78 



P 



val in which the lowest members of the Cretaceous series were accu- 

 mulating in the Old World, it is evident that we must go elsewhere to 

 find the record of the gradual substitution of the angiospermous flora 

 of the Chalk for the cycadaceous vegetation of the Trias and Jura. 



^ In the studies that have been made of the foreign Cretaceous flora 

 it is said that the change was gradual; first, a few angiosperms mingled 

 with the predominating cycads and ferns; and subsequently, the 

 angiosperms becoming more numerous. But it is also stated that no 

 transitorial forms mark the passage from one flora to the other. 



Descriptions of some of the Cretaceous plants of the far West 

 were published in 1869 by myself, in a paper on our later extinct flo- 

 ras, which appeared in the Annals of the N, Y, Lyceum of Natural 

 History, More recently a much larger number have been described 

 by Mr. Lesquereux in one of the series of Dr. Hayden's Reports, de- 

 voted entirely to the Cretaceous flora. 



Within the past year we have begun to open an herbarium of fos- 

 sil plants in the Cretaceous beds of New Jersey, which promises to 

 give us a more accurate knowledge of this flora than has been obtained 

 from any other source. A large number of angiosperms and conifers 

 have already been obtained from these beds, and Mr. Britton of this 

 Society, will spend the coming summer in making further collections 

 from the clays and sands along the Raritan River, so that when we 

 meet again in the autumn I shall hope to be able to report some in- 

 teresting resuhs of this investigation. 



Of the herbaceous and humbler elements of the Cretaceous flora 

 we have as yet little knowledge, but the Cretaceous forest stands be- 

 fore us in well-defined characters. We rather pride ourselves now on 

 the variety, beauty and majesty of our forest trees, but we have reason 

 to believe that the forests of the Cretaceous included at least as large 

 a number of species, and perhaps as imposing and beautiful individ- 

 uals as those of the present day. 



Since the Cretaceous flora consists of so many of the genera now 

 growing in our climate, we must conclude that the climate which pre- 

 vailed during the Cretaceous, within the area of our possessions, was 

 also temperate, and that the theory somewhat widely promulgated 

 that our flora began in the Arctic regions and spread south with the 

 gradual decrease in temperature is without foundation in facts- 



Tertiary Flora,— Th^ flora of North America during the Tertiary 

 ages seems to have been but a continuation of that of the Cretaceous. 

 Many new genera and species were added, and a number of the latter 

 are still in existence, but the botanical aspect of the flora was similar to 

 that prevailing both before and after. During the Tertiary a mild 

 climate extended over the entire North American continent, and as we 

 knovv by the abundant remains of plants discovered in Alaska on Mack- 

 enzie s River, Disco Island and Greenland, a luxuriant flora similar in 

 character to that of our Middle and Southern States was spread all 

 along the northern sea-board. The remains of the living deciduous 

 cypress, Taxodium distychum, have been found in nearly all the Ter- 

 tiary deposits explored, even as far north as Greenland The north- 

 ern range of this species is now about the 36° of latitude, from which 

 we may infer that the average annual temperature of the entire conti- 



