244 THE FLOKA OF THE DAKOTA (iROUP. 



period, wliile the preponderance of Ericacere in the European Tertiary is 

 against tlie supi)ositiou that the phiiits of" tlie Gainopet;d;r liave ])assed, Uiter 

 than those of the two other divisions, througli tlie nioditii-ation of tlieir 

 characters and are thus of more recent origin. 



The orders of the division Polypetala^ are largely represented in the 

 flora of the Dakota Group, especially in the genera to which belong the 

 woody or arborescent plants now generally or even exclusi\ely pertaining 

 to the North American flora. The Araliacese by Aralia; the Ampelidese 

 by Cissus or Cissites; the Cornaceje by Cornus; the Hamamelidere by 

 Hamam elites; the Magnoliacea?, especially by Magnolia and Liriodendron; 

 the Menisperiiiace;Te by Menispermites; the Malvacete by Sterculia; the 

 AceraceiB by Acerites and the Sa})indace;iB by Sapindus ; the Celastrinea? 

 by Celastrus and the Rhamneaj by Ceanothus; the Jnglandea' by Juglans 

 and the Anacardiacese by Rhus. 



A number of the leaves of the Dakota Group are referred to the genus 

 Aralia by clearly defined characters of their nervation and the form of their 

 palmately lobed leaves, while others, which have been separated under the 

 generic name of Araliopsis are like some leaves of the other Cenomanian 

 prototypes or of complex character, A\hich relate them indifferently to several 

 genera; to Platanus, by the size and shape of the leaves; to Sassafras by 

 their trilobate form; or to Aspidiophylluni by the prolongation of their base 

 into a round or dentate shield, etc. As the peculiar polymorphism of these 

 leaves has been separately examined, the present remarks are limited to the 

 distribution of the leaves of Aralia. Eleven species of this genus are 

 described from the Dakota Grouj) ; the finest of them, J. Sapoytanca Lesq., 

 represented by numerou^ leaves, reappears in its more essential characters 

 as A. Looziana in the flora of Gelinden and in that of the Laramie Group. 

 Of the other species of the same tV)rmation, A. tcitiiinerviti Lesq. is repre- 

 sented with a remarkable affinity of characters in A. nni/iisfihba Lesq., of 

 the auriferous gravel dejjosits of California, and als(» in .1. Joiy/enseni Heer, 

 of the Tertiary of Greenland. Heer has described two species from the 

 schists of Atane and one from Patoot, none being recorded from the Upper 

 Cretaceoiis of Wyoming and Montana. From the Cenomanian of Bohemia 

 two species of Aralia are described by Velenovsk}'; t>ne of them, A. decitr- 

 rens, is apparently identical with A. Saportanea of the Dakota Gri^tup. 



None of the fossil species of Aralia can be regarded as closely allied 

 to any of those of the present flora of North America. A. Whitneyi, of the 



