LESQUEREux.] REVIEW OF CRETACEOUS FLORA. 317 



inore numerous poiuts of similarity, in the present vegetation of the 

 Atlantic slope of North America. 



This absence of related forms in the nearest geological series of the 

 Cretaceous, the re-appearance, also, of Cretaceous types in more recent 

 formations, and especially at this time, are perplexing, indeed, to the 

 querist, surrounding the study of this flora with a great deal of uncer- 

 tainty and of difficulty. Who can believe that the dicotyledonous plants, 

 which were destined to take such an immense predominance in the vege- 

 tation of the world, were, from the beginning, the same as they are now ? 

 How suppose that, after their exclusion from the floras of long geo- 

 logical epochs, a number of them have re-appeared anew, with their 

 original characters "? This would seem an anomaly, in contradiction to 

 what is known, or, rather, generally admitted in regard to the succession, 

 themultiplicatiou, and the improvement of types, in following the ascend- 

 ing grade of the vegetable reign in its development. Do we not mis- 

 take in recording, as evident and close poiuts of affinity, what may be 

 mere illusional appearances "? Questions of this kind give to the study 

 of the North American Cretaceous flora a higher degree of importance, 

 but, at the same time, force the paleontologist, who is trying to decipher 

 the hieroglyphic records Df the old floras, to pursue his researches with 

 the greatest caution, reviewing again and again the forms which he con- 

 siders as specific, comparing them from as large a number of specimens 

 as may be obtainable, especially studying their relations with the veg- 

 etable contemporaneous types recognized in the same formations, or in 

 those of another country. This renders the acquisition and the study of 

 new materials constantly desirable, and, therefore, subject the conclu- 

 sions arriv'ed at to possible modifications. For this reason, the first 

 volume of the Cretaceous flora of the Dakota group should be considered 

 as an incomplete memorial, to which successive supplements have to be 

 added by every one who, engaged in paleontological researches, is in 

 position to get specimens of fossil plants from this group. The»present 

 review is one of these supplements, demanded for the reasons alluded 

 above; first, by the discoveries in the Cretaceous formations of new and 

 important materials, modifying, by their characters, generic divisions 

 fixed from insufficient specimens, or adding new species or new types to 

 those which were already known; and, secondly, by the critical notices 

 of learned friends, at home and abroad, who, sensible to the importance 

 of the data oiiered to science by the first exposition of the flora of the 

 Dakota group, have urged me to pursue the work merely begun, and 

 to bring forth, without delay, the results obtained by these new re- 

 searches. 



There is, however, still another and more forcible inducement to re- 

 view successively the data procured by new researches and discoveries, 

 in addition to our knowledge of the North American Cretaceous flora. 

 It is the insufficiency of the m aterials obtainable for the comparison and the 

 determination of specimeusof fossil plants in thiscountry. Messrs. Debey 

 and Ettinghausen began the study of the Cretaceous flora of Belgium al- 

 readyin 1843. After spendingafewyearsinexploringthe Cretaceous for- 

 mation in its geological and stratigraphical distribution and in collecting 

 specimens, having, as they supposed, about three hun'dred species to an- 

 alyze, they published, in 1848, an abridged synopsis or general review of 

 the Cretaceous flora of Belgium, describing then only a new genus of 

 Conifers, and a few species referable to it.* In 1849 they still published, as 



* Ubersicht der urweltlichen Pflanzenreste des Kreidegebirges iiberbaupt, uud der 

 Aacbener Kreidescbichten im Besonderen, in Verb, des nat. Veieines d. preus. Kbein- 

 lande, 1848. 



