the Kansas 



But It must be borne in mind, that neitlier Sequoia nor Taxodium have been found 

 in any part of the globe in formations older than our Cretaceous, 



The flora of the Dakota is more nearly allied to our living trees than to the 

 forests of Europe. That quarter of the globe has no Magnolia, Liriodendron, 

 Liquidamber, Sassafras, Coiiee tree (pymnocladus) or Walnut, yet all are found 

 living with us, as well as largely represented in our Dakota fossils. Europe 

 has no Catalpa, but we have the fossil Protophyllum, which appears to be nearly 

 the same. 



It is also a fact of much interest to note that the proportion of apetalous and 

 polypetalous plants, of imperfect and perfect flowers, in Prof. Lesquereux's list, is 

 very nearly the same in the Dakota irroup as in our living flora. 



According to our present geological knowledge, the American lower cretaceous 

 contains the first and oldest Dicotyledons. Future discoveries may give us a still 

 further antiquity to our forests. But as the early Cretaceous flora has been known 

 for many years, and carefully studied without finding anything of the same type 

 in any of the older formations, it is very probable that we must date the origin of 

 the Dicotyledonous plants with the dawn of the Cretaceous age. 



At the close of the Dakota epoch we know that a long period elapsed, extending 

 to the close of the Cretaceous, duri ig which all portions of the United States from 

 the Atlantic to the Pacific, excepting a few islands, and probably the southern 

 part ot British America, was under the ocean. It was the reign of the large 

 fishes, saurians, etc., found fossilized in Western Kansas, Nebraska and Wyoming. 

 During this time the forests became locally extinct. But their representatives are 

 found in the northern regions in the Upper Cretaceous, over extensive areas, that 

 betoken a continent, or at least continental islands. The leaves and other remains 

 of the forests occur in Alaska, near McKenzie river, North Somerset and Green- 

 land ; and undoubtedly at intermediate points. 



These facts, and the strong resemblance between the floras of the Dakota period 

 and those of Alaska, McKenzie and Greenland, together with their common alliance 

 to our living forests, justify us in concluding that the vegetation of our lowest 

 Cretaceous slowly migrated ; and, the climate in the northern regions then being 

 hke that of Virginia and the Carolmas at the present day, it overspread a large 

 extent of the northern regions, far within the Arctic Circle. When in the Tertiary 

 times, the sunken continent arose ag:iin, the flora returned to its former home. 

 As the Rocky mountains arose in the Eocene it came back by the way of that 

 backbone of the continent, and thince spread over tlie whole of the temperate 

 zone of North America. Those with a preference for mild winters inclined to 

 the western slopes, and others took their way toward the East, as Prof. Gray 

 has narrated. Many small shrubs, protected by the large trees, went and came 

 with them. 



When we consider the long periods covered by the Cretaceous and Tertiary 

 ages, the rate of migration may have been exceedingh' slow. If we allow a 

 century for a life generation of each forest, the seed of the trees need not have 

 been carried more than a single mile in a single generation. Thus slow but 

 sure is the plan of nature's operations. 



