40 



governs at our time the vegetation of the latitude indicated above. All these 

 types are, therefore, present in the North American flora, some of them 

 with scarcely any alteration of forms. 



Professor Heer has the same opinion in regard to the climate of the 

 upper Cretaceous epoch of Greenland as indicated by its flora. He is just 

 now publishing two memoirs, which, besides their great scientific importance, 

 and merely considering the question of the relation of the floras to tempera- 

 ture, are of high general interest. The first describes a group of fossil plants 

 from the lower Cretaceous of Greenland, representing thirty-eight Fucoids, 

 one lycopodiaceous species, three Equisetaceas, nine Cycadete, seventeen Con- 

 ifers, five monocotyledonous, and one dicotyledonous species. These vegeta- 

 ble remains, according to the author, represent types of a tropical or subtrop- 

 ical flora, and this under the 70° of north latitude. There is evidently no 

 relation whatever between this low Cretaceous flora and that of the Dakota 

 group. But in a second memoir, the author describes an upper Cretaceous 

 flora of the same country, which, in its essential types, appears identical with 

 that of the Dakota group. It has 28 species of the genera Populus, Myrica, 

 Ficus, Sassafras, Proteoidcs, Credneria, Andromeda, Dermatophyllites, Dlospi- 

 ros, Panax, Chondrophyttum, Magnolia, Myrtophyllum, Sapindus, Rhus, Legu- 

 ?ninosites, 1 genera, which, with few exceptions, are represented in the Creta- 

 ceous North American flora. What a difference in the types of these two 

 groups of plants from the same locality and of the same formation, one with 

 74 species, 42 of which are cryptogamous plants, 26 phenogamous gymnos- 

 perms, among which are nine Cycadese, indicating tropical climate, and only 

 one dicotyledon; while the other represents only 28 species distributed in 16 

 genera, all dicotyledonous and of types analogous to those of the present North 

 American flora The distribution of such a small number of species in so 

 many genera of distant affinity is, by itself, a fact of great weight in consider- 

 ing the succession of types in their i - elation to geological periods, and confirms 

 the remarks at the close of the former chapter, 2 But it is still more remark- 



1 Heer in letters. 



-New and important information comes just now in confirmation of this remark. From a letter of 

 Count Sanorta, the most ancient flora of the Cretaceous of Bohemia, whoso position is similar to that of 

 the Dakota group, or at tho haso of what the German geologists call tho quadersandsteiu, here imme- 

 diately overlying the primitive formation, is composed mostly of dicotyledonous leaves whose forms are 

 remarkahly analogous to those of the Dakota group flora. The celebrated paleontologist of France 

 remarks that with the dicotyledonous leaves the specimens represent only one species of Conifers ; that 

 the dicotyledonous leaves are large and of varied forms, all apparently representing new types whose 

 exact determination will he tho more difficult that they evidently represent synthetic types, resuming, 

 perhaps, each one. tho character of a whole family, and appeariug as intermediate links hetween many 

 groups of our present order of vegetation, &c. 



