35 



l>y the discovery of intermediate forms, or by the study of larger collections 

 of living plants than those which I have at my disposal. It will be the task, 

 a pleasant one I hope, of other paleontologists to go further into the acquaint- 

 ance with that most interesting Cretaceous flora of ours ; to recognize its af- 

 finities better than I am able to do, and to correct errors of determination 

 which are an unavoidable result of deficiency of materials for comparison. 



§ 7. — Disconnection of the flora of the dakota group from anteced- 

 ent TYPES. 



The remarkable disproportion between the number of genera compared 

 to species in the Dakota group seems at first to corroborate the system so 

 generally admitted now, of a successive development of vegetable forms ac- 

 cording to a supposed rule of progression of more complex forms constantly 

 originating by the multiplication or subdivision of simple organs of inferior 

 types. For, according to this rule, the more we recede in our researches from 

 the present floras toward the more ancient ones, the nearer we come to plants 

 resuming, in organs of the simplest types, all the multiple characters which 

 they are prepared to represent in a continuous series of divisions. In that 

 way the old floras should be represented by simple generic forms and by only 

 a few specific divisions slightly different from the generic characters. The 

 uniformity or sameness of the facies of the Cretaceous flora, with its leaves 

 mostly entire, coarsely veined and coriaceous ; the difficulty of separating into 

 distinct groups, by fixed characters, the numerous forms of leaves which, seen 

 separately, represent different species or even genera, and which, considered 

 in series or in groups, appear undividable into sections, and therefore as refer- 

 able to a same genus, can be, also, admitted as a confirmation of the same hy- 

 pothesis. 



As long as we remain in the domain of suppositions, it is easy to go along 

 in that way, and to ascend from one or more primitive forms for the building 

 up of a progressive scale of vegetables, by mere deviations or multiplications 

 of organs. But until we know more we have to consider the facts. And the 

 conclusion evidently forced, at least in considering the flora of the Dakota 

 group, is, that its disconnection from ancient types is so wide that even the 

 supposition of intermediate, unknown, extinct vegetable types fails to account 

 for the origination of its peculiar characters. 



The limestone formations overlying the coal-measures in Eastern Kan- 



