THE RELATIONSHIP OF THE FLORA OF THE DAKOTA 



GROUP. 



In comparing first the Flora of the Dakota Group to plants described 

 by Heer from Kome, referable to the lowest Cretaceous or Neocomiaii 

 formation, the table of distribution indicates an extremely great difference 

 in the characters»of the constituents. Two species only are common to 

 both these groups of plants: Gleichenia Nordenskioldi, a fern, and Sequoia 

 Reichenhachi, a Conifer. These species are of predominant and persistent 

 Jurassic types, remnants of old epochs. The single dicotyledonous species 

 discovered in the group of plants of Kome, Pojiulus primceva. belongs to 

 the section of the coriaceous poplars, represented at Atane by two other 

 species. No poplar of this section has been observed as yet among the 

 vegetable remains of the Dakota Group. This last flora is, therefore, 

 without affinity to that of Kome. But with the flora of Atane that of the 

 Dakota Group has a marked degree of affinity, 15 species of plants being 

 common to both. They are: Pimis Quenstedti, Sequoia Beichenbachi, S. 

 fastigiata, Thinfeldia Lesquereuxiana, Platanus Heerii, Ficus Mohliana, Sas- 

 safras recurvafum, Diospyros priinceva, Andromeda Parlatorii, Cissites affinis. 

 Magnolia alternans, Magnolia Capellini, Liriodendron 3Ieekii, Sapindlis Mor- 

 risoni. Besides these, Thuites crassus and Myrica Sternhergii of the Dakota 

 Group are so closely allied to T. Pfaffii and M. Thidevsis of Atane that 

 these forms, described under difterent specific names, appear to be mere 

 varieties; and th& same can be said of Ficus prof ogcea diid Aralia Ravniana 

 of Atane, which, as far as can be surmised in comparing figures and descrip- 

 tions, appear identical with Ficus Beckwithii and Aralia Towneri of the 

 Dakota Group. The relationship is the more remarkable as the affinities 

 are not limited to one or a few peculiar sections of the vegetable kingdom, 

 but refer to plants of most of the divisions known in the flora of the pres- 

 ent epoch, at least in that of the temperate regions. Of the 65 genera to 



U)5 



